ACME 1/2 10 tpi help

[THend]

Well, many years ago I bought Alloy, class 2C, 1/2 10 tpi acme rod from McMaster Carr. It had in basic terms, a wobble in it.. might be called runout?

I dealt with it by making the coupling nut float, and I lived with the backlash for many years.

I recently bought some anti-backlash nuts, and now the runout is causing the steppers to miss due to not enough torque to overcome the wobble in the rod.

So, I could get more torque by going to xylotex bidirectional drives $$

I could go back to the sloppy setup ... NO!

Or, I could buy the carbon steel Acme rod from McMaster Carr and hope it is straight... Well I did this and it also has runout/wobble as in it is not straight.

So, I still believe that a straight acme rod would solve the issue.

Where can I get straight acme rod?

Or, how do I straighten out what I got?

Help!

[trubleshtr]

Is the acme rod "fixed" at both ends... if so undoe one end and let it float. You should be ok Providing you have precision alignment on your "rails" and between your 2 rails.
You might want to look at your whole set-up for parallel otherwise. Quick/dirty cheat way is to loosen off one rail slightly and let the "machine" put it where it wants to go if parallel is your issue.

[THend]

Thanks, I did do that and it does help some, but the 36 inch length challenges it. I may have to make something to aid in holding it up. Currently it is in a bearing block on both ends.

The rod is not straight, if it was I'd be fine. I think I'll make something for checking parallel, but only one linear rail is fixed the other side floats.

TH

[stoneyreef]

Send it back, McMaster is great with returns and tell them you want a straight one!

[THend]

Send it back, McMaster is great with returns and tell them you want a straight one!

I'm gonna do that right now. I'm frustrated because I am off all week and I am losing precious time now!

I see that Nook Ind. has some VERY nice acme rod, but it is not cheap.

Thanks!

[jsheerin]

Are you buying the precision acme screws? Such as part number 99030A005? I'm not sure if it makes a difference in whether they're straight or not, but my 4 screws I bought from McMaster a few months ago all look pretty straight.

[THend]

Yup, exact same part number. They are sending new ones as I speak, and I talked to the Rep and they are aware of the "straightness" issue. The ones I received have at least 1/8 inch runout in the center.

The Nook Rep stated that unless you ask for a machined end, they won't straighted out the rod as well.

How would one go about straightening out an acme rod?

I'd just do that if it knew how.