Atlas Th 54 Bull Gear Locking Pin.

I just replaced mine (while still on the lathe) last week after finding that there wasn't any ball or spring in my gear. I used a small brass bolt for the pin. I cut it square on one end and rounded the other end. I too used a spring from a ballpoint pen but I had to check out several pens until I found a perfect fit/length. I made my pin about 3/8" long but the length and comprehensibility of the spring will determine your pin length. I dropped in the spring, dropped in the pin and then compressed it with a thin Allen wrench as I slide the plunger pin in place. Note that the vertical spring/pin hole in the gear also has a horizontal hole for the plunger pin that goes completely through the gear. While fitting the new parts I had them fall out several times through this hole so watch for that. It was very satisfying to hear the plunger "click" when I pushed it in and everything lined up.
 
At some point I'll have to do such a fix to mine. It is beginning to be very annoying constantly having to push it back on.


Regards-Carlo
 
Strtspdlx said:
At some point I'll have to do such a fix to mine. It is beginning to be very annoying constantly having to push it back on.


Regards-Carlo
Click to expand...


Dont wait too long like I did. The plunger in mine actually started hitting the side of the case as the lathe was running. Luckily it didn't take me too long to figure our what the noise was all about. At the time I was pretty sure that I had broken something major.
 
Gentlemen;

I didn't get an answer to my post about pin measurements, so I bought a spare bull gear on Ebay with the pin intact, to get a replacement and see exactly how it was intended to operate.

If you look at the spare parts on Ebay, the bull gear is almost always advertised with the pin in place. There seems to be a not so obvious reason for this, until you try to take the pin out by simply rotating it 90 degrees or so from the plunger...not real easy if you can do it at all. The OEM spring gives a fair amount of pressure on the plunger pin and it's rather difficult to get it out. I got this one out by inserting a thin pointed scriber on top of the plunger when the pin was pushed in to engage the step pulley...easier when the bull gear is out and off the spindle. The plunger hole and pin housing can then be easily examined:

Bullgear1.jpg

Once you pull the pin out, the plunger jumps free, so watch for it:

Pin2.jpg

The pin is 1/2" dia. and about 1 1/4" long. It came with two detents, to be firmly held in place, and in proper position, by the round-nosed plunger, which is 3/16" dia. by 9/16" long:

Pin1.jpg

I believe Carlos posted the original message about his pin constantly rattling loose. It looks like the 'Atlas Engineers' had always intended for the pin to be held firmly by the plunger and its matching detents.

Lou O.
 
Interesting.... the plunger pin on my Atlas does not have that 1/16+" lip on the back end. The back half of my pin is all flat (no evidence of ever having a lip) so it can be pulled out of the gear just by pulling past the detent. I wonder if your was an newer upgrade. The parts drawing doesn't really show it well enough. Could be why so many bull gears have loose or missing parts.
 
Lou
Thanks for the pictures. At some point I'll have to pull mine back apart to install the plunger. As far as I remember it always slid out and never seemed to have a detent. I'm curious as to the actual length of the spring and the coil size also.


Regards-Carlo
 
The direct drive pin in the Atlas lathe Bull Gears looks like the one shown in the photos in Post # 14 except that on most, the knurling isn't as extreme. In order to pull it completely out of the bull gear, you must first rotate it 180 degrees or so.
 
Carlo;
The OEM spring for the plunger is pretty stiff...much stiffer than that of a ball point pen! Using crude measuring techniques (digital bathroom scale), I've determined that it takes about 12 lbs. of force to fully compress it from its relaxed length of 3/8". The dia. is about 3/16" and there are 5 1/2 turns of wire wound, that looks to be about 1/32" dia. (.031). I'm not a spring expert so you'll have to take all this data for what it is - informal observations. Good luck with making one!
Lou O.
Spring1.jpg
 
Pin issue--I can pull the pin out a bit but it doesn't appear to be able to come out enough to disengage. When I've pulled it out as far as it seems to go, I can see the pin between the bull gear and the v-pulley next to it. Any ideas how I can get the pin to go out further and thus disengage, short of removing the headstock spindle? I have given it a shot of WD-40 to see what that does.
 
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