# Cross slide not square to spindle



## David Pollard (Nov 25, 2017)

Hi Guys,
I have a 10” Atlas lathe will a milling attachment.
I had a fly cutter in the spindle, when taking a standard flat cut across a piece of metal in the vice I noticed the back rotation of the tool was taking a significant trailing cut. The tool was set at about a 3” diameter.  From this I deduce that the spindle isn’t at 90 degrees to the crosslide.
Is this adjustable at all?
I have not removed the head from the bed since I have owned it but who knows what has happened in the past.

I suppose I could take a facing cut across a workpiece in the chuck then run a dial indicator across the full face and see what it reads.

Or should I just ignore it?
David


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## ddickey (Nov 25, 2017)

Mount an indicator on or near your chuck and check your cross slide any deviation from zero. I believe this will tell you if your cross slide is square.
If it is square run it along your vise of your milling attachment.
My cross slide isn't square and there is no adjustment as far as I can tell. I thought I also read somewhere that lathes are supposed to cut slightly concave across a face.


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## British Steel (Nov 25, 2017)

HI David, and welcome!

It's normal for a cross-slide to be minutely out of square, we have manufacturing tolerances to thank for that...

A lathe should be constructed to make a slightly concave facing cut, so that faced parts won't rock on a central raised area, the degree of concavity is down to the quality of the lathe - a Toolroom lathe will produce less concavity (at least from new) as more attention (read time, wages) will be put into accuracy - people often refer to Schlesinger's limits for Engine Vs Toolroom lathes.

Correcting alignment isn't a trivial task, I'd recommend reading The Books first - "Machine Tool Reconditioning and Applications of Hand Scraping" by Edward F Connelly and "Testing Machine Tools" by Dr. Georg Schlesinger, possibly also "Foundations of Mechanical Accuracy" by Wayne R Moore to get an idea of what you'd be letting yourself in for... You may find them in the "files" section of one of the machinist web sites, or may have to exercise your GoogleNinja skills...

Dave H. (the other one)


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## magicniner (Nov 25, 2017)

Cross slides on older lathes were commonly set up to give a very small amount of "concavity" on facing cuts, I have seen this explained as a way to ensure close mating of faced parts which might otherwise be affected by anything less than a perfect surface finish, it kind of makes sense but I have not found any conclusive manufacturer documentation. 
I learned very early to use small cutters when milling on my Myford to avoid the problem David describes, with the addition of a vertical milling attachment for the lathe the problem went away and the vertical attachment convinced me to put together a separate vertical milling machine, 
Regards, 
 - Nick


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## British Steel (Nov 25, 2017)

In Schesinger's book, starting about page 56 (in my copy...) are tables of accuracies, not a bad point to start from.

Dave H. (the other one)


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## TeaBagofHorror (Nov 25, 2017)

There are younger data in the German DIN 8605 and 8606.
If someone needs them - just send a message.
Written in German language, of course, but nevertheless I think it is understandable.
They are from 1976, but still current status.


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## benmychree (Nov 25, 2017)

With an Atlas lathe, there is not much to be done about the problem due to the flat ways.  On a lathe with vee ways, the carriage can be re scraped to correct the problem, not so for flat ways.  If you tried to attack the problem by re aligning the headstock, the lathe would not turn or bore straight.


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## mikey (Nov 25, 2017)

Seems to me that you need to determine if you really have a problem. The milling attachment may not have been precisely aligned so how a fly cutter cuts is not really a good indicator of an issue. You would be better off facing a work piece mounted in the spindle and seeing if the cut is really off and by how much. Then you can decide if you have something to worry about.


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## magicniner (Nov 25, 2017)

mikey said:


> Seems to me that you need to determine if you really have a problem. The milling attachment may not have been precisely aligned so how a fly cutter cuts is not really a good indicator of an issue.



It really is. 
When you surface a face with a cutter the orientation of the work or attachment is irrelevant for (X Axis) cuts involving cross slide movement on a lathe, on a mill the OP's reported problem would indicate "Out of Tram" but you cannot tram a lathe X axis (cross slide) as the orientation of the head stock and cross slide are fixed, 
Regards, 
Nick


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## wa5cab (Nov 25, 2017)

benmychree said:


> With an Atlas lathe, there is not much to be done about the problem due to the flat ways.  On a lathe with vee ways, the carriage can be re scraped to correct the problem, not so for flat ways.  If you tried to attack the problem by re aligning the headstock, the lathe would not turn or bore straight.



Actually, that isn't correct.  Although I doubt that anyone would go to the trouble to do it, it would probably be less trouble to do an Atlas carriage than to do one of the single-vee types.  For one thing, you only need to scrape one surface instead of two.  And for another, the included angle that you would be working up against is 90 degrees instead of I assume 60.  The reason only one surface would need to be done is that the gib screws would take care of skewing the carriage around to match the front.  So there would be no need to do anything to the carriage gib.


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## RJSakowski (Nov 25, 2017)

My 6" Atlas has flat ways and the surface that controls the perpendicularity of the cross slide to the spindle axis is at the back side and above the apron, in contact with the front vertical surface of the ways.  It could be lapped or scraped to correct any non perpendicularity issue.  Before doing so, I would confirm that the ways aren't worn and creating the problem.  I would also check the carriage gibs and cross slide gibs for proper adjustment.

To measure perpendicularity, I make a skim cut on a flat plate and sweep the surface with a DTI.  This will provide a measurable indication of the amount of deviation.  I would do this at least at two points along the ways to check for wear in the ways.  If you get consistent values at the two points and you have a variation in your sweep readings, there is likely a wear issue with the carriage.


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## wa5cab (Nov 26, 2017)

Another way to measure the error is to take your facing cuts to the center until you are getting consistent metal removal from the outer edge all the way to the center.  Stop your final cut about 5/16" past center.  Lay the disk on a flat surface and use a straight edge and a feeler gauge to measure the error, if any.


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## MozamPete (Nov 26, 2017)

I had a similar problem (http://www.hobby-machinist.com/threads/cross-slide-facing-adjustment.44572/) and when I took the carriage off it became obvious that it had worn at the guiding surface and the cross slide was no longer at 90deg to the bed. I machined the carriage back to perpendicular and fixed the problem.
The test is to fix a parrallel across the chuck, indicate it and then turn the chuck 180deg and adjust the parallel till you get the the same reading without moving the crossslide. Then feed the crossslide in and see if the parallel is ... parallel to the crossslide travel.


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## David Pollard (Nov 26, 2017)

These all look like good ideas although I doubt I’ll be hand scraping anything unless it is really bad.
I can see what appears to be clamps that attach the head stock to the bed and I was wondering if there was some adjustment there.
It is probably more likely that the slides are worn.
When I first got the lathe the slides were so tight I could not move the cartridge or the cross slide to the full extent of their travel.
I cleaned out all dried goo, oiled it nicely and adjusted the gibs as tight as to allow travel along the full length of the slides.
There are now some spots that are a bit looser than others.
I didn’t think about how head alignment would also effect boring parallel.  I think that is actually not to bad.
So more testing required 
My current project will require facing a 5” diameter.  My material already has a flame cut hole about 1”.
So I won’t be able to test right down to the Center but I think I’ll get a good indication.
The parallel in the chuck also looks like a great test.  I might clamp one to a face plate and shim it as required.
It may be some weeks before I get “hobby” time to do these tests.  I’ll post back here with results.

Thanks for all suggestions 
David


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## chips&more (Nov 29, 2017)

I have now talked to four people in the industry and none of them say the cross is made/set-up to be minutely out of square. It should be 90°. If your/a lathe does not cut flat and square then it’s worn, made wrong or flexed or something. Maybe a manufacture(s) back decades ago used that practice. And then the saying has stuck to the wall and folks today say it like it’s done today…Dave


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## Asm109 (Nov 29, 2017)

Nothing is 90 degrees +- nothing. Its always +- something.
If the cross slide move toward the tailstock as it moves to the center, the part will not sit flat. It will tip and wobble.  Nobody wants that.
The opposite error will sit on the outer rim nice and stable. That is almost as good as a part that is truly flat and perfect from edge to center.
The lathe is designed to 
A) have really small tolerances.
B) tolerances are all on one side of 90 degrees.  That means the nominal design is NOT 90 degrees. 

Because of A the nominal design is REALLY close to 90 but it is NOT 90.


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## Silverbullet (Nov 29, 2017)

Wow lots of variables in this situation. Rigidity comes to mind for most. Swinging a fly cutter ,,,vibration central,,, lots to consider the ways adjustments table lockdown ,,with movements,, in any direction. One reason I hated using mine for milling it works buts sure a PITA,,,. I suspect with all things considered that these all are the reason.


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## ddickey (Nov 29, 2017)

Good video here about checking the cross slide and more.


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## 4ssss (Nov 29, 2017)

Ok, let me be the bearer of bad news, as every comment so far has dealt with trying to fix your problem.  For starters, your machine is old.  Maybe when it was designed,  the engineers thought they could do 2 things with the same machine, but it's not a milling machine, and certainly not built to run a 3" single point fly cutter that creates an interrupted cut,  whacking the front of the part being machined every revolution. (no matter how sharp that cutter is, or how fast it's turning.) To be honest, I wouldn't run a fly cutter in ANY machine,  unless the material I'm cutting is soft and even then at a minimal depth. Every revolution of that cutter against the front of the part is moving SOMETHING, and when the cutting tool goes over it, it springs back, hopefully to the original spot you clamped it, but in reality, the cutter is just doing an interrupted cut in reverse when you go over it. In other words, it goes in one way, and comes out another. Anything that moves on that LATHE, or any other machine  has slop, and no matter how much of it you take up with adjusting the  gibs and by splitting nuts, it will still have slop. That's why it's able to turn. You sound like your expecting accuracy and a microfinish, but in reality, it ain't gonna happen. That's why grinding was invented.


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## David Pollard (Nov 29, 2017)

Hi Everyone,
I'm in no way expecting miracles or a nice finish.  I know it isn't a milling machine and at this point I can't afford one nor do I have room for one.
I also only have single phase power out on the farm which limits me getting a nice mill, and that isn't going to change any time soon.
Having said that I'd say the step on the trailing cut is about .015" at a guess.  I haven't measured it and it is significant.
I only set the swing of the cutter to 3" so I could exaggerate the problem.  I could run up and down with and end mill and it would not be noticeable.

I know it's old and worn (like me) 
I'm just trying to get the best out of it. My best estimate is that it was built in the mid 1930's
What can I say.  It's a hobby 

I'll post again once I have taken some measurements.
David


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## David Pollard (Dec 4, 2017)

Update,
I took a .025” cut across my work piece and measured the step with a micrometer.
It was only about .003”.  It just felt like more when measuring with my fingernail 
I then took a .005” cut and there was no step at all.
After some head scratching I concluded the cross slide (and work piece) is moving away from the tool towards the latter part of the cut and therefore the front of the work piece is swinging inwards torwards the tool causing the trailing cut.

It actually doesn’t sound too bad (no clackity clack) and the finish is reasonable.

From this I conclude the problem is simply a worn cross slide.
For the accuracy I require for my small hobby jobs I’ll probably work with it.

Thanks for all your comments.
David


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## rzbill (Dec 4, 2017)

David,
I know in an earlier post you said that the ways had been cleaned and then the gibs tightened down.
One technique that might help for worn cross slide ways while milling:

I am assuming you have the gibs set loose enough that the power cross feed is useable.
If that is the case, you could consider tightening the gibs further and just turn the very snug lead screw by hand during milling operations.  The success of this is certainly dependant on the amount of 'saddle' shaped wear you have on the dovetail and of course your finished part expectations.  Its possible this could alleviate a .003" shift.

EDIT.  Please excuse.  I'm sittin' here at 0 dark thirty with coffee before heading off to work.  David, I'm curious if you have done any maintenance on the carriage to bed ways interface.  I ask because when I got my Atlas, while relatively clean, it was adjusted very loose.  For example, the carriage had factory shims under the way 'clamps' that hold the carriage to the ways on the bed. There was 0.006" of shim. More shim, the looser the fit.  I removed it all and checked the carriage fit. It was fine without the shims even though the bed ways measured dead on 0.375" with a micrometer. Not sure why the factory shims were there.  Adjusted the gib on the backside of the carriage too.  Nice and solid due to a bed with little wear.  Maybe yours is a similar situation?  Possibly the carriage is jumping around a bit if it has room to move on the bed ways?


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## Dinosaur Engineer (Dec 4, 2017)

chips&more said:


> I have now talked to four people in the industry and none of them say the cross is made/set-up to be minutely out of square. It should be 90°. If your/a lathe does not cut flat and square then it’s worn, made wrong or flexed or something. Maybe a manufacture(s) back decades ago used that practice. And then the saying has stuck to the wall and folks today say it like it’s done today…Dave



It's impossible to make the crosslide exactly 90deg ( +/- nothing !) to the spindle. there always has to be a tolerance . All quality lathes are designed and made to face concave. Your 4 friends need some education !


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## Bob Korves (Dec 4, 2017)

Dinosaur Engineer said:


> It's impossible to make the crosslide exactly 90deg ( +/- nothing !) to the spindle. there always has to be a tolerance . All quality lathes are designed and made to face concave. Your 4 friends need some education !


In "Machine Tool Reconditioning", Page 306, Figure 26.64, the tolerances for cross slide movement are 0 to .0005" for tool room lathes, 0 to .001" for 12" to 18" engine lathes, and also 0 to .001" for 20" to 36" lathes "(To face hollow or concave only on 12" diameter)".  I agree with you, Dinosaur Engineer, tolerances have to give pragmatic results, and Ed Connelly agrees as well.


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## David Pollard (Dec 5, 2017)

I have had the carriage off as mentioned previously when I got the machine I couldn't move along the entire length of the bed.
I think PO had tightened it up as much as he could while down at the head stock end.  The little bracket that holds the carriage slide handwheel gears in place had been smashed at some stage and was all "bodgied" up. I have since replaced that with a new one.  That may say something about how tight it was.

I have cleaned and set the gib so I get reasonable movement right along the bed.

I have had a look at the video posted above where the guy gets a dial indicator and a jimmy bar to measure the movement along each of the slides.
I was of course making my milling cuts with the cartridge locked but I had not clamped the gibs up tight.

Another thing to mention is parting off is nearly impossible for everything except thin walled stuff.
While doing this I can see a tiny bit of "oil movement" on the slides both on the cross and compound slide right in the joint where the two surfaces meet.  I have completed the milling job at hand so now any adjustments I make will simply be to improve things in general.

I do remember seeing a shim under the carriage clamps when I had it apart.  I'm 99% sure I put them all back.
I might just get onto the flat bed with a micrometer and see how worn they are.

I don't think anything is going to help much if I do actually have saddle shapped  dovetails on the cross slide.

Getting slightly off my own topic 
I bought a face plate for this machine a while back.  That is to say it is the right part for the machine but it has not been trued up on this machine.

One thing I'd like to do is true it up but now that we have cast doubt on my cross slide I'm reluctant to try it.
It is about 8" or 9" dia.  Just enough room to fit your hand between the bed and the face plate.
When I put a dial on the OD in runs out about .005 not that this reading really matters.
When i put a dial on the face it runs out about .003
For my hobby jobs this is going to be adequate so I might just leave well enough alone.
I'm only thinking of this as I said before.   I'd like to get it as good as it can be.

BTW I trimmed up the backing plate on the 3 Jaw chuck a while back and cleaned it right out.  That runs < .001 now which is great.

Thanks again for all your thoughts and comments.


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