Tool arm length

[dbrunson]

New to knife making and building a GIB grinder. I have the grinder assemblied and wheels on order from Beaumont. Need to order square tubing for the arms. What length do I need for flat platen, tool rest,small wheel attachment? Are they the same length?
Also, is it better to use cold roll steel or aluminum?

Thanks

[Ed Caffrey]

I would encourage you to use SOLID stock (A36) hot or cold rolled for tooling arms. Tubing just doesn't provide enough mass. With tubing you'll get a lot of noise and vibration that will not happen with solid stock. I also do not like aluminum for tooling arms.....for a lot of the same reasons, plus the aluminum will quickly get "chewed up" from tightening down the "hold down" bolt/handle.

Length is going to depend on the attachment.... obviously, running a small wheel will require a longer tooling arm than running a platen. 24 inches should give you enough to run most attachments.

I'm hoping that you did not built the grinder itself with tubing.....I've seen a number of folks try this, and almost without exception they were disappointed with the results. A grinder is one of those tools that you want to be "heavy" and "solid". Using tubing for just about any portion will cause excessive vibration and noise compared to building it from solid stock.

[dbrunson]

Ed,
I built the grinder from Polarbear Forge kit and welded the base. Was thinking about doing the compress spring that I seen you posted about instead of the rear door spring. What size compression spring did you use? The reason for the length ,I was going to have the Steel vendor cut the CR square bar to length for me. I only have a hack saw.