PDA

View Full Version : Mill clutch not disengaging



Fasttrack
03-05-2008, 01:48 AM
Alright guys, sorry for any ambiguities, I'm new to the mill game. I'm still working on getting a handle on all the lathe manufacturers and what-not!

Anyway, there is an old bridgeport mill here at school, something like a 34" table, 36" if you count the endpieces. It has three (or was it four?) speeds in low and high gear. These are adjusted by changing the belt on the pulleys. We have another j-head next to it but its been setup to cut splines so this old one has been getting alot of use.

When you go into back-gear ... or low gear i guess ... it makes a horrible grinding noise. When you slide the lever to disengage the clutch, it does not completely disengage and the clutch mechanism up on top is really sloppy. I've overcomed the problem by shimming it with a piece of sheetmetal. I'm sure there must be an adjustment for this and was wondering how that adjustment is made.

I hope you all know what i'm talking about :) :o

Peter S
03-05-2008, 04:10 AM
Its more than 20 years since I used or looked at a Bridgeport with J -head (step pulleys), but I still recall a couple of things, including the terrible noise when you get it wrong.

When you move the lever on top of the head it causes two pins to move up or down a ramp (the cam ring). These pins are screwed in and sometimes come loose. From memory you simply tighten them with a screw driver.

Also, I guess you are also moving the other lever on the RH side of the head as well? (Sorry for stating the obvious here).

Looking in my manual - for back gear, move the lever on top to the right, and the lever on the side to the "in" position.

When changing to direct drive the top lever goes to the front position, the side lever to "out".

You are supposed to turn the spindle by hand at this stage to let the clutch engage, it should 'clunk' into place.

Corm
03-05-2008, 07:18 AM
"When you move the lever on top of the head it causes two pins to move up or down a ramp (the cam ring). These pins are screwed in and sometimes come loose. From memory you simply tighten them with a screw driver."

I had the same problem on my step head BP. I had to replace the pins on mine as they were so worn. These are readily available from several BP parts suppliers.

Fasttrack
03-05-2008, 09:48 AM
"When you move the lever on top of the head it causes two pins to move up or down a ramp (the cam ring). These pins are screwed in and sometimes come loose. From memory you simply tighten them with a screw driver."

I had the same problem on my step head BP. I had to replace the pins on mine as they were so worn. These are readily available from several BP parts suppliers.


Aha ... ok, i will look into replacing these. I got it to disengage fine as long as i shim the "cam ring" with a bit of sheet metal. The first thing i did was fiddle with those pins. I thought maybe one was loose but no such luck. Apparently they must just be very worn. Like i said, that whole cam ring can be slid up abuot .1" before it ever contacts one of the pins.

Wirecutter
03-05-2008, 12:45 PM
I caused this problem with my J-head and had to repair it. To shift from low to high range, you flipped the little lever on the side of the head first. Then you swing the lever up next to the drawbar to drop the "spline clutch" (or whatever it's called) into engagement. The instructions on the machine suggest slowly turning the pulley by hand until the unit drops into engagement.

Instead of turning it by hand one time, I did the stupid thing. The motor had been turned off, but the spindle was still turning a little. I flipped the lever up top, and CLANK, it dropped in. Everything was fine until the next time I tried to shift to low range. It would make a terrible noise.

See here:
http://i70.photobucket.com/albums/i106/wires99/shop/JHead_prob.jpg

If it's the same problem, the head needs to be partially disassembled. Everything needs to be carefully snugged back up and reassembled. Allow half a day for the job, and it probably wouldn't be a bad idea to give it a nice clean and lube while you're at it.

-Mark

Fasttrack
03-05-2008, 02:17 PM
Ahh ... this may be a little more complicated than just replacing pins then :( Seems like every time i fix a machine two more go down. The big MSC lathe has got a motor start capacitor issue, the B&S surface grinder autofeed is broken. (I got some pretty nice diagrams and photos from the guys over on PM ... looks like that should be a fun 2-3 day job minimum ... ) and now this!

I've seen kids try to start this machine when one lever was in the high gear posistion and the other was selected for low gear or vice-versa. Talk about bad noises!!! I'm sure that clutch has been dropped into place while the machine was under power, the way it gets beaten. I'll check the pins first, but sounds like it might be more serious.

Carld
03-05-2008, 02:43 PM
Yep, Brrrrrrrrrrrrrrrrrrr WAP. Heard that a lot. Used to work with a fellow named Larry Joe and everytime he changed from low to high you would hear that noise. From then on everytime I heard it I would yell Larry Joe's back. He never stoped doing it. I found you have to give the spindle a sharp twist to set it into the dog clutch.

The pins and/or the cam slot can be worn as stated. I think I made some over size pins to raise the assembly higher on one machine. You may have to do the same.