# Rd14x40 Bed Twist



## jjtgrinder (Nov 13, 2015)

Continued from "Map Errors on Older Lathe".

The RD14X40 has a monster of a stiff bed.  Very deep and well bolstered with large cross members.

After some careful comparison with a good precision level (Mitutoyo .0006/12") I have some twist in my
lathe bed.  I have not quantified the difference at this point.  I am getting a appreciable amount of taper
with the diameter increasing as the distance from the chuck increases (like .005 in 1.5 ").  When i put the
level under the chuck(same place each time) and level the lathe across the bed, then move the level to the
tail end, the back side of the bed at the tailstock end is off the scale out of level high.  According to good solid
information (and logic) , this can contribute to the tapering problem.  After taking the twist out, I will look
at other factors such as spindle alignment (head nod , ect.).

I have "bedded" the lathe to the concrete floor.  I am now making some "clamps" to hold the feet in place
when I need to pull down on a lathe foot-pad.  The lathe is so stiff that if you shim up on the head-stock
backside feet, the whole back side including the tailstock end will lift.  I plan to adjust this very slowly to
achieve level.  When I get one completed I will post a photo and report success or failure.


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## hermetic (Nov 13, 2015)

I am watching with interest! Good luck with it! If you need me, shout up.
Phil


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## Ulma Doctor (Nov 15, 2015)

i wish you the best of luck in straightening the twist.


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## jjtgrinder (Nov 19, 2015)

Here's the arrangement to clamp the lathe down. Not a great drawing. Ask questions if you need to.
	

		
			
		

		
	





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## jjtgrinder (Nov 19, 2015)

I welded a large 5/8 nut on top of the hole in the "foot".  In retrospect, I should have made some "thick washers" and threaded the hole for the 5/8 bolt.  I am now having to make some "caps" that the bolt will pass thru to sit over the nut and take the force of the clamp.  The head of the nut is not very wide to take any clamping force.  The caps are a "slice" off of a 1 1/2" pipe (schd 40) with a washer tack welded to the top.  The clamp is a piece of 3/8"X3"x3" angle iron with a notch to slip under the bolt head and press down on the foot of the lathe.  This will allow me to "jack up" the lathe foot and lock it down.

See next post - I abandoned this approach.


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## jjtgrinder (Dec 18, 2015)

This is the new arrangement.  I decided to cut off the old nuts that were welded on top of the lathe feet.  I then made some "jacking Nuts" (JN) with side tabs which are positioned under the lathe feet.  The tabs come up beside the feet to prevent the nut from twisting.  The feet holes were 5/8' some had to be enlarged slightly.  The JN nut is a 1/2" x 2"x 2" mild steel bored
.578 max minor diameter and tapped 5/8 x 18 tpi to yeild a class 2A thread.  The "Gold" jacking bolt (5/8" x 18 tpi grade 8) passes through the lathe foot and threads into the JN. ( Always start these by hand with oil on the bolt.)  The hold down clamp is a piece of 3" x 3/8" angle iron notched and drilled.  The hold down bolt for the clamp is a 5/8' x 11 tpi grade 5 bolt welded to the iron plate.  There are washers for spacing.  I can shim under the clamp rear foot as needed.  I am ready to level the bead head-stock end under the chuck and then make fine adjustments for twist removal at the tail stock end.


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## jjtgrinder (Dec 22, 2015)

I am reporting back.  This arrangement did enable me to "counter-act" the twist and level the lathe ways near the chuck end and the tailstock end. Get in same plane.
I still have a some taper going on with the "two collar" test-bar test.  I suspect there is some "head-nod" or other miss-alignment between the spindle and the ways. 
I am going to do some testing and see what shows up.


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## 4GSR (Dec 22, 2015)

John,

What measurements are you getting on the two collar test?  Are you doing this with the tailstock or without the tailstock engaged with your test bar?

Ken


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## jjtgrinder (Dec 29, 2015)

I mis-placed the numbers, with no tailstock. I will run some new numbers in the near future put them in a spreadsheet and post them.  Had a LOT of family activity over the Christmas holidays, no time for serious work.


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## hermetic (Dec 30, 2015)

We are your family now son, get back in yon workshop!!


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## jjtgrinder (Dec 31, 2015)

hermetic said:


> We are your family now son, get back in yon workshop!!


YES SIR! 

I was able to level the bed very well with the arrangement for bedding the lathe. 

The headstock on my lathe is out of alignment by approximately .012" over a 10" length in the horizontal plane. The error indicates the headstock chuck is pointing "to the back" (away from the lathe operator.) 
The indications were arrived at using the Rollie Dad's method after leveling the bed with a Mitutoyo precision level.  If I make a test cut on a bar, the taper is larger the further you are from the chuck as if the tailstock is set back to purposely cut a taper ( test cut did not use the tailstock for support).

Looking at the lathe manual and the lathe, there are no adjustments to "swivel" the headstock.   I hate to think about taking the head off and doing any scraping.  I do not see any way to adjust the spindle within the headstock. There is no measurable "slack" in the spindle bearings. Runs quiet. 
Checked for the easy obvious problems.  
Does anyone here have experience correcting this by shimming or some other method?


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## jjtgrinder (Dec 31, 2015)

Looking at the data, I am out very little in the Vertical , this would be head "nod".
I am looking at a remarkable amount of Horizontal error which substantiates the
taper I was getting on test cuts.


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## jjtgrinder (Dec 31, 2015)

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## 4GSR (Dec 31, 2015)

I saw your thread on the Rockwell Lathe group a while ago.  I follow along with your measurements, but I doubt very seriously that the headstock is out of alignment.  Look for tail-tale signs of the bolts holding the headstock in place of being tampered with.  If none, I would look at another method of checking headstock alignment that does not involve using your carriage.  I know you did the vee block check on the vee ways a while back and showed very little change.  I think you may been getting false readings by that method. The vee block could have been resting on part of the vees that were not worn, giving a false measurement.  Your measurements shown in the table tell me that your bed has heavy wear.  But before me saying that, you need to rig up some kind of fixture that will ride on portions of the bed not subject to wear such as the areas between the ways and the sides of the bed.  With that fixture, use a test bar that has a known accuracy to it and mount to the spindle by either the internal spindle taper or a 4-jaw chuck and indicated trued up end to end.  With this arrangement, check headstock alignment.  Using the carriage is not an accurate method of checking the alignment of the headstock.  It only tells you that you have wear in the bed.
Ken


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## jjtgrinder (Dec 31, 2015)

Point well taken, Thank You Ken,  I will progress to a fixture that does not involve the carriage.


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## hermetic (Dec 31, 2015)

.012" over 10" is a lot! Trouble is I have no knowledge of Rockwells at all, so I am going to lurk and watch what comes up. Some headstocks that are "loose" or removabe from the bed, ie theyre bolted to the bed, use eccentrics or adjusting screws to give slight adjusment of alignment, if your lathe has ben moved a lot and lifted on slings it is possible the headstock has moved  but as I said, I have no knowdge of Rockwells, so I can do no more than say, good luck!
hil


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## jjtgrinder (Dec 31, 2015)

My lathe headstock is bolted on with no adjustment for alignment.  I'm not sure that there's a head alignment problem but the data thus far correlates to it.  I am going to apply some additional tests you and others have suggested.


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## The Liberal Arts Garage (Dec 31, 2015)

jjtgrinder said:


> Looking at the data, I am out very little in the Vertical , this would be head "nod".
> I am looking at a remarkable amount of Horizontal error which substantiates the
> taper I was getting on test cuts.


      Don't believe in my expertise in a case this subtle, but I would consider the
possibility that this is an old problem, and foolish re-bedding of the tail stock
has moved the" center" in a tiny orbital error.  I'm not  sure how to measure this ,
but it should exclude the tail stock.    Patience, care, and Good Luck......BLJHB.


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## jjtgrinder (Jan 1, 2016)

Today I chucked up a steel disk 1" thick and 9" in diameter in the 4-jaw chuck.  
I rough faced it  then took a light cut with a new sharp insert at a very slow cross feed rate.  I had a very good smooth resulting finish. 

I took my machinist precision straightedge and placed it across the face of the disk. The face surface geometry was neither convex or concave to any remarkable degree.
(I used a small light behind the ruler).  This was a very encouraging test.


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## hermetic (Jan 2, 2016)

if your headstock is misalinged and actually points away from the operator by 012" over 10" this test will not show up that error as convex or concave on the work. did you notice that you had to take more cuts off the outside edge of the disc in order to clean it up all the way to the centre? that would tend to confirm your 012" misalignment theory.
phil


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## jjtgrinder (Jan 2, 2016)

Hermetic,
Yes, I did notice the outer edge clean up before the center.  If I re-chuck the piece, would I get that affect again?

Again, thank you for your help.
You and Ken have been very helpful.


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## jjtgrinder (Jan 2, 2016)

By the way, I purchased some material to do a true two collar test.  Will do that today.


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## hermetic (Jan 2, 2016)

Yes, you pobably would. if you think about the spindle pointing towards the rear of the bed, away from the operator, that is why you have to take more from the outer edge before the centre cleans up You have to sit down and carefully visualise the error, and it someimes is not easy! So far you seem to have confirmed that the error is the headstock alignment. Have you tried loosening the headstock bolts, giving the headstock a good wriggle about with a bar in the chuck, then tighten them down again. You should not neet to scrape anything, unless the lathe came out of the factory with this fault. It is "JUST" possible that the headstock has been used to lift the lathe at some time, and has shifted, and/or got swarf under it, or  rust started by cutting fluid, just possible, but unlikely! If it were mine I would now be considering an engine crane to lift the headstock and inspect under it, just to be sure, then put it back on and see if it is any different. Also check the underside of the headstock! Have you checked the holding down bolts on the headstock for tightness?
Phil


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## jjtgrinder (Jan 2, 2016)

The two collar test with collars 5" apart.






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## jjtgrinder (Jan 2, 2016)

Hermetic,  I re-chucked and got the same affect as you described.  I do see your point concerning the outer edge. 
I have never touched the HS bolts.  It's possible the previous owner did lift by the HS.  I know they moved the machine three times in its history before I bought it.  I agree, you suggestions to try and reseat the HS would be prudent.


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## wa5cab (Jan 3, 2016)

Hermetic,

No, think about it.  If you could rotate the headstock 45 deg. CCW so that it was pointed out over the back of the lathe, and did a facing cut enough times that you were cutting all the way to the center, you would end up with a 90 deg. cone.  But unfortunately, the fact that a facing cut made a flat disk is not absolute proof that the headstock is parallel with the longitudinal axis.  If you were to set the compound around 45 deg. toward the headstock, and face using only the compound, you would get a flat cut.


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## hermetic (Jan 3, 2016)

which is in effect what he has got, but because the error is only 012" in 10" the cone would be measured in the difference between the front and back faces of the 12" disc, which would not be parralell


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## hermetic (Jan 3, 2016)

it made a disc with two faces that will not be parralell, I was not saying the fact that the disc was flat was proof of anything.  if you face from the edge of the work to the centre, and remove enough metal to clean up, you will have a face perpendicular to the bed, less any errors in the cross slide, regardless of whether it is parralell with the chuck face or not. you getting me?


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## jjtgrinder (Jan 3, 2016)

wa5cab said:


> Hermetic,
> 
> "  If you were to set the compound around 45 deg. toward the headstock, and face using only the compound, you would get a flat cut."
> 
> ...


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## wa5cab (Jan 3, 2016)

Yep.  But the assumption is always that the spindle axis is parallel to the bed axis, and that the cross feed axis is always perpendicular to both.  I started off by saying that IF the headstock spindle was not parallel to the bed axis by an extreme amount and you faced a part (using the cross feed) you would get an obvious cone.  And that if you then set the compound off of perpendicular around to the same number of degrees as the headstock axis error (remember that on the Atlas machines, the "0" on the compound base scale is at the point where the compound is at right angles to the NORMAL or normally assumed, anyway, spindle axis), you would turn the cone back into a flat.  I was just using an extreme error case (45 degree spindle axis error) to show that a facing cut is flat all the way across IFF (if and only if) the cutter path is perpendicular to the spindle axis.  So if one _assumes _that the cross feed dovetail is perpendicular to the bed axis (not yet proven), and you take a facing cut on a part as he did (from the near edge to the center of course), lay a straight edge across the end of the part, and find that it is perfectly flat, then that would prove that the spindle axis was parallel to the bed axis.  What it actually proves, of course, is that the spindle axis is perpendicular to the cross feed axis.


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## astjp2 (Jan 4, 2016)

You may want to do some simple checks of you lathe bed, I made this alignment checking tool to tell me how much wear and twist there is.  Indicator position is critical for getting a good reading and eliminating any vibration with a light oil helps keep the .0001 indicator from bouncing around.  My old bed has as much as .008 wear at the head stock, the new one is about .0006.  When I checked the parallelism of the dovetail, it was less than .0005 after I got the TDI to stop vibrating when I slid the alignment tool along the edge of the ways.  I also have a few ground flat plates (carbide inserts) that I used to put under the ball, it makes for a true flat surface to ride along.  There are many ways to get this measured.  Now interpreting what it is telling me can be a challenge.  Good luck.  Tim


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## jjtgrinder (Jan 4, 2016)

WA5CAB,  
Thank You for the explanation.  That helps a lot to understand the intent of your information.  I think this 

Hermetic,  
Thank You as well, your explanations are a great help to me.  I can understand what is going on. 
I very much like the idea of putting my efforts into "re-seating" the headstock.  I have made a lifting arm that is attached to the headstock cabinet(front corner).  I use that arm to change the chucks and lift anything very heavy on/off the lathe.  I can position this arm over the head and add a supplemental brace to the end of the arm.  With a chain-fall I can then easily pickup the headstock.  

ASTJP2,
Thank you for the photos, I like the setup.  If re-seating the head doesn't improve things, I will most likely head in that direction.
If you were to make another tool, what improvments would you incorporate?


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## hermetic (Jan 4, 2016)

Sorry, got the wrong term, I meant cross slide, not compound! My postulation is that if the headstock is angled slightly towards the rear of the lathe, and you take a cut using the cross slide only, you will produce a flat surface on the end of the bar (eventually, when the end all cleans up) but it will be slightly elliptical, and not perpendicular to the length of the bar. I think maybe less Port and more thinking is required at my end! Having said that, the sun has set behind the yardarm, so it must be time for the remains of the Christmas booze to be finished. Happy new year to all of you!
Phil


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## jjtgrinder (Jan 4, 2016)

Hermetic,  Makes perfect sense to me.

Happy New Year to all of you.


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## astjp2 (Jan 4, 2016)

I need more sizes of snugs and a way to keep everything organized better.  There is a large and small C, I started with the large but it was too big for the inverted V on my lathe so I made another.  They are both gray cast iron.  I have something like 4 each .0005 and 2 each .0001 TDI's but they all attach differently so I need to have a way to attach each one and still be useable.  I would use the tool with a true alignment tool in the spindle to check the alignment of the headstock, yours is a Short #5 MT, contact Brian (millermachineandfabrication@gmail.com) or you can do the Ebay thing and hope for the best  http://www.ebay.com/itm/5MT-Lathe-A...271297?hash=item280a1b93c1:g:XrcAAOSwZd1Vdrvz

This is an accurate way to check your alignment, turning cuts gets you close at one point on your bed, what happens if you move 10" to the right?  The alignment tool and a test bar is what you need if you want it real true.  If your headstock is off, you need to scrape the bottom to get it aligned.  After I am done with my carriage, crossfeed and compound scraping, and 2 new gibs,  I am taking on the head alignment and scraping it in also.  A mind numbing task but worth it in the end.  Tim


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## wa5cab (Jan 5, 2016)

Hermetic,

No.  Given:   That the cross slide moves exactly perpendicular to the longitudinal axis of the lathe (bed) and that the spindle axis is twisted slightly toward the rear of the machine and therefore not parallel to the lathe axis and not perpendicular to the cross slide path.  

To produce an eliptical end on a workpiece mounted in or to the spindle, you would have to have a motor mounted on the cross slide turning something like a face mill and do the cut with the spindle locked.  If you turn the spindle and use a normal cutter in the tool post, you will cut a convex cone.  Twist the headstock so that the spindle is pointed slightly toward the front of the bed and you will cut a concave cone.


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## jjtgrinder (Jan 5, 2016)

Wa5cab,  Thank you for the input, in your opinion , what should I do next?


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## wa5cab (Jan 5, 2016)

I'm not sure.  Do you have or can you borrow a 10x10 or 12x12 surface plate and do you have a 4-jaw chuck large enough to hold it?  If you do, you could start by confirming whether the spindle axis is perpendicular to the cross slide axis at the headstock.


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## jjtgrinder (Jan 5, 2016)

I have a small 6"X 18" surface plate.  I don't think the 4jaw would chuck it, it's a 12" chuck.


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## astjp2 (Jan 5, 2016)

wa5cab said:


> I'm not sure.  Do you have or can you borrow a 10x10 or 12x12 surface plate and do you have a 4-jaw chuck large enough to hold it?  If you do, you could start by confirming whether the spindle axis is perpendicular to the cross slide axis at the headstock.



You are making the assumption that the wear in the carriage has not changed the crossfeed causing it to be off from perpendicular to the bed.  I am still trying to figure out how to measure exact perpendicular between the inverted V and the cross feed dovetails.  I know the crossfeed angle is fixed but if there is much wear (my saddle was rocking on the bed due to wear) it will need to be scraped to realign it.  I know its in Connleys book but I cant seem to find the procedure in checking the alignment.  There is also the alignment of the headstock to the bed, both vertical and horizontal.  You need to have both in alignment or what you have is a parallelogram where the crossfeed cuts perpendicular to the headstock but its not perpendicular to the bed.  Tim


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## jjtgrinder (Jan 5, 2016)

Astjp2, 
Thank You for the supportive posts.  All of you have been helpful.  I like the discussion.
I see from your pictures that you also have a RD lathe.  My saddle does not rock any that I can easily detect.  I did take it off and clean the apron gearbox and the saddle.  There was wear on the saddle surfaces but not so much.  Did you happen to see the measurements I posted on the other thread (under scraping forum)?  There was ,what I
feel like, very little wear.  Not enough wear to cause this rather large taper effect.  I most likely will get a test bar.  I know that the test bar will give a spindle reference.  If I use the carriage to measure against the test bar, I will get a combination error.  But, that will be interesting as a starting point.  I will also go to the effort of taking the head off and re-seating it based on what the test bar shows.    Then I will start digging into the Connley book.  I do not want to "live with" this kind of error.

My way measurements in this post thread:
http://www.hobby-machinist.com/threads/map-the-errors-on-a-older-lathe.39504/page-3

Thank You all.


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## hermetic (Jan 5, 2016)

wa5cab said:


> Hermetic,
> 
> No.  Given:   That the cross slide moves exactly perpendicular to the longitudinal axis of the lathe (bed) and that the spindle axis is twisted slightly toward the rear of the machine and therefore not parallel to the lathe axis and not perpendicular to the cross slide path.
> 
> To produce an eliptical end on a workpiece mounted in or to the spindle, you would have to have a motor mounted on the cross slide turning something like a face mill and do the cut with the spindle locked.  If you turn the spindle and use a normal cutter in the tool post, you will cut a convex cone.  Twist the headstock so that the spindle is pointed slightly toward the front of the bed and you will cut a concave cone.




Damn, yer right! that has spun my head completelyI am not back at my workshop yet, so no access to a lathe, I have been sitting here with an AA battery and a screwdriver trying to mock it up, and finally the penny dropped, thanks for persisting with me!!


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## jjtgrinder (Jan 5, 2016)

This is fun, hang in there guys!


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## wa5cab (Jan 6, 2016)

JJTGRINDER,

No, a 6x18 wouldn't work.  Even if you had some way to hold it, you couldn't rotate the spindle.  And actually, the same is true of the 12x12 and probably of the 10x10 as the diagonal dimension is 14.14".  It might just barely clear the inner edges of the bed but it might not.  So probably a 9x9 would be safe.

Tim,

No, I was working up to proposing a method to determine whether or not the cross slide was perpendicular to the spindle.  Admittedly, if it isn't, the method wouldn't tell you where the problem was, but only that the two axes were not perpendicular.  At that point, the problem could still be headstock misalignment or bed wear.  Or some of both.


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## wa5cab (Jan 6, 2016)

hermetic,

That's OK.  I've done the same sort of thing.  In fact just did last night when I asked jjtgrinder whether or not he had a 10x10 or 12x12 surface plate and a 4-jaw large enough to mount either.  Obviously even if he did, he wouldn't be able to turn the spindle because the diagonal it too large.   

EDIT: And in my statement about cutting a concave cone, I should have added "until the cutter passes the center point of the workpiece".  Because shortly after that you will have a crash probably preceded by some gouging as the underside of the cutter begins to rub.


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## jjtgrinder (Jan 7, 2016)

Tim / 
I weren't so old and lazy, I would dive into the whole re-scrape project.  Maybe when I retire in the near future.  For now I am going to re-seat the head-stock and see what happens.


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## hermetic (Jan 8, 2016)

I think that is what I would do first as well, although I can't really see it being a problem, unless it has been slung from the headstock at some time, the bolts have been loose, and swarf or cutting fluid has got under it. I will say this though, when you strip a lathe, you find fine swarf in the damndest of places and wonder "How the devil did that get there"!
Phil


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