Spindle Bearing preload pm1340gt

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
 
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.
 
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.
 
With a taper roller bearing just loosen the nut and rotate the spindle by hand to relax the bearings and then re-tighten.
 
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.
20171220_124635.jpg

20171220_124821.jpg
 
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.
 
Check the motor pulley and the lathe pulley for proper mounting and looseness and for runout while running.
 
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.
 
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.
 
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