Problems with boring on a lathe.

my experience is that the above/below center issue doesnt matter, if you adjust the angle accordingly. ist not very hard to make a boring bar yourself. q.jpg this one has a cbn insert and was used to hard turn the jaws on the lathe. i even made the screw myself. contrary to popular believe, you dont have to harden/heat treat, as it doesnt make the bar stiffer. all steals have the same modulus of elasticity. carbide is stiffer.

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Hello Dion

How did Your Cubic Boron Nitride survive cutting hardened ,interrupted chuck jaws, and where did You find the CBN?
If it fell off a lorry it would have been difficult to find for an old man like me.
Hardening the boring bar is not beneficial as you say because E-modulus will not change.Hardening migth even diminish inherent damping,not wanted.
Hardening will off course stop wear under the insert but for amateurs this is no isue.
Somehow I like to make tools more than projects.
 
Some worn HSS endmills came my way.Restoring by hand is impossible but resharpening one tooth is very easy.In Europe endmills comme in distinct shaft sizes and I tried to use one for boring in my boringtool holder.Cuts very well and I think I have sharp cutting corners for rest of my life.

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I sharpened my carbide bits and tried it on a piece of scrap that i previously bored. Its not perfect yet but a great improvement. With practice should get better.

Good tip about the worn end mills Farfar. I have one larger one and several broken 1/8" that I'll try to regrind into boring bars.

Hecrip thanks for the tips. Mainly I will be boring 1018-1020, 4130, 4140 and similar steels. Holes will range from about .400 in diameter by about .200" deep, and about .632 diameter and 2" deep. Through holes I'm predrilling with largest possible drill and blind holes I do the same with an end mill .

Here's example of before and after:








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That look about right... Don't forget, you need some cutting oil of some sort. Looks like it was cut dry. Also, reaming is a good thing to do if you need the next level of perfection. Hand reaming won't give good results but machine reaming will. Use thick cutting oil.
 
I always thought that you cut dry with carbide. I'll have to try that. I know about reamers, those are very easy but rather expensive. I'll have to get a set sometime in the not too near future. Since the reamers were mentioned, I have a question about them. Can adjustable reamers be used in lathe or mill? I'm asking because I looked at them and description on the box says hand reamers.
 
FarFar said:
Hello Dion

How did Your Cubic Boron Nitride survive cutting hardened ,interrupted chuck jaws, and where did You find the CBN?
If it fell off a lorry it would have been difficult to find for an old man like me.
Hardening the boring bar is not beneficial as you say because E-modulus will not change.Hardening migth even diminish inherent damping,not wanted.
Hardening will off course stop wear under the insert but for amateurs this is no isue.
Somehow I like to make tools more than projects.
Click to expand...

it survived well, the picture is after all has been said and done. i would never grind the jaws again. i bought it from a local machine shop (they gave me a bunch of other inserts for free), but i guess they are on ebay too.
 
kkcalvin said:
I sharpened my carbide bits and tried it on a piece of scrap that i previously bored. Its not perfect yet but a great improvement. With practice should get better.
Click to expand...

I've noticed that if you already have chatter in a hole it very difficult to get a good finish from it.

Steve
 
Carbide and some lube is a match made in Heaven.

I've never used adjustable reamers so I can't comment much about them. You should not use hand reamers in a machine. Hand reamers are OK for shallow holes and I've used them primarily to clean-up internal burrs. For deeper holes, machine reaming is best.


kkcalvin said:
I always thought that you cut dry with carbide. I'll have to try that. I know about reamers, those are very easy but rather expensive. I'll have to get a set sometime in the not too near future. Since the reamers were mentioned, I have a question about them. Can adjustable reamers be used in lathe or mill? I'm asking because I looked at them and description on the box says hand reamers.
Click to expand...
 
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