Turning a shoulder on a SSTL 3/8 lead screw

[kjoiner]

Hello,

I hope this is the right forum.

I use a Ø3/8, 1/2" lead, 4 start screw made from 300 series stainless steel in a linear actuator. My local machinist is having trouble turning a shoulder on the screw. He tells me that the screw chews up carbide inserts and has recently switched to ceramic inserts ($9 each) and it wears them out as well. He must make roughing passes and then swtich the a new edge to make the finish pass. I recognize two problems with machining the screw:

1. The 4 leads create interrupted cuts that beat up the inserts

2. The threads on the screw are formed by rolling which creates a work hardened surface. The insert must cut against a work hardened surface all the way down to the roots of the threads.

I thought of some options:

1. Anneal the area to be machined - about 1.31" long

2. Grind the area down to the roots of the threads

Both of these options add processes and cost.

Does anyone have suggestions as to what types of inserts would be suitable for dealing with this situation? I've contacted the lead screw manufacturer - Roton - and they understood my situation but did not have any specific solutions.

Thanks,

Kyle

 

[saberblue]

Many of the 300 series SS work handen easily - so it may be a case of looking at the depth of cut so you are not continually cutting thru a work hardened surface. Some times MWF selection and application can reduce work hardening

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com

 

[unclesyd]

Do you have any High Speed Steel tool bits laying around?

If not I would contact someone like Crucible or a good mill supply house and discuss your machining problem. Sometimes HSS bits will outperform WC2 when there is an interrupted cut in SS. You might have to use a shape similar to a cut off bit due to size.

http://www.crucibleservice.com/index.cfm

http://www.metalartspress.com/PDFs/Sharpening_Steel_Lathe_Tools.pdf

We have good success on machining SS with this Tap Magic product as well as the foam.

http://www.tapmagic.com/TMthick.htm