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Thread: Grizzly (G8688) 7x12 Head Stock Taper Bearings

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    Grizzly (G8688) 7x12 Head Stock Taper Bearings

    Hello,

    Still new to lathes and while attempting to part material I broke the plastic gear on the spindle.

    While I have the head stock apart I was going to put the tapered bearings in opposed to ball bearing currently installed in the machine.

    I found a tutorial here:

    Untitled Page

    and new bearings from LMS:

    LittleMachineShop.com - Bearing, Spindle Tapered Roller

    My question is about the rear spacer that will have to be made or shortened.

    Having little experience and now a broken lathe, what is the best way to go about dealing with this part of the upgrade? I am guessing they don't have a spacer that is the appropriate size available.

    Thanks guys!

    Danny

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    Hi Danny,
    I have fitted taper roller bearings to my minilathe. I avoided most of the problems with the internal spacers by making up two washers 1.5 mm thick so that the bearings are effectively the same thickness as the standard bearings.
    Once the bearings have been fitted on the spindle you can try the existing rear spacer for fit by assembling the spindle including spacer and bull gear and then tightening up the spindle nut. Make the nut really tight to ensure that the bearings are well seated.
    The spacer will be too long so decide how much to remove in order to get the bull gear lined up with the tumbler reverse gears. Now undo the spindle nut, remove the bull gear and spacer. Make a tempory spacer from a piece of 1.1/4 polyprop waste pipe. This is available from plumbing stores. The tempory spacer can be just sawn to approximately the right length. Now reassemble the spindle with the tempory spacer, bull gear etc. Now you can use the lathe to trim the old spacer to the right length. The plastic machines easily.
    Finally dismantle the spindle again put on the trimmed old spacer and reassemble.
    The tempory spacer works because there is little strain on the lathe whilst machining the old spacer.
    There is a complete description of this modification on my website:

    Headstock upgrade - mikesworkshop

    The taper roller bearing are certainly a worthwhile mod.

    Mike



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    Hey Mike,

    Thanks for replying.

    The PVC is a great idea!

    Would there be an effective way to measure overall completed length including bearing from raceway to raceway? I can measure the gap between the existing rear spacer and longer rear spacer that sits on the outside of the spindle.

    After trying to learn a bit more about taper bearings my understanding is you donít really want to handle them too much or damage the cage so I want to avoid pulling the bearing on and off unnecessarily.

    Maybe thatís impossible?

    Also what did you torque the bearing down to? (Preload)

    Hey thatís a great website, Iím sure Iíll have more questions as I want to build a carriage lock.

    Thanks again

    Danny

    Attached Thumbnails Attached Thumbnails -moto_0036-jpg  


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    Hi Danny,
    I cannot think of an easy way to measure the raceway to raceway distance with any accuracy.
    I think if you take sensible precautions to prevent damage that the bearings can be pulled on and off. They are not that delicate. They should not be too tight a fit on the shaft. The rear bearing in particular should be able to slide on the shaft in oder to be able to preload the bearings once in place.
    With regard to the preload, initially I torqued down hard and then backed off 1/6 of a turn. After a couple of days use to allow the bearings to bed down I slowly increased the torque a little at a time (may be 1/20 turn) until the headstock became slightly warm after a long spell of running.
    Mike



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    The only spacer that required cutting was the rear spacer that is outside of the housing and before the locknuts.

    I made it more complicated that it was.

    Thanks again!

    Danny



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    I did this upgrade about a year ago using a kit from a seller on ebay named lbakeland, it came with bearings and a shortened spacer. It was messy and a lot of work, and in the end I am not convinced it made that much difference.



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    Sansbury


    I had a totally different experience with results so far.

    I donít get the same vibration noise when turning.

    When I was parting it broke the plastic spindle gear. After the upgrade I had to tighten up gib (sp?) screws because instead of stopping the lathe on over drawing apms it ran right over the tool and forced the carriage to tilt without stopping.

    I would agree that it was confusing; most directions I have read were more like general guide lines which is what brought me to CNCZone in the first place.

    I would add that the Micro Mark kit plus the metal gear spindle kit from LMS saved time as opposed to finding material lying around to make draw bars, inserts for pushing and pipe that would fit over the spindle and not crush the cage on the bearing or apply pressure on the rear side of the spindle.

    Next mod is a carriage and tail stock lock.


    Danny



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    There's a guide here, which is what I used to do this. The one thing you'll see going through this is that they used some tools (notably a bearing puller) that most average home shops don't have.

    C3 Mini Lathe Bearing Change

    I will say there was some improvement in parting off, but it was an incremental change. I haven't tried turning anything hard to see if there's an improvement there--before I changed the bearings I had tried, and given up, machining some ballscrews. What disappointed me was that my surface finish didn't improve any, and no matter how much I played with the preload, my spindle starts to heat up much faster than it used to over 1000RPM, which I use quite often--so much that I'm now cautious about running it long at top speeds.

    It took me most of a weekend of messy work, and I kind of knew what I was doing and had some tools to do it, and the end result was only, IMHO, slightly better. Dollar-wise, it wasn't expensive. But, in hindsight I'd say that unless you were really unhappy with the lathe as-is, I wouldn't dive into this upgrade. I was basically happy before, so not sure how much I got out of the exercise.



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    Quote Originally Posted by drmico60 View Post
    Hi Danny,
    I have fitted taper roller bearings to my minilathe. I avoided most of the problems with the internal spacers by making up two washers 1.5 mm thick so that the bearings are effectively the same thickness as the standard bearings.
    Hi,
    I'm prepairing to repalace bearings on sieg (actualy rotwerk) 7X12 lathe.When I look at original and tappered bearings measurements on: Mini lathe headstock mods
    It appears that difference in lengt is 1.25mm not 1.5mm. So, why making spacers 1.5mm thick?



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    Hi mbole,
    I have just spent 2 hours stripping my spindle to check the washer sizes and they are in fact 1.25mm thickness. I made an error when I put the page on my website and copied the error when I replied to the original post.
    I will correct the website article.
    Thanks for pointing this out
    Mike



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    Wow!
    I didn't expect such radical and immediate action (but probably, I will do the same )
    Thanks.



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    Hi Mbole,
    I spent a long time checking and rechecking the bearing dimensions before I made the washers to ensure that they were correct. After your posting I checked again and agreed with the 1.25 mm washer thickness. I then just had to go and check the actual washers on the lathe
    When I made the taper roller bearing mod I made sure that the end bearing was a tight sliding fit so that it would be easy (relatively) to remove the spindle again if necessary. The end bearing must slide in order to be able to adjust the end play in the bearings.
    Are you going to use the "washer" method? I found that it was a relatively straight forward mod to do.
    Mike



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