Question About Ball Detent Clutch Adjust On A Jet Gh-1340a Lathe

My unplanned project lathe came with a ball detent clutch that was not mentioned or shown in the manual. I have looked at a number of Jet Lathe manuals and have not found one that provides definitive information for this type clutch adjustment. The newer model Jet lathe uses a slip clutch but that manual did not provide much help on how to adjust it either. I did find a Grizzly manual that gives instructions about their ball detent clutch as shown below:


Again, this does not seem like enough information to properly protect a lathe. I have no idea what the “normal work load” is. I would think the clutch should transmit enough torque to take a certain defined cut and not damage the lathe gear train. It would be nice if the required setting could be measured with a torque wrench applied to the feed rod side of the clutch. I don’t want to cause more damage learning to use the lathe once I get it operational!

Has anyone adjusted one of these clutches and how did you determine the setting?

Thanks in advance.

Benny
The Orphanage Never Closes

Are you sure that the lathe originally came with this clutch? Could some previous owner added it?

CHuck the grumpy old guy

What you want is for it not to slip until it is almost ready to bend or break something on your lathe, and then you want it to slip for sure. You could always try tightening it until you break something to find out, but I do not recommend that approach. 8^) On the other end, you can make it set obviously too light and then keep tightening it until you are not seeing any slips while doing normal, heavy work. The issue there is that when you are threading and it slips, you will probably scrap the part. So, I agree with you, there should be some sort of test that can be quantified, but I guess Jet did not want to break or ruin things while finding the limits. Unless someone here knows better, you might be on your own...

My lathe has a shear pin on the lead screw coupling for that purpose, and the lathe comes with ONE spare. I have not broken the pin yet, nor broken my lathe, so I am either good or lucky...

It might also be a good idea to call Jet and ask for help, and see if there is a Yahoo group for your model lathe. You may be able to find help from people who have already addressed the problem there.

ch2co said:

Are you sure that the lathe originally came with this clutch? Could some previous owner added it?

CHuck the grumpy old guy

Click to expand...

The clutch is original. I have a unused freight damaged machine for parts and it has the same. The operator manual is wrong but the parts manual shows the ball detent clutch.

Bob Korves said:

What you want is for it not to slip until it is almost ready to bend or break something on your lathe, and then you want it to slip for sure. You could always try tightening it until you break something to find out, but I do not recommend that approach. 8^) On the other end, you can make it set obviously too light and then keep tightening it until you are not seeing any slips while doing normal, heavy work. The issue there is that when you are threading and it slips, you will probably scrap the part. So, I agree with you, there should be some sort of test that can be quantified, but I guess Jet did not want to break or ruin things while finding the limits. Unless someone here knows better, you might be on your own...

My lathe has a shear pin on the lead screw coupling for that purpose, and the lathe comes with ONE spare. I have not broken the pin yet, nor broken my lathe, so I am either good or lucky...

Click to expand...

Bob,
You are both good and lucky.

My problem is I don't know what a "normal load" cut is for this machine. I kind of hoped that someone on the forum has an idea of what the largest turn cut this lathe is capable of making safely. I am both retired and a hobbyist so I will set the clutch for less than the max as I don't get in a rush anymore.

The parts manual that I have is also wrong in that it shows a spring pin (same part numbers) holding the feed screw to the gearbox and the connecting the ball detent clutch to the feed rod. That is the way I received this lathe, spring pin in both. The parts lathe I got has a brass shear pin in the feed screw and a spring pin in the feed rod detent clutch from the factory. I have thought about putting a shear pin in both just to be safe. The problem now is I need to determine the max load setting for the clutch and the part number for the correct shear pin and get some extras pins ordered.

Thanks guys,

Benny
The Orphanage Never Closes

Bob Korves said:

It might also be a good idea to call Jet and ask for help, and see if there is a Yahoo group for your model lathe. You may be able to find help from people who have already addressed the problem there.

Click to expand...

Bob,
Sorry I missed you post earlier.

I have contacted Jet and talked with one of their parts people before I purchased the lathe. The person I spoke with believed it was still a current machine when I gave him the model number. I have since learned that you have to go by the stock# and that this is an older machine. The manuals I got with the machine are not even on the Jet web site, they provide little in the way of adjustments, plus they are full of errors.

The dealer that sold me the lathe is working with me but their mechanic that knows every thing is very busy and often out in the field.

I am hoping for help here from someone with this or similar lathe model experience.

Benny
The Orphanage Never Closes

Set your quick change for the most agresive feed and operate the thread half nuts . Set your clutch to handle that fast feed . Don't be cutting any thing at the time just feeding that should get you close.

I think the ball detent clutches are only ment to activate in the event of a crash , e.g. the tool post and chuck start to jam together.

I've got a ball clutch on my 13" lathe, i've never heard it kick in even when pushing cut depthes that have made the tool post twist.

I find i start getting a little tense if doing a 100th DOC , I was trying to keep it light the other day after I started pushing the work back through the chuck insted of cutting too much feed.

You have a seperate feed and threading bar so the problem of it kicking in during threading won't be an issue (the half nuts will just jam and everything will start bending) (panic)

When attempting silly deep DOC start with lowest feed rates and work up.

Bob mentioned the shear pin protective devices, I had one on an old lathe that had been replaced with a roll pin, thats very very bad :0 the way all the gears revesed after the motor stoped to alow the twist in the drive bar to be releved was quite interesting to watch (not enouh I would do it again though)

You could try jamming the lathe with somthing soft like wood and hand turning the chuck to test it's function.

Stuart

Benny -

I have an older Grizzly 12x24 lathe. The feed lever on the carriage lets you select either lengthwise feed (up) or cross feed (down). Center is neutral. I'd not had it very long, and was doing a lengthwise cut toward the chuck. Got to the stopping point and accidentally lowered the feed lever too far, crashing the tool into the side of the work. I gotta admit I had things running a bit fast at the time.

Loud noises, of course, before I hit the e-stop. I assumed I'd eaten a gear in the saddle. In the process of dismantling it dismounting it, I saw the feed drive rod come apart. Lo and behold - the very ball detent clutch you first posted about! Did some thorough checking, and nothing was broken or bent.

I did adjustment the clutch any when I reassembled it, and have no idea where the PO had set it. But I've never had any problems with the feeds, and the clutch did its thing when it was needed. I'd surmise that the setting is not critical. There's probably a huge difference in torque on the rod between even heavy machining and a tool crash.

PS - I've since added a swing-away stop that prevents lowering the feed select lever too far when disengaging from lengthwise feed.

Wow! I've had a Jet GH-1340W for many years and never realized that it had a safety clutch.