Milling Question First Timer

The T nut is most likely machinable, but that doesn't mean that it is make from soft carbon steel. It could be a tool steel that is fairly hard/tough or a higher carbon steel and cutting that with HSS end mills will require a much slower cutting speed (RPM) than a soft carbon steel.

Also, those are import end mills. My experience with the ones I have had in the past is that they must be run much slower than a nice quality USA grade.

So, if it was a tool steel and I was using a 3/4" import end mill, I would probably be running it at around 300 RPM max and see how that goes. Cutting oil is good, but a spray mist would be better and recommended.

As others have stated, you can take a heavier cut. With a 3/4" end mill taking a 1/4" x 1/4" cut would be fine. I would NOT climb mill unless a very light finishing pass (as stated by others).

This is how we learn... we've all been there. Trail and error. Keep up the good work!

Ted
 
many HSS end mills die from taking too small of a cut under too light (slow) feed rate. The rule is the tool needs to have force to insure it bites into the material it is cutting. if it is just "skimming" the edge will dull and begin to overheat.

Learn to read your chips. Steel will tell you everything you need to know by looking at the chip. Color, and even the finish on the chip itself. Use a high powered magnifier and look at the surface of a chip. If it is smooth almost mirror finished you are cutting and not skidding/grinding away the stock.

Different steels will have different "tells" in regards to the color you achieve and the simple rule is blue to black is bad. Blue to brown is is borderline.
 
Invest in a bottle of Dykem layout fluid, no self respecting machinist would be caught dead without it; helps you make sharp, clear scribe lines on the work that make it easy to sneak up on the desired dimension without overshooting
 
markba633csi said:
Invest in a bottle of Dykem layout fluid, no self respecting machinist would be caught dead without it; helps you make sharp, clear scribe lines on the work that make it easy to sneak up on the desired dimension without overshooting
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Seems like many people prefer Sharpie these days, well the YT machinists anyway. Keith Fenner calls is Sharpem. Lol.

I still prefer Dykem or proper layout fluid. Permanent marker is convenient but it comes off too easy especially with certain cutting fluids. Unfortunately my lathe is white & when the Sharpie "washes off" it stains the paint. I don't mind my lathe looking dirty or the paint chips but it annoys the heck out of me when there are blue stains in the paint. :D
 
Thanks guys for the encouragement,today I was going over how it was cutting from the very first pass to the last which it was just getting worse with each pass.Just for giggles and grins I am going to try the same bits but in some steel that come from HD just to see how it does.I have trammed both directions and the vise so see what happens.Thanks again for staying with me
 
Good afternoon guys,good news.After doing a fresh tramming I put in a 3/4 plate then using one of my bit from the other day I gave it a try which it just would not cut.So I put in a new bit 3/4 and made a pass of .010 I'm all smiles.Next I made a .030 pass at 500 rpms and no strange noises nor sounds like something was straining.Even if see those small marks guys its as smooth as glass.I know,I know not much of a test but wanted to stop for now and glote alittle while I'm ahead.Maybe those first two bits were not as sharp as the others or I just mess up and did not see what was going on.So going with the second excuse for now but I'm all smiles. Sorry for the poor pic,dang phonemill.jpg
 
Make sure to Never climb mill on a manual machine except for finishing passes.... that may have been part of your problem..... If your machine has a rack and pinion X axis feed Absolutly No Climb Milling the table will be pulled in by the power of the spindle and its scary as hell....
295041
 
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turnitupper said:
And do not mill RUST ! It will take the edge off cutting tools faster than the old eye blink.
John.
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Dont even try to cut rust with a cut off wheel it is much harder than the material underneath and will wear down the wheels very fast....

If you have to mill a hard coating or a case hardened part its better to mill deeper than the hard case on the first pass rather than taking small depth cuts untill you get past the hard case... Less overall wear on the end mill....
 
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