ACME Threading

[JssParticipant @jss]

Am I doing something wrong here?

I’m in the process of cutting a 10tpi ACME thread for a Potts column type milling spindle. As the work is long and relatively slender I’m using a travelling steady bolted to the top of the cross slide. This should be more rigid than the original Drummond design of steady. The downside is that the fingers have to be withdrawn at the end of each cut and pushed back in contact with the work before the start of the next cut.

The problem that I have is that the process of cutting the thread throws up a significant burr which I’m having to remove with a file every couple of cuts and is spoiling the look of the thread and is time consuming. The fingers of the steady have been fitted with hardened steel tips so, hopefully shouldn’t be suffering too much.

Is there any way I can stop the burr forming?

[JasonBModerator @jasonb]

A traveling steady usually fixes to the saddle and therefore does not need adjusting every time you feed in the tool. If your topslide can rotate to 90deg then you could set it so it is at right angled to the lathe axis and use the topslide screw to put on the cut which won’t alter the position of your cross slide mounted steady.

Looks like you are cutting dry, a good application of cutting fluid such as CT90 or Rocol RTD would also help

[bernard towersParticipant @bernardtowers37738]

Can you not set your compound to 1/2 the angle, you shouldnt get a burr with that method.

[JssParticipant @jss]

Jason, thanks for the reply. The original Drummond design of travelling steady was designed to be bolted to the back of the saddle and had a large slot to allow the cross slide to pass through it, as you may know. I hadn’t thought about turning the top slide through 90 degrees though, I might try that.

The picture was posed, I have been using plenty of cutting fluid.

Hi Bernard, I have done that when cutting standard threads but not sure about ACME threads. Might try that if all else fails.

Thanks, John.

[David George 1Participant @davidgeorge1]

I have just been cutting a new thread for a M Type cross slide and have used the traveling steady as standard for the first time. The thread was extra long and worked well with the traveling steady .

David

 

 

[SillyOldDufferModerator @sillyoldduffer]

What is sort of steel is it?  Burring might indicate an unlucky choice – a steel that doesn’t machine well.

Dave

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