Help with quarter rib jig

there are three holes to allow for different distances from center. If you are making one for yourself and will always use the same setup one stylus holder hole should be plenty. 

So why would you want different distances from center? The distance from the center of rib to center of barrel is set in the jig.  Also why are the holes different sizes?

Need to get a 45 degree router bit but the jig is mostly done and the quill clamp is

Ray: 
This is just speculation from a hobbyist, but I think the stylist hole diameters are the same and that the dimensions called out (.500, .625, .700) may be for the rib stock material width. If you use one fixture for all three widths you would have to shim the .500 width out from static jaw .100 and the .625 width .0375 from the static jaw to be centered on the stock. The distance dimensions given (3.00, 3.062, 3.100) would give be the distance from the center of your endmill to the centerline of the stock. 

Good luck.

That makes perfect sense!  Thanks so much! 

As DSchrank said. The jaw of the fixture is static, so as the width of the rib gets wider, then your center line holes in the quill fixture must also lengthen to keep the cutter in the center of the wider rib material.

Most ribs, will only be .500 or .625 wide, since 1987 when I made this fixture up I think I have only made 3 ribs that were .700 wide. So If I had to do it over again I would only ream two holes in the quill fixture for the .500 and .625 width material.

Have lost track of how many .500 and .625, and even a couple of .562 wide ribs I have made using this fixture. Those you machine the rib as .625, and once mounted on the barrel, set your milling machine up and carefully remove a bit off each side on the upper sides. Then take the rib off and finish cutting the lower sides on along the very bottom contour. and now you have a .562 wide rib by using the .625 set up on this fixture

The holes in my quill fixture is .562", I had on hand some prehard 4140 in that diameter, but you could also make those holes .500 in diameter. Try to get the set screws on the center of the holes, and then you can mill a shallow flat on the stylus body to match up with the set screw

What rib material I use is 1" square 12L14 bar stock, why 1", well it leaves you enough vertical material to play with. Also I set it up and surface both sides down to the final width, this removes the cold drawn surface and removes a lot of side to side stress.

depending on what sizes of barrels you have you may wind up with two slightly different 45 degree router bits to cut the impression side. To wide of a flat nose and the small barrels will lay on the flat and not center well. Where a larger flat will reduce the amount of material needed to make the impression for the larger barrels

I have 2 ribs coming up to make in July, so if anyone who reads this wants to drop me a email with a subject of quarter rib. You can get my email address from the Guild directory. I plan on taking more pictures as those two upcoming ribs progress, and can send out pics and a short description of each step of making a rib

James Wisner

Thanks, I look forward to some pictures.  Why do you use 12L14?  I was thinking about using 4140 or plain old A36 hot rolled.