What am I doing wrong?

[matzo]

Is there some secret to getting clean cuts? My lathe recommends 125 RPM and lubricant. They turn out decent but require some clean up with a wire brush and file. I am not taking deep cuts.

Can you grind an accurate 60 degree HSS tool? If so, try a 15 degree relief angle on both sides and stone a 1/64" flat at the nose. Hone both sides and the top accurately. Use sulfur-bearing cutting oil (thread cutting oil from your local hardware store works) as a lube. Thread cutting is a high-pressure operation and sulfur-bearing oils work well for this. As Ted said, it is very difficult to beat the finish produced by a really sharp HSS tool, especially one that is ground with increased relief angles to reduce tangential cutting forces.

I ground a 1/2" HSS blank to your recommended specs and was totally blown away with the quality of the cut, no additional cleanup required with wire brush or file.
Thanks
Brian

 

[mikey]

... no additional cleanup required with wire brush or file.

Yeah, that's what I found, too. Much easier to hold tighter tolerances when the tool actually cuts what you dial in.

 

[Aqua-Andy]

Matzo, don't feel bad. I made this same mistake just a couple of weeks ago while trying to cut my first threads. The folks here got me sorted out and my threads look great now.

 

[jlsmithseven]

I don't know if anyone said this yet, but....are you threading this between centers or having that entire piece sticking out of the chuck jaws? It looks to me that it is bending as you're threading...you need to turn it between centers if this is happening because it looks like Aluminum and that bends pretty easily compared to Cold-rolled steel.

Also, which way are you threading from left > right or right > left. And which way is your chuck turning, towards or away from you?