Tail Stock Too High?

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pdhntr

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Tailstock Too High?

Not sure what to do in this situation.

My tail stock measures out .005 high with the quill unlocked, .0075 locked. I am thinking of taking the base and getting it milled down some.

Even using a floating reamer holder, I would like the axis to be a little closer, right?

Thanks for any help.

Jim
 
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how long has your lathe been in its current spot ??

maybe a bend in the frame that happened in moving...let it sit for a while...

just a maybe
 
mike in co said:
how long has your lathe been in its current spot ??

maybe a bend in the frame that happened in moving...let it sit for a while...

just a maybe
Click to expand...

Hi Mike,

I hope that isn't it. Its a new lathe, been leveled since August. Checked the level again and it looks good.

Checked the height with a 20 inch bar, a 12 inch bar and swept a tailstock center a couple of inches from the spindle center, and captured a thin feeler gauge with both points. All measurements were close, and the feeler gauge leaned over to the left. With a magnifying glass you can see the tailstock center is just a little high when compared to the spindle center.

Thanks though.

Jim
 
Jim

New lathes come with the tailstock a few thousands high, usualy .002-3 .
They wear in over time and use. After a lot of use they are usual a few thousand low.

Hal
 
Cheechako said:
May be too obvious, but, shim the headstock?

Ray
Click to expand...

Dang............I knew there was something I was forgetting.

I got so focused on getting the tailstock the correct height, I forgot to look at the headstock to correct the problem.

I did take a passing glance at the headstock mounting some time ago and saw the mounting studs on the chuck side and that looked pretty straight forward for shimming. But it looked like I would have to get inside somehow for any other mounts. Sooooo.........I promptly forgot about it.

Thanks Ray. I will take a much closer look tonight and see what I can do.

Sorry guys for waisting your time on such a simple question.

Jim
 
shimming the headstock will not solve the problem as well as most think. To start out with, it's time to level the machine, and then do a proper alignment. You'll need at least one .0005" level 10" or longer (two are prefered), and a good piece of ground strait steel tubing a minimum of twelve inches long (18" would be great) that's about two inches in diameter. At least one .0005' wand type dial indicator will also be needed.

1. remove the chuck and all tooling, and very lightly stone the way and top of the compound

2. set the level lengthways on the compound. If you feel it having anylind of a rocking motion as if the top of the compound is not flat you got a problem. If it is, I recommend putting a little bit of modeling clay under the level to get it level. Donot move the level!

3. now go around the base of the lathe and check all the leveling pads to see if they are tight. Also check all the lag bolts to see if they are tight. If not put a little tension on them till they are

4. crank the apron in as close the the spindle nose as you can, and the cross slide in to center. Readjust the level to where it reads zero. Now crank it towards the tail stock; note any movment in the buble, and adjust the leveling screws or lag bolts to bring that area back to zero. Go back and reset the level to zero at the starting point. Check all the pads under the headstock for loose pads or lag bolts. Check everything again as before if you made an adjustment at the headstock (I'd go ahead and pull the tail stock while you at it to give you much more travel with the carriage).

5. if all checks well, then turn the level 90 degrees so it in line with the cross slide travel. Start at the spindle nose and adjust everything again to get it all level. If you make any adjustments, you'll have to repeat step 4 again. The idea is to get the bed strait.

6. reinstall the chuck, and insert somekind of a strait gauge bar in the chuck (you may have to indicate it in to where it's true with the spindle line.. Take the dial indicator, and sweep the top of the gauge bar; making note of the error you see. If it less than .00075" your OK. Now do exactly the samething, but 90 degrees to the top 9 oclock is best). These tests will show the spindle centerline to the ways.

7. now reinstall the tailstock (assuming the spindle line is strait) and indicate a dead center in the tail stock. You may have to make an adjustment in the tail stock alignment side to side as this is normal. Also before reinstally the tailstock, I'd recommend stoning the bottom lightly to remove any bumps and hickeys. Now if you are showing error with the quill in the locked position (less than .0025" is normal); you got a problem.
(a.) Extend the quill out as far as it will go, and yet be clamped solid. Indicate the quill at the 12 and 9 oclock position with everything clamped
down solidly. If it's not strait with the ways it may need some work (less than .001" is what it should be). Forget machining the surfaces if it
.0075" or less! You end up making it worse.
(b.) assuming that the that he quill is above center and not parallel with the way centerline; it's time to find the problem. First split the tail stock
where it slides for adjustment. Put the bottom part back on the lathe bed, and clamp it down. Now run the indicator over the maiting surface
to see if that part is parallel. Mark the error you see. Next you'll need a surface plate to check the other half against the quill centerline.
(c.) if you see error in the base, it's best to scrape it back to being parallel (you can't get there in the average machine setup without an elaborite
fixture). I usually just scrape them right off the machine ways. The top half will not be so easy! If it's parallel, then it's easy. If not, your in
for a little bit of work. The real problem here is finding something to rub the surfaces with ( a very small surface plate)

sometimes you can fudge a little bit with the leveling screws to take a couple thousandths out here and there added together, but you really can't do much about the factory headstock alignment without messing everything else up. If the headstock is solid and square, then don't touch it. Email me if you need help
gary
 
Are you positive there's no chips, foreign material under the tailstock, or between the top and bottom parts of the tailstock? It takes only a speck to cause the center to be up .005.

Indicate your center, take it out and turn it a little and re indicate it, you'll find your center is never going to indicate up perfect, It's the nature of the beast, Tailstocks were never meant to do high precision work.

You may, with enough fiddling, get your center to indicate up to your liking, but the minute you move it all bets are off, as to whether it will ever repeat at that point.

If you are indicating your tailstock, and then moving it to use it, then you have no idea where it really is.

It's similar to a vice on a mill, or a chuck on a lathe,, once you remove the part, you will never get it back perfectly true again.
 
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I have rechecked the level, but I don't know if I am using a level that will work for a lathe. I am new to this aspect. I will have to research more on lathe levels.

I have also checked several times if there is any swarf between the sliding and mating surfaces of the tailstock.

The way I came to the .005 height is I put a 20" bar between centers and did a fine cut on the tailstock end. I indicated the height (and zeroed) with a .0005 dial with a mag base on the carriage. I removed the bar. Without touching anything but the carriage wheel, I returned the carriage with the indicator to the headstock. I then put the bar back in the centers, but the turned area is at the headstock and indicated .005 low. I rotated the bar to check how far off the centers were and they were .001 runout so I think the centers are running pretty straight.

I then did the same thing again, only this time used a 12" bar and got the same .005 height on the tailstock. I then swept the center in the tailstock (with it moved close to the headstock) and got a max of .006.

Moving the tailstock back and forth, removing the centers, putting on and removing the faceplate, taking the tailstock off and checking for swarf etc. I was amazed at the repeatability of all of my measurements.

Once again, with centers moved up to each other, the tailstock is high. Its high at 20" inches, 12 inches and center points. If the level is off, I would think there would be more variation in these measurements. However, I will do some more checking into the proper level.

Thanks so much for all the help.

Jim
 
pdhntr said:
Not sure what to do in this situation.

My tail stock measures out .005 high with the quill unlocked, .0075 locked. I am thinking of taking the base and getting it milled down some.

Even using a floating reamer holder, I would like the axis to be a little closer, right?

Thanks for any help.

Jim
Click to expand...



If really bothersome or critical to a particular machining job (most high tailstocks are not), an easy fix is an adjustable center, several manufactures provide them and there have been some examples in the past of members making their own, see the following example (first I came across in a search);

http://www.sherline.com/1201pg.htm
 
Don said:
If really bothersome or critical to a particular machining job (most high tailstocks are not), an easy fix is an adjustable center, several manufactures provide them and there have been some examples in the past of members making their own, see the following example (first I came across in a search);

http://www.sherline.com/1201pg.htm
Click to expand...

Hi Don,

The high tailstock will not cause any problems for most of what I do.

My only concern is pushing a reamer. I wanted the force on the reamer to be as axial as possible, but if I use a floating reamer holder, is .005 high going to cause a problem??

If not, then I won't worry about it for now.

Thanks.

Jim
 
100% of all tailstocks are shipped about .002" to .003" above center, and most cross slides are shipped between .0015" and .002" above the centerline. But .005" is too high! Leveling a machine as a rule will get in the range of being close, but the end user is expected to do an alignment after leveling the frameworks. If the frame is not lagged down to the floor you may never get it strait (Monarch is about the only lathe I know of that can simply be leveled and then tweeked without lag screws).

Try this:
take a piece of 1" drill rod, and insert it in the chuck. Indicate it in as close as possible (couple tenths would be about right). Center drill it with a small center drill (about 3/16" diameter, and Thompson rod would be much better). Mark the high point on the drill rod and of course the amount it's out. Do the other end exactly the sameway. Put the drill rod between centers, and indicate it from one end to the other; top and one side. Move the tail stock to where it reads zero on the side. Now check your reading on top. If the .005" is still there you can fudge it a little bit by cranking down each leveling screw for about .001" on the indicator ( have the carriage about eight inches away from the center in the spindle). By moving each leveling screw to where it raises the headstock .001" you should gain .004" (don't worry about the true level of the frame). Once you do this, leave the machine alone for about a day, and reindicate the rod (it will settle a little bit). If your showing .0025" at the spindle; adjust the two leveling screws that are closest to the spindle nose about .003", and then put enout pressure on the two at the rear of the headstock to raise it about .0005" on each screw for a total of .001". Reason I said to do this off of two centers is that there's often a problem with the chuck jaws not be exactly strait unless they are cut in with a spider. The high point notations are for calculating out the error in the indicating process. Also make note of the fact that 98% of all indicators made cannot be turned upside down, and then compair the reading with one at the 12 oclock position. Beg borrow or steal an Interapid .0005" indicator for a final check. (I'd be glad to loan you one by the way)
gary
 
Jim, I have been in the Machine Shop Business for a long time, and in my opinion you are worrying about something that is of no consequense.

We have lathes that go all the way from a little 10" Monarch EE to a big NR Leblond that will swing 52 inches and work over 40 feet between centers, and every thing in between. I doubt the tailstock is dead perfect on any of them, including the brand new Kingston 26x80 we just put into service.


If nothing weird is happenning, just don't worry about it. ...........jackie
 
jackie schmidt said:
Jim, I have been in the Machine Shop Business for a long time, and in my opinion you are worrying about something that is of no consequense.

We have lathes that go all the way from a little 10" Monarch EE to a big NR Leblond that will swing 52 inches and work over 40 feet between centers, and every thing in between. I doubt the tailstock is dead perfect on any of them, including the brand new Kingston 26x80 we just put into service.


If nothing weird is happenning, just don't worry about it. ...........jackie
Click to expand...


I dont want to sound like a parrot just repeating what Jackie said, but I agree with his viewpoint...........Don
 
I wouldn't use a floating reamer holder. Make yourself a pusher and made correctly it won't matter how the tailstock indicates.
Butch
 
+1 on Listen to Butch

Not only listen to Butch but be careful about shimming headstock.
If the ways are parallel to the axis of the spindle, shimming the headstock can cause that to go away unless of course you shim front and rear of headstock. Even then you need a way to check that you keep headstock axis parallel to the ways.

Tailstock is normally a little high to allow for the weight of workpiece that will cause the extended quill to droop a little.

Jim
 
Tailstock is normally a little high to allow for the weight of workpiece that will cause the extended quill to droop a little.

Jim

The best answer yet. We were taught this 37 years ago as apprentic machinists
 
Butch Lambert said:
I wouldn't use a floating reamer holder. Make yourself a pusher and made correctly it won't matter how the tailstock indicates.
Butch
Click to expand...

OK Butch, I am confused again. What the heck is a "pusher"?

I thought a floating reamer holder was a type of pusher.

Jim
 
Go to the PT&G website. I believe they have a picture of the Bald Eagle type of pusher. Mine is very similar to it. Send me an email and I'll see if I have a photo of mine and I'll email it to you.
Butch
 
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