Mill mark question

S

Shotgunone

Joined
Oct 1, 2000
Messages
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I have been wondering how to decrease the amount of mill marks or swirls that you have when you use an end mill to remove metal. Is there a secret to reducing the amount of swirling you get from the cutter or is there a special type of cutter, speed, fluid or ???? that will give a nice clean milled finish?
 
Tony,
I've had the best luck using a 2" face mill with carbide inserts. Enco has a decent price on them and they come with an R8 or straight shank.
Some guys prefer a fly cutter.
The secret with any of them is using a good dial indicator and making sure every thing is flat and level with the cutter.
Speed and feed do have alot to do with it also.
 
Tony, no doubt, what Kit said. I have been able to reduce milling marks a little with regular end mills, by a veeeeeeeeeeery slow feed, and only taking off a thousands at a time at finish. PITA, but it helps.:)
Another way, kinda radical, but it works, is to get a 120 grit, 6" depressed center grinding wheel, get the arbor that will allow you to chuck it in the mill, and make your finishing cuts with that. It basically amounts to turning your mill into a horizontal surface grinder. :eek:
 
I was asking a Boeing machinist this type of question, and when he looked at my work he said I had done well (to my surprise). The point being you never get rid of them entirely with your metal cutters. He said a stone is one of the best ways to eliminate the machining marks. The other points mentioned here I'm sure would help to minimize the swirls. Outside pieces could be sanded on the flat platen, or disk. If anyone else has any tricks for maximum smoothness, I too would like to hear them.
 
Tony, with smaller cutters under 3/8" I've found that high speed steel leaves a more shallow mill finish then carbide. Its still there but HSS doesn't seem to dig in as deep as carbide. The HSS may also produce a burnishing effect not seen with carbide cutters.

I've found that a light finishing cut with some cutting fluid produces a nicer finish. You can get small stones and break off a piece to clean up small areas and Cratex wheels also do a decent job.
 
Oh yeah, new, sharp, good quality mills made a big difference in the final finish. I find myself saying; "I think I'll break out a new cutter for this one." For less critical operations I use the older mills.
 
I am repeating an above suggestion but - very shallow cleanup run(s) reduce chatter.

Roger --- and I have never milled yet without it showing buy the use of end mills only.
 
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