Need clever way to convert flush router templates to bushing template

[John Coloccia]

I have a bunch of router template that I'd like to turn into bushing templates, i.e. I need to make them bigger so I can use them with a bushing. Does anyone have any clever ideas for doing this, other than starting from scratch and rebuilding all the templates by hand?

[Prashun Patel]

John-
I'm missing something. Don't you want to make the templates SMALLER to accomodate the bushing offset?

[John Coloccia]

John-
I'm missing something. Don't you want to make the templates SMALLER to accomodate the bushing offset?

There are mostly inside templates, i.e. I'm routing cavities and things of that nature, so I want to make the inside template larger :) I should have been more specific. I think it's the same problem either way and can be generalized by saying that I want to use the current template to make new templates where additional material is removed from the template to accomodate the bushing :)

Basically, a frequent operation I perform is routing cavities that are 1"+ deep, and it's far simpler to do this with a bushing and a 1/2" bit because I don't have to worry about bit length, where the bearing ends up, etc. I've built jigs that accomodate bushings, but now I want to convert some of the templates I already have or have purchased. I'm trying to get to the point that one router setup can make ALL, of most, or my routes. I've found the process of changing bits not only time consuming but horribly error prone.

[Garrett Ellis]

John-
I'm missing something. Don't you want to make the templates SMALLER to accomodate the bushing offset?

Probably depends on if they are inside or outside templates, right?


What if you use a rabbeting bit to cut ~half the depth, then go back and flush trim the rest of the depth to the initial cut. I think this is going to be hard with any complex templates though... your curves/corners will become less pronounced.

[Jerome Hanby]

I think he has it right. Imagine a simple template to cut a 3/4" slot with a bearing guided bit. If you switched to a guide bushing, the slot would be less than 3/4" so hou would have to make the template larger (more than 3/4" wide opening) to cut a 3/4" slot.

On making a bigger template, could you use the original template with a bearing guided rabbet bit to make a new template? I think you could find a rabbet depth that would match what you need to accommodate the bushing.


John-
I'm missing something. Don't you want to make the templates SMALLER to accomodate the bushing offset?

[John Coloccia]

I hadn't thought of using a rabbeting bit. Hmmmmmm. That sounds like a pretty good idea, actually! I typically use a 1/2" bit with a 3/4" bushing, so that gives me an offset of 1/8"....and that's got to be a pretty standard rabbet size.

Brilliant. Thanks!

(BTW, for those that always get confused with bushing offsets, it is simply the difference in radius, which is another way of saying 1/2 the difference of diameters. So in my example, a 1/2" bit (i.e. a 2/4" bit) with a 3/4" bushing is 3/4 - 2/4 = 1/4....and half of that is 1/8".....or if you prefer .75 - .5 = .25, and half that is .125 ).

[John Coloccia]

Well, it turns out a rabbeting bit won't work because all of the rabbet bit diameters I can find are too large. I want to be able to pickup 3/4" features. However, what WILL work is a 3/4" flush cut bit with a 1/2" bearing, and there's nothing exotic about this particular combination.

[Jerrimy Snook]

227774

John,

Will something like this work?

Jerrimy

[Floyd Mah]

An overhead pin router would work. I mounted a router on the arm of a radial arm saw and used a pin below it to cut the cavities when I made the Les Paul Gibson copies. If you use a pin that is a different diameter than the cutting bit, you can enlarge or shrink the template by whatever amount you choose. Just use a drill bit (the non-cutting end) as the pin. You have a whole box of different sizes in the usual assortment. Plus the pin router setup is ideal for guitar making, since you can control the workpiece and also see the cutting action as you work. My only mistake in using it was to take too big a cut once. Otherwise, it's a perfect setup. I made my own templates using thin mdf and mounting a 1/2" bearing on my guide pin.

[Walter Plummer]

I have used small radius round over bits (1/16" - 1/8") to cut from one side then finished up with a flush trim bit from the other side. If you look at the RO bits they all have a straight section above the radius which is in effect a small diameter rabbet bit. You might have to lower the RO bit for a second pass to make sure you have a good surface for the bearing of the flush trim to ride on. http://www.woodcraft.com/PRODUCT/2001857/19371/WOODRIVER-301006-ROUND-OVER-ROUTER-BIT-14SH-116R.ASPX?refcode=10INGOPB&gclid=CPjOoO21-64CFUXc4AodZG23yg

[Larry Edgerton]

I have had to do that before, let me think a minute. Say I needed an 1/8" I used a rabbiting bit with a bearing that will allow an 1/8 cut, run around the pattern cutting half of the thickness. Flipped it and used a flush trim bit run in the rabbit I just made with the other router.

Unless I am not understanding what you need..........

Larry

[John Coloccia]

I have had to do that before, let me think a minute. Say I needed an 1/8" I used a rabbiting bit with a bearing that will allow an 1/8 cut, run around the pattern cutting half of the thickness. Flipped it and used a flush trim bit run in the rabbit I just made with the other router.

Unless I am not understanding what you need..........

Larry

That's exactly it, except all of the rabetting bits I see are larger radius, but I know I can easily get a 3/4" flush trim bit at my local Woodcraft, stick a 1/2" bearing on it, and I've made a rabbeting bit with a smaller radius :) The key was using a rabbeting bit to do it. That just didn't occur to me until someone mentioned.

I actually do have a rabetting bit that will work, but I reserve it for binding ledges and wouldn't dream of trashing it on plywood and MDF.

[Larry Edgerton]

There are times that you can use a bushing and a bit of the same or larger size by using a short bushing.

For example you need to use an existing inside pattern but want the hole to be 1/16" larger radius. You use a 1/2" OD bushing and a 5/8" straight bit dropped just below the pattern. You may have to shim pattern height to make it work but it is another option. Using a combination of different bits and different bushings you can enlarge by just about any dimension.

Do I have you confused yet? I confuse myself some times.....Larry

[Walter Plummer]

This should be small enough. http://www.amanatool.com/bits-fv/mr0100_mini_bearing_rabbet.html

[John Coloccia]

This should be small enough. http://www.amanatool.com/bits-fv/mr0100_mini_bearing_rabbet.html

You nailed it, Walter. My original idea with the 3/4" bit ended up being a bust. It would work in theory, but finding a bearing that is thick enough killed it when I actually tried it today. There are ways of making it work, but the Amana bit just works right off the shelf, and is even smaller, allowing me to capture finer details is necessary.

Jerrimy's idea would actual work just fine as well and is very simple to assemble from off the shelf Whiteside components (always my first choice for router bits). The only downside is having the router bit extended over the item I'm trying to route, and that is always my last choice for router table work. I know Whiteside will also make custom bits, and their turnaround and pricing is quite reasonable, actually. On the next iteration, when I start dulling the Amana bit, I will probably see if Whiteside can make me some and I'll buy a small batch that should last be a lifetime :)

Thanks again, everyone.

[Craig Behnke]

I second the Pin Router method. It can be used to make exact size copies from a template. Sets up quick on a router table and is simple to use. The pin router arm costs about 50-75 i think. Here's a link showing it pretty clearly:

http://www.youtube.com/watch?v=r9eNSFdq0qw