threadmilling 3/4 -10

[cuttergrinder]

How many passes and what feed and speed would you guys run on a 3/4-10 treadmill. I'm threading mild steel 1 7 /16 deep with a full length Allied treadmill. It is .495 dia. I've used it before but this time i got 1 hole and it broke. i was running 3087 rpm and 5" feed and taking 3 radial passes. The first at 65% the second at 30% and the third at 5%

 

[706jim]

One thing to consider is your 5ipm feed. If that is at the cutter centerline, its quite a bit more at the cutter OD. Try reducing that feed. I did thread milling in 3/4 mild steel. Single pass only but feed was a lot less than 5ipm.

 

[cuttergrinder]

ok thanks that is .001 per tooth. it's a 5 flute treadmill. I figured it would do it. I actually have ran that feed before when threading s7 but this mild steel didnt like it. Also I forgot to mention that I was climb cutting

 

[RCS Machine]

I found that Harvey Tool has a really good feed and speed calculation for threadmills. You calculate the difference between the major thread dia and the cutter dia and in the end you get the feed rate. For a 3/4-10 I run 3.7 IMP and 2122 RPM with 5 .010 passes and 1 finish pass. Thsi is with a multi form threadmill in in P20 and 4140PH. Been using their calculations for a long time now and haven't broken a cutter yet. Knock on wood now that I said that.

 

[MaxPrairie]

http://carmexusa.com/contentonly.aspx?file=pdf/151-164_Mill-Thread_Technical_Section.pdf

Carmex is who I typically use. The pdf attached has a lot of good info. For that big of thread, my first choice is an indexable. Seems like you would get quite a bit of deflection with that long and heavy of a cut.