Cast iron milling problem

[kdoney]

I am using a mini mill to mill the lead screw mount bracket for a mini
lathe. The bracket appears to be cast iron, although I have no way of
finding out what type. The program tries to mill conventionally and climbing. I have tried 2 straight center cutting flutes, 4 straight, slow and high spiral center cutting flutes. I have tried them at slow speed and slow feeds, slow speed and high feed and fast speed at high feed. Duh, it still always tries to gouge into the work either at the start or end of the cut. Slow speed means about 400 rpm and fast is about 1700. Feeds where either 5 or 10 IPM. The cutters are all 3/8" shank and cutting diameter. Some are HSS some are carbide coated and non coated.

[HuFlungDung]

I suspect your machine is just too mini for the job. But, try slow spindle speed, and shallow depth of cut, and relatively steady but coarse feedrate. You didn't describe your cutter diameter, or the depth of cut and width of cutter engagement. Generally on machines without ballscrews, conventional milling is safest. This method prevents the cutter from "hogging in" by the backlash amount, which it will certainly do if it is climbing. Once it takes that initial monster chip, everything goes to hell real quick and its hard to tell after that what went wrong

[RotarySMP]

How are you holding your end mills? Most minimills have a morse taper spindle, and you have to crank morse taper collets in pretty tight with the draw bar to stop a mill digging in.

Please don't tell us you have chucked the end mill in the jacobs chuck which is supplied with the mini-mill. If you did, then that is your problem right there. Chucks are for twist drills drilling straight in and out. For milling you must use collets or mill holders.