Uneven Part Diameter on Cylindrical Grinding Machine

Hi all,

I'm a new guy here. Nice to meet you all.

I have a question regarding cylindrical grinding machine.

When I need to cut a cylindrical part using the machine, I had difficulties on getting the cylindrical surface to be even thru out the length.

Although I already adjust the chuck jaw (3-jaw) to get the run out in between out limit which is 26 microns, but still the problem was not improving.

How can I improve on my uneven surface issue?

Does changing to 4-jaw chuck will help me on this?

Thanks for your advice..

Are you grinding all the way across ? or up to a shoulder ?

Post a picture or drawing of the part with some diameters that you have measured.

I'll assume since you are talking chucks that it is a Universal Cylindrical grinder

Work head (that you put chucks on) is likely ROTATABLE - you can set it at any angle

Do you KNOW it is set inline with table traverse?

With chucks, if you are trying to use tail stock for support any misalignment of work head will fight that process

To get no fight, put the chucks on the floor and use a dog to drive the work between centers

Here is a photo of a shaft about a Meter long, no chuck, between dead centers, and supported by Universal Back Rests.

It has no unevenness

The work head is the rotate part and the tailstock will act as the guide for my machining part.

You can have a look in my attached picture.
I need to grind the cylindrical area on my part up to the shoulder.

Does the back rest will help me in improving this?

This looks like a brand new machine.

Have you contacted the manufacturer to see what they suggest?

Maybe there is just some adjustment to the table to be done.

T_A_Z said:

You can have a look in my attached picture.

Click to expand...

Eek. Get someone who knows what they are doing to come over. Your whole setup is all wrong.

Take the chuck off, put the part between dead centers, drive it with a dog, dress the wheel, set your limits, set your tarry valve, take a skim cut, measure both ends, get rid of the taper, grind to size, take a spark-out pass.

If you are grinding to a shoulder (can't see from your dinky photo) then you need to dress the side of the wheel as well.

Don't stand in front of the wheel when you turn it on.

Get an experienced guy to come give you a day's worth of lessons.

28um or .001 is a very wide dimension for such a nice grinder, Should run .0002 TIR one end to the other easy.

If the head end is running.00025 out of round running it well grind .00025 more off one side and the leave .00025 on the other side... plus it will run .00025 above and below the wheel center... It will be round but not on the same center line as the tail. Head end not running true and the machine center point angles and part center angles may not fit well on a short part adding more possible error.

Part centers not lapped true can perhaps add error.

One handy method is to keep a 60* center grinding wheel .. throw on the wheel , fresh dress and tickle the head end center even one held in any chuck….. then you can run the head end live or dead and it should be true and true to tail height. Yes you could turn the wheel head angle to dress wheel for centers grinding but I like to avoid doing that… even if needing to fab-up a slide dresser.

Looks like your tail center is held in a drill chuck? And it looks like a thin diameter stub center…or is that a mandrel? The tail even if dead should be on center to the wheel center also.

*Head and tail center running dead is the best starting position then figure out the rest of possibles.

*Hard to tell from here your part or set-up

Also.. are you backing away then coming back in for one end and then the other? with that a tickle dress and mounting an indicator to bump off a stop might be good... making a .0005 go/no gauge may be needed, (.0007 tir may be Ok gauge)

A good lathe hand would know much of this (post #7) if not able to find a grinder hand.

Someone may say get a test bar.. but that can change with the part length different than the test bar..

Often better is to measure both part ends diameters.. then with a fresh dressed wheel and wheel parked come in to hand feel each end and read the dial to see the same or the numbers that make the correct part end differences that would make the table true (straight)..

Should be able to get a decent machine .0003 (or so) close with not making a spark.

It would help to have a better definition of uneven surface. I’m assuming the grind area is the very small diameter going up to a shoulder OR it could be the larger diameter (short seal surface maybe???).

I can see a reason for you having a 3 lobed surface (chuck not square to the mount surface OR headstock not parallel & concentric to the footstock). I can also see a reason you may have a diametric or concentric problem measuring 12:00 vs 90° (the part major mass is not concentric with the axis of rotation, making the whole thing out of balance).

You can check the chuck quickly with a GOOD bar chucked in it & testing near the chuck & then testing some distance away from the chuck (NO footstock for this test). You can also test the spindle parallel to the bed here using a surface gage with pins against the bed at 9:00 to the bar (don’t test for parallel with a mag base from the wheel housing)…

The out of balance problem can show up as 2 different diameters at 90° (lighter, slender part) OR out of concentric (stiff part but the wheel is loitering with the load going up and over speeding when the load is going down). Both are corrected by offsetting weight on one (if you’re lucky) or both ends (if you are not lucky).

Good luck
Matt

To quote myself

Work head (that you put chucks on) is likely ROTATABLE - you can set it at any angle

Do you KNOW it is set inline with table traverse?

Click to expand...

I would be interested in an answer to the question

You could turn the work head to grind the head stock center in place.. that way it could turn and still be dead on center. Yes dog drive off the same chick jaw. Yes it would be good as long as you did not tale it out or remove the chuck.

Yes then would have to again do what Johnodor said KNOW it is set inline with table traverse? and lined up with the tail.

Do what michiganbuck said or put it between centers. One rule my Dad told me and he has been grinding for 55 years is to never ever run a chuck onto a live center. You will never make a good part. So change your setup and I think your problems will go away. If you most run it that way you should only hold on to the shaft by just a little bit. Like 3mm or so. What brand of machine is that?

BTW would you send me some Panang Curry, Paratha and Murtabak. HAHA

Get rid of that live tailstock center and use a dead center, get rid of the chuck and drive the work with a dog. The only place to use a chuck on a grinder is without a tailstock.

johnoder said:

I'll assume since you are talking chucks that it is a Universal Cylindrical grinder

Work head (that you put chucks on) is likely ROTATABLE - you can set it at any angle

Do you KNOW it is set inline with table traverse?

Click to expand...

Hi Johnoder,

Thanks you for your sharing. Sorry I did not answer your question.
Basically I know the Headstock need to align with the table and the tailstock as well.
I had no problem with that.

Based on your sharing, I'm really interested to know detail on the back rest.
Does the back rest has any spring or damper to balance back the force from the wheel?
OR is it a rigid and static fixture?

Your guys are really helpful. Thanks a lot guys.

Donovan said:

Do what michiganbuck said or put it between centers. One rule my Dad told me and he has been grinding for 55 years is to never ever run a chuck onto a live center. You will never make a good part. So change your setup and I think your problems will go away. If you most run it that way you should only hold on to the shaft by just a little bit. Like 3mm or so. What brand of machine is that?

BTW would you send me some Panang Curry, Paratha and Murtabak. HAHA

Click to expand...

I will try every method that you guys suggest and see which is the best approach for my process.

Anyway, by the time I send you those food, it will not be edible. haha...
Come over Malaysia, we still have a lot of food to offer

TAZ.. let us know how you solve this problem.. You could do better explaining the part and how you hold and drive it..if a one-up or production part.. if on a mandrel or centers to the part..what is on the tail end.

4 jaw could be better but with grinding tolerances any part or center held in a chuck and not ground-in will have run out and wobble if run live or dead.

Buck.

Lots of fine adjust the way Brown & Sharpe designed their Universal Back Rests. Of course this was many years ago. They were developing these concepts and building these machines 120 years ago.

T_A_Z said:

Hi Johnoder,

Thanks you for your sharing. Sorry I did not answer your question.
Basically I know the Headstock need to align with the table and the tailstock as well.
I had no problem with that.

Based on your sharing, I'm really interested to know detail on the back rest.
Does the back rest has any spring or damper to balance back the force from the wheel?
OR is it a rigid and static fixture?

Your guys are really helpful. Thanks a lot guys.

Click to expand...