# making a router template/ sanding concave curves



## music321 (May 29, 2012)

I'm trying to make a router jig. I actually have a piece made out of plastic which is the same size and shape as the shape I want to route. The problem comes in making a template. I can trace the piece of plastic, and get an outline of it. I can't use this to make a template though because the template must be slightly bigger than the shape. This is because of the template guide on the router. It is of a greater diameter than the width of the bit. 

any ideas?

The second problem is in actually making the template guides. I can very easily make straight lines and convex curves with a saw (to get close) and then with a sander (to finalize the work). I simply feed the piece into the stationary belt sander very slowly and carefully, and then get to within a hair's width of where I need to be. I can't do this with concave curves, though. The problem is that I can't use the belt sander (or a stationary disc sander, for that matter) to work the inside of a curve. The face of the sander is flat, essentially. So, when coming at a surface that curves away from the sanding face, it's pretty easy. When coming at a surface that curves toward the sanding face, the face is too thick. does anyone have any solutions to this?

thanks.


----------



## jschaben (Apr 1, 2010)

music321 said:


> I'm trying to make a router jig. I actually have a piece made out of plastic which is the same size and shape as the shape I want to route. The problem comes in making a template. I can trace the piece of plastic, and get an outline of it. I can't use this to make a template though because the template must be slightly bigger than the shape. This is because of the template guide on the router. It is of a greater diameter than the width of the bit.
> 
> any ideas?
> 
> ...


 
If you have the right size part, you could just use a flush trim bit to make the pattern. Just switch the guide bearing around to make the pattern larger or smaller as required. ie, use a 1/2" bit with a 5/8 or 3/4 bearing to make the pattern larger and a 3/4" bit with a 1/2 or 5/8 bearing to make the pattern smaller. If making smaller, just tape some 1" square pieces of 1/4" MDF between the blank pattern and the part to keep from damaging the part. :smile:


----------



## johnnie52 (Feb 16, 2009)

Sounds like you're using the wrong bit and bushing. What you need is a pattern bit. That is basically a flush trim bit with the bearing near the router as opposed to being at the far end of the bit. With a proper flush trim or pattern bit you do not need a bushing on the router and it produces exact copies of whatever you use as a guide.

As for your second question. I suggest a Google search on making chair seats. I remember seeing several of them that used a router and a guide to produce the "cupped" surface. Then either hand sanded of sanded using a finishing sander like a B&D Mouse.


----------



## Diyguy41 (Nov 28, 2012)

Pattern bit for sure

I had had good luck sanding concave curves using a "ghetto spindle sander" which is basically a drum sanding spindle chucked into my drill press. Works really well actually. For the really tight sanding I bought some very thin sand paper strips. Wrap around your finger on opposite hands and go to town 

One can not over emphasize the need for plenty of clamps and double sided tape when using a template to router hard woods 

Good luck and have fun!


----------



## GROOVY (Apr 27, 2008)

I have used a cotter pin and split pins just insert a strip of sanpaper in split. stick it in drill press ....


----------



## music321 (May 29, 2012)

thanks


----------



## Pirate (Jul 23, 2009)

For sanding a template that has concave curves, a spindle sander (oscillating is much better) works great.
For a home shop like mine, the Rigid oss/belt sander is a much used tool.
Numerous times, when designing a convex curve into a project, I use a sanding sleeve to mark the curve. That way, the sanding sleeve, fits the curve and sanding takes seconds.
I'm into old arn machines, and the oss/belt sander is the only machine I bought new for the shop. And with the lifetime guaranty, might be my last!


----------



## Jory (Feb 19, 2012)

*Concave curves for a router template*

All the other suggestions will work but there is also a simple hand method. a very thin piece of wood, plastic or metal can be bent and sticky back sandpaper attached. For large diameter curves I have used flexible metal rulers. For very tight curves the heavy plastic packaging material that makes new purchases such a pain to open can work. 
Also on the question about the size of the templete. The other comments are right you do not want to have a guide mounted on the router base. You want a flush trim bit. these are available with a bearing at the top or the bottom of the bit. A spiral router bit will give you a much better surface than a straight cutting one.


----------

