Boring a Hole in 4140 steel

[ricotututi]

Hello
Help, help please

Can somebody give me some advice in how to make a .187 to .1875 hole in a 4140 steel, I have tried almost everything reamers boring bars and I'm having problems holding size.

Also if somebody has experience in turning 4140 material, I'm havin problems braking the chips all I get is a very stringy chip
thank you

[big_mak]

For your stringy chip problem, what kind of tool are you using?

For reaming, try carbide tipped or solid carbide reamers.

Is your reamer running true? How much material are you leaving in the hole?

[ricotututi]

Hey big mak

for my chip problem I'm using a 55-deg diamond insert with a .015R

for the hole problem I already try carbide reamers and my reamer it is running true. I tried boring it first and then ream but after running a few parts I get some parts undersize

[big_mak]

What DOC are you using for the lathe tool? Feed?

What speed and feed are you using for the reamer?

[ricotututi]

I 'm turning a .621 stock diam down to .375 finish size at about 300sfm


for the reamer I tried anything from between 400-1500Rpm with a feed rate of 6 - 13 IPM

[ricotututi]

by the way The length of the part I'm turning is about 21 inches

the bore hole is only .400 deep thru hole

two different parts

[big_mak]

As for turning, to break the chip, you must make sure that your depth of cut is larger that the tool nose radius. Your feed should be around 0.010"per rev.

U using CNC for reaming? Try using G85 to Feed in feed out. How big is your hole before you are reaming it? I'd make sure its only around 0.182" or so.

[big_mak]

You have a follower rest?

[ricotututi]

I'm using a CNC Swiss machine for both parts and I did tried feeding IN and Out and my hole size is .182 diam.

[big_mak]

with a swiss type machine you should be able to get a good aggressive feed on the turning part.

As for the Reamed hole, areyou getting enough coolant to the tool?

This can be tricky because with a small reamer the chips can fill the flutes and keep the coolant from getting to the cutting edges.

Maybe just maybe try for the fun of it ream with G83 to let the chips come out and get coolant to the tip of the tool.

It's easy for us to come up with ideas when we're here. Always a different story when you're at the machine.

[ricotututi]

well believed or not I can only go up to .007 feed rate before I get an overload alarm, I think the machine just don't have enough horse power to rip the material.

As for the hole I'm going to give it a shot to the G83 ... tomorrow

Thanks big mak for your help and Ideas if you have any other ones please post it I will check them tomorrow .. I think is time to give it a shot to try to sleep with all these ideas

[mxtras]

You might be work hardening the material. Are you using coolant? Keep the material cool during machining.

It sounds like you may have work hardened your piece.

Scott