Problem with Bridgeport backgear

Not really sure what model the mill is but from what I've read it is a 2J head. The problem is the backgear won't engage. The mill seems to run fine in
high but won't switch back to neutral or low. I know I'll probably have to disassemble to top part of the machine to find out why but I wanted to ask if anyone has any info on this problem or advice for what parts I need to remove to gain access to the backgear.
Thanks,
Steve
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On 6 Mar 2006 07:20:50 -0800, snipped-for-privacy@macoc.com wrote:

Are you sure the release at the top of the head is working? They do wear and the release lever will not drop the transfer gear down.
This is something you are likely going to have to disassemble the head to find out. Should take you about an hour or so.
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3
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snipped-for-privacy@macoc.com wrote:

What, exactly is the problem? Do you mean the handle can't be MOVED to the low-range position, or the machine locks up the spindle when in the low range? Either problem may come from the same area. The direct-drive clutch is disengaged by pulling up on the driven (front) pulley assembly. The whole pulley assembly in its bearing mount lifts up about 1/4". There is a cast iron ring with two cam slots in it that fits around the bearing assembly on the top of the housing. It has 2 1/4" pins that ride in the cam slots. Rotating the ring lifts the bearing and the pulley. These pins are a bit weak, and get chewed up until they can bind, shear off, or just get really loose. You can unscrew them with a straight-blade screwdriver, but don't take both out at the same time, or the pulley assembly will drop to the bottom. Sometimes you need to rethread the holes in the bearing mount to the next larger size and make new pins on a lathe.
Anyway, in either case, this area should always be inspected for wear and damage.
If the handle moves part way, but won't go fully into low, then you often need to turn the spindle 10 - 20 degrees to put the spur gears into alignment. Don't change the hi-low setting while running, although you have to change the vari-speed pulley setting while it IS running.
Especially since you say you can't get it even into neutral, it sounds like binding in that cam ring. If the problem is the pins and cam, you don't have to take anything off to see it. Just do one pin at a time so you don't drop the pulley.
Jon
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replying to Jon Elson, Edke6bnl wrote: great explanation I have two sets of stripped threads for the 1/4 in pins. I will need to do what you say and tap them larger and make new pins. but for now I just put a .025 shim under the ring and it slides better than ever. I did find that to put the pins in I could put the rubberized arms of my channel lock pliers under the pulley and lift up the assembly to align and reinstall the pins
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replying to Jon Elson, Edke6bnl wrote: great explanation I have two sets of stripped threads for the 1/4 in pins. I will need to do what you say and tap them larger and make new pins. but for now I just put a .025 shim under the ring and it slides better than ever. I did find that to put the pins in I could put the rubberized arms of my channel lock pliers under the pulley and lift up the assembly to align and reinstall the pins
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