Hard turning

[ATG]

I'm trying to hard turn a 35 inch long shaft with 60-65rc. I'm getting chatter on my sl30 LB BB lathe. I'm currently only taking .0025 per side with a surf of 400 and a feed of .005.

 

The problem is chatter. The shaft begins to hum and this creates chatter.......any suggestions.

 

 

thanks

[ToolMan184]

What insert are you using? It is best to use a smaller radius on a shaft with that length. What size is the shaft?

[Guest]

quote:

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The problem is chatter. The shaft begins to hum and this creates chatter.......any suggestions.

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I wound up with a "good" case of tennis elbow in my left arm from holding the shafts so they would not vibrate.

 

Can you use a steady rest to support the shaft and machine it in 2 ops?

[Kevangel]

sometimes holding a deadblow hammer near cutter helps....(contact helps dampen vibrations)

 

+1 on smaller cutter radius to reduce vibration.. maybe even positive rake??

 

would it help to take .006 per side?? where tool can take a better bite? I don't know very much about hard turning as we do lots of precision grinding .0001 stuff.. I've turned a few long 420SS 32-38RC shafts and a little change in RPM or feed can make a big diff. in vibration on those.

[ATG]

I'm using a dnmg 432 sumotomo bn250 cbn.

[ATG]

Another quick question I could not remember it’s a u call out to cut a taper on the OD correct.....

[ToolMan184]

use a DNMG 431.

[Randy Morton @ Clem Industrial]

In a past life I had similar problems on a machine, dependant on the finish you are trying to achieve...we wound up using a .004" radius DNMG tool. I think it was classed as DNMG 430.5 (or something similar). We used the KM brand, and it worked great, in a positive style.

 

+1 Toolman, if you have a smaller radius, then go with what you have, if not, get the rep in and trial one or two... =] The .004" rad. inserts are used for high finishes, low feeds (as you have) and small DOC (as you have). May work well for ya!

[calnet42]

If you have room, you could try sticking a magnet (mag-base) to the tool as near as possible to the cutting edge.

[ATG]

Well i did try the 431 still no luck....

[Rick Henrickson The Boeing Co.]

are you using your tail stock, what size tool nose rad?

[ToolMan184]

Check how rigid your set up is. To hard turn it must be rigid to get good results or you will pull your hair out. How many parts are you doing? Is there anyway to dampen the part or tool to reduce the chatter?

[ATG]

Well depending on how this xxxx works out, well do many shafts or keep sending them to the grinder...........everything seems to be pretty rigid. I'm using an iscar holder. A Ritter driver plate and a Royal live center......

[ATG]

oops I mean all works out

[Ron Branch @ Verisurf]

We grind our shafts that long leaving .01 for the grinder faster, better finish, and more accurate to send it over to our grinding department than trying to turn without a follow rest. That long unsupported is not going to be pretty anyway you stack it. Good luck but IMHO going in a backwards direction with a part of this nature without some kind of a support.

[dpg752@TGI]

Did you try using SSV (Spindle speed variation).

 

 

[*]X2 Mill/Lathe

Solids

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[Kevangel]

quote:

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A Ritter driver plate

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Are you saying "this is being turned between centers"? Then you have very little dampening...wow

[Hardmill]

Your going to need a little more stock to finish, id say .005 side min.

Then find a good CBN insert to get good turning results.

 

 

PEACE

[steve f]

Is your lathe a Haas "sl30 LB BB"?

 

There's a local guy around here that bought a new haas lathe and had to hang a 5 gal bucket of used carbide inserts off the turret just to dampen vibration on general turning for heavy cuts. Probably not the most rigid machine no matter how the setup is.

[Dan@home]

A deeper cut, enough to barry the tool nose radius with a low surface feet and max feed rate as much as you can get away with, should help.

 

Dan.

[ToolMan184]

We hard turn D2, 58-62 HRc from 4" - 6.5" Dia. x 34" long almost every week. We use J & M Diamond CBN tools. We leave .060" finish stock and can finish them in a little over an hour. Much faster than grinding them. And we hold the tolerance to within .0005" - .0007".

 

If you are turning them between centers, I would say that is where your problem is at. That is not a good Hard turning set up. Could you make a set of soft jaws and chuck them?

[Kevangel]

quote:

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Could you make a set of soft jaws and chuck them?

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Thats what we do and really crank the center in to build pressure against shoulder and bigger chucks will give more dampening if your spindle motor can handle it without burning up. 10 in. chuck is better than 8 inch, etc on borderline cases.

[Guest]

You know some moron at the start of this suggested this

 

quote:

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Can you use a steady rest to support the shaft and machine it in 2 ops?

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Still a valid question.