# Spindle Bearing preload pm1340gt



## JBowlin (Dec 18, 2017)

I've been doing some gunsmithing with my new lathe and another smith ask me today if I had ever checked the spindle for end play...I replied that I hadn't since the lathe was fairly new I assumed this was set at the factory. He went on to say I should check it by chuck some small bar stock in the chuck and tightening the tail stock chuck on the same bar,put an indicator on the face of the check and run the quill in and out and note movement of indicator. 

I did this with an interapid .0005 indicator as he said it should be less than .001 and boy was I surprised when I seen .0035 each direction in and out. 

So following the instructions for tightening the spindle bearings I moved the lock ring about a quarter inch radially and let the lathe run at 1100 Rpms for 20 minutes. Bearings were at 76* F and room was 62*. Checked play again and it seems that I made zero progress in eliminating any of it. 

I'm I on the right track or am I chasing my tail??

Thanks in advance. 

Jb


----------



## pdentrem (Dec 18, 2017)

In the shop at work, we let the two spindles in our Landis grinder run over an hour before starting anything. The surface grinder is turned on and left on all day. As the equipment warms up, the slop in the system is slowly reduced and/or eliminated. 
I would run the lathe for an hour and keep checking the temperature as you do so. At some point peak temperature will occur, then check. Another thing is the bearings may not be completely settled in the casting or on the spindle and you may still be taking up that with your adjustments. If you tighten the adjustment too much, the bearings will run hot and the casting area where the bearings sit will naturally feel hot. Warm is good, hot is bad. 

BTW new bearings will run hotter for a time and change the oil a couple times in those first few hours of use.


----------



## JBowlin (Dec 18, 2017)

I've had the lathe for a little bit so it's not "brand new" but less than 6 months. 

Total tonight I ran the lathe for an hour only stopping to remove rear bearing cover check the temp directly on the bearing , making adjustments and rechecking movement. I have now moved the nut over an inch radially and no improvement on play and hottest temp I got was 94*. I do have a correction on the speed though...thought I was at 1100 rpms but I was at 780 I think. I had it as fast as it will go with the belt in slowest position. 

Speaking of Oil, I do need to change it again but can't remember for the life of me what oil to use.


----------



## wrmiller (Dec 19, 2017)

JBowlin said:


> I've had the lathe for a little bit so it's not "brand new" but less than 6 months.
> 
> Total tonight I ran the lathe for an hour only stopping to remove rear bearing cover check the temp directly on the bearing , making adjustments and rechecking movement. I have now moved the nut over an inch radially and no improvement on play and hottest temp I got was 94*. I do have a correction on the speed though...thought I was at 1100 rpms but I was at 780 I think. I had it as fast as it will go with the belt in slowest position.
> 
> Speaking of Oil, I do need to change it again but can't remember for the life of me what oil to use.



Mobil  DTE,  or  equivalent,  Heavy/Medium circulating oil (from the manual). 3.5 Quarts.

Just a suggestion, but if you are not running your lathe for an hour to warm it up prior to using it, then I wouldn't suggest doing so to take measurements. I go out, fire mine up and run it right away. I'm not going to stand around for a half hour or more to let the machine warm up. And if I let it sit for an hour before using it again I have to warm it up again. Nope. Not going to happen.

Run it cold, measure it cold. But that's just me.


----------



## JBowlin (Dec 19, 2017)

wrmiller said:


> Mobil  DTE,  or  equivalent,  Heavy/Medium circulating oil (from the manual). 3.5 Quarts.
> 
> Just a suggestion, but if you are not running your lathe for an hour to warm it up prior to using it, then I wouldn't suggest doing so to take measurements. I go out, fire mine up and run it right away. I'm not going to stand around for a half hour or more to let the machine warm up. And if I let it sit for an hour before using it again I have to warm it up again. Nope. Not going to happen.
> 
> Run it cold, measure it cold. But that's just me.




Remembered the oil shortly after I posted and already ordered it, but thank you. 

I agree with your logic but so far checking cold and adjusting cold and then warm and adjusted warm ...neither have yielded any improvement


----------



## Clock work (Dec 19, 2017)

It is my understanding that a surface grinder and it's high-precision spindle bearings are in a different precision class from those found on lathe spindles. If this is indeed the case, the thermal equilibration phase will do more for the surface grinder than the lathe. Thinking about what occurs as a spindle warms up, you get a slow movement over long time frames (minutes)... not things that cause impulsive (hundredths of a second to occur within a cycle of rotation. On the surface grinder, I can see this causing an error that is significant relative to the rated accuracy in the grind of a part that takes minutes to complete... the first several passes taking a different bite than the last passes. Relative to turning and facing operations on the lathe, and considering the accuracy of the lathe bearings, shorter window over which the error can grow through warmup and perhaps not significant when viewed thru the lens of the lathe bearing's rated accuracy. But setting thermal aside completely for the moment...

If you want to know the spindle runout, just measure the spindle if at all possible. There's significant opportunity for other effects to be creeping in to your measurement... a cascade of error sources are potentially being attributed to the spindle:   spindle error + chuck error + work piece shape error (is it actually round?) + work piece registration error including whip. 

I check my spindle by removing the chuck and indicating the spindle directly. The outer surface of my chuck adds more error to this. When I chuck up a piece of stock or drill rod, I see more, though these sources are within my control to some degree. Nearly every piece of stock I put in my 3-jaw needs to be convinced to run out minimally... multiple minutes of indicating the piece and ensuring it's chucked up parallel and concentric to the axis of rotation. 

Perhaps an interesting analogy... in my real life, I own a company that sells WICKED precise electronic measurement tools. With 1000's of customers, and multiple decades of being in that business, I have met at MOST one guy that had the know-how to hit/use the asymptotic repeatability of our tools... i.e. operator error frequently dominates the total error term. Good luck!


----------



## JBowlin (Dec 19, 2017)

Clock work said:


> It is my understanding that a surface grinder and it's high-precision spindle bearings are in a different precision class from those found on lathe spindles. If this is indeed the case, the thermal equilibration phase will do more for the surface grinder than the lathe. Thinking about what occurs as a spindle warms up, you get a slow movement over long time frames (minutes)... not things that cause impulsive (hundredths of a second to occur within a cycle of rotation. On the surface grinder, I can see this causing an error that is significant relative to the rated accuracy in the grind of a part that takes minutes to complete... the first several passes taking a different bite than the last passes. Relative to turning and facing operations on the lathe, and considering the accuracy of the lathe bearings, shorter window over which the error can grow through warmup and perhaps not significant when viewed thru the lens of the lathe bearing's rated accuracy. But setting thermal aside completely for the moment...
> 
> If you want to know the spindle runout, just measure the spindle if at all possible. There's significant opportunity for other effects to be creeping in to your measurement... a cascade of error sources are potentially being attributed to the spindle:   spindle error + chuck error + work piece shape error (is it actually round?) + work piece registration error including whip.
> 
> ...




Thanks for your reply and some very good points, but I'm not checking spindle runout. What I'm checking is movement in and out of the chuck within the bearings it rides in. The runout was checked on the spindle the day I set the lathe up and I can't remember the number but I do remember being impressed..lol


----------



## jbolt (Dec 19, 2017)

Just for giggles do the same test but place the indicator on the face of the head stock at the same level as it was on the chuck.

You could also mount a TDI to the chuck with a mag base and measure off the face of the head stock while you do the push/pull test.


----------



## Bob Korves (Dec 19, 2017)

Clock work said:


> I check my spindle by removing the chuck and indicating the spindle directly. The outer surface of my chuck adds more error to this. When I chuck up a piece of stock or drill rod, I see more, though these sources are within my control to some degree. Nearly every piece of stock I put in my 3-jaw needs to be convinced to run out minimally... multiple minutes of indicating the piece and ensuring it's chucked up parallel and concentric to the axis of rotation.


Agreed.  Try to do your best to check the bearings, not the flex of other stuff between the bearings and your indicator.  You can not check the bearings directly, but you can check the spindle which is directly connected to the bearings.  As jbolt pointed out, mount the indicator to the headstock, not a train of stuff sliding on the ways.  Eliminate all the middle men, as much as possible...


----------



## Mitch Alsup (Dec 19, 2017)

JBowlin said:


> What I'm checking is movement in and out of the chuck within the bearings it rides in. The runout was checked on the spindle the day I set the lathe up and I can't remember the number but I do remember being impressed..lol



The Grizzly manual for my 12-36 lathe specifies that you are to remove the chuck(s) and measure the plate that holds the chuck.
http://cdn2.grizzly.com/manuals/g4003g_m.pdf
page 75
Once you get all of the play out, add 1/16" (3-odd degrees) turn to set preload. Install chuck, run for a while, and check again.


----------



## JBowlin (Dec 20, 2017)

Update...

Moved my indicator to the headstock and checked again and only .0002 movement. So there's obviously some flex throughout the headstock. 

Now that I know that I hope I didn't preload bearings too much. I may just back the nut off and whack the spindle with a dead blow and start over to be safe, although after running it for 20min today at 780 rpm the bearings were only 15-20* over ambient 

Thanks for all the replies...I would have never thought about flex in the headstock, and I would have never got to zero on indicator either


----------



## jbolt (Dec 20, 2017)

Excellent! 

I'm not a fan of whacking spindles. Pre-load should be adjusted with the nut. 

When I rebuilt my previous lathe I did all sorts of checks and was shocked at how much the machine flexed with what I felt was moderate pressure. It was driving me nuts until I conceded that since I was able to hold the tolerances I thought the machine was capable of I wouldn't worry about it.

The one that really killed me was mounting a TDI on the cross slide with the needle against the tool post and then moving the carriage and getting a few tenths of movement on the TDI. Just the pressure of the rack and pinion gears was enough to flex the cross slide.


----------



## JBowlin (Dec 20, 2017)

I'm not a fan of hitting the spindle either but once you tighten the nut the only way to unload the bearing after loosening the nut is hit the spindle...I'll probably use a block of wood against it. Unless someone knows of another way.


----------



## jbolt (Dec 20, 2017)

With a taper roller bearing just loosen the nut and rotate the spindle by hand to relax the bearings and then re-tighten.


----------



## mksj (Dec 20, 2017)

FYI, I checked my 1340GT today as to neutral "0" and pressure on the chuck with the tailstock, it is 3 years old but not a lot of heavy use. At most I was able to get just under 0.001" of inward deflection with maximum tailstock pressure. More ideally, one would remove the chuck and check the movement directly on the spindle mount, and use a block of wood on the center of the spindle to apply pressure and evaluate inward deflection. I had unmeasurable lateral runout of my spindle when I checked it a while back, but you can get about 0.0005 of lateral deflection pushing on the mounted chuck and measuring round stock in the jaws. 

It is also possible that that a chuck may not seat perfectly to the spindle mount, so one could also see more deflection on it vs. directly on the spindle.

Deflection using a Starrett 0.0001" dial indicator.


----------



## JBowlin (Dec 21, 2017)

Unloaded bearings and readjusted per the method of mounting DTI directly to headstock and have .0003 of inward deflection. That's good enough for me. Thanks for the help guys. 

Now I gotta figure out why I put a link belt on and have a vibration now...and yes it's going the right direction with the tabs trailing.


----------



## Downwindtracker2 (Dec 21, 2017)

Just out of curiosity, what type of bearings ?


----------



## Bob Korves (Dec 21, 2017)

Check the motor pulley and the lathe pulley for proper mounting and looseness and for runout while running.


----------



## JBowlin (Dec 21, 2017)

Factory bearings as this is a 6month old machine....I tossed the stock belt day one and got a Goodyear belt and it ran pretty dang smooth ....I bought the link belt after reading all the raves about it and since I was there working I decided to go ahead and put it on...but so far it's not an upgrade.


----------



## Downwindtracker2 (Dec 21, 2017)

My Taiwanese DF1224g just had cup and cone roller bearings, nothing fancy or expensive . I replaced the 25 year old Polish ones with Timken brand. I was expecting K-taper roller bearings and with a thrust . A dead blow is likely softer than a block of wood.


----------



## mksj (Dec 21, 2017)

You may try different belt tensions. Different thoughts on th use of link belts, anything is better that the stock belt. Many belts will take a set when stopped, and then you will get some vibration. I have been using the Gates Tri-Power which is a notched belt with good results. You will need a BX-24 and a BX-25, as the stock belt is somewhere in between the two. Single phase motor can cause a bit more finish issues for some.


----------



## sanddan (Jan 5, 2018)

Mark, is the BX-25 for the higher speed pulley configuration?


----------

