Seat back "notch"
 

Drawing 30 shows that a recess in the lower end of the F-637B seat back braces, .040" deep and 9/16" long, should be cut so that the bottom hinge surface will be flush with the rest of the forward surface of the F637B. Just curious how others have done this, other than taking it to a machine shop or having your own milling machine. I'm thinking about simply using a belt sander with frequent checking to get it right, since whenever I have tried to use a grinding wheel on aluminum, it just clogs up the surface of the wheel.

Anybody found a better way?

Used a flat top woodworking router bit in a homemade router table. It came in a door hinge mortise kit I think I got at Home Depot. It looks like this one. If you want just the bit, look for a mortising bit. Also used a roundover bit for rounding F-637C so it would nest in the back of the seat skin. A little noisy but cut fine.

Careful!
 

I've heard that grind aluminum on a bench grinder (stone) can be extremely dangerous. The wheel can load up the voids with aluminum, the aluminum can expand and the grinding wheel can explode. Could kill you. :eek: This is likely mentioned in the owners manual if still available.

I used a file to create the notch.

Notch
 

I have a lathe and mill in my basement. It took more time to set up than it took to do the work. I have found both tools to come in handy on my 7A project. I will be using the lathe to cut down the roll bar support to the proper length this weekend.

In the words of "Bones" McCoy:

"My God man! Use a file!! :)

I've exploded two bits, it actually fell apart rather than exploded. Then again it was only turning 1900 rpm.

I just spent time with the belt sander. Took a while, but worked great.

Used a table saw
 

I just used my table saw. Set the blade to remove the correct amount of material. Run across blade, slide over a blade width and do it again, repeat till wide enough.

don't complicate it
 

Belt sander and/or file...quick and easy.

A file worked great for me