View Full Version : Jet Lathe Head
07-11-2007, 08:47 AM
Working on a 1988 Jet 1340 PBD. ( belt drive) When I open the top door and manuely engage low gear by pulling the pin out the spring loaded pin in the front gear, and moving the (double geared shaft) froward by engaging the lever on the outside back of the rear gear box, and everything locks up. I have two of these lathes and the other one when you pull the little finger wheel out of the front wheel and twist half a trun, it allows the front gear to free wheel. I'm wondering if the engangement pin has broken in the little round knob that you pull out and turn half a turn to disengage the front gear is, like I said broke and is not allowing it to disengage. I tried taking the gears and pullys out. I took off all the allen nuts in the belt pullies, took off the double large locking nuts on the rear of the main drive shaft and taken all the allen bolts off the rings on the front and rear face plates and tried to hammer the shaft out and it didn't budge. Anyone know where I can get a disassebly picture or manuel or advice on how to take it apart?
Thanks for your time.
07-11-2007, 11:28 AM
I would expect that you could call JET or their US Distributor, and obtain a copy of the Operating Instructions and Maintenance Manual for your lathe. If that fails you could contact Enco or Grizzly and ask for the same manual for their lathe of similar likes. The parts may not be interchangeable but the assembly is most likely similar. I would expect that the Spindle Assembly for the Chinese belt drive lathes to be basically the same for lathes 10"-13".
I had to service the spindle in my lathe some time ago. It is a 1236 Belt Drive Distributed by Enco. The work was fairly straight forward. In the Parts List of the manual there is a diagram of the Spindle Assembly which referenced close to 100 parts. This diagram was a little difficult to follow in black and white. If you color the diagram it becomes clear how these parts interface.
I hope this helps
07-29-2007, 03:52 PM
I had a Jet 13x36 PBD lathe for a long time and replaced the spindle bearings on it a couple of times. If I had have been able to find the correct seals for it when I replaced the bearings the first time, I would have not had to have done it the second time. Because the seals leaked, it was hard to keep oil in the spindle bearings. I no longer have the lathe and the manual that I had went with the lathe. If I remember correctly, there is a collar on the left hand side of the lathe spindle when looking at it with the top open that has a set screw that has to be loosened off. The gears and set of three pulleys slips on the shaft. There is a large gear on the right side of the spindle that has the button that allows the lathe to go into back gear. The large gear is a press fit onto the spindle. To get everything out, I took the jam nuts off the spindle and removed all the gearing attached directly to the spindle. Then took the bearing cover off the left side of the spindle and removed the bolts for the bearing cover on the right side of the spindle. I took two steel bars and placed them between the large gear and the housing on the right side of the spindle. Then beat the spindle out towards the right side of the spindle using a wooden block and large hammer beating on the block which was placed on the end of the spindle. You have to get the left bearing off and the large gear off the spindle to remove the spindle from the headstock. While you have everything off, I'd suggest going ahead and replacing the spindle bearings with Tempkin bearings and also replace all of the oil seals. The second time I replaced the bearings, I was able to get all the correct oil seals from Allied Bearings in Tulsa, OK. All of the oil seals except one were easy to get and were metric. One small seal didn't make sense the way the size was listed in the owners manual. It was written down as a metric numbered seal, but turned out that it wasn't metric, but a US seal. It was something like 275x237x312. The numbers aren't right, but an example as I don't remember what the actual numbers were. It turned out the 275 would have been 2.75 x 2.375 x .312 or 2 3/4" x 2 3/8" x 5/16". There was only one company that made that particular seal whatever the actual numbers are and it had to be special ordered. The rest of the seals they had in stock. Most of the seals have the number printed on the seals, so you should be able to find them from the seals. I would also suggest replacing the drive belt while you have it apart. I think it's a b belt, but I would replace it with a green power belt instead of the B belt. If you replace it with a B belt, you will be doing it again later. I tried using one of the belts that comes apart and is adjustable for length, but that didn't work well. The green power belts will last a lot longer than the B belt's.
As to your problem with the engagement pin, you are probably right in that it is probably broke in two. When you pull the head and twist it, it probably is not pulling the whole pin out of engagement. Run a feeler gage in between the gear and the pulley. If the pin is not engaged, you should have clearance directly behind the head of the pin. If it's broke in two, the feeler gage will show that the pin is still in place no matter which direction you have the pin turned.
One of the faults that I had with my PBD is that I could not get chatter out of my threads when using the backgear. I got around that by installing a Hitachi VFD on the lathe and a 3 phase motor. The VFD allowed me to run the lathe on the high speed side only and adjust the speed with the variable controller from the VFD. Running on high speed did away with the chatter and also made the lathe a quieter running machine than the original Taiwan motor.
I hope this helps and is not too long from when you originally posted. I don't get on this board often and didn't see your post until today. The little belt drive Jet lathe makes a good lathe especially with VFD control. If I had been able to find the seals more easily when I rebuilt the lathe, I wouldn't have replaced it, but would have kept on using it. It's just about a perfect size for a gunsmith lathe which is what I do.
Jet no longer has parts support for the PBD lathe.
07-31-2007, 09:20 PM
You can get copies of the manuals online even if it isn't listed, I e-mailed them with a model description and they found the manual and e-mailed a copy of it to me.