# Mini Lathe Tapered roller bearing upgrade issue



## ddeen (Dec 6, 2018)

First post here.  Hoping to get help with an issue I am having with my lathe.  

My lathe is a micromark 7x14.  I have had this thing for close to 10 years and really enjoy making little parts with it.     I updated my mini lathe with tapered roller bearings in Sept of this year.  I have been trying to do web searches on early failures on the bearings but looks like I may be a minority with this problem.  I was getting a lot of internal noise after about 2 months of light use of the lathe.  I disassembled it last night and sure enough the new bearings were very loose.  I am looking for guidance on whether I should just go back to the non tapered bearings or any tips for properly installing the bearings to avaid early failure.    Thanks.


----------



## TomS (Dec 6, 2018)

ddeen said:


> First post here.  Hoping to get help with an issue I am having with my lathe.
> 
> My lathe is a micromark 7x14.  I have had this thing for close to 10 years and really enjoy making little parts with it.     I updated my mini lathe with tapered roller bearings in Sept of this year.  I have been trying to do web searches on early failures on the bearings but looks like I may be a minority with this problem.  I was getting a lot of internal noise after about 2 months of light use of the lathe.  I disassembled it last night and sure enough the new bearings were very loose.  I am looking for guidance on whether I should just go back to the non tapered bearings or any tips for properly installing the bearings to avaid early failure.    Thanks.



Sounds like you need to snug up the bearing preload nut(s).  Also check to make sure the left side bearing is a slip fit on the spindle.  If it's tight the bearing won't move easily and adjusting the bearing preload will be much more difficult.


----------



## ConValSam (Dec 6, 2018)

Plus 1 to TomS suggestion.

If you search "timken bearing preload procedure" a number of publications from Timken show up: any one is a good place to start with how much preload makes sense.  Although I did not look, I have little doubt there are also YT videos showing the process.


----------



## mikey (Dec 6, 2018)

Welcome to HM, ddeen!

I don't own a 7X lathe so my opinion is worth zero BUT if this were my lathe, I would go find a decent set of bearings, maybe ABEC 3. Nachi, SKF and FAG make good tapered roller bearings. Then I would set preload with the same method Emco uses on their precision lathes to preload it.  

Emco sets preload with no gears attached - just a bare spindle. Using a standard chuck that fits the lathe, they spin it hard by hand and adjust preload to allow 1-1.5 revolutions before the chuck stops spinning. Now, this might seem sort of crude but Emco lathes typically run quiet, smooth and accurate. My personal Emco lathe has zero spindle run out and has maintained that since the lathe was made in the mid-late 1990's so maybe crude but very effective.

Just food for thought.


----------



## pacifica (Dec 6, 2018)

mikey said:


> Welcome to HM, ddeen!
> 
> I don't own a 7X lathe so my opinion is worth zero BUT if this were my lathe, I would go find a decent set of bearings, maybe ABEC 3. Nachi, SKF and FAG make good tapered roller bearings. Then I would set preload with the same method Emco uses on their precision lathes to preload it.
> 
> ...


another way to set pre load: put a wrench on the nut you are pre loading, attach a string to wrench end , attach other end of string to a scale( https://smile.amazon.com/Dr-meter-E...129377&sr=8-1-spons&keywords=fish+scale&psc=1. ) pull the scale to the pounds you need for preload.That's the way recommended by Harrison for their lathes.


----------



## mikey (Dec 6, 2018)

pacifica said:


> another way to set pre load: put a wrench on the nut you are pre loading, attach a string to wrench end , attach other end of string to a scale.



Funny, but that is also the procedure I use to set preload on the steering stem bearings in my sportbike. Thought it was unusually anal but now I'm thinking ... maybe not.


----------



## john.k (Dec 6, 2018)

When you set up taper rollers ,always rotate the spindle as you tighten the adjustment,until the rolling drag is too great,then back off the adjuster enough to get the proper preload......The reason for this is that the taper rollers will stick in the cup out of position if you dont rotate while adjusting.......Now you might think this unlikely,but I have seen big truck wheel bearings with 1/4" of endfloat because this precaution wasnt taken,...........Then recheck after a few minutes running..............More bearings are ruined by running loose than tight......Correctly adjusted bearings should run warm,not hot.......Taper rollers will seize without sufficient oil due to the sliding end load on the thrust face.


----------



## ddeen (Dec 7, 2018)

Thanks for all the tips everyone.    I do not think I can use the force guage tecnique because the rear bearing does not slide freely on the shaft.  I will get the bearings Saturday.  I let you guys know how it goes.


----------

