View Full Version : Boring Head Help

01-01-2010, 04:12 PM
How do you figure speed and feed for a boring head? Lets say i have a 1 in. hole to start with that needs to be 1 1/4 in. Also do you hand feed or use the power feed this would be on a bridgeport mill. This would not be a through hole.

01-01-2010, 04:47 PM
I run about like I would on a lathe and use the power feed. Set the quill stop to kick the feed out of gear at the bottom of the hole.

01-01-2010, 05:04 PM
Power feed on bores.

01-01-2010, 08:18 PM
What is the material your boring? That makes some difference.

This is a Bridgeport, right? I assume it is.

I would use the largest diameter, shortest boring bar that would work in the bore.

I would bore with the power feed of course and stop short of the bottom and then hand feed to the bottom using the stop on the quill.

Never power feed to the bottom of a blind hole unless you like to tear stuff up.

Assuming it's steel I would take .050" on the boring dial @ .0015" feed @ 80 rpm until about .050" from the final size. Then I would take .040" out, then sneak up on the final size in small increments.

See how much I have to assume when you don't give enough info.

01-01-2010, 08:42 PM
I did write that i will be useing a bridgeport and yes this is on steel.

01-01-2010, 09:00 PM
:o opps, mised the BridgePort part. Be careful boring to the bottom, things happen real fast down there.

You can experiment with the feed, maybe .003" but not .006" and/or faster rpm.

01-01-2010, 09:03 PM
Thanks for the help!

01-01-2010, 11:27 PM
By the way, when putting a boring bar in the boring head push it in all the way and then pull it out about 1/4". Sometimes the end of the bar interferes with the feed screw on the head. Also, take care to align the cutter edge straight out from the center of the head. Turning the cutter one way or the other will make it cut positive or negative rake.

01-01-2010, 11:38 PM
80rpm sounds wayy to slow for a 1" diamiter, especialy if hes using one of those brazed carbide boring bars..
1" at 80rpm is 20sfpm cutting speed!
even with HSS you should be able to do 400RPM (100sfm)
double that likey for carbide.

Oh, I guess offset weight is an issue. I wonder why boring heads don't have counterweights? Anyway id still crank the speed untill it starts rocking and rolling except for maybe the finishing pass. or just counterbalance the head somehow.

PS: Id really take care at the end of a blind hole, ALL your chips will fall to the bottom of the hole and stay there, boring bars have NO flutes to extract chips with (Unless your someone who turned an old HSS endmill into a boring bar. mmm thats a kinda cool bonus feature)
Basicly id recommend obcessively vacuuming out the hole, especialy before doing the last bit of depth and the finishing pass.

loose nut
01-02-2010, 11:20 AM
Will running a boring head to fast cause it to "wip" out and bore over sized, for example-taking a light final pass at a higher speed to get a better finish.

What effect does having the lower part of the head cranked way out to bore a large hole have on the speed etc. this would be running in an out of balance condition, will this effect the bore.

01-02-2010, 01:15 PM
You can get vibration from a boring head but not much on the average size heads. I like to start slow and speed up rather than start high and say :eek: aw geez while grabbing for the switch and brake.

Peter N
01-02-2010, 01:32 PM
I agree with Carl, it's quite easy to get vibration and chatter on boring heads, so I tend to run them slow-ish. Not quite as slow as Carl, but I'd probably take 0.025" and run it around 300 rpm or so at the finest feed.