Hello,

I purchased a set of the standard bits that Taig sells with their mills. I am using them to cut parts out of 1/4" ABS. I have noticed that after cutting about 4 3"x5" peices that the bits become dull. I assume they are dull because when new I could see very small chips and now the plastic loads up and begins to melt resulting in a very bad cut. When new the cuts are perfect.

My question is, is this wear normal for ABS cutting? I am using the 3/16" endmill that has 2 ends. I also assume that these bits are high speed steel and this is the cause of my wear. Can anyone recommend a bit that will last?

I would be amazed if the cutters were actually dulling from cutting ABS. They will load up if you cut too fast. With plastics, you have to either cut slowly, so the cutter doesn't heat up, or use coolant (air will generally do). You have to keep the RPMs down, as that's what causes heat buildup, which is what causes the cutter to clog. Also, you should be using 2-flute cutters, to reduce clogging.

Regards,
Ray L.

I've got the pulleys on the mill set to the slowest speed possible. I do have the feed rate up fast so Ill try and slow it down. Yes, the bits are 2 flute.

You are talking about High Speed Steel (HSS) tooling. Many plastics are surprisingly abrasive to HSS, particularly black plastics. We machine black Delrin and ABS and have found HSS tools give a very short life. Try using carbide.

Yes, this is what I was thinking, its just hard to believe that plastic dulls the bit so quickly. The ABS I am cutting is black.

The "black" in plastics is usually carbon black.
These are (at the microscopic level) rough 'rocks' of carbon that are quite abrasive on HSS cutters.

I.E. use carbide. If you want the cutter to last very long.

hth, Pres

Thanks everyone! I guess I will have to get some carbide bits.