What's new
What's new
By:
Advanced search…

Long Soft Jaws Causing Chatter

J

JBNimble

Plastic
Joined
Mar 17, 2019
I now have 3 sets of 4" long soft jaws for my HAAS 10" chuck. For a year, I have been turning 303SS and Acetal in diameters up to my 3" capacity. I have had ZERO issues with surface finish. Last week I tried some smaller parts from 1" and 7/8" 303SS. This is the first time I have used this soft jaw set, but it's identical to my other sets, except for diameter range. My groove turn tool was yelling at me and leaving horrible surface finishes in O.D. turning. I ruled out everything with the cutter, tool, block and turret. Solid. Straight. On spec. Today I yanked the 3 jaw chuck off and mounted my Royal 16C collet chuck. Instant success! So, I have a working solution, but I prefer the 3 jaw chuck because I can do faster setups across all part sizes. So now the question:
Any ideas how to make the 4" long soft jaws work on smaller diameter bar? Vibration seems to be an issue no matter what I try.
I have tried the full range of chuck hydraulic pressures, speeds, feeds, y-offset below centerline, etc. The jaws close on the outer end just before the near end, exactly as they do with my other jaws which work great. But 1" and less bar comes out looking like a beaver chewed it.
 
What diameter did you machine the jaws for? By soft jaws, I assume you mean they are aluminum, not steel. I would expect a collet setup to be much more rigid, but less accommodating of raw stock size differences
 
As a quick fix, put a piece of masking tape on the clamp surface of each jaw only out at the end and see if that solves the chatter issue. I bet the jaws are not clamping your stock tightly at the outer end.
 
In my experience, when you get down to 1-1.5" and smaller, making sure the jaws are right on size, and not cheating, makes a big difference. For a first op, undersize jaws with oversize material will give 6 point contact which often works ok. Your post makes it sound like you had equal problems with .875 and 1" dia material with your 1" jaws. Which sounds like your jaws are possibly oversize from 1", or are splaying out from the chuck pressure.

Also, when you say it's the first time you've used this soft jaws set, it sounds like you didn't just bore these on this machine? Steel or aluminum? You could be losing clamping force if they're steel and you're spinning them fast.

If this is bar pull work you're doing, any reason you have to use 4" long jaws instead of normal jaws?
 
I've found when boring long soft jaws I have to program in a few tho taper even when I use a ring on the face of the jaws. Or run the chuck pressure higher when you are boring them but thats a bit of a guessing game cause being loose in the back can be just as much of a problem as the front
 
Scott314 said:
In my experience, when you get down to 1-1.5" and smaller, making sure the jaws are right on size, and not cheating, makes a big difference. For a first op, undersize jaws with oversize material will give 6 point contact which often works ok. Your post makes it sound like you had equal problems with .875 and 1" dia material with your 1" jaws. Which sounds like your jaws are possibly oversize from 1", or are splaying out from the chuck pressure.

Also, when you say it's the first time you've used this soft jaws set, it sounds like you didn't just bore these on this machine? Steel or aluminum? You could be losing clamping force if they're steel and you're spinning them fast.

If this is bar pull work you're doing, any reason you have to use 4" long jaws instead of normal jaws?
Click to expand...

Aha. Yes, I did bore the I.D. at 2", so I'm sitting on tangent points on all my stock sizes less than 2". They are steel. When the chuck closes, they close on the tips first and then the back, so I feel like they have a good grip. I was worried about centripetal acceleration, so I played with a wide range of chuck pressures but that made no difference.
 
Why on god's green Earth aren't you using a Collet?

Even a Collet closer held in Chuck jaws is better than regular jaws, at that diameter.

R
 
litlerob1 said:
Why on god's green Earth aren't you using a Collet?

Even a Collet closer held in Chuck jaws is better than regular jaws, at that diameter.

R
Click to expand...

Because my entire turret (20+ tools) and part catcher are all dialed in for my 10" chuck. I AM running my 16C Royal collet chuck this week, but it took 2 hours to swap chucks, pull tools and move the catcher. My normal changeover between parts is minutes with drill changes only. I would LOVE to run collets on everything, but z clearnaces are a problem for longer tools.
 
JBNimble said:
Because my entire turret (20+ tools) and part catcher are all dialed in for my 10" chuck. I AM running my 16C Royal collet chuck this week, but it took 2 hours to swap chucks, pull tools and move the catcher. My normal changeover between parts is minutes with drill changes only. I would LOVE to run collets on everything, but z clearnaces are a problem for longer tools.
Click to expand...

1cc223-300x283.jpg

Not fancy, use your soft jaws. Chuck the OD of the closer. No change in Z clearance.

R
 
JBNimble said:
Because my entire turret (20+ tools) and part catcher are all dialed in for my 10" chuck. I AM running my 16C Royal collet chuck this week, but it took 2 hours to swap chucks, pull tools and move the catcher. My normal changeover between parts is minutes with drill changes only. I would LOVE to run collets on everything, but z clearnaces are a problem for longer tools.
Click to expand...

Theres a type of collet pad that you can use in your chuck jaws. I forget the name of them. there sweet. you cut a set of jaws to hold the pads. you never have to recut the jaws again and you can hold a huge range of round sizes, including cut to size pads.
Warney swasy maybe?
 
litlerob1 said:
That "boring ring" makes me laugh. I'm not taking 13.28 minutes to bore jaws LOL.

R
Click to expand...

No wait, its a 2 part video. It's like 29:12 :D

By the way Jack, 1" material in a 10" 3 jaw is fine, especially for 1st op short run stuff. I run 3/4 and 1" material all the time when the 5c collet lathe is setup on other jobs. The only drawbacks are the usual...less tool clearance if yer trying to fill up the turret (although it sounds like your using long, OD profiled jaws to clear), and more inertia. It's more of a hindrance on small parts when you're doing a 2nd op, IMO.

The collet pad jaws, and Royal 5c closer are good ideas, and I'd like to have both in my box of tricks at some point, but keep it simple...Either batch together your chuck jobs and collet jobs to spread out the changeover time if you can, or just do it in jaws. If you need the 4" long ones cut down on the OD to clear your tools, consider relieving the back couple inches of the ID a little oversize, and just finish boring the front couple inches to size, clamping on a plug just behind the finished bore.
 
You must log in or register to reply here.

Similar threads

1
Help chatter while machining a shaft (CNC lathe).
2 3
Replies
41
Views
2K
Sandy171
S
Hobbes4Pres
Corner Radius End Mills and Soft Jaw Profiles
2
Replies
29
Views
2K
rjwalker1973
rjwalker1973
D
Soft Jaws to hold cylinder
2
Replies
26
Views
2K
604Pook
604Pook
BOB-OO
Looking for a small precision 4 jaw independent chuck (3"or4") Recommendations?
Replies
4
Views
482
implmex
I
A
How deep should I bore soft jaws?
2
Replies
32
Views
3K
rjwalker1973
rjwalker1973








 

ABOUT PRACTICAL MACHINIST

With more than 10.6 million unique visitors over the last year, Practical Machinist is the most visited site for metalworking professionals. Practical Machinist is the easiest way to learn new techniques, get answers quickly and discuss common challenges with your peers. Register for the world’s largest manufacturing technology forum for free today to stay in the know.

Learn more about us.

STAY CONNECTED

Facebook Instagram YouTube LinkedIn Pinterest Twitter Tiktok

Register Become a forum member. Register today.

Sign Up Sign up for our e-newsletter.

© 2024 Copyright Practicalmachinist.com. All Rights reserved.

Back
Top