I've been tinkering with different ways to profile boards for about a year now. Planar cribs and router bridges have both frustrated me. Sniping from the planar was bad enough to make me throw that idea out right away. I also had problems with the router bridge designs out there because they didn't seem accurate or repeatable enough for me. I'm sure they're fine for a lot of people but I just couldn't get them to feel right and ended up ruining any test pieces I ran through.
The pictures here are of a prototype to test my design and I think it'll work well. The 1/4-20 bolt is recessed to allow smooth motion over it.
A collar with a washer allows me to adjust the rail up or down with .05" accuracy per quarter turn. The operation is smooth and just requires an allen wrench. If I loose my place I can just crank it down to zero and start over.
The brass insert is threaded to screw into the base of the bridge and holds very well. Plus I like brass and think it looks cool.
The last picture shows the final product somewhat. I only bought enough parts for 3 adjustment screws to basically test the design and this mockup is made from scraps I had laying around. The final product should be basically done some time this weekend, at which point, I'll be excited to test it.
I'm building router bridge too. My rail made from 1 1/4"x 1/4" steel and have some flex imo it have to be at least 3/8 thick or supported every 6 to 8 inches.
collar with allen wrench interesting idea but I think locking screw will ruin thread on the bolt. My thoughts were to use shims and torque wrench this method can be very accurate. Only I'm not sure how to correctly get intermediate measurements of thickness at points of support
The set screw will absolutely wreck the threads. But that bolts only purpose in life is to sit there with a collar on it, so I'm ok with that. 6" spacing seems to work on mine too. Waiting on collars from McMaster to finish it up.
First time I've ordered from McMaster and, I must say, they don't screw around with shipping. You want it you got it.
Either way, I think it'll work. The base will need some kind of secure fastening otherwise it gets pulled up by the rail. I'm thinking the same kind of insert built into the work bench will do nicely. Adjustments are easy and relatively quick. The ash rail is about as solid as anything else I can think of and doesn't sag at all between the bolts.
at first, couple months ago, I planned to go same way as you do. Currently decided to go little different direction. don't have final results because it's not complete yet.
He's in my idea: each rail built from three components
1 plates on the bottom which bolted to the table
2 template of the shape you want to make
3 top rail which breach ride on.
template doesn't have to be perfect because rail will smooth them out. As longer templates identical this set up should be accurate
