Quick feed/speed question for my TM-1

[maxine]

I ruined two 1/2" end mills yesterday trying to do what should have been a very simple op on my TM-1. Can I get some advice please?

I have a piece of normalized 4130 round. I was cutting a centered through hole in it. I predrilled the hole out to 1/2" diameter no problem. Then I was going to drop in with a 1/2" carbide end mill (coated Kennametal, solid carbide, 2 flute, flood coolant, one brand new, one barely used) and machine the hole out to 1" diameter. Stepping (ramping using a 0.25" ramp length) down 0.15" at a time. Then one circular pass leaving 0.015" for a finish pass in a later op. Then step down and go around again. And so on. I needed to bore down to a depth of 1.4" to break through. Both times I made it down to about 0.5" before the end mill was completely dulled down and rounded over badly on the end.

I must have my speeds/feeds wrong somehow. I have rarely done steel so I used references to set the parameters. If you were going to do the op described above what settings would you use?

Thanks guys!

Maxi

[Geof]

You probably destroyed the mills because they were re cutting chips.

Pre drill much larger so you are only removing about .05 maximum with the mill. Run at around 200SFM with a feed of about .001 per tooth and use a four flute cutter ramping down helically at about 0.1 maximum per circle.

Do not pilot for the pre drilling use a split point drill in a single pass.

[maxine]

Originally Posted by Geof You probably destroyed the mills because they were re cutting chips. Pre drill much larger so you are only removing about .05 maximum with the mill. Run at around 200SFM with a feed of about .001 per tooth and use a four flute cutter ramping down helically at about 0.1 maximum per circle. Do not pilot for the pre drilling use a split point drill in a single pass.

Yeah unfortunately the largest drill bit that I have is a 1/2". That's why I was trying to use an end mill to do the rest. I was running it at 250 SFM and had the feed set for 0.0015 per tooth so you must be right on the chip recutting. With no larger drill how big of a radial cut could I take with the end mill?

Maxi

[Geof]

Something like 0.05 radial, 0.05 or less pier circle and .001 per tooth. Plenty of coolant to try and flush the chips through the hole. You cannot avoid recutting but if they are thin chips the cutter may survive.

PS I bet these two posts of mine are the first ever on the zone from the Galapagos Islands where I am on vacation.

EDIT I put in the wrong depth of cut, now changed.

[extanker59]

Do you have space below the part for chips to fall out?


On a different note:
Geof wrote "PS I bet these two posts of mine are the first ever on the zone from the Galapagos Islands where I am on vacation."

Tell us about it! What's it like? Still a lot of wildlife? I think I remember that it's been made into a park? What country owns the islands? Those giant turtles always impressed me the the most (in pictures) although the place is supposed to be chock full of different animals. If you talk about this on a different thread, point me in the right direction. Thanks.
Chris

[maxine]

Originally Posted by extanker59 Do you have space below the part for chips to fall out?

Yes the part is mounted in a fixture with at least 1.5" of room below where coolant can flush things out if they will fit through the 1/2" center hole.

Geof I will go over to the shop and try again today with the axial and radial cuts you suggest. Thanks for the help. If that doesn't work I guess I will go buy a big drill bit on Monday. I don't have much need for one that big. Just the occasional part like this one. But chewing up 1/2" carbide end mills is expensive. I could have bought a drill by now.

By the way you should be glad you are in the Galapagos. There is a 45 mph wind blowing down the Frasier River Valley today and it is COLD here.

Thanks again for the help gents!

Maxi

[Geof]

Originally Posted by extanker59 ...Tell us about it! What's it like? Still a lot of wildlife? I think I remember that it's been made into a park? What country owns the islands?... If you talk about this on a different thread, point me in the right direction. Thanks. Chris

I plan on setting up my own website and will have pictures on it. To answer some of the questions the country is Ecuador and all the islands are park and marine reserve and the wildlife is unreal.

[littlerob]

Originally Posted by Geof PS I bet these two posts of mine are the first ever on the zone from the Galapagos Islands where I am on vacation.

Yeah, have fun with all that, must be a nice climate change for you....Bastard

Robert

[maxine]

Geof the radial and axial settings you suggested along with as much coolant flush as I could get aimed into the pocket worked out well. Thank you.