Back gear Pin??

[randyjaco]

As you may have read in my earlier post. I am the owner or a brand new 40-year-old 101 28990 lathe. Forty years is a long time for an unmaintained piece of machinery to sit in a garage in Southeast Texas. Everything needs to be disassembled and reworked. I now have all the major components separated. I can't seem to get the back gear pin to move. I presume that the aluminum boss has corroded and locked the pin in place. I even made a tool to move it and just managed to bend the tool. It's really stuck. It has been soaking in Kroil for the past two days. Anybody got any suggestions for getting it loose? I would prefer not to have to disassemble the spindle assembly but that seems like the only solution
Will that pin rotate in place or does it just slide in and out?

Thanks
Randy

 

[markba633csi]

I think based on the machine's history I would pull the spindle and check the bearings
The pin should rotate normally but there's so little fighting room in there
You could keep soaking and tapping, maybe it will free up in a couple more days
Mark

 

[martik777]

Hit it with an impact hammer (make aluminum tool to fit)

 

[markba633csi]

I think that might be excessive since we are dealing with zamak here (bullgear)

 

[wa5cab]

There is an owner drawn drawing of the pin in Downloads. Look at it so that you know what the pin looks like.

Regardless of whether it would be safe to hit the direct drive pin with an impact hammer or not, there is no room and no way to bring such a hammer to bear on the pin.

Randy,

There is a hole drilled between two bull gear teeth that goes down toward the spindle, through the hole that the direct drive pin is in and on maybe half an inch past. To assemble the bull gear, you first drop the spring in the hole, then the plunger, and finally stick a special tool down the hole and compress the spring. While holding the spring compressed, you stick the direct drive pin in the hole and up against the tool, and while withdrawing the tool smartly, snap the pin in over the ball end of the plunger. Anyway, you need to also put some penetrating oil into the radial hole as the spring and plunger may also be stuck.

 

[chippermat]

There is a hole drilled between two bull gear teeth that goes down toward the spindle, through the hole that the direct drive pin is in and on maybe half an inch past. To assemble the bull gear, you first drop the spring in the hole, then the plunger, and finally stick a special tool down the hole and compress the spring. While holding the spring compressed, you stick the direct drive pin in the hole and up against the tool, and while withdrawing the tool smartly, snap the pin in over the ball end of the plunger. Anyway, you need to also put some penetrating oil into the radial hole as the spring and plunger may also be stuck.

Do you know if the detent plunger ball and spring is positioned so on the other applications as well (i.e. indexing pin and half-nut app's)?

 

[pdentrem]

Try a hair dryer or hot air gun to expand the bull gear to attempt to release the steel pin. Keep adding “release all” fluid. Hopefully you will be able to carefully turn the pin a tiny bit to break the bond. Once you can turn it, you should be able to slowly twist, push and pull until removed.

If I recall correctly, it requires that you twist the pin a half turn to push the detent ball and spring down into the drilled hole and then pull out the pin. Keep your fingers close to catch the ball as it likely will be driven out by the spring.
Pierre

 

[wa5cab]

Basically yes. Except that yesterday about the direct drive pin I mistakenly wrote "ball" when it is actually a plunger (rod with a ball end). With the other two, it is actually a ball. The detent ball and spring for the index pin would be compressed in the same manner as for the direct drive pin. In the case of the detent ball for the half nuts, you would assemble the guide, half nuts and studs, stick the spring in the blind hole in the apron, put the ball into the hole in the guide, and attach the guide to the apron, which compresses the spring.

The special tool I mentioned is just a piece of steel rod that's a slip fit in the hole with the bottom about half an inch cut away on the side so that the pin is partially over the ball before you pull the tool out and snap the pin past the ball.

 

[chippermat]

Thanks much, wa5cab.

 

[martik777]

I think that might be excessive since we are dealing with zamak here (bullgear)

If you use low PSI, you can vary the impact force. Make a slender aluminum chisel with a hole or slot on the end to grip the pin, I've used this approach many times to free up stuck valves, morse tapers, brake calipers etc without damaging the part.