tips for adjusting buck chuck?

My suggeston would be to mark the adjusters, probably with magic marker, A, B, C, D. Then dial in the A, C axis as best possible. When you are satisfied switch to the B, C axis and dial that in.

Recheck the A, C axis and repeat until satisfied.

When you simply find the high spot you wind up chasing your tali round and round, as you found out. Also remember when doing anything that resembles this, ie four jaw work, many small adjustments are far better than trying to do it in a few large adjustments!

Good luck with your new tool!

Errol Groff Instructor, Machine Tool Department H.H. Ellis Tech

860 774 8511 x1811

These are well-known as low quality units. I suggest you send it to me for evaluation. It's probably not worth keeping.

:^)

The backing plate is held to the chuck body with some screws - these should be slacked off somewhat to allow the adjustment to occur, and snugged down more and more as you get 'close.'

Like any four jaw chuck, if the axis you are not adjusting on, is very very tight, you will have trouble tweaking the axis you are adjusting on. So don't snug down the opposing screws for one axis all the way, until the other axis is also close to being 'in.'

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

I think you did it about right. The other posters have some good ideas. You shouldn't have to do this very often. I suggest, tho, that you keep going, looking for something better than .001" runout. I installed a new 3 jaw on my old Atlas 10" lathe a few years ago, and got it to 0.0004 TIR. I check it from time to time, but it stays there quite well. On the other hand, when I was taking evening machine shop classes, my instructor had a "set-true" type chuck that he used on dividing heads. When he would chuck up a piece, he would center the work by moving those adjusting screws. He was pretty good at it, typically taking only a minute or two to get the job done.

Pete Stanaitis

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joel wrote:

I've got a Burnerd grip-tru adjustable three jaw chuck. It uses three centering adjusters at 120 deg intervals - I expect these are similar to your true-adjust system.

Centering with three adjusters can be much harder than with four adjuster systems (e.g a 4 jaw chuck). A 4 jaw chuck behaves much as you would expect it to.

The method that I use is pretty standard:

2 Zero the clock to half way between the minimum and maximum readings

4 Use both adjusters to zero the clock for this pair of jaws

If you've zeroed the clock carefully this will be within a thou or so first time round. A repeat cycle will reach tenths. The nice thing about this sequence is that you are not chasing your own tail - successive adjustments are always 90 deg apart so that each is independent and does not foul up the previous adjustment.

Three adjuster systems can be made to behave in the same way but the method is a little less obvious. The trick is achieve the 90 deg separation by rotating a pair of adjacent adjusters simultaneously - one in and one out.

2 Zero the clock to half way between the minimum and maximum readings

4 Use No 1 adjuster to zero the clock

6 Simultaneously rotate adjusters No 2 and No 3 to zero the clock

Step 6 causes the chuck to move in a direction 90 deg away from step 4 so the two adjustments are independent. A single cycle will get you pretty close. If necessary execute a second full cycle - don't be tempted to just tweak the odd adjuster - its only too easy to start chasing your own tail!

If you're having trouble with the final locking disturbing the settting carry out steps 1-6, fully tighten the locks and then slacken the adjusters so that they no longer control chuck position.

Slightly ease off the locks and GENTLY use a lump of brass to tap the chuck to final concentricity. Fully tighten the locks

Jim

--For starters get a dial indicator that reads to .0001"; it should be possible to dial in a Buck to +/- .0002" or so. Very handy for machining something all over..

(snip)

Jim's instructions are good. With a little practice you should be able to get it dialled in to under a thou in a couple of minutes. A good DI and methodical approach gets it done.

The trick about keeping the mounting bolts a bit snug and bonking the chuck with a brass drift is very useful in minimizing shift on final tightening.

I have a very nice almost new buck 6 jaw. I can adjust it to zero at one setting (say 1.25 inchs). When I put in a 1/2 inch part, I will get

Yes -- it enables you to tune out all errors at a single diameter. Others will have varying degrees of error remaining. You'll probably wind up with a minimum error at other sizes which represent precisely an integer number of turns of the scroll plate inside. Other positions will have greater errors to varying degrees.

Essentially -- you're making it into a single-size collet.

Enjoy, DoN.