Cross Slide Binding

D

ddickey

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Apr 21, 2016
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Yesterday after locking the cross slide for the first time ever I now notice a binding in certain spots of travel. Before I pull it apart any guesses what is going on?
I also notice when I lock the carriage the cross slide is harder to move.
 
What's the possibility that you have swarf somewhere where it doesn't belong? Have you ever taken it apart
and really cleaned that assembly before? I would just take it apart and have a look.

What lathe do you have?
 
My guess is that the locking screws were looser then you have them now and you are feeling the wear in the fit.
 
The crews are loose.
No the lathe is new.
It's an Acra ERL 13x30. I'm going to pull it apart later today.
 
If it's new, I would definitely want to clean things up. New Chinese machines usually
needing a cleaning/lubrication session before they work smoothly.
 
It is Taiwanese. It worked perfect until I locked it down once.
Heading out now.
 
Hi ddickey,
unfortunately, the gib has been slightly bent and is creating resistance.
fortunately, the gib can be removed and straightened.

if you have a surface plate, it would be easy to see the bend.
otherwise you'll need to lay it on some thick glass or a mill table or otherwise flat reference
you could then sweep the gib with an indicator, to ascertain the bend height
then straddle the gib on parallels, with the parallels about 1/4 the distance from the end of the gib
now you can press the gib back into shape either manually or by hydraulic means.
if the bend is small you may be able to use a block of wood as a tool to depress the gib, or your hand may work too
if the bend is larger or sharper, hydraulic means may be necessary.

with either method you'll need to compensate for deflection.
my rule of thumb is 1.5 of the error.
so lets say the gib is bent .004",
you'll depress the straddled gib .006" and then re-check the error
rinse and repeat until the gib is flat :grin:

another rabbit hole would be to run the compound surfaces across a blued up surface plate, but then scraping would soon follow ;)
 
Got her back together. First thing I started monkeying around with the split nut. My old lathe had the same design where it is split in two and a wedge, pushed by grub screw can move them away from each other to take up any backlash. I think it was a little tight from the factory so adjusted that seemed to help some.
Then I checked the gib and ended up loosening it some, maybe a bit better. The gib and cross slide are nicely scraped, at least it looks nice. I did not blue anything up. My first thought was a bent gib also. The gib is high in the center on one side but not the side I would think. When you lay it down on the surface plate with the face of the gib that makes contact with the grub screw it is high in the center. My first thought was maybe they compensate some for when it is locked but that doesn't make sense. I did not straighten it, yet.
 
Ulma Doc you were right. Pulled the gib out and got it straight. It's much better now. Guess I won't lock the saddle again. Not sure exactly how much it was out but I did see .005", needed to push significantly more than 1.5 times the error though to get it straight.
 
Hmm I don't see how locking the carriage would affect the cross slide- maybe we're not quite on the same page as far as terminology?
You should be able to lock/unlock the carriage at will till the cows come home, so to speak
Mark
 
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