Atlas 10100 carriage slide screw bearing...

[56type]

I'm replacing the carriage slide screw bearing (item#7 in the parts list, part# M6-46) and I had a few questions..... Namely has anyone replaced this particular part before ?? If so did you have any problem with the indicator reference mark for the cross slide dial not coming up to the vertical 12 o'clock position ?? How did you solve it ?? Shim it or turn the shoulder to get alignment ??

I have another carriage that I bought stripped where I lucked out and this part was still attached so I removed it when I repainted the carriage, so I had a spare. Removed the same part from the carriage that was on the lathe and when I installed the spare I noticed it was over 3/4 of a turn to get the indicator mark to come up vertical. I may be wrong here, but I'm guessing Atlas struck the indicator mark AFTER the part was securely attached to the carriage, hence my problem.

Why would I replace such a part you may ask...Well whoever struck the original notch was either somewhat angry or took the job very seriously (or PO whacked it again to deepen it) as it is much wider than I believe it should be. It caused me enough frustration in use that I decided to swap it out for the spare I had on hand. Thanks.

 

[wa5cab]

I think that you are correct that the index mark was made after assembly. Otherwise the angular location of the thread start on the saddle and the angular relationship between the thread start on the bearing and the mark would have to always be the same. The only way to fix one that is off would be to shim the bearing out. But unless you got lucky with the shim thickness needed, you could waste a lot of time and money getting the mark to exactly 12 o'clock,

 

[56type]

I think that you are correct that the index mark was made after assembly. Otherwise the angular location of the thread start on the saddle and the angular relationship between the thread start on the bearing and the mark would have to always be the same. The only way to fix one that is off would be to shim the bearing out. But unless you got lucky with the shim thickness needed, you could waste a lot of time and money getting the mark to exactly 12 o'clock,

I was thinking about that and and believe the answer may be a shim assortment pack like this one I found at Fastenal...

https://www.fastenal.com/products/details/7041838

It offers the correct ID & OD sizes as well as various shim thickness from 0.001-0.125 (despite the typo listing max. thickness of 0.0125). I should be able to reasonably expect to get alignment once tightened into place, or at least I hope so. I made a cursory check with feeler gauges last night with the index mark a few degrees before TDC which showed a 0.010" shim may solve the problem, though the way the carriage is cut to slightly recess the part once tightened makes it difficult to obtain an accurate measurement.

 

[wa5cab]

OK. I wasn't aware that anyone offered a shim pack with that wide of a range. The only thing that you would need to make certain of would be that the shim OD is slightly smaller than the OD of the spot face.

 

[56type]

Problem solved..... I found a brass washer that was the correct ID & OD. Only thing I had to do was shave 0.015 in. off the thickness for the correct fit and cut a clearance flat to allow the cross slide to pass over the washer once everything was installed. I painted the index mark yellow and used a couple of coats of Krylon matte clear to seal the yellow in the index mark and protect from rust.

 

[wa5cab]

Good job.