CNC LATHE THREAD (SCREW CUTTING)

[moonman5]

Hi All,

Can anyone help?
I am trying to create a 20mm x 2mm pitch thread on low carbon (free cutting) Mild Steel, I am getting a poor finish? under a magnifying glass the surface looks "torn"

I have tried several small cuts (0.10mm) different spindle speeds (up to 400 Rpm, obviously I have no control over the feed as the acceleration rate is controlled by the spindle speed,

I have tried leaving just 0.05 to 0.075mm for a final finish cut using a different offset in the tool list,

I am using a coated ER-AG60 Insert flooded with coolant, strangely HSS worked better but the tool life deteriated quickly and I have quite a few to do,

Can anyone give me any hints on spindle speed, insert (Tip) type?

At the moment I am having to leave them plus on dia and then run a die down them and my arms are starting to hurt!

Thanks for any advice,

Allen.

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[djr76]

you have the right shim? I would try going faster rpm like 1500-2000

[moonman5]

Hi djr76,

Thanks for you help, the right "shim"? by this do you mean the cutting insert?, and 1500 Rpm, that will be pretty scary watching the z axis move at a 2mm pitch rate, that sounds fast!
I have got up to 500 rpm and then lost my bottle because the federate looks bloody quick!

Thanks again for your help,

Allen