Atlas MFC - loose and jammed arbor?

Hmmm, you mean the one on the end that has the set screw? That’s the nut?
 
Yes, The only safe way to tighten it is with a modified pin spanner, with the pin replaced by a screw with the same threads as the set screws. Remove one of the set screws to do that.
 
Hmmm. Never seen a pin spanner. Have a link to one online I could use? Assume tightening by hand wouldn’t cut it.
 
Go to

www.mcmaster.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
www.mcmaster.com www.mcmaster.com

Note that the noun "spanner" means either a box end or open end wrench in the UK but in the US it doesn't.

The specific type of pin spanner with a loose threaded pin is not carried by McMaster but must be what the factory used to adjust the preload on the spindle bearings. A standard fixed pin spanner would damage the threads for the set screws in the collar. And a small pipe wrench would damage the OD of the collar. A correct size standard pin spanner could be modified by pressing the pin out and replacing it with a short socket head cap screw that fit the set screw threads. The two set screws would of course have to be temporily removed.
 
I loosened mine with a small pipe wrench - and I did mangle the surface somewhat. The lead slug under the set screw grips the threads well, so it takes a bit of torque to break it loose.

I was able to get the preload on mine by threading in a screw and using the screw as a handle (apply force close to the nut so you don't bend the screw.) It doesn't take a lot of torque to get the preload, so that worked OK.

In hindsight I should have made a tool - something like WA5CAB described, or maybe a large thin nut-shaped piece with an ID that slips over the Atlas nut and a radial hole for a screw to engage the Atlas nut.
 
Another way that one could make a simple tool would be to get a large hex nut (either UNF or UNC) for approximately the nominal diameter of the collar, bore the threads out until the nut is a slip fit over the collar, and then drill one hole through one of the flats on the hex that will match up with one of the tapped holes in the collar. Use a socket or hex or countersink the hole and use a flat head screw not quite long enough to reach the lead or brass plug to lock the nut to the collar. Then use whatever you have that fits the nut to turn the collar.
 
I ended up using electrical tape on some channel locks and managed to loosen it without marring the surface. It did not take much torque to get it off, so it's possible someone has taken it off in the past.

Incidentally, what is the "pre-load" torque? How do you know when it's tight enough?
 
Atlas gave a procedure for adjusting the bearing (or maybe it was for their lathes), but I seem to have lost them. If I recall correctly, it involved snugging the bearing then running the spindle for awhile to allow the parts to heat up and expand, then snugging it again?

In the absence of directions, I would just tighten it until there is no play in the axial direciton. Maybe then run it for awhile to be sure that play does not develop and, if necessary, tighten it again while warm to remove that play. Any axial ply is bad, but having the bearings too tight is bad too.

Maybe Robert or someone else can help.
 
I assume by axial, you mean longitudinal along the spindle?

Who is Robert?
 
brandon428 said:
I assume by axial, you mean longitudinal along the spindle?

Who is Robert?
Click to expand...
Robert aka wa5cab, keeper of the Atlas scrolls (forum) and general all around nice guy!
 
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