Tr8-2 double start tap

[Grant Gunderson]

Trying to find a Tr8-2 double start tap for a bearing press project I’m workin on. I was able to find a single start tap in that trapezoid thread but no double start. Otherwise anyone have a good source for single start TR8-2 trapezoid threaded rod?

I’m stuck with having to use an 8mm screw diameter for this project.

Thanks.

 

[Steve_P]

Have you checked McMaster and MSC?

 

[Grant Gunderson]

Have you checked McMaster and MSC?

Yes. No luck with either.

 

[Steve_P]

I've never seen anything but a single start thread on a puller or press. Why are you wanting to use a multiple start thread? I have seen them on linear motion screws, ball screws and IIRC Acme threads. Nook Industries makes a lot of automation products, but you should also be able to find them on McMaster if you look under ball and acme screws. My advice would be to go with something that's readily commercially available.

 

[Grant Gunderson]

So the issue is 8mm seems to be a very odd size. Lots of double start threaded rods available in that size, (apparently it’s common for 3d printers) but not double start taps. Single start taps in that size are common, but the threaded rod isnt.

I did find some on Amazon, but my experience with the Chinese makers is it’s often miss labeled and both times I’ve ordered single start thread I’ve received double start.

I’m trying to avoid going to a larger diameter as I have something like 100 drifts tgat would all have to get re-drilled.

 

[larry_g]

Trapezoidal Lead Screw Nut TAP Tr8x2 Tr8x4 Tr8x8 – Makers Hut

makers-hut.com

Found the above and found some other references to a tr8-4 thread. Should you be searching for a -4 in your description?

lg
no neat sig line

 

[Steve_P]

Multi-start isn’t an option once you choose the pitch, its defined. This means a steep angle thread, a very coarse pitch. This means it immediately backdrives once force is released- and is not suitable for a puller. So again, I don't see what you're doing here.. look up efficiency and backdriving

 

[CallumRD1]

I'm also confused as to how you'd want to implement a multi-start thread in a bearing press/puller. I made mine with normal M8 threads because for any kind of moderate use, it's not going to wear out and if it does, I just replace the tapped part of my handles or the rod itself, either being a nominal cost from the perspective of how much I have into the press/puller parts.

A double start nut would have a lot of trouble not backing off under any kind of load. Those kind of threads are commonly used on CNC mills where a servo is holding the screw still under loads rather than relying on inertia and friction alone.