How To Remove Arbor Driver On An Atlas Mill?

[JPMacG]

This probably should be obvious to me.... but it is not. How do I remove the arbor driver from the spindle on an Atlas mill? For example, if I want to use an end mill in the spindle? I know that the driver unscrews from the spindle, but how do I prevent the spindle from rotating? There is nothing to hold.

 

[Ulma Doctor]

if you engage the drive belt and hold the pulley with your left hand while loosening the drawbar nut, you should have a good shot at it!
loosen the drawbar a good estimated 3-6 threads and give the drawbar end a firm smack with a lead, brass or other soft hammer.
this will loosen the spindle collet or other MT2 tooling for dismounting.

 

[ogberi]

I recently managed to get my own arbor driver unstuck. It took about 8 soakings, several hours apart with PB blaster, and I ended up disassembling the spindle and grabbing it in my mill vice with wooden slats to protect the spindle's surface.

I drilled 2 holes in a piece of 1" wide by 2-3" long, 1/2" thick mystery steel out of the scrounged bucket to match the diameter and center to center of the pins. No exact measurements needed. Then I welded on a cheap metric socket and used a 3/8 drive cordless impact driver to give it hell. Took a few 10's of seconds of running the impact on it, but it finally came loose.

I don't recommend doing that and using the backgear as a spindle lock. A strap wrench on the pulley may work, but that would be hard on the pulley where the bull gear pin drives it. Heat may be an option, i never tried it. Removing the spindle may be the safest way to remove it.

I left mine on for the longest time, simply because it protected the threads, and I had not thought of using an impact on it. But I hated the pins on that thing spinning. Big snag hazard, just waiting for anything to get too close. Flings chips everywhere.

I'll try to dig out the tool i made to take a picture tomorrow.

 

[JPMacG]

Thanks Ogberi and Ulma Doctor. I eventually got mine off by putting the spindle belt on the largest pulley, tightening the belt tension more than normal, and holding the counter shaft pulley with a leather glove. My arbor driver was not stuck - just tightened from normal use.

I wonder what the original designers were thinking. Providing no way to lock the spindle and no way to grab the spindle other than the pulley seems like a major screw up. Did they have in mind that we would use the back gear with the bull gear pin engaged? Is that safe?

 

[ogberi]

The back gears are absent in my machine (the eccentrics that rotate them in and out were Zamak and crumbled to dust), and my arbor was glued on with 60+ years of cutting oil that had seeped into the threads. I wouldn't use them anyway, just because I'm paranoid like that.

When I made a new arbor for the Atlas horizontal mill, I left extra meat on the shoulder that the arbor driver threads up to. I cut two flats in it for a wrench, and now use that to tighten/loosen the drawbar, or when installing/removing the arbor driver. It added maybe 1/4" or so to the spindle's length sticking out the front, which is 1/4" more stickout to loose rigidity, but it's worth it for the ability to use a wrench on it. I haven't seen anything in the Atlas literature that specifically states how to remove the arbor driver, though.

I need to get some shop time so I can make a spindle thread protector for my spindle, now that the drive arbor is off of it. Already dinged a thread on accident (dropped a part), but it cleaned up with a triangular file.

 

[34_40]

This probably should be obvious to me.... but it is not. How do I remove the arbor driver from the spindle on an Atlas mill? For example, if I want to use an end mill in the spindle? I know that the driver unscrews from the spindle, but how do I prevent the spindle from rotating? There is nothing to hold.

You don't remove the arbor driver, it's the arbor that drives the tool. On one end of the arbor it is tapered (morse taper # 2) and there is a long bolt that threads in from the opposite end, this centers and "clamps" the arbor to the machine. If you want to use an end mill it will still need the MT2 on the end opposite the cutting end, and it will need to be threaded 3/8" - 16 too.
I don't have a picture handy but I hope that helps!?!?!

 

[JPMacG]

I may have used the wrong term when I said arbor driver. The part I wanted to remove was the threaded collar with the two pins shown in the attached photo. The collar screws onto the spindle and the pins engage the arbor. Sorry about the confusion.

 

[wa5cab]

Jon,

The part that you described is properly called the Arbor Driver. Although many of the Atlas mills turn up without one, I wouldn't try to operate the mill with the arbor without it. If the taper shank ever spins in the spindle, you won't like the consequences.

Like the chuck on many an Atlas lathe, PO's often went decades between removing (or trying to remove) the arbor driver. This actually falls under the "operator head-space" category. But unfortunately, Atlas didn't bother to caution against doing this in any of their literature. Although the arbor driver is mentioned in the mill manuals, they never say how to remove it. The same is true of removing chucks in the lathe manuals. However, in the Manual of Lathe Operations (MOLO), the method given for removing a chuck from the spindle is to lock the back gears (engage them without pulling out the back gear pin). Then insert the chuck wrench in the chuck and pull smartly toward you. The MOLO doesn't say what to do if the first try fails to loosen the chuck. My SOP over 30 years has been to try it a second time, which has never failed to work. I'm sure that the same procedure will work for normal removal of the arbor driver.

However, if you buy a mill and it has the arbor driver screwed onto the spindle, I would treat is the same as a new to you lathe that arrives with a chuck installed, unless you know that the PO followed good practice of periodically removing either. In other words, treat it as stuck and use an alternate method to hold the spindle while you attempt to get the driver unstuck..

Another matter is that although Atlas supplied a tool for pulling out the back gear pin, they never to my knowledge supplied a spanner for removing the arbor driver. I would recommend that you make one from a 12" piece of 1/4" steel bar stock. Drill six equally spaced holes to fit the pins on the arbor driver pin circle diameter.

 

[VSAncona]

The two drivers I have both have a shallow hole on the rim for a pin spanner.

 

[wa5cab]

Right. My brain must have been on vacation two weeks ago. SOP for routine removal of the arbor driver is to engage back gears without pulling out the direct drive pin and use a pin spanner of the proper size. Position the spindle first such that the spanner is in a convenient position. However, your back gears are inoperative and in any case I wouldn't use the back gears the first time on any mill or lathe that I just acquired with anything screwed onto the spindle. There is no way of telling how many decades it has been on there. Use a large strap wrench wrapped around the large spindle gear (bull gear). Do not of course use a chain wrench.