Anyone know a trick for tightening both head bolts at once?

[RJSakowski]

You may be referring to my post a few weeks back: https://www.hobby-machinist.com/thr...ou-make-in-your-shop-today.67833/post-1079531 Note that this idea is a compilation of several others work. It’s still working great.

It doesn’t have the oomph for locking the head and column. This cam lock device looks promising. I wonder what the equivalent tightening torque is?

I was wondering that myself. What you really need to know is what is the tension on the bolt. On my RF30 clone, it takes about 1/4 turn to go from free to full lock and the thread pitch is .091". Since the poster is also turning about 1/4 turn, the slope of his cam must be similar. For the 50 lb-ft. of torque that I am using, the clamping load is about 4,500 lbs per fastener for a total of 13,500 lbs (per repairengineering.com). Given the short arm and that two bolts are being tensioned, I doubt that the poster is applying that much torque to each bolt.

 

[bulgie]

I was wondering that myself. What you really need to know is what is the tension on the bolt. On my RF30 clone, it takes about 1/4 turn to go from free to full lock and the thread pitch is .091". Since the poster is also turning about 1/4 turn, the slope of his cam must be similar. For the 50 lb-ft. of torque that I am using, the clamping load is about 4,500 lbs per fastener for a total of 13,500 lbs (per repairengineering.com). Given the short arm and that two bolts are being tensioned, I doubt that the poster is applying that much torque to each bolt.

I agree with your analysis but cams have one advantage, the leverage starts at a minimum — fast travel while the force is low (call that zero°) — then gradually (sinusoidally?) ramps up to a maximum, right when you've closed it all the way at 90°. Or you can use less eccentricity to where you need to use more than 90° of cam to get the travel you need, which gives more leverage.

Some cams (bicycle QRs for example) are designed to go a little over-center, for security against unlocking, but I'm pretty sure we have enough friction that it'll never unlock by itself from vibration. Going over-center "wastes" some of your leverage and slightly reduces the clamping force, so I will clock the cam to be right at maximum travel when the hand lever hits the head casting.