Sheldon Spindle Bearings Break In.

Jay-z

Jay-z

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Finally getting around to installing some new headstock spindle bearings in my trusty EXL 56B. Original factory bearings being replaced with Timken class 3 brgs and cups. The question I have is, what would be a suitable break in time and speed for the new bearings/cups. Given the price and availability of these parts I only want to do this once.

Jay
 
Not sure if you belong to the Sheldon group on Yahoo, but John Knox is a retired employee of Sheldon and provides expert advise.

There are some recommendations for "break-in" of precision bearings on high speed spindles from their manufacture, but our Sheldon's are not in that class. I've never read anything to indicate you need to break-in a precision bearing. The bearings are either adjusted correctly or not.

On first start, I would run for 30 seconds, stop, and repeat several times. Reverse direction and do the same. This is just to insure the oil is well distributed within the bearings. When the pre-load is set right the headstock will get slightly warm after running for 15-20 minutes at the highest spindle speed, but never uncomfortably warm. You should be able to lay your arm on it and run it for 8 hours without over-heating.

Once you are happy with the pre-load, there should be no "break end" period.

Here's a PDF from Timken with a ton of info. Notice, there is no mention of "break-in" for precision taper roller bearings.

http://www.timken.com/en-us/products/Documents/Engineering Section.pdf

From their guide:
"Generally, the ideal operating bearing setting is near zero to maximize bearing life. Most bearings are set with endplay at assembly to reach the desired near zero setting at operating temperature when mounted."

I got a question if you don't mind me asking. What did the bearings cost you? Are they Timken? Did they come with a cold preload endplay spec?
 
CraigB1960 said:
(snip)
Here's a PDF from Timken with a ton of info. Notice, there is no mention of "break-in" for precision taper roller bearings.

http://www.timken.com/en-us/products/Documents/Engineering Section.pdf

From their guide:
"Generally, the ideal operating bearing setting is near zero to maximize bearing life. Most bearings are set with endplay at assembly to reach the desired near zero setting at operating temperature when mounted."
(snip)
Click to expand...
I agree with Timken's approach. The only real reason for preload is to allow for differential heating of the various components. Think automotive wheel bearings with occasionally hot brakes near them, and warming the bearings via multiple paths. Our lathes are not so much like that. If there is no play, the bearings are doing what they are supposed to do -- provide anti friction with zero unwanted free movement. Any preload should be just enough to not allow play under cold running as well as with certain warmer components, or to make up for differences in metal coefficients of expansion in the various components. Overdoing preload just reduces bearing life and robs power with no offsetting gain. Of course, I do try to adhere to the overriding maxim of "RTFM" (read the manual!) and just do what it says...
 
CraigB1960 said:
Not sure if you belong to the Sheldon group on Yahoo, but John Knox is a retired employee of Sheldon and provides expert advise.

There are some recommendations for "break-in" of precision bearings on high speed spindles from their manufacture, but our Sheldon's are not in that class. I've never read anything to indicate you need to break-in a precision bearing. The bearings are either adjusted correctly or not.

On first start, I would run for 30 seconds, stop, and repeat several times. Reverse direction and do the same. This is just to insure the oil is well distributed within the bearings. When the pre-load is set right the headstock will get slightly warm after running for 15-20 minutes at the highest spindle speed, but never uncomfortably warm. You should be able to lay your arm on it and run it for 8 hours without over-heating.

Once you are happy with the pre-load, there should be no "break end" period.

Here's a PDF from Timken with a ton of info. Notice, there is no mention of "break-in" for precision taper roller bearings.

http://www.timken.com/en-us/products/Documents/Engineering Section.pdf

From their guide:
"Generally, the ideal operating bearing setting is near zero to maximize bearing life. Most bearings are set with endplay at assembly to reach the desired near zero setting at operating temperature when mounted."

I got a question if you don't mind me asking. What did the bearings cost you? Are they Timken? Did they come with a cold preload endplay spec?
Click to expand...
I am a member of the Sheldon Lathe group and have spoken with John Knox about a variety of things. Very knowledgeable man . Unfortunately headstock bearings were not one of our topics .

If you can find the bearing with the cup then you are doing pretty good . I had one that came like that, and another that I had to source separately. After it is all said and done the price was around$300 for both bearings and cups. No other information was provided with them.

I have set preload on many many tapered roller bearings. I was just checking to see if there was sort of " special"procedure for Percision tapered bearings.

Jay
 
I'd just start slow and ramp your way up to full speed over maybe 6-7 hours time. Provide more than adequate lubrication, watch for overheating or any strange noises.
 
Atlas Press recommended a cold (ambient temperature) preload of about 0.002" on their 10" and 12" Timken equipped spindles. Actually, they don't say 0.002" cold preload. They say to tighten the threaded retaining collar on the left end of the spindle 2 teeth of a 32T 16 DP spindle gear. I never bothered to calculate whether that amounts to 0.002" or maybe a smidge more. I'll have to measure the thread pitch. But their rationale (which they do explain) is that at operating temperature, the spindle gets about 0.002" longer.
 
This is the email I received from John Knox


Hi Jay, Be sure the small brass pads are under the setscrews on the bearing adjusting nut, very lightly bring up the adjusting nut while rotating the spindle by hand until there is just a very slight drag when turning the spindle. Lock the setscrews and that’s it. During the first few weeks of normal running the lathe check to see if there is any indication of heat on either the front or rear bearing housing, if either bearing feel more than slightly warm they may be too tight, let them cool and check again the next time they are in use for a while. After some amount of running the bearings will feel as if they don’t have the “drag” they did in the beginning but resist the urge to tighten them up just a bit. (BTW if the brass pads are missing under the setscrews on the bearing adjusting nut Aluminum may be used to replace them. Regards, John K


He also noted that there should only be 1 or 2 tents movment in the spindle . Hope this information helps out other Sheldon owners.

Jay
 
OK. Looks like Sheldon went for zero preload and tolerated any shaft expansion.
 
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