Clocking on a 4 Jaw indepdent

FWIW, my method.

Having centred the work, more or less, by eye.

Apply a clock (I use a Finger clock, on a magnetic base on the Cross Slide ) to the top of the bar, and Zero on what looks to be the high point..

Rock Cross Slide to and from. The highest breading puts the clock on the cenytreline..

Rotate chuck by 180 degrees and note reading

Rotate 180 degrees agian and tighten upper jaw / slacken lower jaw until clock reading is halved .

Rotate chuck 90 degrees, and repeat above procedure.

Sometimes merely tightening one jaw a little (NO additional leverage on the chuck key!!!! ) will produce the final wanted result

Continue these actions until the clock reading is as small as you wish.

(With a 0.0005" finger clock, any reading less than one graduation is acceptable to me. )

The more often yo do it, the easier it becomes., As already said, Practice Makes Perfect..

Howard

Double post. Apologies

Howard

Edited By Howard Lewis on 21/10/2022 11:22:29

This is the exact method I use. I’m no machinist, but can often get things centred to within half a thou in one go, mostly two though.

With two chuck keys, it’s a doddle, and with my NOGA dti stand with fine adjustment *at the base*, I actually find the process quite therapeutic (the base mounted fine adjuster makes zeroing the dti laughably easy because you don’t actually touch it or the arm, therefore there’s no spring back).

This is the exact method I use. I’m no machinist, but can often get things centred to within half a thou in one go, mostly two though.

With two chuck keys, it’s a doddle, and with my NOGA dti stand with fine adjustment *at the base*, I actually find the process quite therapeutic (the base mounted fine adjuster makes zeroing the dti laughably easy because you don’t actually touch it or the arm, therefore there’s no spring back).

Dear All,

I predominantly use the four-jaw independent as it is more flexible as I can chuck round, hex, square and rectangular. I used to take ages to dial the work in but with practice I can now do it very quickly. I do quite a bit of work using square stock.

I also use the Hopper method but with a deviation which I will eliminate in future. What I was doing was finding the jaw with the lowest point on the dial, holding it at the 9 o'clock position, setting zero, rotating 180, taking the reading from the dial gauge, setting zero to half of the reading, release the back jaw just the right amount, tighten the front jaw one thou too much (ie less than zero) and then tighten the back jaw to bring back to zero. I would then correct the other pair of jaws but would inevitably have to rest zero at some point in the process.

Hopper's method is superior because it determines the correct 'zero' immediately and should be even quicker. I can't wait to try it!

John

Just when I get good doing it that other way..................

Yes, you immediately get the target zero position, so it doesn’t matter where the jaws are when you adjust them. In theory you can nail it in two chuck positions every time. Very satisfying when you do it.

Interesting to read the preferrence split between one or two chuck keys. FWIW Vic, I found the best thing I ever did was make a spare chuck key. With a really poor short term memory using one key was painfully slow for me. Did I just turn the chuck 90 or 180? Did the workpice need to go toward or from me? Which way did I need the clock to turn? Plus, with one key you can only travel a few thou at a time within the range of snug to tight on the jaws.

With two keys in opposing horizontal jaws, I find it's so easy to traverse the workpiece until the clock zero setting (set 1/2 way between max eccentricity) is achieved, then rotate to the other jaw pair and repeat. One more chuck rotation using one key to tighten only, and that trims out the last 1/2 thou TIR.

Somewhere on the internet, I have seen the suggestion of making two identical chuck keys in brass to twiddle one clockwise and the other anticlockwise, to move the work between opposite jaws until clock gauge shows zero error. Repeat with the other two jaws. Final tighten with a proper chuck key, watching the gauge needle. This is similar to Alan Qurashi's method. The two small keys were of course, a square at one end and the other end knurled for finger grip. I made them and find them more efficient than struggling with one proper key shifting from one socket hole to the next. Another chuck setting idea that I have seen and used, is to mark any two adjacent jaws, red paint or black marker pen and once work is set up, don't move those jaws again. Only release the job with the other two jaws and use same jaws to clamp the second, identical job and so on, effectively using the marked jaws like a jig. Why not use a plunger type gauge in the toolpost and fit an "elephants foot" attachment, so exact centre line achieved quickly every time.

HTH

Edited By DMB on 22/10/2022 22:31:12

Edited By DMB on 22/10/2022 22:32:19

Because exact centreline does not matter (within reason!) . Dial indicator could be mounted say 100 thou below the centre line on say a 1" diameter job and will still read 0-0 when there is no runout. And when it reads one thou of runout, the actual runout will be so close to one thou as to be irrelevant. Set it on centre by eyeball and it will usually be much closer than 100 thou and will work just fine.

I use a plunger dial indicator permanently attached to a piece of 3/8" square bar that is held in the toolpost. Set the dial indicator plunger to eyeball centre height once and it is always right. But other times I use the usual magnetic base and set plunger height by eye. Works just fine too. No need to make simple stuff hard.

On rectangular blocks, I use two indicators , one on each face. And two short keys to get at the jaws. Some machines have guarding , that prevents the use of two indicators.

Or you can scribe two diagonal lines corner to corner on the rectangular block then very carefully centre pop the intersection with a fine prick punch. Then set that to run true either by just sticking the tailstock centre in the pop mark or by placing a second dead centre between the pop mark and the tailstock centre and using a dial indicator on that. (You have to have a dead centre that was made with a centre hole in the tail end. Not all do.) It will get you within a few thou, allowing for line thickness and centre pop positioning etc.

Can anyone please point me to the MEW article mentioned by Hopper? Thanks, Chas

Hi Chas. How is the LMC going?

I don't have the mag copies to hand but a quick scan of the index PDF leads me to believe it would have been in Issue 239, Page 68. Author Pirttimak, Jouni, Title Quick Centering: An Easier Way