pic: 2169 'not so summer' off-season project teaser

[Arpan]

Originally Posted by llamadon

Thanks!
3. It is a tapped hole for 1/4 #20 thread. This coupled with the bolt and bolt holder create linear motion with the bearing blocks, allowing for tensioning.

Semantics, I know, but the notation is 1/4-20

Also, one thing that I might worry about here is galling on the aluminum threads in the blocks. It's rare with aluminum, but it sucks to say the least.

Galling is cold-welding between your screw and your nut material (in this case the aluminum) because the oxide layer of the aluminum wears away (this is why stainless steel fasteners can be a bad idea, the oxide layer wears away and they gall even worse than aluminum) .

I've only had it happen to me once before, but it makes the screw pretty much impossible to remove save with a drill.

Some ways that you can prevent this:


1. drill and tap your hole for a larger size and use key-locking inserts to put in a nice steel thread. This solves all problems and is my preferred solution.

2. Apply a PFTE-based compound onto the threads (or powdercoat / alodize/ anodize the material). Also solves most of your problems

3. use coarse threads with a loose fit (not really practical here)

Failing making any changes to the part:

4. Don't over tighten! Use a torquewrench and tighten to a low torque.

5. Tighten the bolt really really slowly. This keeps heat from building up too much.