Thread: Runouts on machinery

My bung knee in preventing me from doing much in my shed. I can only stand for a few minutes before needing a rest so just for something to do I decided to measure some runouts on my machines.

Except for the spindle measurements the measurements are performed on the shank of a 10 mm milling cutter held in various chucks.

The drill press is from the budget end of the spectrum so I was not expecting much but it seems to OK at the spindle but the chucks leave a bit to be desired.
The original keyed chuck was replaced by MT3 keyless chuck #2 as soon as I bought the DP.

The 5" 3 jaw lathe chuck seems pretty bad to me, I had notice that there was a problem when using that chuck and I wonder if anything can be done about that - take it apart and clean it up?

Screen Shot 2018-07-29 at 7.36.54 pm.png

I realize this is a bit like opening up a dirty laundry hamper but I would be interested to know what others measure on their machines.

What exactly was the runout figure on the 4 jaw, just the body?

That 3 jaw is pretty bad, thats like 0.010" id try chucking some larger objects and also test the repeat-ability, then probaby relegate it to welding duty and buy a new one. Grinding the jaws is all well and good but it still wont repeat well.

Originally Posted by caskwarrior

What exactly was the runout figure on the 4 jaw, just the body?

That 3 jaw is pretty bad, thats like 0.010" id try chucking some larger objects and also test the repeat-ability, then probaby relegate it to welding duty and buy a new one. Grinding the jaws is all well and good but it still wont repeat well.

OK will do. The 3 jaw 5" has hard a hard life. This machine was a student machine and this chuck was the one that was left on the machine for student use.

Hi Bob,

The runout on that 5" Chuck is quite a lot ! I get around 3 thou on my original Myford narrow body 3 Jaw and around 5 to 8 thou on my new 5" 3 jaw depending upon size gripped. It seems better on larger diameters, which is what I bought it for. Using home brew soft jaws of course I can get precision collet levels of runout.

I think I've described my soft jaws on this forum at some time, but here is a picture anyway

Small_Gear-02.JPG Soft_Jaws-01.jpg 30-07-2017-006.jpg

The first two pictures show the first soft jaws I ever made and the last one some I made recently.

You could try rotating the 3 jaw chuck around on it's mountings - it may be that one hole combination is a little more 'concentric' than another.

Michael

Question, If I buy a new lathe chuck and backing plate, how do I ensure sufficiently accurate alignment between the two?

Mount the backing plate to the lathe, and turn a spigot to match the one on the chuck body.
The lathe should be the one on which the 3 jaw scroll chuck will be used, to maximise accuracy.
Independent 4 jaw chucks don't matter so much.

An experienced turner told me that when making the spigot, sneak up to the finished size.
The last cut should produce just cast iron dust rather than swarf.

Hopefully there is enough meat on the backing plate to allow you to face enough off it so that you can get a micrometer rather than a vernier on to the mounting boss to measure it easily.

If there is take a light cut over the OD of the backing plate, measure the OD, check to see what the register ID is and machine to suit the chuck register and then face the backing plate back until you have minimum clearance for the boss to clear the depth of the register for the chuck.

If the chuck mounting screws come in from the back of the chuck , Mark the PCD for the mounting holes before removing the backing plate from your spindle, you will have to then mark out the holes for mounting using dividers, centre pop and drill then mount chuck.

If you have a rotary table , dividing head and milling machine there is no need to mark the PCD.

If no dividing head or rotary table just use XY coordinates.

If chuck mounting is from the front just eithe use transferpunches to mark hole positions or just use a drill of appropriate size to mark the backing plate and then drill the tapping drill size.

If the backing plate does not give you enough material to give you a suitable land for measuring with a micrometer you will need to use verniers , not the best option but doable.

Hi Bob,

You like measuring things. Jaws not only have a correct order they can also have correct slot. Now if thats the case they should be numbered, but you could try the other 2 options and see if that improves things.
I've read that runout can be effected by which socket is used to tighten the chuck.
Never checked either, I'd hope it doesn't make that much difference but wont take you to long to check.

Originally Posted by Stustoys

Hi Bob,

You like measuring things. Jaws not only have a correct order they can also have correct slot. Now if thats the case they should be numbered, but you could try the other 2 options and see if that improves things.

The slots and jaws are numbered but I guess its worth a try.

I've read that runout can be effected by which socket is used to tighten the chuck.
Never checked either, I'd hope it doesn't make that much difference but wont take you to long to check.

Tried that but it makes less than 0.01mm difference.

Bob,

My green lathe came with a 5" Burnerd 3 jaw and an unused, still in the box, light pattern Burnerd 6" 4 jaw. The latter is my chuck of choice if I'm trying to hold something with a reasonable degree of accuracy. The 5" isn't accurate and I use a TOS in its place which I bought new from Fiora's. The Burnerd does see occasional use because it has a larger bore than the Czech. None of my 3 jaw chucks are particularly accurate. Fiddling, re-positioning and retightening sometimes achieves an acceptable amount of runout for the job at hand. Sometimes it proves to be an exercise in frustration. I also have a 80mm Burnerd Griptru 3 jaw whose jaw adjustment makes adjustment of a 4 jaw chuck seem easy in comparison.

As far as spindle runout goes, the green Hercus ARL measures about 0.0003" TIR with a DTI running in spindle bore. That is the same TIR as Timken state as the maximum for the class C precision bearings that are installed in the lathe. Not bad for a lathe made in 1969. The 13's vertical spindle shows nary a flicker of movement on a tenth indicator and while I have never bothered to measure it, I imagine the horizontal spindle probably shows less. In contrast, both Waldowns would rival paint stirrers for accuracy. Horses for courses.

Hope the knee is improving.

BT

Originally Posted by Stustoys

...Jaws not only have a correct order they can also have correct slot. Now if that's the case they should be numbered, but you could try the other 2 options and see if that improves things.

Originally Posted by BobL

The slots and jaws are numbered but I guess its worth a try.

Having once mixed jaws on a chuck, I can say that the difference is many times greater than the improvement you are chasing (it would be roughly a 1/3 of the pitch of the scroll)

Michael

Originally Posted by Anorak Bob

Bob,

My green lathe came with a 5" Burnerd 3 jaw and an unused, still in the box, light pattern Burnerd 6" 4 jaw. The latter is my chuck of choice if I'm trying to hold something with a reasonable degree of accuracy.

This. I have the same chuck on my Chipmaster. If I need to hold something dead nuts true I always use this chuck. In fact I reserve it strictly for jobs like this so it stays perfect.

If the 3 jaw is consistently out on pretty much its full gripping range then hard-turning the jaws might fix it. The other 'solution' is to turn say 1mm off the register, open the screw holes about the same and tap it into alignment with the screws just loosened, then re-tighten the screws. It is now an adjust-true chuck of the 'poor man' variety.

Personally I'd rather set up my 4-jaw. I have 3 of the 5" P-B 3 jaw chucks and all of them are buggered as far as I'm concerned.

PDW

Interesting to hear the views on the 3 jaws. I do use my 4 jaw for precision work but as a blue apron wearer that has not happened often up until the last couple of years.

Hope the knee is improving.

Unfortunately it's gone backwards in the last 2 days.
Tried to go down to the shed yesterday to muck around with the 3jaw but couldn't stand for more than a couple of minutes.
Seeing the doc again tomorrow about the knee and other things.

When I bought my chinko lathe (over 10 grand cost) I checked the 3 jaw chuck, 007" run out, I pulled it off and cleaned the mountings and tested it again, 007".
I pretty well only use it for hex bar and I prefer the 4 jaw anyway.
One thing to remember when checking spindle runout is that a taper has 2 ends, if the back end is out it will also produce run out in whatever is sticking out the front.
So I guess that really the best way to check a spindle is with a good alignment bar.

cheers, shed