Jet GHB 1340 thread\ half nut issues - beginner

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spro
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by spro » Mon May 13, 2019 3:36 pm

The "hiccup" could be the lead screw traverse play. When the clamp nuts are applied, the weight of the carriage causes the lead screw to slam back against the gear box or the tail support. A new bush or precision shims would minimize that.

spro
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by spro » Mon May 13, 2019 6:52 pm

If the lead screw was actually bent, we have to think about the point of impact. Generally, if if fell to a cement floor, there would be other damage to the feed screws/ handles and stuff that wasn't mentioned. I'm trying to think of where that happened and you need to remember where you saw it. The apron could have been at any position and it acts as a guard in most cases. However, it has its limits. The apron is connected to the saddle in a precise way and was originally aligned correctly .. The bed ways we see are not the whole thing ( sorry this is old stuff to many here) . There are flat ways under the bed ways which contain the saddle tight yet just right for smooth movement. All this goes away after an upset and should be checked.

David2011
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by David2011 » Fri May 17, 2019 3:47 pm

cattleman99 wrote:
Sun May 12, 2019 5:00 pm
Feed rod works fine, I misspoke. I threaded some pvc today and the threads are perfect, but I can still see and feel a little hiccup when the half nuts are engaged. The hiccup didn’t seem to effect the threading capabilities. Should I simply not worry about it?
If I owned this lathe I would be looking for the cause and get it fixed promptly. It may seem to work OK for the moment. The problem is that you will have very rapid wear and as the half nut or other parts important to precision wear excessively your precision will go away. In a worst case scenario the lathe could be damaged to a point that repair would be very difficult.

David2011
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by David2011 » Fri May 17, 2019 4:01 pm

Another thought: Do you have the same "hiccup" near the headstock, in the middle of the travel and at the right end of the travel? If the lead screw is bent I would expect the amount of drag to vary as the carriage is repositioned. If the lathe is working correctly there should not be any perceived drag related to the lead screw.

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NP317
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by NP317 » Fri May 17, 2019 10:27 pm

Not understanding what you mean by "little hiccup" it is difficult to make recommendations.
Most lathes, when engaging the split threading nut, will require a moment of pressure before the half nut closes over the lead screw. This is normal.
If this is what you are referring to, then I suggest there is no problem.

But this may have nothing to do with what you are trying to describe!
~RN

curtis cutter
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by curtis cutter » Sat May 18, 2019 9:08 am

Reading these posts brought a question to mind. Although I clean my lead screw prior to any use, how is the proper way to lubricate it?
Gregg
Just let go of it, it will eventually unplug itself.

John Evans
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by John Evans » Sat May 18, 2019 12:26 pm

curtis cutter wrote:
Sat May 18, 2019 9:08 am
Reading these posts brought a question to mind. Although I clean my lead screw prior to any use, how is the proper way to lubricate it?
Way oil in squirt can .
www.chaski.com

John Hasler
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by John Hasler » Sat May 18, 2019 1:34 pm

cattleman99 wrote:
I can still see and feel a little hiccup when the half nuts are engaged.

Does this happen only as you engage them or does it continue for as long as they remain engaged?

curtis cutter
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Re: Jet GHB 1340 thread\ half nut issues - beginner

Post by curtis cutter » Sat May 18, 2019 2:41 pm

John Evans wrote:
Sat May 18, 2019 12:26 pm
curtis cutter wrote:
Sat May 18, 2019 9:08 am
Reading these posts brought a question to mind. Although I clean my lead screw prior to any use, how is the proper way to lubricate it?
Way oil in squirt can .
Thanks John. Then I have been doing it correctly.
Gregg
Just let go of it, it will eventually unplug itself.

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