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Hello from a new hobby machinist! And a question about tapered roller bearings in a HF 7x10

Discussion in 'MINI-LATHE & MINI-MILL INFORMATION' started by onthefence777, Jan 23, 2017.

  1. onthefence777

    onthefence777 United States Swarf Registered Member

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    Hello! I am a youngish and mechanically inclined newbie to machining.

    I have read and studied a lot, and have begun my hands on learning of machining with my HF 7x10 mini lathe. While I am fascinated with lathes and want to eventually become adept in utilizing this great tool, I do recognize that I am ultimately much more interested in mill work. However, I do not have the funds to get into the world of milling yet, so I want to make the most of what I have.

    I bought my mini lathe off of craigslist for somewhere around $250 a few years back. It was in pretty rough shape; surface rusted ways, the power feed did not work, no change gears were included, and the carriage and crossfeed slide had worlds of slop in them.

    I cleaned up the ways real good and it is now rust free, and with the help of the information on the mini lathe website, I was able to adjust the carriage and cross feed gibs so that everything moves fairly smoothly. But even after that, I was still getting a lot of chatter and chuck run-out, so I decided that changing the spindle bearings was in order. Since I was digging into it anyway, I decided to upgrade to tapered roller bearings.

    There is simply too much preload on my spindle bearings. At high speeds, the motor quickly (within 15 seconds) ramps the speed down quickly and then stops, and the chuck is very tight after I stop, for about 30 seconds until it cools down. I now know that I did not turn down the rear spindle spacer enough. It measures 31.64mm/1.2455", where I now know it should be more like 29.46mm/1.160". So I know I need to correct that.

    I worked from a couple different references for the bearing upgrade, but I notice now that I also overlooked part of step 62 of the arceuro guide - I must have missed where it said that "the outer spacers require a shoulder turning to clear the bearing cage" and the illustration points to the outer spacers located inside of the headstock.

    Did any of you that upgraded to the taper roller bearings do that?

    Thanks, any advice is greatly appreciated.
     
  2. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    My 7x10 did not need the 2 bearing spacers cut. I checked them for clearance and there was plenty. It started out as a harbor freight 7x10 and is now a 7x16. I purchased it in 2014 new. The Arceuro instructions are for I think a C3 model and the HF 7x10 is I believe a C2. Did you make the inner rear bearing a free fit on the spindle shaft? You should be able to slide it on the shaft by hand. Have you tried loosening the spanner nuts and making end play. If you loosen the nuts are you able to get the spindle to slide forward? If not then the rear bearing may be too tight on the shaft. In that case even though you loosen the nuts the shaft would stay in place and still have the same pre-load. Loosen the nuts , put the hi/lo shift in neutral and try turning the spindle. If it is difficult to turn you may need to take the spindle out and check those spacers for clearance. It is not difficult to remove the spindle, no need to remove the headstock. Unplug the power Cord. Just remove the change gears and rear gear plate and spanner nuts. Remove the 3 screws from both plastic bearing covers. Remove the rear bearing cover. Slide the spindle forward. The spacers and internal gear will stay in place in the head stock with the spindle out. You can check for any problems and correct them. Check the spacer fit and file down the end of the spacer until there is clearance.

    Roy
     
    Last edited: Jan 23, 2017
  3. onthefence777

    onthefence777 United States Swarf Registered Member

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    This is a model #33684 CM 7x10 Lathe, so C2 as far as I know. I did loosen the spanner nuts earlier to try to make end play earlier. The lathe will run at full speed without bogging down now, but I am getting no end play from the spindle at all, at least as measured by a very close eye. So I figure that's the problem.

    I used my neighbors press to install the bearings, and no, I did not clean up any bearing surfaces. I will slide the spindle forward tomorrow and look closer.

    Thanks!
     
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  4. royesses

    royesses United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Yes the spindle rear bearing surface needs to be cut down to allow a very close fit. The inner bearing race hould slide on the spindle with as little clearance as possible. The front bearing can be pressed on to try to keep runout as small as possible. I put my spindle in the lathe ( I had a new spindle) and used some 220 grit wet/dry sand paper to reduce the diameter of the rear bearing only. Then I cleaned up with 400 grit. You are removing nor more than .001 usually so stop and check frequently. Each time you check let the spindle cool first for a couple of minutes so you get an accurate feel.

    Roy
     
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