Jet 12x36 lead screw comes out

[hweaver@gci.net]

I'm new here and new to owning a metal lathe. The lathe is new and when I engage the lead screw it walks out of the tail stock end of the lathe. Once it gets about 1.5 inches out it stops turning. I can screw it back in but it just comes out again within 30 secs of turning the lead screw. Does anybody know how to fix this? Thanks in advance.

[John Evans]

Is the lathe,new or new to you? If new call Jet. But Jet sold several 12X36 lathes over the years that had different carriage drive systems ,a picture from 5-6 ft back and one close up of the head stock end would help. Several things come to mind 1 a broken sheer pin at the head stock end where the lead screw goes in. Can you move the carriage back and forth with the hand wheel ? If the carriage lock is engaged that would cause the sheer pin to brake.A friend of mine was a tool dealer here in Phoenix and for the last several years JET did not sell any 12X36 ,13X40 was the smallest ,that was as 18 months ago.

[hweaver@gci.net]

It is new model GHB-1236 and I will contact Jet. The carriage moves even when it shouldn't. It is locked until the screw stops turning and then it will move with some resistance. along with this the thread counter doesn't move and it should at least until the screw moves out far enough that it stops turning.

[Harold_V]

The carriage moves even when it shouldn't. It is locked until the screw stops turning and then it will move with some resistance. along with this the thread counter doesn't move and it should at least until the screw moves out far enough that it stops turning.

For starters, note that the longitudinal feed or halfnuts should not be engaged if the carriage is locked. To do so is asking for damage to the machine.

Note that when the lead screw is turning and the carriage is being propelled by the screw, the thread indicator doesn't turn. It would also not turn if the screw was moving while revolving, instead of the carriage moving.

Most lathes have interlocks so you can't engage the feed and half nuts at the same time. Is it possible that yours has a problem and the feed and threading were engaged simultaneously ?

H

[John Evans]

As I said a picture of the right end of the lead screw and bed would answer several questions. Everyone of these style lathes it was impossible for the lead screw to come out as the bracket on the right end would prevent that from happening as the end of the screw is smaller than the threaded part. You are refering to the threaded rod not the smooth key slotted feed rod ? Just looked at Jet's web site and I see they are selling 12x36 again, and it looks just like my Acra Turn save the paint work.

[John Evans]

Just went out and looked at my lathe ,the lead screw will slide through the end bracket. You should have a sheer pin of some sort in the left end where the screw joins the gear box. And of course the the screw should have a cross hole in the end where it goes into the gear box shaft.