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hwingo
02-27-2009, 11:50 AM
Hi Guys,

Though we've touched on this in a different thread, and following along with Torker's post, Back To Basics ..... 4-jaw Chuck, I would like to share a problem I've recently encountered.

I hope you guys have a solution to this problem but I would also like to how WHY this is occurring.

I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?

When I finally get my steady rest installed and the dead center removed, should I be able to correct the .008" run out using the steady rest?

Harold

dp
02-27-2009, 12:01 PM
I wonder what would be revealed by placing the 12" bar on knife edges as used for balancing grinding wheels. It may have relaxed asymmetrically since being turned.

BillH
02-27-2009, 12:15 PM
Hi Guys,

Though we've touched on this in a different thread, and following along with Torker's post, Back To Basics ..... 4-jaw Chuck, I would like to share a problem I've recently encountered.

I hope you guys have a solution to this problem but I would also like to how WHY this is occurring.

I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?

When I finally get my steady rest installed and the dead center removed, should I be able to correct the .008" run out using the steady rest?

Harold
Hwingo, reading your past posts, you seam to get very upset when everything is not perfect. You expect a new milling machine to be delivered and ready to roll and be perfect in every way. You expect there to be no assembly required, and you expect things to work perfectly.
What you must realize is that this is simply not how the world works. With your lathe, it was not made perfectly at the factory, the workbench it sits upon is not perfectly flat nor level, and your dead centers are not perfectly centered. Your tailstock is not perfectly aligned to the center line, the ram on the tail stock will not be within .001 as you move the ram in and out on ANY of the axises.
Your 4 jaw chuck is not perfect either. Sure maybe you can dial out any radial play, that does not mean the mounting surface of the spindle and chuck are perfectly set in plane. You can dial it in perfectly at the chuck, but 12" out it can be off by .010. The lathe bed itself probably has some twist in it and you need to level the bed with a precision level.
A good machinist is not some one who knows how to do all the operations, a good machinist knows how to get the accuracies out of his machine tools given the imperfections he has to deal with.
What I think you need is a reality check and to realize how things really are. I don't suggest you start using a mic or dial test indicator on everything or you will have a stroke.

TGTool
02-27-2009, 12:30 PM
Hi Guys,

Though we've touched on this in a different thread, and following along with Torker's post, Back To Basics ..... 4-jaw Chuck, I would like to share a problem I've recently encountered.

I hope you guys have a solution to this problem but I would also like to how WHY this is occurring.

I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?

When I finally get my steady rest installed and the dead center removed, should I be able to correct the .008" run out using the steady rest?

Harold

I think it means there was a chip in one of the center holes, either when it was originally turned or when it was remounted. If turned originally between centers and of equal diameter at both ends, it will stay that way between any set of centers or the fourjaw and tailstock center as you have it mounted now.

If you inspect the tailstock center now and are sure there's no chip or burr there now, you can re-establish the center with a steady rest the way John
Stevenson illustrates repairing Bridgeport motor shafts.

oldtiffie
02-27-2009, 12:36 PM
Hi Guys,

Though we've touched on this in a different thread, and following along with Torker's post, Back To Basics ..... 4-jaw Chuck, I would like to share a problem I've recently encountered.

I hope you guys have a solution to this problem but I would also like to how WHY this is occurring.

I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?

When I finally get my steady rest installed and the dead center removed, should I be able to correct the .008" run out using the steady rest?

Harold

Harold.

As you turned the part between centres the outside diameter will be concentric with the centre-drilled holes in each end - so the job should be OK.

Part of the problem may be with your 4-jaw chuck - even though it is within the manufacturers specifications.

It is quite possible that the chuck, while holding the job "spot on" at the adjacent to the chuck had a pretty good/long grip on the job if it is well into the chuck jaws if the jaws are causing the job axis to be "off line" and describing a conical shape when it is turning.

The chuck will easily make the tail-stock quill move in a circular motion - driven by the centre in the quill, and the centre driven by the job.

Have a look at these specs and you will see that the off-set out from the chuck jaws is allowed:
http://i200.photobucket.com/albums/aa294/oldtiffie/3-jaw_chuck_specs1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/3-jaw_chuck_specs2.jpg

You can get the same effect if the chuck mounting has a problem (negligible most times) as it may cause the chuck to "throw".

I suggest that you grip the part with a lot less length and put shims (copper - or anything soft) between the job and the jaws and use your steady rest as we described in a previous post.

I suggest that you read this post by Forrest Addy as well as the rest of the thread as Forrest and others explain it all very well:

http://bbs.homeshopmachinist.net/showpost.php?p=423804&postcount=33

http://bbs.homeshopmachinist.net/showthread.php?t=31931

Evan
02-27-2009, 12:39 PM
I'm not going to venture any guesses without knowing more about the actual circumstances.

What was the material being turned and in what state was it to start with?

How do you know that you didn't turn in a taper? Did you check the piece? Have tried swapping it end for end? Does the runout appear as a gradually reducing value as you approach the chuck? Does it show an even circular pattern as the piece is rotated slowly by hand? How much runout does it exhibit without the center? Can you change that appreciably by bumping the piece with your hand?

DR
02-27-2009, 12:42 PM
Your chuck could be off. Just because it dialed in with zero runout close to the chuck doesn't mean the jaws are true, parallel, to your lathe bed.

This is not a good or accurate way to verify tailstock alignment.

aboard_epsilon
02-27-2009, 01:07 PM
Hi Guys,

Though we've touched on this in a different thread, and following along with Torker's post, Back To Basics ..... 4-jaw Chuck, I would like to share a problem I've recently encountered.

I hope you guys have a solution to this problem but I would also like to how WHY this is occurring.

I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?

When I finally get my steady rest installed and the dead center removed, should I be able to correct the .008" run out using the steady rest?

Harold

it's simply this :-

Youve just found out why, that to do the most accurate work ..people turn between centres....even when, they have the finest lathes with the finest chucks .

all the best.markj

oldtiffie
02-27-2009, 01:22 PM
Harold.

You are on a steep learning curve as well all are or have been to varying degrees at different times, but you are doing very well.

A 4-jaw chuck with just enough grip to drive a part with the other end on the tail-stock centre or held in a fixed steady-rest (explained in an earlier thread) will get you there.

As said, "between centres" while the ideal is not always the optimal method, not is it always practical.

If I recall correctly, you are going to drill and bore some pretty deep holes from each end in which case the steady rest will be needed.

I hope you have read some of the recent threads and posts on the value of "soft jaws" on a 3-jawed chuck.

I highly commend one of those chucks - which have "2 -piece" jaws (the "top half" is removable and is replaced with a "soft" (aluminium, brass, mild steel) "bolt-on" jaw - and a couple of sets of the "bolt-on" soft jaws" as well.

You will find life so much better and faster - and rewarding too.

cuslog
02-27-2009, 01:27 PM
This may or may not be relavent, it also may or may not be correct, but I'll throw it out anyway.
When using my 4-jaw, (especially if using much projection out of the chuck) I found that I could dial it in perfectly at the chuck but still show out of round a few inches out from the chuck (worse as you get farther away). What I've been doing is clamping it "gently", dial it in at the chuck, move to the tailstock end, "tap it in" then go back to the chuck end. Sometimes I have to go back and forth 2 or 3 times before I get both ends running true. Kind of "sneaking up on it".
Not sure if this is correct but it has been working for me.
My amateur "take on it" is that the chuck jaws just aren't perfect and the workpiece gets gripped ever so slightly "off" and the farther out from the chuck you measure, the more apparent it becomes.

S_J_H
02-27-2009, 02:33 PM
I've turned a 12" long piece between centers having no taper. Now the stock is round. Chucking the piece in a new 4-jaw and dialing in the piece to zero at the chuck (using .0005" indicator), I've determined the tail stock end has at least .008" runout .... with dead center in tail stock!

What in the world is going on?
Why did you remount the piece with a 4 jaw and tail stock center instead of between centers the way it was originally turned?
Anyhow that's the nature of the game. You'll need to check and adjust your setup every step of the way.
If you must use the 4 jaw now, then adjust it true at the chuck and then you'll need to "tap" it true at the far end.
Since the tail stock is probably not located at the exact same spot on the bed and torqued exactly the same to the bed, and the ram not at the same extension, there is no way the tail stock center will now be dead on.
Just tightening the tail stock down to the bed with differing torques will effect the position.

Steve

lane
02-27-2009, 07:43 PM
Both cuslog and SJH had the right answer .Any time you chuck something in a 3 are4 jaw chuck you must indicate at 2 Two places . near the chuck and out at the end of the part . tap the end around till true and adjust chuck jaws as needed at chuck end . you may move back and forth 3 are4 times before get it straight and running true.

hwingo
02-27-2009, 09:24 PM
Hi Guys,

There seems to be a theme with many of the post referencing the work being secured by "too much chuck-jaw". Enclosed is an image of how much is in the jaws. I have a feeling that I may have too much secured by the jaws. Also, Oldtiffie and others have mentioned placing copper or aluminum between the work and jaws. As you can see, I did place thin strips of aluminum between the jaws and work. I used metal from an aluminum soft drink can. Perhaps it's too thin.

Oldtiffie, the learning curve for me is steep .... but I am trying to learn. With that having been said, thank you for your words of encouragement; it's up-lifting and much appreciated. I am always trying to improve accuracy and the only way I will learn is to ask questions of those having been there before me.

To answer one of the questions, the reason I took the work from between centers is to drill a deep hole through the center of the work. The only way I know to hold the work is to secure it in the chuck.

I was hoping that by turning the piece between centers I would reduce axial run-out. Obviously there are other demons with which I must contend.

Evan, the only way I was able to determine that the work did not have a taper was to measure both ends after turning between centers and to run my indicator from one end to the other before removing the work from between centers.

The run-out which I am experiencing must be the direct result of the way I set up for drilling and this seems to be an inherent problem that nearly everyone faces. The next thing is to break out the rubber mallet and give the work several gentle taps. Nothing ventured .... nothing gained. If this brings things more into line, I will set up the steady rest as was discussed in a different thread. This should help.

Maybe in time I can acquire a chuck with soft jaws as was suggested.

Addendum: Just went to the shop, screwed in the dead center a wee bit more and now I am down to approximately .002". Once the steady rest is in place I just may be able to keep things straight when I begin drilling my hole.

Harold
http://i234.photobucket.com/albums/ee38/hwingo_2007/PaddingJaws.jpg

oldtiffie
02-27-2009, 09:48 PM
Good reply and a very good pic Harold.

Grip about a third of that length - keep using the aluminium packing/protective strips too as that's fine.

Nothing is lost - the situation is easy to recover and get back on track - if it needs it.

Set up the fixed steady - up near the chuck as in a previous post - while the job is "trued up" - slide the steady to the tail-stock - past the end of the job. Release the job in the chuck, slide it forward by 2/3 and re-set it up with your indicator first at the chuck end and then at he tail-stock end ("tap" the job with a short thick/large-ish bit of bronze - use it as a combined "dead hammer" and "dolly" as it doesn't "bounce" and with care, doesn't mark either. Put a bit of aluminium where you are going to hit as that will help too).

Now put the steady on the job - both ends of the job are now "right" and "true-ed up".

Now you can use your tail-stock quill to start drilling as required. I'd suggest boring each drilled hole say 1" or so deep to suit the next drill in the sequence as it will counter any inadvertent "wander-off".

Never mind some of the "barracking" from the side-lines if its not helpful.

Just take it easy and "hasten slowly".

Best of luck.

Carld
02-27-2009, 09:52 PM
Harold, if you turned the shaft between centers and the center holes were clean and the centers were clean then the shaft should be concentric with the drilled centers.

Are you saying the shaft has .008" runout without the tailstock supporting the end of the shaft or with the tailstock supporting the end of the shaft. If you chuck up the shaft and "0" it at the chuck and then check it at the far end without any support it will almost always have runout. If you want to do it that way you need a steady rest and know how to set it up.

I can tell you that if you try to drill the end of the shaft without support the hole will not be centered even with the center drilled spot there. The shaft will flop around and the drill will wander. You need a steady rest OR chuck the shaft with only a few inches sticking out and indicate it in at the chuck and at the end until it is "0" to your satisfaction.

Your best results will be with a steady rest.

hwingo
02-27-2009, 10:23 PM
Hi Carld,

What I was saying .... or meant to say .... is, I had .008" run out at the tail stock end with the dead center snuggly fitting the center hole (or at least I thought it was snug). Without the dead center in the center hole I had about .018" of run out. Some of this has changed because when I "firmed up" the dead center (screwed it in a wee bit more) my run out is now only .002" thus I had no need for "the hammer". It would appear that the center was not securely placed in the center hole since a significant correction has occurred.

I figured that if I didn't get things as true to center as possible that my hole would be badly off and for that reason I wanted to get the work "smack on" if possible.

Thanks for replying Carld. How's everything in Kentucky? Mom said she was hit hard with ice (my home town Dawson Springs, Ky.)

Harold

BillH
02-27-2009, 10:38 PM
Hi Carld,

What I was saying .... or meant to say .... is, I had .008" run out at the tail stock end with the dead center snuggly fitting the center hole (or at least I thought it was snug). Without the dead center in the center hole I had about .018" of run out. Some of this has changed because when I "firmed up" the dead center (screwed it in a wee bit more) my run out is now only .002" thus I had no need for "the hammer". It would appear that the center was not securely placed in the center hole since a significant correction has occurred.

I figured that if I didn't get things as true to center as possible that my hole would be badly off and for that reason I wanted to get the work "smack on" if possible.

Thanks for replying Carld. How's everything in Kentucky? Mom said she was hit hard with ice (my home town Dawson Springs, Ky.)

Harold

To put a perspective on things, .002 is half the thickness of a human hair.

doctor demo
02-28-2009, 02:38 AM
Harold, I have read Your post and the replies and I don't think anybody mentioned the possibility that the headstock could be out of alignment.

If You chuck up a test bar that is known to be straight and round, and indicate it true at the chuck and the free end or as close as possible, then without turning on the lathe, mount the indicator on the tool post and on center run the carrage from one end to the other. If You have indicator reading changes the headstock needs to be re-aligned. The longer and stiffer the test bar the more accurately the alignment can be checked and dealt with.
But as mentioned previously the lathe should be leveled first.
I hope this makes sense to You, as it is not easy to describe.

Steve

dan s
02-28-2009, 02:56 AM
Harold

Have you checked to make sure your tailstock ram is parallel to the ways both vertically and horizontally? If it not parallel, your run out will depend on how far the ram sticks out of the casting.

Carld
02-28-2009, 09:53 AM
Harold, the storm in western central Ky was bad. The ice damaged and destroyed a lot of trees and power lines. It was a lot of work restoring power there.

Back to machining and the .002" runout your seeing could be from the dead center when you turned the shaft between centers if you used a dead center in the tailstock to turn the work. The center has to be left loose enough to keep from gauling the center hole so the center may no longer be concentric. It would be wise at this point to buy a good live center for future work and contrary to some opinions they last a long time and do accurate work.

If you have a steady rest you can true up the center to concentric by using the tailstock to hold the shaft and adjust the fingers of the steady rest on the work. The shaft will be slightly off center when you remove the tailstock but that's no problem. Now grind a cutter so it will fit into the center hole and cut the 60 deg taper and clear the back side. Set the compound at 30 deg, put the cutter in the tool post and using the compound, feed the cutter into the center hole to true up the center. I have done it that way for years repairing the centers in the end of shafts that have been beat up or damaged. I have cutters ground to rework several sizes of center holes. If you need a picture I can do that.

Now your ready to drill the hole and tap it. I start with a center drill that has an OD as big or slightly bigger than the drill for the tap. That way the drill has a better chance of staying in the center of the work as you drill the hole with the tailstock chuck.

If you don't have a steady rest you need one for sure. If you make long shafts or do repair work to long shafts steady rests are indespensable. You can sometimes just chuck in close to the chuck and support the end coming out of the head stock but with just 12" long that would be hard to get centered inside the spindle.

Get a steady rest.

hwingo
02-28-2009, 11:01 AM
Doctor demo, Dan S, and Carld,

Thanks for your suggestions. I've come very close to getting things in order due in great part to constructive assistance and beneficial suggestions offered in this thread. Those having offered constructive assistance, i.e. alternate ways of achieving remedies to various problems, have been a great help.

The majority of my problem was the direct result of my lack of knowledge when performing setup. I believe that my machine is capable of doing precision work (by my definition) and it was simply a matter of calling on the more informed to help me "get on track".

I recognize no fault with aspiring to be as precise as possible. One desire is to learn the limitations of my equipment; the other is to learn the limitations of my abilities. Together, I will have learned more. Yielding to mediocrity is not an option. It's my nature to learn and excel at my endeavors.

A BIG THANKS to those offering remedies and support.

Harold

Carld
02-28-2009, 12:45 PM
Harold, always strive for the best you can do but not perfection. To do less than best is to deprive yourself of a learning experience. Your limits may not always be in the machine, it may be in you so don't dismiss the machine as incapable but think of ways to make it work for you. It is said that perfection is only found in God and not in man.

A good machinist can make good parts on a bad machine. A bad machinist can't make parts on a good machine. Don't fall into the latter catagory if you can help it.

Thought and creativity are your friends and use them all you can.