Gear racks question

Quick-adjusting nuts are simple to make. The body is a short cylinder with a blind hole for the plunger. Cross-drill and tap the plunger, then mill out the threads on the side that protrudes. Drop a compression spring into the hole, install and press the plunger and and slide it onto the threaded rod.

Timing belt pitch is based on the linear spacing of the teeth on the belt, unlike spur gears, which are designed around even numbers of teeth on rationally dimensioned diameters. Though it won't be quite as stiff and accurate as a gear rack, you can use a stretched timing belt as a rack. English pitches are .200, .375, .500, etc. There are also metric timing belts, as well as alternative tooth designs that are stronger than the traditional trapezoidal teeth. If you consider this alternative, I'd recommend using a steel corded urethane belt.

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-- Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).

Add an overdrive to the adjustment crank or use a power adjustment and the easier and less expensive screw drive. Heck even a direct crank wheel with a 1/4" hex extension in the middle so you can coarse adjust with a cordless drill/driver and then finish by hand.

Yeah, familiar with those. I didn't go into enough detail. I want to use the rack for positive quick adjustment, but be able to make fine adjustments, with a dial indicator to arrive at final dimension. Idea is to be able to calibrate back gauge, then be able to quickly shear or bend to size. Well, on the finger brake it's not so cut and dried, but you get the picture.

I believe DiAcro uses the quick adjusting nuts stock, but I didn't get back gauges with either unit.

Jon

Appreciate the suggestion! But timing belts don't lock tooth to tooth like a cut rack will. I'm looking for some real precision and repeatability. I see multiple applications for the idea, if I can find rack with an appropriate pitch. Of course, if I had time, I could make my own racks, but that sort of free time is a long way off... :(

Jon

Sigh, looks like I'm out of luck. Well, maybe tonight I'll Google linear Hirth coupling and see if I can find anything. Don't need that level of precision, but that's essentially what I want.

Or, back to the drawing board...

Jon

Jon: use any dimension rack and buy a calculator? $10 bucks for a fancy one.

Hul

J> > see

The quick nuts adjust like regular ones. You could make your own back gauge from 1/2-20 threaded rod and Bridgeport nuts.

jsw

I recently got an old Unisaw table saw that uses a rack and pinion system for adjusting the fence. I think that Craftsman used the same system on some of their old table saws too. Maybe if you find an old Craftsman table saw that has one of those, you can adapt it to use as a stop for your shear.

Wasn't looking to use a rack and pinion for adjustment, rather using a long section of rack and an opposed section in a clamp setup for rapid adjustment to known locations in some even increment. But dual racks with pinions, and a digital caliper would make for rapid adjustment and precision.

It's just that the rack seemed like a neat idea.... I should post a picture of the stop I made for the Roll-In saw. Probably will after I finish a related accessory that will also use the rack.

Jon

Yes, I'd like to see it when you get the chance.

I saw something like that at a woodworking show one time, was a whole system, used plastic racks for positioning workpieces on saws, router tables and drill presses. Incra-jig or something like that.

Stan

I see now from one of your later posts what you're trying to do. Trapezoidal or AT tooth belts won't lock together in that fashion, but at least some of the other tooth forms will. I have a 3mm pitch HTD belt here that meshes face to face with no play.