Speed For Milling On A Lathe

T

Tozguy

Active User
H-M Supporter Gold Member
Joined
Feb 15, 2013
Messages
2,963
I plan to spin a 1/4'' four flute TiNi coated end mill in the spindle of my lathe to cut a 5/16 slot in the end of a 1.25'' round piece of medium steel.
The end mill has a 3/8'' shank and will be held in a MT3 holder. The speed range of the lathe is 60 rpm to 1200 rpm. At what speed should the spindle be run for this job?
 
I'm not sure what "medium steel" is but if its something like 1018 or 1020 then a cutting speed of about 100 sfm for a 1/4-1/2 dia. cut is about right. This works out to about 1200 rpm when taking a cut of about 0.156" doc. It's the same as it would be in a mill.
 
Spindle Speeds for the mill or the lathe used to mill are the same. 1000-1200 RPM is fine.

"Billy G"
 
Thanks for the help. I know zero about milling.
The markings on the steel are no longer legible so I have to guess. It has a dark scaley surface that is hard on tools but after getting under the 'skin' it cuts OK with brazed carbide. It isn't the easiest steel to cut but I manage.
Since the upcoming milling cut is on the end of the shaft, a HSS tool with TiNi coating should be OK.
 
Last edited:
Sounds a lot like 1144 - I really like that steel! Use cutting fluid and feed so you feel a slight resistance to the cut - it should go fine. Just don't dwell or it may work harden.
 
Thanks mikey,
re cutting fluid, should it be mostly for lubrication or cooling?
I have some tapping fluid but also some water based cooling fluid (Universal plus).
 
If you have a flood coolant system then that would be great. Otherwise, just use the tapping fluid and you should be fine. I was thinking that with this mystery steel, I would try reducing the DOC to maybe 0.80" and see how it goes. This is 1/4 the diameter of the end mill and should work okay.
 
Anywhere from 800 to 1200 should be good. Just listen for any anomalies or vibrations and if present adjust speed accordingly.

Make sure to use collets, a endmill holder or a 4-jaw. Don't use a 3 jaw, the slight runout of them will wear some flutes of the endmill faster than others, and will cause vibrations and a wider cut than you want in most cases.
 
The plan is coming together:
Use MT3 Sheldon holder with set screw.
Speed 900 rpm
DOC .080 '' (mikey was the .80 you mentioned above a typo?)
Squirt tapping fluid on cut
Power feed with cross slide at rate of ?? (need help on this)
 
Yes, a major typo. ).080" is what I meant.
 
You must log in or register to reply here.
Back
Top