How terrible is a36 mild steel to machine on a Tormach 1100?
I just got my machine setup a few weeks ago, I've made a few cool things out of wood and now I'm taking several practice cuts in 3/4x3x3 a36 mild plate before I cut my first real part out of 4140.
I'm running one of these fine YG X-power 1/2" TiAlN corncob roughers and it works great at 0.2doc 0.15woc 25ipm at 3240 rpm OR 0.5doc 0.05woc 24ipm at 3240. Trying to keep around 0.001-0.002ipt.
Are those numbers good for a36??
I was hoping for something like 0.5doc .15woc at 20-25ipm but pushing further down (like 0.25doc!) or wider by a couple thou makes the machine sounds more like a table saw cutting really hard wood! Almost screaming, ear pro mandatory.
Other notes:
- Fogbuster and Tormach Dynacool coolant.
- Stickout 0.83in in a setscrew TTS holder, I cannot move it in more because the flat on the bit, but I could go to a collet. Drawbar cranked down but not with a torque wrench.
- Climb milling.
- I had some luck at 3470rpm and 25 ipm and 0.25 doc 0.15woc, but it was not what I'd call cutting butter, you wouldn't want to be without hearing protection!
- I've tried rpm's around 2k at 10ipm 0.001ipt 0.25doc 0.15woc and a several recipes in the 3ks - it just hates any deeper than 0.2!
- I tried out a Niagra 1/4" TiAlN 4F rougher. That will do 0.2doc .075woc 3500rpm at 16ipm. Same problem with that bit if I go deeper or faster! I choked this one up onto the pocket just before the cutter starts and it helped me push it, hopefully that won't make it break easier.
- This issue with and without scale on the metal.
- It's pretty smokey at 3470, the chips are not bluing but they're hot enough to melt plastic, and the bit and material are cool afterwards.
Ive been cutting 416 and 17-4 heat treated on my 440. Pay attention to sfm and chipload. I do a lot of high speed toolpaths. A good starting point is 250 sfm and .001-.002 chipload and 15% radial cut and 1x diameter for depth. With a 1/4 em 5flt, .3125 depth of cut i can get 25 ipm. Stickout is .500.
I tried out Nutzilla's recommendation, and things improved slightly by watching the SFM at lower revs, but even dropping to 200sfm @ 0.001ipt was squeaking some... This should not happen, so I suspected the setup!
3" x 3" x 0.68" (faced 0.75") boiler plate on edge, on 0.5" parallels, in the vise - what's the worst that could happen?!!! I guess 1.5" stickout is a lot when it comes to climb milling mild steel that thick. Should have thought about that!
I flipped the part horizontal in the vise with 0.5" hangover on one end, and started making 0.5" doc x 0.15" woc passes. ZERO chatter / squeaking / squealing like a stuck pig!
I quit at 380 sfm, 30ipm - 0.0026ipt. The machine cut it like butter!
Thanks for the help in troubleshooting, I will be much more careful with setup in the future!!
Last edited by GearsNBeers; 06-22-2017 at 01:43 AM.