Sunday, February 06, 2005


Making Radiused Dishes

I don't think "radiused" is a word, but I use it anyhow. In my last post I showed a pictured of the rails I made for the router to ride on to make spherical and cylindrical sanding boards out of mdf.

Here's a pic of one dish that is almost finished. Those are two 24" diameter, 3/4" thick pieces of mdf glued together. I did this to add stiffness and prevent warpage, otherwise it gets pretty thin towards the center with the 15' radius. I still had a couple inches to go on this one.

I'll explain the Captain Safety getup in a little bit.

I started at the outer edge, and worked my my way towards the center in kind of a spiral pattern as I spun the dish. Often the bit would take hold and would actually start spinning the disc for me, though it quickly would get too fast to where I didn't feel like I was in control. Anytime you're handling a 1/2" wide 2" long bit with a supersharp edge spinning at 21,000 RPM's, it's a good idea if you feel in control the whole time.

Here's a finished dish. I decided to make two of them since I had gone through the trouble of setting this all up.

The next one is cylindrical instead of a spherical dish, so it uses rectangular pieces of mdf. I added the second set of rails to the base, and clamped on straight pieces on each side to guide it under the router rails. Then I would move the router back and forth along the rails, taking about a 1/4" wide swipe at the board each time. The boards are 24" long, so that's 96 times of pushing the router along the rails per board. I made two of them and I was a little worn out.

I had read warnings about how much dust will be generated making these things, but I didn't quite wrap my brain around the concept till yesterday. I really wish I would have made a vacuum attachment for my router jig so a vacuum would be running the whole time. The first two pictures were taken after I had vacuumed away piles of dust. The third picture illustrates that a little better, though keep in mind that amount of dust pictured was generated only buy routing out a couple inches of the 24" length of the sanding board. There was dust everywhere.

Here are some tips for those considering making these yourself:
1.) If you don't need a cylindrical one, and most people don't, you can buy these dishes on eBay for about $40 or so each. Do that.
2.) Get a good respirator. There were times when the wind would shift a bit and I'd have dust blowing up into my face. Those cheap little dust masks don't really do it.
3.) Use goggles. Every once in a while, I'd feel some little chip of something graze my forehead, and I know there were things hitting my goggles that would have not felt comfortable in my eye.
4.) Use ear protection. That router is loud and you'll be running it for long periods of time with your head close to it. I'm sure my neighbors were just loving me yesterday.
5.) Move anything within a ten foot radius of your set up, as it will be covered with dust. I had a bunch of tools on a nearby ledge, and had to clean everything up before I brought it back in. That mdf dust is nasty and sticks to everything.
6.) For real, if you don't need a cylindrical one, and most people don't, you can buy these dishes on eBay for about $40 or so each. Do that.

You still might be confused about why I'm making these things. You'll find out what the deal is later on when I start using them.

Dear Ken Doll,
Let me explain something. I love music. I love guitars. But I don't understand a ding dong thing you're saying. You may recall that I only have a GED and I was kicked out of Geometry at Burke, so all of your mfd 1/2" dust radius router talk is making me want to take a stiff drink (I already have, in fact). But just because I don't know what in the heck you're talking about stop you from making this fine instrument. I am hanging in there with you to the bitter end. I'm yours.

The Cardigan Cowboy.

p.s. I weld stuff.
It'll make sense eventually and you'll think I'm some sort of genius. Next time you're holding an acoustic guitar, look closely across the top and back and you'll notice that they're not actually flat but slightly arched. It has to do with that. They're just giant sanding blocks.

I think you need to start a blog for the metalworking stuff.

Not too long ago I had to toss out my first boombox I ever had, which I bought from you at Richman Gordman's when I was in the sixth grade. 'Twas a sad day. If RG still existed, I would have tried to return it just for fun.
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