Router w/ negative template

[Chip Buchholtz]

Hi,

Say I want to cut a hole in a table to fit an irregular but mostly cylindrical piece. The pattern (the cylinder) is a negative pattern; it's the shape of the material to be removed.

The only approach I can come up with is to fix some template material on top of the cylinder, and use a flush cut router bit with a bottom guide to cut a positive template the size of the cylinder plus the diameter of the bit.

Then, I use the positive template with a template following bushing to cut the hole in the table. The hole in the table will be smaller than the hole in the positive template by the bushing radius - the bit radius.

For example, if I'm using a 3/4" diameter bit (3/8" radius) and a 2 1/4" bushing, 2 1/4" = 9/4" diameter, 9/8" radius.

3/4" = 6/8" = 9/8" - 3/8" Is this the best way? Assume that the "cylinder" is not regular, so I want to trace it and not just measure the diameter and cut a circle of that size. And, tracing around the cylinder and then carefully cutting inside the line doesn't work because I'm clumsy and impatient.

I'm really looking for a general procedure for cutting an opening the same size and shape as an object, using a router. Seems like there should be a better way to do this, but I can't think of it.

Thanks,

--- Chip

[Morris Dovey]

| I'm really looking for a general procedure for cutting an opening | the same size and shape as an object, using a router. Seems like | there should be a better way to do this, but I can't think of it.

We had a thread on this not so long ago. Try the link in my sig.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Chip Buchholtz]

: | I'm really looking for a general procedure for cutting an opening : | the same size and shape as an object, using a router. Seems like : | there should be a better way to do this, but I can't think of it.

: We had a thread on this not so long ago. Try the link in my sig.

Thanks - I knew that that was >one< way of doing it, I just couldn't get myself to believe that there wasn't an easier way. I guess you are saying that using an intermediate template and different size bushings is the only way to go.

Thanks,

--- Chip

[Morris Dovey]

Chip Buchholtz wrote: | Morris Dovey wrote: || Chip Buchholtz wrote: | ||| I'm really looking for a general procedure for cutting an opening ||| the same size and shape as an object, using a router. Seems like ||| there should be a better way to do this, but I can't think of it. | || We had a thread on this not so long ago. Try the link in my sig. | | Thanks - I knew that that was >one< way of doing it, I just couldn't | get myself to believe that there wasn't an easier way. I guess you | are saying that using an intermediate template and different size | bushings is the only way to go.

Not at all - but you /did/ ask for a general procedure.

If I were doing this, I'd take a photo of the object, import the image into my CAD package, trace the shape I wanted, export the tracing as a DXF, and pass the DXF to my CNC router control program for cutting.

There's /always/ more than one way to skin a cat...

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Lowell Holmes]

snip

solid brass router inlay kit works really good for me. Norm used it on his show one time. I think I may have to make some butterflies to join a table top like Nakashima featured on his work. If I do, I will certainly use the inlay kit.

[Chip Buchholtz]

: If I were doing this, I'd take a photo of the object, import the image : into my CAD package, trace the shape I wanted, export the tracing as a : DXF, and pass the DXF to my CNC router control program for cutting.

Good point - actually, a very useful suggestion.

Where I work they have a CNC laser um, "milling machine" is the best description I can come up with. It's in a different department, but I'm told that they don't mind doing little projects for people.

If I go that route, I'll have to decide whether I just want to use CNC to make the template, or have the CNC machine make the final cut.

Thanks!

--- Chip

[Morris Dovey]

| Smarty pants :)

Not intentionally - I've just given up on trying to hide how lazy I really am. :-D

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[dadiOH]

Smarty pants :)

[Tom Veatch]

Well, it's one alternative, but for those of us who neither have nor have access to numerically controlled tools in our basement/garage/etc. workshops, I'm not too sure just how useful the suggestion is.

Tom Veatch Wichita, KS USA

[Morris Dovey]

| Well, it's one alternative, but for those of us who neither have nor | have access to numerically controlled tools in our | basement/garage/etc. workshops, I'm not too sure just how useful the | suggestion is.

It wasn't actually a suggestion. My intended contribution was in the form of a link to a web page with some very simple geometry/algebra shwing how to select guide bushing/router bit sizes so the job can be done by anyone with a hand-held router with a base plate that allows using bushings.

In case you missed it, I've repeated it below. If it seems not useful, there's an e-mail link at the bottom of the page for improvement suggestions.

I only mentioned the CNC approach when asked if the guide bushing/template method was the only way the job could be done and if there wasn't an easier way. It was not intended to cause rancor - only to illustrate that other (and easier) methods existed. That Chip has access to CNC tooling at work is a happy coincidence.

Sorry if I rubbed your fur the wrong way.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Lowell Holmes]

really nice work. If I had a reason for a CNC set up I would do it in a heart beat.

If the op will look at the router inlay kit and determine how it works; with a set of guides (Delta) and different diameter straight router bits, he can come up with what he's looking for. I can visualize making a bushing that will do exactly what the kit does.

I bought the kit when I was building a bed for my daughter and I had ruined a piece of wood that cost more than the kit did and I had several hours in the piece. I was able to make a dutchman with the inlay kit and the repair is barely visible. I put it on the back side of the bed and saved myself money, time and I have a new tool in my collection. :-)

>

[Tom Veatch]

Oh, no, no! You didn't "rub my fur the wrong way" at all. No offence was taken or intended. My reply was to the "good suggestion" comment and was simply questioning the value as a "suggestion" for those of us who are CNC challenged. I'd be tickled pink to have a CNC presence in my shop and am eat up with envy for those who do.

Tom Veatch Wichita, KS USA

[Morris Dovey]

| I'd be tickled pink to have a CNC | presence in my shop and am eat up with envy for those who do.

No reason you can't have one in your shop - there are plans and parts available on the web so you can build/assemble your own. They aren't particularly cheap, but you can buy a controller kit and steppers for less than the price of a Festool Domino - and control software can be downloaded for free. You already have the computer.

As with any new tool, it takes a while to learn to use it well - and if you'd like a coach, you have a volunteer.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Tom Veatch]

On Sun, 19 Aug 2007 03:19:00 -0500, "Morris Dovey" wrote: ...

Thanks, Morris. I appreciate the offer and if I ever get some of the higher priority roundtoits and honeydos worked off I may well take you up on it.

I was following the building of a CNC router by the author of the DVD magazine "Woodworking at Home", but either don't have all the episodes or he didn't finish before I let my subscription expire. It's something I want to do, but higher priority tasks are interfering.

Tom Veatch Wichita, KS USA