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How can I remount soft jaws without having to rebore?
- Thread starter newcomer
- Start date
- Replies 26
- Views 4,435
Mike1974
Diamond
- Joined
- Nov 5, 2014
- Location
- Tampa area
I don't think you can. You are talking about jaws that located by serrations? Tall order IMHO, you want .0004" runout with removable jaws.
Joe Miranda
Titanium
- Joined
- Oct 19, 2004
- Location
- Elyria Ohio
The point of using soft jaws is to ALWAYS rebore in order to achieve maximum concentricity to spindle C/L. That's the whole point.
Booze Daily
Titanium
- Joined
- Sep 18, 2015
- Location
- Ohio
They also need to go on the same lathe they were bored on. When I do this I can usually get .001-.002 TIR.
chip_maker
Stainless
- Joined
- Jan 14, 2006
- Location
- Moira, NY USA
I've had good results by:
1. turn the chuck pressure way down.
2. just barely tighten the t-nut screws.
3. chuck a part.
4. tighten the screws you have access too.
5. remove part and tighten all the jaw screws.
6. turn up chuck pressure to normal.
.0004 is pushing it though. Using this method has yielded me .0005 best. But for you it's worth a try.
Of course jaws should be numbered and always used on the matching master.
Everything should be spotless also.
1. turn the chuck pressure way down.
2. just barely tighten the t-nut screws.
3. chuck a part.
4. tighten the screws you have access too.
5. remove part and tighten all the jaw screws.
6. turn up chuck pressure to normal.
.0004 is pushing it though. Using this method has yielded me .0005 best. But for you it's worth a try.
Of course jaws should be numbered and always used on the matching master.
Everything should be spotless also.
Orange Vise
Titanium
- Joined
- Feb 10, 2012
- Location
- California
The serrations do a good job locating the jaws radially and axially, but the jaw nuts do all of the side to side locating. Nuts need clearance, and that clearance translates into azimuthal positioning error. It's not much, but to consistently get under 10um, you would need tighter fitting jaw nuts than standard. It doesn't help that on a lathe, positioning error gets doubled when measuring diametric runout.
If you don't have a lot of parts to make and can spend a few extra minutes, chuck the part under low to medium pressure and tap it into position with a brass hammer and test indicator, then set the chuck to working pressure.
If you don't have a lot of parts to make and can spend a few extra minutes, chuck the part under low to medium pressure and tap it into position with a brass hammer and test indicator, then set the chuck to working pressure.
chip_maker
Stainless
- Joined
- Jan 14, 2006
- Location
- Moira, NY USA
A bunch of years ago I did a job for a local workholding manufacturer who had a customer with this same problem.
What we ended up doing was, measuring the width of the opening in each master jaw. From there we made numbered T-nuts and soft jaws with .0001-.0002 clearance between the t-nut and it's corresponding master jaw and soft jaw.
The customer was looking for .0005 or better t.i.r. and this worked out well for them.
Of course chuck condition will also affect the op's t.i.r.
It may not be feasible for the op, but doesn't Schunk or some others make chucks that address this issue?
Interesting...
I can see how that would kinda locate things providing you did this on the initial bore. Good idea I never thought of doing it that way.
Brent
Just bore them, that's why they are called soft jaws. Repeatability to .0004" would be interesting, amazing, unlikely, fantastical, unrealistic or just a waste of time. I can bore jaws in about 2 minutes, I have a jaw boring macro that I input the starting diameter and the depth and the chucking diameter, away I go.
Robert my ±2
Robert my ±2
allloutmx
Titanium
- Joined
- Mar 6, 2013
- Location
- Rochester, NY
Precision Air Chucks On Northfield Precision Instrument Corp.
We use these especially for grinding. takes a little more work when you make your jaws but they are mint when you get into tighter tolerance work
We use these especially for grinding. takes a little more work when you make your jaws but they are mint when you get into tighter tolerance work
Dave K
Diamond
- Joined
- Mar 21, 2004
- Location
- Waukesha, WI
If you're running parts where you need to hold that close of a tolerance, I wouldn't even take the chance, even if you figured out a way to do it. Boring them is going to be your best bet, so I would actually want to bore them every time.
joeblow86
Plastic
- Joined
- Apr 19, 2014
- Location
- Edmonton, Alberta, Canada
Are you using a Jaw boring Ring to load the jaws prior to boring them? You should be.
Stuart Caruk
Stainless
- Joined
- Feb 20, 2007
- Location
- Ridgefield, WA
Go ahead and mount them without reboring... I just got a great paying gig because the last shop that ran the parts was too lazy to rebore the jaws and the faces of the part were out of parallel by over .004". I redid the parts to a tolerance of less than .0002" And their accumulated error dropped way down and they found significant improvement in the process. I've got several months worth of work lined up from this customer now as a result... A little extra effort typically pays dividends in the long term.
wheelieking71
Diamond
- Joined
- Jan 2, 2013
- Location
- Gilbert, AZ
What do you do if:
You need to clearance the corner for a sharp part?
You need to clamp on more than one diameter?
I am struggling with lathe jaws right now.
Trying to find a strategy that is faster.
And, somehow cheaper. But, I think that may be a lost cause.
cnctoolcat
Diamond
- Joined
- Sep 18, 2006
- Location
- Abingdon, VA
Undercut the corner, either with and ID grooving tool, or a boring bar with triangle-shaped insert.
At the same time? That's a "machining 101 no-no".
Now if you are flipping a part and re-clamping for op 2, that can be done, with careful design of how you bore your chuck jaws.
I hardly ever do this though, as there's really no -net- time savings versus just running all the parts on op 1, then changing or reboring the jaws, then running all the parts on op 2.
Only advantage to flipping a part and running op 1 and op 2 together is you will have a finished part when done.
ToolCat
gregormarwick
Diamond
- Joined
- Feb 7, 2007
- Location
- Aberdeen, UK
Plenty of times it's unavoidable though. I have soft jaws that span multiple diameters, large radii, tapers. Yes it's difficult to ensure contact everywhere it's needed but sometimes on odd shaped parts there is no other way.
