Thread: Setting up in a 4 jaw independant

The way I've always done it is with 2 keys and the DI in the tool-post.

Initially I try and centre by using the rings in the chuck face, using keys in each pair of jaws. With practice this will get you down to within 0.5mm easily.

• "preload" the DI by winding the cross-slide in until the DI is around mid-range.
• Rotate the chuck by hand and watch for the lowest reading on the DI needle, at this point I set the bezel so the needle is now on 0.
• Continue to rotate until you find the highest reading on the needle
• Calculate half the highest reading and rotate the chuck until the needle points to that value. Once there, reset the bezel so the needle is now pointing to 0.
• Rotate the chuck until one set of jaws are in line with the DI plunger and use the 2 keys to move the jaw pairs until the DI reads 0
• Repeat for the other pair of jaws.
• Finally nip each pair of jaws up using equal pressure on both keys and you should be OK.

It sounds complicated but it's quite simple in practice. I can generally get it done in a couple of minutes.

If I'm really playing about I use the one key tightening, if things get to tight I start loosening with one key also.(though the term fannying about springs to mind ....... though sometimes you just want it as close as you can get it. so as its my time I knock myself out lol)

One other thing I think should be added. Dont tighten one pair of jaws until the other pair is "pretty close". If you end up with a side load on one pair of jaws and then you loosen them it will mess you up in both directions.

Stuart

Much appreciate all the replies everyone.

Can you explain the method that you used in setting up the length of brass bar in your lathe with the steady.

Was the od of the brass concentric.

The way I was taught to set up a steady

1. Get the chuck end reasonably close
2. Cut some aluminium strips to put under the chuck jaws
3. set up the chuck end with a dial indicator
4. Move the dial indicator to the end of the bar and KNOCK it around with a piece of brass till it's running true
5. repeat steps 3 and 4 until there's minimal runout at both ends of the bar
6. screw in the steady rest till it just touches the bar

I hope this makes sense here is a photo of a job I did today at work you can see the aluminium.

Just a comment I thought I would toss in. Keith Fenner tightens one jaw first and then loosens the opposite one. Reverse to most people. I have not tried it yet myself.

Dean

Another thing to think about is the quality of the chuck. I have a cheap chinsy one on the Mars (considerably lower quality than even a fuerda), and it is no where near as easy to finely adjust as the either the 10" Pratt or 12" TOS ones i have for the Antrac.

It's not that difficult when you have a system.

I just use a plain old (and I mean old) Starrett surface gauge to set the runout by eye, and then use a test indicator to do the last bit.

If you adjust opposing jaws to centre, you avoid the quarter runout issues that can occur.

No big deal.

Where possible, it's always handy to use the tailstock centre to check workpiece runout.

You can often use the tailstock live centre to centre the job and bring the jaws into it. Makes it pretty simple.

I only ever use one key.

Rob

Originally Posted by welder

The way I was taught to set up a steady

1. Get the chuck end reasonably close
2. Cut some aluminium strips to put under the chuck jaws
3. set up the chuck end with a dial indicator
4. Move the dial indicator to the end of the bar and KNOCK it around with a piece of brass till it's running true
5. repeat steps 3 and 4 until there's minimal runout at both ends of the bar
6. screw in the steady rest till it just touches the bar

I hope this makes sense here is a photo of a job I did today at work you can see the aluminium.

welder mentioned an important part of the fixed steady set up.. the aluminum packers.
with a long job supported by a 4 jaw and a fixed steady the packers between the job and chuck jaws
allow the work to turn without deflecting..for this purpose a brass ring 3 or 4 mill thick 10mm wide with a hack saw cut
thru it. slide over the work . goes between job and 4 jaw jaws.

.

Originally Posted by Stustoys

Use two chuck keys

I made a second small key. Small so that I could clear the headstock at the back. But I found that it also takes a little practice even with two chuck keys. ;-)

Originally Posted by azzrock

welder mentioned an important part of the fixed steady set up.. the aluminum packers.
with a long job supported by a 4 jaw and a fixed steady the packers between the job and chuck jaws
allow the work to turn without deflecting..for this purpose a brass ring 3 or 4 mill thick 10mm wide with a hack saw cut
thru it. slide over the work . goes between job and 4 jaw jaws.

.

So the packers allow the 4 jaw to act as a pivot point and allow some angular movement while being supported at the other end by the steady?

Simon

The packers allow you to do two things

1. Allow the work to pivot in the jaws to clock up the front and back of the shaft
2. 2 prevent making the work with jaw marks.

Originally Posted by welder

The packers allow you to do two things

1. Allow the work to pivot in the jaws to clock up the front and back of the shaft
2. 2 prevent making the work with jaw marks.

Thanks Andre. Can I assume that if a very expensive and accurate 4 jaw was used then pivoting should not really be needed since it would be expected that the chuck would hold the shaft parallel to the bed anyway or have I missed the point on this? That workpiece looks like an impeller from a rather large pump.

Simon

I made this little tool from a broken old screwdriver. I use it as a second key when adjusting. But I found it is also very handy to quickly set the jaws or to reverse the jaws, as the small handle can be turned much faster than the bulky T-key. I highly recommend you make your own (and clan the flux better off the square brass tip than I did, it caused the brass to turn greenish after many years....)
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To accurately set a 4-jaw chuck for non-round workpieces, I put a very faint center punch on the face of the workpiece. Then I use a "spring loaded pump center" and a DTI. There are many plans for such a pump center. Too lazy to go out and take a pic, I just googled "pump center" and found this: Free Metalworking Project Plans: Spring Center (Metal Lathe, Mill) | Projects In Metal, LLC
The one I made is much more slender and longer, so I can use it as a wiggler. Here pics of a wiggler in action Wiggler - a center finder for the lathe
The combination of a pump center and wiggler in one tool is ideal for 4-jaw chuck setting. The spring loaded wiggler is held on the right in a tailstock dead center, and on the left engages the center punch in the workpiece. The spring preload hold the workpiece against the chuck so it cannot fall down whilst adjusting. With some ptractice, you can set the chuck in under 2 minutes, and very accurately so indeed. Make yourself a spring loaded wiggler, it is an easy to make project and you will use it very often and it will last for many years to come. Chris