Atlas MFA (3 step) belt sizes

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dockterj

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What belt sizes fit on an MFA? The pulleys seem to be a bit too small to use standard cross section belts, unless it is ok for the belt to sit 1/8" proud of the pulley?

From the parts list the part numbers I am looking for are:
M1-57A Motor Belt
M1-58B Spindle Belt

Only hit I could find for M1-57A was this (can't post a link - 3LKA280) which seems to be about right except the belt sits proud of the pulley.

I've been unable to find any hits for M1-58B. Same situation, a 4L belt sits proud, but a 3L belt bottoms out.
 
dockterj,

I don't have the generic belt numberss for the MFA motor or spindle pulley but your post is internally contradictory. Generic number for 3LKA280 is 3L280 (3/8") and you say that it sits proud of the pulley. But in the last sentence, you say that the 4L belt sits proud, but a 3L belt bottoms out. Which did you really mean?
 
The motor and spindle pulleys take different belt cross sections. The 3L sits proud on the motor pulleys, but bottoms out on the spindle pulleys.
 
dockterj said:
What belt sizes fit on an MFA? The pulleys seem to be a bit too small to use standard cross section belts, unless it is ok for the belt to sit 1/8" proud of the pulley?

From the parts list the part numbers I am looking for are:
M1-57A Motor Belt
M1-58B Spindle Belt

Only hit I could find for M1-57A was this (can't post a link - 3LKA280) which seems to be about right except the belt sits proud of the pulley.

I've been unable to find any hits for M1-58B. Same situation, a 4L belt sits proud, but a 3L belt bottoms out.
Click to expand...
The belts on my Atlas lathe sit about 1/8'' proud as well its not an issue.
I spent way too long not enjoying my machine looking for belts that didn't.
 
I still can't say what the belt length is but at least as shipped from the factory, the motor belt and the spindle belt are the same section as on the Atlas 6" lathe, which is 3L or nominal 3/8" section. If a new 3L belt bottoms out in the pulley groove before it goes tight in the vee, you have either a worn-out or a wrong pulley. And the motor pulley should be the same as on the 618 lathe. The MFB and MFC have different belts and pulleys.
 
Also, according to the factory parts lists, the two belts are M1-57 and M1-58 on the MF and M1-57A and M1-58A on the MFA. Since the motor pulleys are the same on the two, there must have been a length adjustment on that belt. The first manual that I have found on the "B" models calls for a M1-58C spindle belt. And the 10" motor pulley and 12" motor belt. I do not know what happened to the M1-58B. Where did you find it mentioned?
 
Some photos with a ruler next to the belt/pulleys would help. It seems your setup is not orignal.

I have an MF, using 3L320 from motor to shaft, and an M-28 (like a 3L280) from jack shaft to spindle. 4 pulley spindle. The belts sit just above the pulley as they should.
 
w5acab - sorry I mistyped the part number. I triple checked my fist post and still screwed it up. The part number for the spindle belt is as you said, M1-58A not B.

ub27Rocks - do you have an MF (4 step pulley) or an MFA (3 step pulley)?
 
wa5cab - interesting that the MF and MFA have the same part number for the motor pulley and the 2 step pulley it drives. The countershaft hanger and bracket were changed going from the MF to the MFA, so a belt length change seems to be the most likely thing.
 
OK. Thanks.

The motor pulleys for all of the 6" lathes and all of the mills were the same part from the 1930's until the 1980's except for one dimension. Early ones had 1/2" bore and later they started making them for 5/8" bore.

ub27Rocks says that he has an MF, with 4-groove pulleys.
 
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