# back gear alignment



## fast204 (Mar 4, 2017)

Hello, have a quick question. I replaced my headstock on a model 101, went from a babbit bearing setup to a Timken bearing, when I put the back gears on both of the back gears are off to the right of the bull gear. Is there a way to adjust the position in this directon? its off by about 1/16th. any info is always appreciated.
thanks,


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## wa5cab (Mar 4, 2017)

There really isn't any left-right adjustment for the bull gear.  The 10-245R/L brackets are pinned to the headstock.  First, center up the back gears between the brackets by loosening the set screws in the two 10-253 Collars.  Make sure that the collars will move on the eccentrics.  Put about .002" of shims temporarily between each collar and the adjacent gear.  Tighten the set screws and pull the shims.

Then pull out the direct drive pin in the bull gear.  Loosen the set screws in the bull gear and the 10A-89 collar on the spindle.  Align the bull gear with the small back gear and tighten its set screw.  With the loose collar, push the cone pulley lightly up against the bull gear and tighten the collar set screws.  Confirm that the cone pulley spins freely and has minimal end float.  Readjust if necessary.  Finally, confirm that the small spindle gear lines up with the large back gear.  If not, all that you can do is compromise and make the misalignment equal on both ends.


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## fast204 (Mar 4, 2017)

I will take another look at it tonight. It almost looks like I could loosen the back gear support shaft and push it over to align both the back gears to the headstock in one try as they are both off in the same direction by the same amount. Is that considered an incorrect way to go about what I'm trying to accomplish? I could post a few pictures after work tonight if that would help.


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## wa5cab (Mar 5, 2017)

Sean,

One of the problems with Atlas Illustrated Parts Lists is that the ID of parts like collars and washers is more often than not drawn either too large or too small, making it impossible to determine with confidence what part they fit over.  The back gear subassembly drawing is a good bad example (although not the worst I've seen, by a long shot).  I do not have either a 10" or an early 12" headstock here to pull the back gears off of and figure this out.  So if you have not already done so, please go to DOWNLOADS and download the file Craftsman Lathe 12 101-27430_27440 12X24-36 Rev5.PDF.  It is at the moment at the top of the list of some 2000 files because I just updated it.  So you won't have to bother with drilling down to the Atlas level to find it.  The scan of that document is a little better quality than the otherwise identical one in the 101.07403 parts manual.  Go to file page 5 and look at the back gear assembly at the top of the page.  

Tell me whether the ID of the 10-167 Wave or Crinkle Washers and the 10-253 Collars are large enough to fit over the 10-251 and 10-252 Eccentrics.  In the drawing, their ID is too small.  But logic says that they should be large enough.  If their ID's fit over the eccentrics, then selective positioning of the collars will allow shifting the two eccentrics (and the back gears) a little bit left or right.  Shift to the left will be limited by the 10-254 Handle hitting the 10-245R Bracket.

Ideally, the back gears should have about 0.004" end float between the two eccentrics.  If it is significantly more than that (say greater than about 0.008"), purchase some bearing shims in the proper thickness to reduce the end float to 0.004".  And as I wrote earlier, you can also shift the pulley and gears on the spindle slightly left or right if necessary.  Finally, when you have everything else right, loosen the set screw in the left 10-253 collar, flatten the Crinkle washer slightly, and re-tighten the set screw.  Repeat for the right ones.  This puts some friction drag on rotating the two eccentrics and will prevent them from vibrating out of (or much worse into) gear engagement while the lathe is running.


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## fast204 (Mar 5, 2017)

After taking all of the info you provided me into account I went down to the lathe with my computer, your info and the exploded parts view and began to tinker my way through it. What I came up with is yes, the ID of the crinkle washer and 10-253 collars is large enough to go over the eccentrics, in fact it looks as though it is clamped to the eccentrics to keep the shaft and gears in proper position.

Once I loosened both of the 10-253 collars I was able to tap the right side eccentric (10-251) to align the small back gear with the bull gear. I then moved on to 10-243, the large back gear and found that I actually had to move it back towards the tailstock a bit. The set screw was easily loosened and using a minimal amount of force I was able to set that gear in line with the smaller gear on the spindle.

At that point I just followed the rest of the setup you gave me and made sure to set both of the 10-253 collars about .003" each off of the supports. The friction on the eccentrics for engagement and dis-engagement feels perfect. There is ample room between the handle and the 10-245r bracket. The only thing I did notice was that the back gears are not perfectly square to the head stock (and they most likely have never been judging by the tooth wear pattern) so I am going to make some new brass shims to get them a little closer and hopefully get the lash set better.

Thank you for taking the time to respond!!
Sean.


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