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Routing/guide Bearing Question


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I'm new to routing so any help would be much appreciated...

I have a hardtail strat which I would like to rout for a vintage tremolo.

My question has to do with the proper bit and guide bearing to use.

Specifically, I would like to start routing the tremolo cavity from the top surface of the guitar but am unsure how to ensure keeping the walls straight once you get deeper than the template.

I would imagine a guide bearing comes into play but I'm unsure how this all works.

Any bit/guide recommendations and/or technique explanations?

Thanks very much in advance!


I have the 2HP Ryobi plunge router if that info helps.

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To actually answer the question the bearing on the bit follows the template until it reaches the bottom of the template. From there it just follows the edge left by the previous cut.

The bit looks like this

I would suggest a thicker template made from 3/4" MDF or plywood. This way the first cut with the router is not so deep as to bog down the router.

You could do as he says clear out some material with a forsener (i know thats spelled wrong) bit. I dont bother personally. Its just as fast to use the router.

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Thanks for both your replies...I think I've got to the bottom of my problem.

Originally I had purchased a Ryobi 1/2" straight bit with a 1/4" shank (and no guide bearing). I returned this today and instead got a Porter-Cable 1/2" straight bit with a 1/2" shank (also no guide bearing). My router will take both shank sizes.

This is what I ended up with tonight:


Guitar Guy - thank for the link you provided. These are the bits I had been looking for but could not seem to find!

I was hoping that having the shank the same size as the cutting tip will allow me to follow the template outline as I go deeper into the wood (without need for a guide bearing). Looking now I guess the risk I run with the longer bit I have is that it may eat into the template even after I am past it.

Thanks again for your help...looks like I may make another return and go for one of the template bits Guitar Guy recommended.

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Just my 2 cents here, but you have to have something other than just the shank of the router bit to bear against the template and the cavity once you're past the template. That router bit is zinging alosn at a pretty good clip and will butn the crap out of whatever it bears against.

The bit that is being sidcussed, I believe, has a bearing on the middle portion of the bit. This keeps things cool and unburnt.

You can use the bit you have linked to if you use a template guide attached to your router base. This is how I do almost all of my router work, and have for better than twenty years.

It is also easier on your router and bits if you use a Forstner bit to rough out the cavity first.

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Thanks for your reply.

I did return my first two bits and picked up one with the bearing in the middle like you and Guitar Guy had suggested. This one is also by Porter-Cable and is called a Pattern bit specifically for routing with patterns/templates.

I'm going to do at least a few practice runs this weekend (hopefully) since I'm so new to all this. Thanks also for the suggestion on the Forstner bit - I think I will try to pick one of those up, too.

One other question: can you explain the "template guide attached to your router base" a bit further or provide a link to a photo? I'm not sure exactly what you mean and I'd be interested if it will help produce better results.

Thanks again!


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One of these days I'll figure out how to post pictures amd links.

Till then, a template guide is a type of bushing that fits on the bottom of your router base. They come in a huge number of diameters. Think of it as a tube that sticks down frm the center of your base and the routher bit sticks down futher through the center of it. I thnk that this will get you to one.


I use the one 1/16" larger than the diameter of my bit and make my pattern that much smaller. Most of the guys who post here don't like them for no stated resaon other than you have to undersize your pattern.

The advantages are:

1) you use straight cutter bits which are bunches cheaper than pattern bits.

2) You never have a bearing go bad and have it either scorch your work, or even more fun, have it pop off all together and the bit digs into your work ruining it.

I've done most of my routing this way for a long time. I have pattern bits, but I only use them for weird applications.

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I like the idea of using the bushing to save money on bits, but I've found its cost me more in wood! :D I guess I'm just not good at doing the math and the measuring needed to change the pattern sizes. Doc, I don't spose we could con you into doing a tutorial for us?

Also, if you are going to use something like Myka's neck jig, you really need a pattern bit.

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I use a guide collar that attaches to the router --it has a circular lip that follows the edge of the template.

It doesn't route exactly according to the template --there's a gap of about 2 mm (or more if you choose smaller bits).

After I've routed with that, I use a bearing bit to clean up the walls to the edge of the template. At that point you can use the bearing bit to do the full depth of the pocket (because you're only taking off a thin layer from the walls).

I like the collar because it's easy to control --especially if you're new to routing.

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My wife has agreed to teach me the ins and outs of posting pictures so , when i get some time I'm going to do a couple of quick tutorials, mostly with routers. Till then,

1) get yourself a decent compass. By this I mean one that will pretty much lock in place. Make a paper pattern for what you want to rout. Make it the exact size.

2) set the width of the compass point to the pencil by putting one against the cutting edge of your bit and the other against the outside of your collar.

3) draw a new line inside the edge of your pattern by running the point of the compass along the outside edge while you keep the pencil at as close to 90 degrees to your outside edge as you can.

4) Cut out the new pattern. No math this way.

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Also, check that your bushing and cutter are concentric. I have 3 routers, and none of them have concentric bushings, so you have to ensure the same portion of the bushing rides the template, or your route ends up crooked. I decided the acuracy wasn't good enough for me, so I stick with bearing bits.

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Also, check that your bushing and cutter are concentric.  I have 3 routers, and none of them have concentric bushings, so you have to ensure the same portion of the bushing rides the template, or your route ends up crooked.  I decided the acuracy wasn't good enough for me, so I stick with bearing bits.

I had the same problem with my ryobi. The spindle is only out about.010" but thats enough to make the flaw visible.

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This is what I mean by a collar:


("gabarit" is the template/ "decalage" is the offset between the collar and the bit)

I don't know how concentric mine is (probably not very since it came with the cheap router) but like I said, I use it for the first couple of steps --then use the bearing bit flush against the template.

My straight bits cost me 9 euros each but my bearing bit cost me 50 euros...

That tip came from Mattia by the way...it really helped me a lot!

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