# Jet Gh-1340a Lathe Stock No.321350  An “unplanned Project” Adventure



## bcall2043 (Jan 24, 2016)

I posted here (http://www.hobby-machinist.com/threads/questions-about-a-jet-lathe-gh-1340a.38860/) with some questions about this lathe that I found and liked but had no plan to get another project machine. I thought about it for a while but did it anyway. It is an illness! 

I need to get this lathe usable as soon as possible as I have promised my only operational lathe to a friend as soon as this one is up and going. It will probably take longer than I was planned because of the cold weather as I have no heat in the shop. I promised myself last winter that I would get heat installed before it got cold again but I did not keep that promise.

The dealer provided me with a hardcopy of the operator’s manual and a photocopy of the parts manual that matched the stock number on the machine tag. I have a little concern about the validity of these as they seem to show gray machines and the lathe I received is white but the “Stock No.” matched everything else looks okay. I checked the Jet tool website and they did not have these manuals available for download. I will try and convert these to PDF for anyone that may need one in the future. Meanwhile I am finding what appear to be errors in the manuals and will try to cover these issues as I work through this project. 

The Jet numbers for these manuals are listed below:

Operator’s Manual  Part No. M-321350  Dated 4/94

Parts List    Part No. M-321350-1    Dated 4/94

Making use of the cold weather I have been spending some time looking at the web for information on this lathe and other import machines of similar design in order to get a sense of what is right and wrong with my lathe and manuals. I will try telling what little I have already found out so far about this “unplanned project” and try not to get long winded in the process. 

The dealer was kind enough to let me tear into the lathe in his warehouse before I committed to the purchase. The first thing I noticed wrong was the cross feed did not work. The screw that connects the cross slide to the feed-screw nut was missing but I suspected more was wrong as there was a box of new and old parts on the skid beneath the lathe. That box contained a new feed screw and nut, a used feed screw/nut set and a mystery gear. I installed the new feed screw set along with the missing screw– problem fixed!

The dealer had his mechanic connect power to the lathe and we checked out the gears. The gear drive and all sounded and seemed ok except the carriage did not move. The mechanic quickly found that the output shaft from the gearbox was turning but the ball- detent overload clutch was not. He pulled the clutch back and found the balls were missing. This began to worry me!  

I asked the dealer if I could inspect the carriage to see if there were more problems and he said OK. I removed the apron and found where the mystery gear fit.

The photo below is of the back side of the apron showing where the gear should be:



The shaft where the gear should have been was damaged. I noticed the gear shift for the carriage/cross feed was a little difficult to shift. This could have caused the damage if not disengaged in time causing a crash. 

Has any other owners of the style seen damage like this? Am I correct in assuming that this damage is caused by hitting a shoulder or chuck when turning and should have been prevented by the ball detent clutch if adjusted properly? 

Benny
The Orphanage Never Closes

*Edited to correct manuals to 321350. Could not correct title stock number to same.*


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## bcall2043 (Jan 27, 2016)

I am concerned about correctly repairing the damaged apron and insuring that I identify and correct the problems that have caused it. I first looked at my hardcopy manual to see what it had to say about the protective features built into my machine. On page 10 of the operator manual #M-321350 it says the following:

*“Leadscrew and Feed Rod*

*The leadscrew (B Fig. 9) and feed rod (C, Fig. 9) are mounted on the front of the machine bed. They are connected to the gearbox at the left for automatic feed and lead and are supported by bushings on both ends. Both are equipped with brass shear pins.”*


My lathe had no “brass shear pins” on the leadscrew or the feed rod as received. It came with 5mm spring pins in both locations. The operator manual makes no mention of the ball detent clutch on the feed rod. However the parts manual #M321350-1 does show a ball detent clutch on the feed rod with the same pin described as “Part No. *GB879-5x35*………Description *PIN*…………..Size *5x35*……..Qty *2*” shown in both leadscrew and feed rod. I spent a few minutes in the cold shop today and brushed the black protective stuff off the shaft couplings of the parts machine which is “as shipped” by the manufacturer except for the freight damage the start of cleanup. The parts machine has a brass pin in the leadscrew and a spring pin in the detent coupling. I suspect that both operator and parts manuals have errors in this area. I need some spare shear pins before I try to learn the operation of the machine in case I make a mistake. I also checked the diameter if the hole through the leadscrew and it is a straight 5mm hole. This leads me to think the shear pin is a straight one.

I called the dealer and he promised to get with his mechanic and find a part number and spares. Also asked him about some others parts for an extra option accessory I spotted the last time I was there. It was on a desk in the warehouse so he needs to determine that it is available for sale and establish a cost. Maybe he will help feed my hobby illness some more!



We are predicted to have temperatures in the 60’s the weekend. Maybe I can get some more accomplished cleaning the parts machine and getting the project lathe operational. I have included a photo of the shaft area of the parts machine so you can see the black protective stuff on the shafts. I move the carriage and pushed some of the coating into a wad but It not as bad as it looks. What looks like rust on the lower right end of the feed rod  is just more protective stuff that will scrap off with a finger nail or scrubbing with solvent.

Benny
The Orphanage Never Closes


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## Steve Shannon (Jan 28, 2016)

I think those pins might be part GHB1340A-12B. Look on page 18 of manual M-321357A. It shows two pins at the left end. Each is 5mm x 35mm. When I get home Friday I'll post a snip from my computer. I don't know how to do that on the tablet yet. 


Sent from my iPad using Tapatalk


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## Steve Shannon (Jan 28, 2016)

How's this?






Steve Shannon, P.E.


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## Steve Shannon (Jan 28, 2016)

Now I'm just playing with cropping:




Steve Shannon, P.E.


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## bcall2043 (Jan 28, 2016)

Steve Shannon said:


> I think those pins might be part GHB1340A-12B. Look on page 18 of manual M-321357A. It shows two pins at the left end. Each is 5mm x 35mm......



Steve,
Don't you ever sleep?

Thanks for the lead but I think my project lathe uses two different pins. The parts machine, which I have not taken apart yet, seems to confirm this. I need a 5mm brass shear pin in the lead screw and a 5mm spring pin in the feed rod at the ball detent clutch end. I found a manual online and did a series of clips into the one picture shown below but have lost the manual number for the time being. It also shows two different part numbers for the pins. Just not sure the part numbers are correct for my machine yet.


I had to go into town this morning to take the wife for some physical therapy.  I took the opportunity to go by the tool dealer where I purchased my lathes. The guy that sold me the lathes said that he thought most of the jet lathes used the same shear pins but the guy who works on the machines and would know for sure was at a customer site working on a machine so I'm still waiting to get some pins. We went through his work bench desk are but found no pins.

My parts manual and the one shown in above picture shows a 6mm diameter for the ball detent clutch which is also missing from my project lathe. I went trough my horde of steel balls and did not find a 6mm diameter but did find a 1/4 inch one. It seemed to fit fine but takes some of the clearance out of the holes. I believe 1/4 inch will work fine if the notches in the mating clutch part are closely aligned. In any event I have the parts needed to get it operational in the parts machine. I do want some spare shear pins before I start trying to use the machine. I am sure to screw up until I learn the lever controls.


Benny
The Orphanage Never Closes


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## bcall2043 (Feb 17, 2016)

Steve Shannon said:


> I think those pins might be part GHB1340A-12B. Look on page 18 of manual M-321357A. It shows two pins at the left end. Each is 5mm x 35mm. When I get home Friday I'll post a snip from my computer. I don't know how to do that on the tablet yet.
> 
> Sent from my iPad using Tapatalk



Steve,
You may be right. However looking at the parts machine that I have they look different, one brass, and one spring pin. I could be mistaken since the parts machine is still covered in the black preservative stuff. I have not cleaned and taken it apart yet, too cold in the shop. The cold hurts as you get older!

I went by the dealer yesterday and their service mechanic gave me a couple of brass shear pins that he thought should fit my machine. they were  metric taper pins size, 5mm x 35mm. I checked the project machine which is apart and it seems to be 5mm straight holes for both the lead screw and the feed rod. I should know what fits for sure as soon as weather warms and I get the parts machine cleaned and disassembled.

I spoke with the service tech about repairing the apron on my project lathe while at the dealer yesterday. Based on our discussion I am leaning toward taking the complete carriage and apron assembly from the parts machine and placing it on the project machine. That should be easier than rebuilding the apron with new parts taken from the parts machine.

Waiting for and looking forward to warm weather!

Benny
The Orphanage Never Closes


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## Steve Shannon (Feb 17, 2016)

Benny,
When you have scavenged all the parts you want off that extra machine I might be interested in any that might accidentally fit my 1336 PBD Jet (if there are any)
Good luck with the warm weather. It's been really nice here. 


 Steve Shannon, P.E.


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## PatMiles (Feb 19, 2016)

Benny,
I can tell you EXACTLY what happened to your lathe as shown in the pic at the top of this post. Whoever was operating the power crossfeed on the apron did not disengage it before it came to the end of the travel. This will shear teeth off of the 22 tooth bronze gear (#06429) that was on the end of the shaft that is in the pic. Doing so also deformed the  slot in the shaft (GHB1340A-06714) and probably bent the shaft itself. I have done this twice to my machine due to inattention on my part. The brass shear pins for both feed rods WILL NOT shear if the machine does bind up for any reason. I have been the victim of this twice. Instead of replacing an inexpensive brass shear pin I had to replace the bronze gear and shaft. Yes it was my fault but it sure would have been nice if the shear pins had done their job. 
I am in the process of replacing the gear and shaft now and am seriously thinking of drilling the center out of the pins so if I am asleep at the wheel again they might just give way and save me some money.
PM me if I can help you with the rebuild of the apron as I am not on this board much.


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## bcall2043 (Mar 4, 2016)

PatMiles said:


> Benny,
> I can tell you EXACTLY what happened to your lathe as shown in the pic at the top of this post. Whoever was operating the power crossfeed on the apron did not disengage it before it came to the end of the travel. This will shear teeth off of the 22 tooth bronze gear (#06429) that was on the end of the shaft that is in the pic. Doing so also deformed the  slot in the shaft (GHB1340A-06714) and probably bent the shaft itself. ...........................



You may be correct as to what was going on. One additional thing I have determined is that the feed lever that switches between cross feed and carriage feed is hanging up. This could contribute even if they were paying attention. My plan now is to take the complete new carriage and apron assembly from the parts lathe and place it on the project machine as soon as weather allows. I can then place the apron repairs on the project list for repair at a later date.


Benny
The Orphanage Never Closes


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## bcall2043 (Mar 17, 2016)

PatMiles said:


> Benny,
> I can tell you EXACTLY what happened to your lathe as shown in the pic at the top of this post. Whoever was operating the power crossfeed on the apron did not disengage it before it came to the end of the travel. This will shear teeth off of the 22 tooth bronze gear (#06429) that was on the end of the shaft that is in the pic. Doing so also deformed the  slot in the shaft (GHB1340A-06714) and probably bent the shaft itself. I have done this twice to my machine due to inattention on my part. The brass shear pins for both feed rods WILL NOT shear if the machine does bind up for any reason................



Pat,
Sounds like your lathe has a brass taper shear pin or does it have a straight shear pin? The machine dealer gave me a couple of brass taper shear pins that he thought were the right ones for my project machine. However today I took time off from outdoor spring cleanup and pulled the shear pin from my parts machine. It is a 5mm x 37mm straight one with notches (photo attached). This should work if material and notches are properly designed  and machined.  I am going to make a drawing of it and see if a friend of mine can use his company's  spectrometer to determine the material for future reference. I may also make a longer shear pin for the ball detent clutch just for good measure in case I adjust it incorrectly. All the adjust information I have been able to get for the ball detent clutch  is so vague!





PatMiles said:


> Benny,
> I can tell .........................................
> PM me if I can help you with the rebuild of the apron as I am not on this board much.


I plan on moving the carriage/apron assembly from the my parts machine to the project machine as that is the fastest way. I can then make repair parts for the apron as a project. It will make great spares in case I screw up learning the new lathe. 

Benny
The Orphanage Never Closes


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