Using a Router - a question

[fobits]

I've just acquired a router, something that I've never used before, and have a couple of template bits en route from Stew-Mac.

Before I start chopping on my guitar, I'd like to run the plan past the more experienced people here.

The tremolo opening is now blocked with soft plywood stuck in with Elmer's glue. I made a botch of that job and plan to cut it all out, down to fresh wood, and do it over.

This time, instead of making the hole first and sanding a plug to fit, I think it would be better to do it the opposite way.

1) Make a plug using a table saw and a piece of sandpaper stuck down on a flat table. That should keep it straight and square.

2) Set the plug on the guitar, exactly where it will go, and snug pieces of plywood against it on all four sides. These will be held down with double-sided carpet tape and will form a guide for the router.

3) Use a template bit to cut the opening straight down from the guides.

In theory, the plug should fit precisely, except for a bit of rounding at the corners. In practice.....?

Does that sound like a good method, or is there a better way?

[UnklMickey]

Frank,

i don't know much at all about routers.

but i'm pretty sure, with the right bits and collars,

you should be able to use the same template to cut the plug AND the opening that the plug fits in.



i'm sure one of the Lutherie experts can expand on this.

or tell me i'm totally out in left-field.



unk

[bjg]

that sounds fine you just need to be careful of a few things

1. direction - I'm assuming you don't have a router table so you will be holding it. Router bits spin clockwise so make sure you are going with the direction of the bit - left to right. this is very important both safety wise and to try and cut down on burning. generally it works well to go in small circular motions.

2.depth - don't try to go too deep at once or you will burn the wood, hurt your shinny new router and possibly yourself. You said it was soft plywood so i would probably do about a half inch at a time max

3. another thing is to be careful to keep the router flat. when half the router is hanging off the edge this can be difficult especially if it bites a piece of the wood. this is important so you don't have these uneven indents and depths.

also is your router a plunge router? you know because you can move the base up and down while routing. you should be able to set a max depth then lower it into the wood. otherwise it is a good idea to drill a hole first then lower the bit into that hole if you have a fixed base router. Though you can just lower a fixed router into the wood it can get a bit hairy.

a couple other things since it seems like this is your first time. GO SLOW. this will ensure your safety and will help keep the wood from burning. don't try to do too much at once. also make sure you wear eye and ear protection. finally work in a well ventilated space, outside works the best. these things kick out A LOT of dust and it goes everywhere so save your lungs and energy by moving outside. or if you can hook up a vacuum into your router that will help also.

[sumgai]

bjg,

Good answers to Frank's questions, but needs more cowbell.

In order to keep the router from diggin in and taking off like a runaway train, the important thing is to excavate wood in the opposite direction of the spinning bit. When you are routing with the bit 'below' the wood, as you face it, move left to right, as you said. When the bit is 'above' the wood, move right to left. Follow this practice as you do vertical sides - move bottom to top on the left side, and top to bottom as you do the right side. In short, your easy-memory key is to think "always go clockwise".

Also, in a plunge router, the base remains stationary - it's the motor body and bit that moves vertically. In tight spaces, pre-drilling an entry hole is good for non-plunge routers, but in bigger spaces, just start in the center by tipping the router at an angle, and go from there. If it feels "hairy" to do this, then practice on some scrap until you get the hang of it.

Finally, go slow only in the overall procedure. Going too slow in the actual chipping process greatly increases the chances of burning the wood. One should take small bites, if you will, taking time in between each short excursion in order to check one's progress. Experience will tell you when to back off and take a reality check, and when to just keep on chooglin'. That experience is best garnerd on scrap wood of a similar nature - plywood, particle board, hard woods, soft woods, all of them act and respond differently. Obtain suitable scrap from Home Depot or a local lumber yard, and practice, practice, practice.

But otherwise, good advice to Frank. The bit about safety earns you a +1.


sumgai

[sumgai]

unk,

Frank,

i don't know much at all about routers.

but i'm pretty sure, with the right bits and collars,

you should be able to use the same template to cut the plug AND the opening that the plug fits in.

i'm sure one of the Lutherie experts can expand on this.

or tell me i'm totally out in left-field.

unk

I'm having a difficult time imagining how one template can be used to cut both the cavity in the body and the plug that goes into it. One operation is inside, the other is on the outside. Perhaps you meant to say the plural version "the same templates" or even "the template set"?

Given a the diameter of a bit, even if two different bits are used, a template is either larger or smaller than the workpiece by the radius amount of said bit. (Actually, we're talking about the roller bushing here, not the cutting surface of the bit itself.) This mans that you can't simply cut a piece out of some wood/plastic/metal/whatever, and call both pieces a template set. One of them is going to have to be much smaller or larger than the other, that difference being the diameter of the roller bushing on the bit. Which, if I've done my math correctly, should result in placing the bit into the wood at the correct spot to make both the plug and the cavity a tight fit.

But I'd be remiss if I didn't add "ymmv". ;D


sumgai

[fobits]

Unk -

you should be able to use the same template to cut the plug AND the opening that the plug fits in.

If somebody has found a way to do that, their brain works better than mine. I can't think of a way to do it, unless you can find a bit of zero diameter. Perhaps a laser router?

bjg and sumgai -

Thanks for the advice and encouragement. I poked around on the Internet before buying it, to learn something about the tool and how it's used. I was already planning to do the things you mention.

Router bits spin clockwise so make sure you are going with the direction of the bit - left to right

Check. Go clockwise around the inside of an opening, and CCW when cutting around the outside of something.

don't try to go too deep at once or you will burn the wood

The bit has a cutter part a little longer than a half-inch, and I don't plan to cut even that much on each pass. Slow and careful does it.

...keep the router flat. when half the router is hanging off the edge this can be difficult

The plan is to use quite large pieces for the guide, so they will extend over the sides of the guitar and allow the router to slide around without tipping. If I can find something of the right height to support the ends, where they stick out, so much the better.

also is your router a plunge router?

It is a plunge type, but I don't plan to use it as one. I think it would be better to lock it at the desired depth and start it in a big pilot hole. It only takes a few seconds to drill one, and all the plywood is coming out anyway.

That experience is best garnered on scrap wood of a similar nature - plywood, particle board, hard woods, soft woods, all of them act and respond differently. Obtain suitable scrap from Home Depot or a local lumber yard, and practice, practice, practice.

Yes indeed, good advise. I don't think I'll have to make a trip to Home Depot for scrap wood - I have a whole workroom with enough scrap to practice for a year. I don't believe that any of it is basswood, though.

Thanks again, guys.

<edit> Sumgai posted the reply above while I was writing this one. I didn't mean to amplify the point he makes, which he explains quite throughly himself </edit>

[UnklMickey]

fobits said:

Unk -

you should be able to use the same template to cut the plug AND the opening that the plug fits in.

If somebody has found a way to do that, their brain works better than mine. I can't think of a way to do it, unless you can find a bit of zero diameter. Perhaps a laser router?...

Frank,

i think you left out some of the important details when you quoted me.

unklmickey said:

...but i'm pretty sure, with the right bits and collars,

you should be able to use the same template to cut the plug AND the opening that the plug fits in....

again, i've never done this, but i believe they use a larger collar that keeps the bit farther away from the template when cutting the hole.

and a smaller collar when cutting the plug.

sumgai said:

....Given a the diameter of a bit, even if two different bits are used, a template is either larger or smaller than the workpiece by the radius amount of said bit. (Actually, we're talking about the roller bushing here, not the cutting surface of the bit itself.) ...

what i was referring to was using straight bits, without roller bushings.

the collar rides against the inside of the template.


unk

[fobits]

again, i've never done this, but i believe they use a larger collar that keeps the bit farther away from the template when cutting the hole.

and a smaller collar when cutting the plug.

Hummmm. I've been doing some sketching here, and I believe you're right. I think it could be done that way, but with a catch.

The template would have to be a different size than the plug and hole. If it was a female template, it would have to be bigger, scaled up just the right amount to allow for the width of the cut and the sizes of the collars. If it was a male template, it would have to be smaller.

I'm not sure about the curves, if they would scale properly or not. Probably so, but I don't remember enough geometry to be sure.

That would be a good way for production work, but calculating the size and making the template would be a lot of preparation for just one.

It could be done, though, I was wrong about that.

[UnklMickey]

well, as i said before, "i don't know much at all about routers."

i'm just remembering something that i overheard years ago.


it does warrant investigation.

you would need to compensate, adding to the size of the template,

but, if the collars and bit are sized correctly,

it seems like the one template would get you a plug that fits the hole precisely.



this is a topic where we could probably use the Lutherie skills of:

"RW (stbZ)"

although, since his post-count has now exceeded 500, i guess we could call him:

"RW (E.A.G.S.)"


(eventually attained god status) [Bugs Bunny mode] " aint i a stinka!" [/Bugs Bunny mode]


even if he can't help, i'm sure that should get his attention, and he'll ring in.




unk

[Runewalker]

Yes, I've stood aside on this. As I have experience with routers but mostly on molding and finish carpentry. I've never had first the right tools, then the guts for routing guitar bods. I have some confidence that I can figure it out, but a) I balked at Stewmac's prices on guide bearings, and b) Having not done it I don't think I qualify to advice.

I did a bod way back and my process, while workable, was not pretty. It was old school, chisle work. I don't recomend that.

In this endeavor NM bjg and Godman SG give good counsel, applicable to all wood working.

My experience with basswood was that it was not a resistent wood like oak or maple or birch, so it may go quite rapidly. Part of the trick will be on how you secure the template. Many use screws, some are big enought to clamp and give room for the router.

So I must stand aside, Godlike or not.

Even Zeus knows his limits, which in and of itself is quite godlike, thank ye Unk.

Good luck, and please share what you learned.

RWZ

[sumgai]

Well, I know that I missed something here. I forgot to mention that when using the router on the outside of a piece, such as cutting the plug, you need to reverse the directions I gave for using the router inside of the workpiece. Go counterclockwise when moving the router around the outside of a workpiece.

Now, that said, I'd like to address the use of collars, roller bushings, or whatever they're called. In theory, most of them are larger then the bit which they ride on. But larger cutters (bigger than 1/2") might have same-diameter bushings, making measurements and calculations easy. So we're all standing around the work bench, sucking down suds, and poking/prodding at the templates. I use the plural for a reason, we'll see why in a moment.

If we want to cut an inside hole (a cavity), then we need to have a template that completely surrounds the intended hole. We are going to cut away material from the inside. And since we want to make a plug to fit that hole, we need to mount a template onto a different workpiece, and follow that around the outside. Given my use of one template, one job, I think I'm on firm ground by saying "a set of templates" here, but I'm open to discussion.

Now we need to know what size those templates have to be. Well, let's use some real world measurements. Our target cavity is 3" across by 6" long, and the plug has to fit as snugly as it can. If we use a 1/2" cutting bit (straight), and it comes with a 1/2" roller bushing, then we can easily see that the template can indeed be the same size as the intended hole. The only rub would come along if we had a bigger collar/bushing than the bit itself. At that point, we'd need to offset the template size by the amount of "the radius of the collar minus the radius of the cutting bit". (If the collar were somehow to be smaller than the cutting bit, then we'd reverse that those two numbers. But that's unlikely - we'd be undercutting the template, and that's considered risky business.)

Fortunately, the same thing applies when cutting the plug. We can use the same dimensions as the plug itself, if the collar and the cutting bit are the same diameter. So this almost vinidicates unk's position, except for the inner/outer part about needing two templates. As Rune points out, there's no way to cut such a pair out of a single piece of material, short of a laser cutting tool. (And how expensive would the final product be, hmmm?) But by cutting them from two pieces of stock, and with a little bit of finishing work, we can make make an inner template slide snugly into an outer one, and once that's done, we're home free.

Of course, all this has been done for you. Merely jump onto eBay, and search for "Strat templates", and looky there, won't wonders never cease. ;D

Good luck!


sumgai

[fobits]

Given my use of one template, one job, I think I'm on firm ground by saying "a set of templates" here, but I'm open to discussion.

That's an interesting brain-teaser. Certainly it could be done with two templates. The question is whether it could be done with just one, using different-sized bushings to move the cutter away from the template.

I've gone back and forth on this one. First I thought it was impossible, then that it was possible. Now I'm leaning back the other way.

It could be done on a straight side and around a gentle curve, but a tight curve couldn't be duplicated on both pieces.

Consider a square corner. It could be cut on the plug, but there's no way to make a square corner in a hole.

One bushing would have to be bigger than the other. Consider a place on the outline that one bushing would fit into, but the other wouldn't. That part would be missing entirely on one piece.

That's my current thinking anyway, although I can hardly claim any expertise in the field.

Of course, all this has been done for you. Merely jump onto eBay, and search for "Strat templates", and looky there, won't wonders never cease

Thanks for the tip, but I think I'll use the method that I described in the beginning. Nobody has pointed out any serious flaws in that plan, and it doesn't require spending any more money

[UnklMickey]

fobits said:

...Consider a square corner. It could be cut on the plug, but there's no way to make a square corner in a hole....

that sure does blast a "hole" in the one template idea. (pun inteded)

i doubt the router experts have figured a way to get the same radius on the plug as in the hole.

but who knows?

maybe a few $$ in a book would be well spent.

even if the pros just finish the hole square by sawing, chiseling, and/or filing, to match the plug, there might be other tips in a book that would help you in other areas.

but, which book?

guess i'll once again go back to that original statement i made in my first reply.



at any rate, whatever you do, be sure to let us know what works and what fails when you actually do the job.


oh yeah, one more thing:

you already know this, but it bears repeating.

practice -- many times -- on scraps, before doing the real thing.


okay 2 things,

also, measure TWICE, cut ONCE.

"i don't know WHAT happened........... i've cut the darned thing 3 times, and it's STILL too short!"



unk

[sumgai]

unk,

.....
i doubt the router experts have figured a way to get the same radius on the plug as in the hole.
....
unk

That's easy, just a bit of math, and you're done. Or, if you feel math-challenged that day, try this.....

Draw your template outline on your workpiece.
Measure the bushing diameter, and draw that radius (1/2 diameter) into each corner.
(You may draw "construction" lines to help your layout, if you wish.)
When the radius has been drawn in, flush with and tangent to each straight line, cut the template out of the stock.

The finished template, be it either an inner or an outer piece, will have radiused corners, forcing the router to cut the same dimension corner for each workpiece. The resulting plug should fit snugly all the way around in the cavity.

Simple, no? Sadly, you're still doing this twice, due to the kerf of the cutting tool (saw, router bit, whatever). I recommend that when making the cavity template, position the blade so that it is halfway across the pencil line (the tool is not slightly into the template area, it is slightly into the "cavity" area), making the cavity I skosch undersized. Conversely, make the plug template by positioning the blade halfway across the pencil line (the tool is slighly outside of the plug, not slighly into the template area) so as to make the plug an RCH larger. If necessary, sand the plug template until it fits within the cavity template, but it shouldn't take much of this, if any at all.

Obviously, these templates were just made to be used with only one size collar and cutting bit. You'll thank yourself later if you take a moment now to write the proper size on each template piece. Just for future reference, you understand.


sumgai

[UnklMickey]

sumgai said:

...I recommend that when making the cavity template, position the blade so that it is halfway across the pencil line (the tool is not slightly into the template area, it is slightly into the "cavity" area), making the cavity I skosch undersized. Conversely, make the plug template by positioning the blade halfway across the pencil line (the tool is slighly outside of the plug, not slighly into the template area) so as to make the plug an RCH larger. If necessary, sand the plug template until it fits within the cavity template, but it shouldn't take much of this, if any at all....

Frank,

i assure you, all this eye-balling, "skosch"ing, and sanding, is not what the router pros had in mind.

using 2 templates leaves much room for error.

doing things by sight and "skosch" introduces even more room.


using a single template and exchanging collars, insures that the straight sides will be a PRECISE fit.

even if the template is slightly out of square, or the sides are not exactly parallel, any errors are duplicated PRECISELY in the hole and the plug.

as you pointed out, the corners ARE a problem. even with a small diameter bit, the hole with have a radiused corner and the plug will not.

so afterward you will need to either square up the corners of the hole, or radius the corners of the plug.

both of those paths will lead to extra work and some possibility of poor fitting in the corners. the smaller the diameter of the bit, the less work needed.



since it is obvious that neither Sumgai nor I, know much about routers, i suggest you either take everything that has been written in this thread with a liberal dose of salt, or even ignore everything except the prudent safety guidelines, AND:

unklmickey said:

....maybe a few $$ in a book would be well spent.
...

spend the dough, get the know!

professionals find ways of making things work, so that the process itself eliminates errors.



unk

[sumgai]

unk,

since it is obvious that neither Sumgai nor I, know much about routers

Sorry, I'm not gonna take that one laying down.

I've been using woodworking tools since I could stand up without training wheels, and power ones since about 11 or 12 years old, without supervision. My father was an old-world wood butcher, and the fact that I've still got all my digits intact should stand as testimony to his teaching abilities.

I rather think that there are at least two schools of how to do things. One is to act in what I call an officious manner, and plan everything out to the last degree, then forge ahead and d@mn the torpedoes. These guys may seem anal retentive, but I prefer to think of them as inexperienced - they haven't yet learned what's important, and what to ignore. This class of wood-wanker will use ultra-high precision instruments, pore over spreadsheets or calculators for hours on end, and use templates or jigs whenever possible, even for nailing fence boards to stringers. In short, they don't trust either their eyes (or their eye-to-hand coordination), nor do they trust their instincts.

Contrast that to a guy who measures carefully, but due to experience, does not re-measure again and again. He knows that no matter how careful he is, Murphy will have his way, so he plans on getting even with the blighter later in the game. He draws a pencil line, and fires up the tool. He watches what he's doing, and finishes the cut before the Type A dude has even bought his first piece of wood. At that point, our Mr. Casual tests the fit of the two pieces - he does not rely on, nor does he give a fig for, the measurements nor the pencil lines. They were guides, and that's all they were. For him, the proof is in the pudding.

Now, I don't know if you were referring to something else in our overall discussion, but I was talking about how to make a pair of templates. For a moment there, it looked like you were speaking to the job itself, presumably after procurring the templates from some source.

i assure you, all this eye-balling, "skosch"ing, and sanding, is not what the router pros had in mind.

But you then go on to speak directly to the template issue itself.

using 2 templates leaves much room for error.

doing things by sight and "skosch" introduces even more room.

Man, that's not just harsh, that's ignoring all of the previous discussion that's gone before.

Mick, if you can figure out, or if anyone here can figure out, how to use one template to make both an Inner and an Outer piece that will fit together, I'll call you my daddy on the downtown courthouse steps, and give you two hours to draw a crowd. Even if you were to use a 'kerf-less' cutting tool (a laser, perhaps?), you'd still have some difference in size between the two pieces. In summary, I'm saying that without two templates, don't plan on cutting both a plug and a hole that fit even reasonably well.

using a single template and exchanging collars, insures that the straight sides will be a PRECISE fit.

even if the template is slightly out of square, or the sides are not exactly parallel, any errors are duplicated PRECISELY in the hole and the plug.

as you pointed out, the corners ARE a problem. even with a small diameter bit, the hole with have a radiused corner and the plug will not.

so afterward you will need to either square up the corners of the hole, or radius the corners of the plug.

both of those paths will lead to extra work and some possibility of poor fitting in the corners. the smaller the diameter of the bit, the less work needed.

What I described in my earlier diatribe was a methodology used by countless craftsmen for innumerable years. If I must, I'll post a picture of the layout to make the set of templates. However, I now just now realized that I can shortcut some of the debate by introducing another element.

If one were to first use cardboard for the layout material.......
Draw lines on cardboard.
Cut along line with a very sharp knife.
Remove one piece from the other. Fit them back together. Observe that the slack between them is d@mned small.
Now fit each piece of cardboard to it's associated workpiece.
Draw lines inside/outside as appropriate.
Carefully cut to the edge of the pencil line, removing the line as you cut. Do NOT cut into the workpiece beyond the line, or you will have a gap between the two templates.
If you wish, assemble a temporary jig to assist in cutting these lines at the appropriate places.

The use of cardboard as a pre-template, and the use of the knife to separate the two pre-templates, allows us to make sure that our fit is as close as humanly possible, before we've even cut our templates out of stock. But I assure you, Mick, that a paranoid craftsman would still cut for a tight gap, and sand as needed to open it up for a perfect fit. It's just the way we do things. Time and experience has proven too often that we don't have to re-do the job because of customer dissatisfaction, we don't waste time with all that prior calculation stuff, and we waste almight little material, whenever we can help it. It's just our way of life.

And yes, I used these skills for several years, about a quarter century ago. I built pool and billiard tables for half a decade. Loved it, wish I could still do it. But the music, she's a calling me to her bosom.

Room for error, indeed. Why do you think we have fine-detail tools to hone the last little bits into shape? For Ken to make a mini-Strat for Barbie?

Frank,
Yes, get a book, I agree with that one. In fact, Sears sells one of the best I've ever seen, Routers and other Power Tools. $10 at your nearest Sears outlet, or probably available online. Covers all kinds of stuff, not just routers, a regular gold-mine of info.


sumgai

[UnklMickey]

sumgai said:

unk,

since it is obvious that neither Sumgai nor I, know much about routers

Sorry, I'm not gonna take that one laying down.
....

you can take it laying down, standing up, bending over, or insist that you're not gonna take it.

but these facts remain, i admit I don't know much about routers.

and regardless of how much experience you have with other woodworking tools,

your lack of knowledge of how to compensate for the diameter of the bit,

between routing the opening and routing the plug, when using a single template,

tells me, you don't know all that much about routers either.

you probably do know more than i do about routers.

(some, is of course more than almost nothing.)

but you are lacking in some fundamentals that are key to this particular issue.

sumgai said:

....Man, that's not just harsh, that's ignoring all of the previous discussion that's gone before....

yeah, that happens all too often around here.

i just thought it was my turn to do that. lol

sumgai said:

...Room for error, indeed. Why do you think we have fine-detail tools to hone the last little bits into shape? For Ken to make a mini-Strat for Barbie? ...

well, if that's the kind of thinking thats permitted, the single template plan is already complete. regardless of any slight errors in size, parallelism, or orthogonality, in your making of the template, the plug is PRECISELY the same size as the hole.

so then it would just be the matter of squaring off the corners of the opening with a chisel, or rounding the corners of the plug with a belt sander.

then ease the bottom edge of the plug, with a round-over bit, to make the initiation of insertion easier, apply a bit of glue, then pound in the plug with a scrap of wood and a hammer.


but i don't consider the hand work inconsequencial.

that part should be eliminated.

sumgai said:

...Mick, if you can figure out, or if anyone here can figure out, how to use one template to make both an Inner and an Outer piece that will fit together, I'll call you my daddy on the downtown courthouse steps, and give you two hours to draw a crowd. Even if you were to use a 'kerf-less' cutting tool (a laser, perhaps?), you'd still have some difference in size between the two pieces. In summary, I'm saying that without two templates, don't plan on cutting both a plug and a hole that fit even reasonably well.....

a bold challenge indeed. i'm gonna hold you to that!

although i could be act like a weasel, and say that we're already there,

the issue with the hand work on the corners, IMHO makes this process not quite good enough.

so i'll be looking for a solution that will maintain the same radius on the corners of the plug and the opening.




unk

[sumgai]

unk,

We're both getting too verbose to quote each other.

I believe I have already given explicit instructions on how to make a properly radiused corner for both the plug and the cavity.

Gonna hold me to it, eh? Looks like it's time for some diagrams. Let's start with the basic template outline:



Now let's add the four corners that have to be curved. The assumption here is that we'll be using a 1/2" diameter router bit. I have shown each corner in successive progression - initial layout lines, lines trimmed back to the sides, and radiused corner (the two lower corners have been rounded off):



So in case anyone is having difficulty seeing those corners, let's have a close-up:



In reality, the previous illustration is what the final version of the Inner template looks like, just before all four corners have been radiused to 1/2". But that will only let us cut the plug. We also need an Outer template to help us cut the cavity. That template is cut from a larger piece of stock, and with all four corners radiused, it looks like this:



You'll note that I've already cut away the material inside, where the router bit will go, so you don't see any layout lines. These are the exact same as for the Inner template, shown above. The secret here is to cut along each line such that you remove the lines, but you do not allow the cutting tool to enter the stock from which you are cutting templates.

This results in a matching set of templates, Inner and Outer, that should fit snugly when assembled together. The reason for that, and not coincidentally, the reason that the final products will also fit together snugly, is that the corners have been rounded to the same radius as the collar of the router's cutting bit (1/2"). In both cases, the router will follow the curves without hesitation, producing curves instead of straight corners on the plug that would later need modification (rounding off). While you could rely on the fact that a straight corner on the Outer template will also yield the same results as my version here, the fact is, the router will come to a dead stop when the corner is a right angle, and you have to change direction manually, all the while trying to keep the same travel speed. The rounded corner provides a much smoother transition from one side to the next, making the cut less error-prone.

So here are the two templates together, side by side:



Now, we need to visualize where the router bit will be positioned as it does its work. For the Outer template (the cavity):



And the same for the Inner template:



Now comes the fun part. Can anyone see any way to use the same template piece to guide the router in making both the plug and the cavity? I will stipulate that unk has posited the condition of “using the right bits for each operation”, but the fact is, they don’t make a collar that is 2.5 times the bit diameter. That’s what it would take, to use the same bit, but just change the collar. Not to mention that the template itself will be larger than the final dimension. The math for figuring all this out is an exercise best left to the reader. ;D

Plus, there is the bugaboo about the fact that you’d be cutting a plug away from the center of the template. When the cutting bit is near the end of the cut, there is no support for the work piece, and it will twist out of position, causing you a minor headache. Either of these reasons should suffice to convince the reader of the need for two templates to do the job.

Any questions?


sumgai


p.s. FileCabin is back online!! Hooray!!!!! I need to duck out for the evening, but I'll be back with more illustrations over the weekend to make some of my recent contributions (hopefully) more clear.

[fobits]

I now regret that I ever started this thread.

Has it occurred to either of you guys that there might be more than one way to do a job, and none of them are written on the sky in letters of fire?

It all started, if anybody remembers, when I outlined a method in which the female guide is derived directly from the plug, with no intermediate steps. I asked if anybody could point out any problems with that approach.

Since nobody has, I'll assume that it's flawless and is the One True Way(tm). Anybody who suggests a different way is bound for hellfire and eternal d*mnation.

Weep and repent, oh ye blasphemers and heretics.

[sumgai]

Frank,

I'm taking your epistle in a tone of humor, don't worry. ;D

And of course you are correct in that you can make a template from an "as built' existing piece. But therein lays the rub.

If you already have such an existing piece, and you refuse to ever have a similar piece again, come bloody hlll or highwater, then fine, make your one-off template, use it, then toss it. But if you're contemplating the future, and not just for yourself but possibly for others of like mind, then you may want to hang onto that template. Only now, it's a single piece in need of a mate. You can make a matching template directly from that, or you can construct a pair of them as I've outlined above. Either way, you have two separate templates in your hand.

We, unk and I, purposely ignored the "already got half of it" part of your message because we're more interested in helping forum members prepare for the future. I'm sure you are too, but it now sounds like you have already cut the plug, possibly with right angle corners, and you're wondering if you can make a matching template for the cavity. The answer is, of course, yes. But how much additional work must be done in order to make the plug fit the cavity?

All I tried to point out was that if you think ahead, you'll end up with a tool (pair of templates) than can be used to reduce the overall time spent on the job - the plug will fit the cavity the first time, or very closely fit it, with minor sanding of imperfections at the most. Cutting the plug with a table saw and getting right angles, then going back to round them off, possibly with a router "round-over" bit, is tedious, and if the plug is small, the job is dangerous to the worker(because the router is not stable (the base wobbles).

Sharing the tool is part of the game, that's all.


sumgai

p.s. A better tool for rounding off the corners would be, if you happen to have one, a 'shaper'. That's nothing more than a router turned upside down and installed into a special table. Worth its weight in gold just for the safety value, but also allows an extremely accurate degree of repetitiveness.

[fobits]

...it now sounds like you have already cut the plug, possibly with right angle corners, and you're wondering if you can make a matching template for the cavity.

No, I haven't started any of it yet, but despite all the arguing back and forth, that's still how I plan to do it.

I'm not wondering if I can make a template from the plug. I'm wondering how well it will fit after routing. In that respect it seems to be the same as your method except, as you note, the template will be a one-off instead of permanent.

Some good points have been made. I agree with your advice that the template for the hole should be made a "skosch" smaller. If the hole turns out too big, that's a serious problem, so it's better to err a bit on the small side.

Thinking about that, I've modified the plan to include putting one or two layers of masking tape on the inside edge of the guide, where the ball bearing will roll. That will make the hole exactly 2.03 tiddlies smaller.

But how much additional work must be done in order to make the plug fit the cavity?

That's the main thing I was asking (at least by implication) in the first post, when I asked if anybody saw any problems.

It seems to be the same as your method, but seeming and knowing aren't the same.

We, unk and I, purposely ignored the "already got half of it" part of your message because we're more interested in helping forum members prepare for the future.

All right, I can see that. OTOH a method which doesn't require so much preparation might be of interest too.

BTW, neither you nor Unk have explained how to hold the plug while cutting around it, or how to support the router while it's being done. That sounds like another complicated tool. A table saw does have it's advantages.

the plug will fit the cavity the first time, or very closely fit it, with minor sanding of imperfections at the most.

Heh. "Minor imperfections" sounds better than the skosching and eyeballing that drives Unk wild

As a matter of curiosity, what is a perfect fit for a wooden plug in a wooden hole? A ten-thousandth of an inch all around? Five thousandths? Does epoxy resin cause the wood to expand, the way that water-based glues do? If so, by how much?

There are so many unknowns that it seems strange to talk of an (undefined) perfect fit. I'll settle for a good fit, with straight sides and no bumps or wavers or ripples.

Anyway, I'm not really upset. It just seemed that you and Unk were both fixated on you own methods, and neither is willing to admit that the other could possibly be right about anything.

Fun and games.

Frank

[sumgai]

Frank,

Fun and games indeed!

But how much additional work must be done in order to make the plug fit the cavity?

That's the main thing I was asking (at least by implication) in the first post, when I asked if anybody saw any problems.

It seems to be the same as your method, but seeming and knowing aren't the same.

No, there is a pretty good amount of difference between your intended method and mine. I am starting from blank pieces of wood (stock), and you are starting from the premise of an already existing piece (the plug you will soon cut). Where we differ even more radically is that I am planning ahead to avoid the square corner problem. If I've been reading your posts correctly, you seem comfortable with "making the corners fit" after the plug is initially cut on the table saw.

Which brings up:

BTW, neither you nor Unk have explained how to hold the plug while cutting around it, or how to support the router while it's being done. That sounds like another complicated tool. A table saw does have it's advantages.

You're correct, I've glossed over this one. Normally speaking, a template needn't be "pristine", one can mount it do a work piece directly. Screws are common, glue not quite so. Low-tack adhesive is now available for jobs like this, making it a fast and smart way to go. No filling screw holes afterwards, and all that mess.

I did say something about using a shaper (upside down router in a special table) to do the rounding off. This is much safer, but if you don't have the tool already, then it'd be expensive for a one-off. Perhaps a friend/relative/local school shop? Otherwise, just take your time, clamp the plug between two thick pieces of scrap, and use the router in a normal manner. The extra scrap is to help you support the base of the router, to reduce the chance of tipping it, and ruining your rounding-off job.

As a matter of curiosity, what is a perfect fit for a wooden plug in a wooden hole? A ten-thousandth of an inch all around? Five thousandths? Does epoxy resin cause the wood to expand, the way that water-based glues do? If so, by how much?

There are so many unknowns that it seems strange to talk of an (undefined) perfect fit. I'll settle for a good fit, with straight sides and no bumps or wavers or ripples.

Fit is in the eye of the beholder. Or as Rune might say "Fit happens". ;D It depends on how much work you intend to put into the finish. If you don't care about a detectible line, mighty close is good enough. If you have to hide the line, then let the plug exceed the cavity by a thousandth or two, and sand accordingly.

You are also correct to consider the effects of glue on the wood. Seasoned wood will not swell or contract as much as green wood, so try to not use the "fresh" stuff. Any kind of glue will work here, unless you anticipate exerting a lot of stress through the seams (not across them). In that case, I'd definitely use a resin glue, but short of that, any carpenter's glue is fine. Just give it a full day to dry before working it (prepping it for the finish coat(s)).

in re: admitting someone else could be right about something.....
I admit that I was rather "challenging" (being a difficult boffin) in making my statements, but I did say that I'm open to anyone coming up with a method of cutting two items with only one template. I even gave a hint as to how it can be done, provided the proper parts are made (which I do doubt, but I could be surprised in learning otherwise).

There, I believe that tidy's things up a bit, don't you? Oh, wait, what have we here....

That will make the hole exactly 2.03 tiddlies smaller.

I forget, is a tiddlie equal to one RCH or one BCH? ;D

Is there a web page with a conversion chart for that? ;D


sumgai

[fobits]

Just to stir things up again.....

---

The design of an inlay kit is actually rather simple. A small
diameter bit passes through a small collar, much like a
normal guide bushing setup. The trick part is a removable
bushing that fits on the collar. When installed, the bushing
positions the bit to cut the recess for the inlay. Remove the
bushing and the bit is now correctly located to cut the
outline of the inlay, sized perfectly to fit the recess.


The template has to be thick enough to prevent
the collar from contacting the work. Also, the opening
has to accommodate the collar alone (Left) and the
removeable bushing (Right) so the inlay piece fits the recess.

---

This was swiped from an article at:
www.newwoodworker.com/rotrinlays.html

Here they are using a very small bit to cut a recess an eighth of an inch deep. It would have to be scaled up a good deal to cut a deep plug, but Unk's one-template theory is sound. The kits already exist, at least on a small scale.

[sumgai]

Frank,

Nice find. As I said, and you've now answered it in a 'round-about way, it can be done, if one can secure a collar bushing that is 2 1/2 times the diameter of the bit. Looking at your pix, I'd say that was pretty close, wouldn't you? And if one looks close enough, and takes a bit of parallax into consideration, then one should see that in the left photo, the left-most edge of the bit is exactly where the right-most side of the bit is sitting in the right photo.

This should work, although I'd want to practice with it for awhile. And I'm still leery of trying to cut a final piece out of material to which the template is not secured directly (the plug). That must be some kind of Rube Goldberg-like clamping arrangement to keep the plug from skipping around as you finish up the cut.


sumgai

[fobits]

Well. This isn't the sort of post that anybody likes to write.

I was quite proud of the method described in the beginning, which I thought was more simple and easy than the alternatives, and would give equally good results.

It seems that there is a problem with it, one which I hadn't considered.

I stuck the plug in place with double-sided tape and pushed the guides up tightly against it. They were held down by more double-sided tape.

All was bright and beautiful....



I made several cuts, going down as far as the half-inch bit would reach. It wouldn't go far enough with the guide on top, but that isn't a real problem.

Everything was still looking good....



Since I had a smaller 3/8" bit, I used it to cut back further into the corners, making a tighter radius which would require less sanding on the plug.

That's when disaster struck....



The lesson here is that double-sided tape ain't magic. It can come loose and allow the guide to slide out of place.

If I had been using either Sumgai's or Unklmickey's method, I wouldn't have been using a four-piece template. It would have been a one-piece template with lots of area for the tape to grip.

If any others have been following this long thread, I have some advise - don't use the fobits method! If you do, then at least buy the kind of tape that says "Stronger Than Gorilla Snot" and check it before each cut.

It is fixable, by cutting the opening longer and making a new plug, but right now I need some recuperation time before going at it again.

[sumgai]

Frank,

I commiserate with you.

FWIW, I might have done the same thing - if I were only going to do this job once, I might not have cut a complete template out of one piece of stock. Four correctly dimensioned pieces should have worked just as well, for what you're doing.

What I would have done differently is to use 200mph tape to hold the top together as I aligned things, then I would have turned over the assembly and taped that surface too. And I would run the tape at 45deg. angles, for a bit more strength in all directions.

Other than that, I think you were doing it right, you just fell victim to Mr. Murphy. Which I've also done, giving me the hind-sight of taping both the top and the bottom of makeshift jigs like this.


sumgai

[fobits]

Thanks, Sumgai.

What I would have done differently is to use 200mph tape to hold the top together as I aligned things, then I would have turned over the assembly and taped that surface too. And I would run the tape at 45deg. angles, for a bit more strength in all directions.

That's a good idea. I'm not familiar with 200mph tape, but good old duct tape is strong on a clean surface.

The plug/guide assembly could be put together on a table, then the template moved onto the guitar as a unit.

Unklmickey, in a PM, had another suggestion. The plug and guides could be put together on top of another piece of plywood, using double-sided tape. After removing the plug, the top layer would be a temporary 4-piece template. After routing around the opening, the bottom layer would become a solid one-piece template. If anything went wrong, you haven't lost much.

Although I've finished the routing on the guitar, I was curious about how well it would work. I spent much of the afternoon in the workroom, going though it as a demo and incorporating your suggestion about the tape.

It came out very well. After a bit of sanding to round the corners of the plug, it fit into the template perfectly.

I took photos at each step, and in a week or so I'll work up another illustrated article. Right now I suspect that people are getting sick and tired of reading about me and my router ;D