# Play in cross feed and compound



## ARC-170 (Sep 23, 2020)

On my Atlas Craftsman 101.07403 I'm not able to accurately turn a diameter. When I get close to the final measurement, if I rely solely on the DRO I'm usually off by a few thousandths. I've been able to make a deeper or shallower cut by moving the cross feed in or out. I'm thinking this is not good!  Well, I noticed the cross feed has about 0.018" of movement and the compound has about 0.012" of movement. I've tightened everything down (I think), so I'm wondering if this is indicative of screw wear. 

Is there a way to lock the cross feed and compound in place? Maybe a mod I could do?

As a workaround, when I get close, I take measurements, then move the cutter so it just starts to cut, then look at the DRO and move in the required amount. I was able to turn a steel rod to within 0.001" of spec. However, that was more luck than skill; I stopped short to check and it turned out to be what I needed.

Any advice or solutions?


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## mickri (Sep 23, 2020)

All machines have some backlash.  No way to eliminate that.  There will also be spring which I believe doesn't show on a DRO.  But then I don't have a DRO so I don't know.  My lathe has 0.007 to 0.008 backlash on the compound and the cross slide.

I often have the same problem as you are having when turning to a diameter.   When I am turning I never use the compound and bring it as far back as I can to eliminate flex in the compound.  I line it up with the cross slide  Then snug the gibs down so I can't move the compound.   What I do after taking a cut is to back off the cross slide at least 40 to 50 thousands.  This ensures that when I move the cross slide back in for the next cut I have taken all of the backlash out of the cross slide.  I also do all of my measurements with a micrometer.  Never use a caliper when I need a really accurate measurement.  Even with this I rarely hit a diameter spot on.  If I can get within 0.001 I am happy.


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## mike44 (Sep 23, 2020)

Not familiar with an Atlas lathe.  Assuming the compound and cross feed are adjusted  properly , at least as far as you can then. The fix you did was proper. I have digital scales on the X axis and Z axis ( tail stock)  but not on the Y axis. I start by turning the cross feed til it moves . Then continue in the same direction , clockwise til the cutter touches the work. I then set the micrometer to 0.  This does not actually eliminate back lash but works around it. You did the same thing but with your DRO. I do not think the lead screw  has any thing to do with the back lash on the X axis. 
Possibly a worn lead screw on the cross feed would cause back lash but I doubt it. Not positive but I think the cross feed lead screw would not get enough wear , unlike the X axis lead screw. If there is an Atlas forum, you should be able to answers there.
mike


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## AGCB97 (Sep 23, 2020)

ARC-170 said:


> Is there a way to lock the cross feed and compound in place? Maybe a mod I could do?


If the gib screws are easy enough to get at you could replace one of them with a thumbscrew, even a DIY one. I've done that on my 100 year old Springfield.
Aaron


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## markba633csi (Sep 23, 2020)

Sounds like you need to re-adjust all the gib screws on your carriage, including the compound. It's a fiddly job and takes time, but the results are worth it.
You want to find the point where the parts are just tight enough but not too tight to prevent smooth sliding.  One or more of the gib strips may be worn and need to be replaced.
All lathes have backlash so you just take that into account when using the machine.
-Mark


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## JPMacG (Sep 23, 2020)

I lock the gib screws on the cross feed and compound prior to my final cut.   Also, I make practice cuts to see the actual cut versus the amount I move the cross feed (or compound).  This is particularly important for very light cuts.  For example, a change of .001 on the dial might make an actual cut of .002.  I think this is because of flex.   I can achieve .001 accuracy on diameters with some care, but it is not easy on these light machines.  If I need better than .001 I use a file.

Note that just the act of locking the gib screws can cause movement.  The whole process requires practice and patience.


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## craniac (Sep 23, 2020)

I have the same problem on my 1937 Atlas and have been able to get reasonably accurate diameters by following pretty much all the advise given above: tight gibs, replace a gib screw with something easy to tighten, use the cross slide not the compound for the most part. I would add that you can sometime get some additional backlash if the nuts on the cross-slide screw are loose at the dial. There is a thread on that somewhere that I read. Might try searching that.

This only thing I differ with in the above postings is the statement that youdon't see wear in the cross-slide lead screw. My lathe is quite old though, but you can see wear in the middle of the screw, and the nut, being softer, has considerable wear- even more that what you're seeing. This is a well documented problem with solutions being getting a replacement nut. They are available but not cheap around $40-$50.

I don't expect to work to tenths- though I sometimes get there by accident. It requires constant awareness of the backlash and being careful to back out each time. I also use a dial indicator and don't rely on the cross-slide dial, which I can barely see anyway.

You can do it.

Tim


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## Bi11Hudson (Sep 23, 2020)

Having learned to use a lathe BC (before computers), I don't have any use for an electronic gizmo DRO. Larger dials would serve the same purpose. Using trig on the compound helps as well. Mine stays at 29* most of the time. As much to keep the hand wheel out of the way as threading. That gives .866 feed, an odd size. Adjusting to 60*(M/L) gives 1/2 the feed. As the angle increases, the feed decreases. But it gets hard to work in your head.

The Atlas machines, including the Craftsman (mine is a 101.27440) have a rather aggressive longitudinal cut. It doesn't relate directly to your question, just something else to keep in mind.  However, with a finishing cut, you might consider a smoothing pass before moving the cutter. This in addition to the comments above about tightening the gibs. My machine has a lot of wear but I compensate for it by tightening the gibs for smooth work. And never depending on backward adjustments. I always allow for backlash on smooth jobs.

Not the proper video, it just happened to be in memory. But can lead to the proper one. . .




.


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## ARC-170 (Sep 24, 2020)

The gibs are new and adjusted a bit on the tighter side. Everything else is snug, like it's supposed to be. I just find it hard to believe there is no way to lock these down.
I thought of a solution as I was drifting off to sleep about adding a lock screw to the bank of gib screws. There's room on the lathe and the parts would fit in my mill vise so I could drill them properly. I found a YouTube video where they guy did the same thing. Anyone done that with these lathes, or see an issue if I do it? I'd like to keep the gib screws out of this, so that means a new hole. Thoughts?


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## jaek (Sep 24, 2020)

Stefan Gotteswinter had a very good video about how to cut accurate diameters in the presence of backlash:


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## Bi11Hudson (Sep 24, 2020)

Any machine will have some backlash. That  is a given. Mine is old and "loose"  meaning in this case around .030. I often see more on other's. The best I've ever seen is .003. The best suggestion is that when it's fairly low, compensate for it and go on about business.

Gibs: They should be tight and evenly adjusted. As in all should have the same snugness. They should be so tight but not so much as to give trouble moving the whatever by hand. Pushing by hand, it should not be so loose that it moves when you bump it. But you don't want it so tight that it takes a pry bar or "come along". Tight and snug are very personal concepts. What you consider snug, I might consider tight. And a real machinist might consider loose. My machine (Craftsman 12") has wear in the center of the gibs. They are adjusted so they are snug on each end. But things are too loose in the middle. I found some knobs that fit hex capscrews. No link, this was way back BC. I have three gib screws down the side of the cross slide. I removed the center one, replacing it with a cap screw and one of the knobs. When I adjust for a cut, the screw is loosened, the slide moved, then the screw tightened finger tight. Just how tight depends on how I feel that day.

Leadscrew/Nut: When the machine is(was) new(or freshly ground), there was little or no play in the nut. This is in part from the gibs. The tighter the gibs, the faster the nut wears. That's why the nut is a softer metal. It wears rather than the screw. Up front, unless you have replaced the nut yourself, assume it to be worn. It will need replacing someday. When is a matter that you must decide. I have a couple of "zero backlash" devices in my mind. But they are far too large for a machine slide. The best one was for a plasma torch "X-Y" table I built for a friend. At 5 inches high and 4 wide, it would be a little too big for a lathe, even a shipyard lathe. A double nut with a spring in the middle would work. But how strong a spring? Best bet is to adjust in only one direction. For an inward adjustment, back out 100 thou and take it back in only 098.

.


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## wa5cab (Sep 24, 2020)

ARC-170 said:


> The gibs are new and adjusted a bit on the tighter side. Everything else is snug, like it's supposed to be. I just find it hard to believe there is no way to lock these down.



What do you mean by "lock these down"?  The gib screws should already have lock nuts.


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## mickri (Sep 25, 2020)

I think that he means to have a screw of some sort to lock the compound and cross slide in place like you can lock the carriage in place.


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## wa5cab (Sep 25, 2020)

OK.  As I have written several times in the past, the simple solution is to replace one of the three or four gib screw/nut combos with a T-handle locking screw such as the Atlas 9-508 Gib Lock as found on the 500A Milling Attachment.  I did that on my 3996 more years ago than I like to think of.


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## mickri (Sep 25, 2020)

That's what I would do.  And I might do that.  Especially on the compound.  I only use the compound for threading and to cut short tapers.  The rest of the time I have it locked in place by tightening down the gibs.  I have even thought of removing the compound and making a tool post to fit in its place.


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## wa5cab (Sep 25, 2020)

There are two sources for backlash in the cross feed and compound feed on an Atlas lathe.  One is running clearance between the cross feed or compound feed screw and nut.  This is not adjustable and can never be zero as there must be some clearance or you would not be able to turn the crank & screw.  The other is cross feed or compound feed screw end float.  This is adjustable and by careful differential adjustment of the two nuts that retain either crank, can be reduced to about 0.001" to 0.003" before the crank begins to feel as though it were binding.  This adjustment should only be made while the cross feed nut is run completely off of the end of the cross feed screw.

Beyond that, you should from the beginning get into the habit of always approaching the setting for making a cutting or threading pass only in the direction to increase Depth Of Cut (DOC).  If you go too far, back up half a turn or more and start over.


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## ARC-170 (Sep 25, 2020)

Thanks to all. I think replacing a gib screw with a bolt or t-handle locking screw is the way to go. I just wasn't sure it would affect the gib adjustment, but from what you're all telling me, it will be just fine.

This is the Atlas 9-508 Gib Lock as found on the 500A Milling Attachment:


Maybe I'll make one.

Seems like a socket head bolt would work as well. I'd have to keep the Allen key handy, though. Maybe I could turn down the head of a hex bolt? Just musing aloud here. Let me know what's best.


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## mickri (Sep 25, 2020)

You might be able to find a thumb screw.  Looks like Grainger has them in all sizes.  https://www.grainger.com/category/fasteners/screws/thumb-screws.

If I was going to make one I would use a common machine screw and weld either a washer or short piece of steel rod to the head.


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## wa5cab (Sep 26, 2020)

If you use any common screw, you will still have to put a dog point on it.  And if you use a common screw, you will need to modify the head, or use a wrench to tighten it because otherwise you will not be able to apply enough torque to tighten it enough to properly lock the slide.  That is why the factory made the locking screw the way that they did.  And the only standard screw head that might be tall enough to drill for the solid pin or roll pin is the Fillister head.  If you try to cross-drill a socket head, which otherwise would probably be tall enough, you will probably break the drill tip of the bit when part of it breaks out into the socket.


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## Bi11Hudson (Sep 26, 2020)

It seems others have "smoothed" my comments for me. I had to leave in a hurry when something personal came up. 

I would suggest a way to fabricate a larger head screw if I may. A knurled knob, threaded in the center, will give the grip you need. LocTite and crimping will hold the knob. Crimping is easily done with a center punch and a 3 pound drilling hammer. A small setscrew would look nicer, even a pin through the edge of the thread. The concerns would be clearing the rounded top of the slide. And not so long as to foul the tail stock. The knob can be quite large so long as these points are considered. 

For what it's worth a socket head setscrew is not so hard it can't be cut. I have cut down several diametricly to use as socket wrenches. And making the rounded nose on the gib end, of course. Conceded, I was using carbide cutters at the time. Granted, most of my work is small, but a Nr8-32 setscrew does fits that description.

I avoid any specialty tools lying around. Things should be set up to do by hand whenever possible. In theory, all you should need at hand is the square headed wrench and the chuck wrenches. And whatever measuring tools are needed for the job at hand, of course. With several chucks at hand, even that gets busy. I have done the (Atlas) shaper and the (Atlas) horizontal mill the same way. The 7/16 clamp screws are now 3/8, same as the feed screws. The mill has two wrenches that fit every operational fastener. Maintenance is a different matter, but needs specialty tools there anyway. Set-up should be simple as possible.

.


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## big o (Sep 28, 2020)

ARC-170 said:


> On my Atlas Craftsman 101.07403 I'm not able to accurately turn a diameter. When I get close to the final measurement, if I rely solely on the DRO I'm usually off by a few thousandths. I've been able to make a deeper or shallower cut by moving the cross feed in or out. I'm thinking this is not good!  Well, I noticed the cross feed has about 0.018" of movement and the compound has about 0.012" of movement. I've tightened everything down (I think), so I'm wondering if this is indicative of screw wear.
> 
> Is there a way to lock the cross feed and compound in place? Maybe a mod I could do?
> 
> ...


     My Atlas 10100 MK 2.had the same problem, the backlash was in the cross-slide nut. My post is in Members Projects (Atlas cross-feed
     alignment play)  Hope this helps.

Any advice or solutions?
[/QUOTE]



Any advice or solutions?
[/QUOTE]


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## wa5cab (Sep 29, 2020)

All manual lathes have the same "problem".  That is why you learn to only set the cross slide or the compound slide from one direction.  If you go a little bit to deep for the cut that you want to make, you back up past the point where the slide starts moving again and try it again.  It is just the nature of the beast.


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## yendor (Sep 29, 2020)

Has anyone tried Clausing for this part.
It was also used in the Atlas Milling Attachments


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## wa5cab (Sep 29, 2020)

Last time that I checked, they still had it.  If you only buy the gib lock, the shipping cost will be most of your expense.  So if you need any other parts, now would be a good time to buy them!


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## ARC-170 (Oct 1, 2020)

I got a socket head cap screw and machined a dog point on it to the same dimensions as the existing screw (good thing I have a lathe!). Seems to work, but I have yet to machine anything since I did this. I was able to lock down the compound and the cross slide so there was no play, though.


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## mickri (Oct 1, 2020)

This is on my to do list.


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