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

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

I find i start getting a little tense if doing a 100th DOC …………………..

You have a seperate feed and threading bar so the problem of it kicking in during threading won't be an issue …………………….

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 …………………………………….

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

Stuart
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Stuart,

Thanks for you input.

1. You first point is a good one and I think that the previous operator/s have jammed it way too many times. The gear that meshes with the worm gear that slides on the feed rod was missing when I got the lathe. There was a new gear in the tool box but the shaft it mount on is damaged and needs replacement.

2. What size and brand lathe did you take the 100th DOC on I would really like to learn what is a reasonable DOC would be for my lathe?

3. I agree, having separate lead screw and feed rod is a good thing!

4. You are very correct, roll pin do not act as shear pin very well.

5. I am thinking along that line of a static jam and check. Maybe I can rig a lever on the feed rod and use a spring scale to see what torque it takes to strip the ball detent clutch. I am also thinking of doing the same on the (factory set) parts machine before I take it apart for parts. I don’t know yet if there is any rust damage in the sleeve bearing at the tailstock end. The machine was stored in a three sided building for an unknown period of time. I will have to make sure that all the parts are cleaned and lubricated first.

hman said:
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.
Click to expand...
John,
You raised a good point about the feed lever and learning to use it safely. I have not had a chance to operate my lathe so I looked at the manual again and went into the shop and looked at the lathe again. What I have is similar to the manual illustration below.
Jet Apron Feed.jpg
There is a pin in the lever that rides in a slot milled behind it to prevent what happed to you. The slot consist of a horizontal central portion with a vertical and downward slot at each end. It looks idiot proof to me so I should be okay. The parts machine I have works very smooth but the project machine does not. There is some kind of damage that will have to be corrected. I have the apron off the machine but have not taken it apart yet. Too cold in the shop!

Benny
The Orphanage Never Closes
 
bcall2043 said:
Stuart,

Thanks for you input.

1. You first point is a good one and I think that the previous operator/s have jammed it way too many times. The gear that meshes with the worm gear that slides on the feed rod was missing when I got the lathe. There was a new gear in the tool box but the shaft it mount on is damaged and needs replacement.

2. What size and brand lathe did you take the 100th DOC on I would really like to learn what is a reasonable DOC would be for my lathe?

3. I agree, having separate lead screw and feed rod is a good thing!

4. You are very correct, roll pin do not act as shear pin very well.

5. I am thinking along that line of a static jam and check. Maybe I can rig a lever on the feed rod and use a spring scale to see what torque it takes to strip the ball detent clutch. I am also thinking of doing the same on the (factory set) parts machine before I take it apart for parts. I don’t know yet if there is any rust damage in the sleeve bearing at the tailstock end. The machine was stored in a three sided building for an unknown period of time. I will have to make sure that all the parts are cleaned and lubricated first.


John,
You raised a good point about the feed lever and learning to use it safely. I have not had a chance to operate my lathe so I looked at the manual again and went into the shop and looked at the lathe again. What I have is similar to the manual illustration below.
View attachment 121862
There is a pin in the lever that rides in a slot milled behind it to prevent what happed to you. The slot consist of a horizontal central portion with a vertical and downward slot at each end. It looks idiot proof to me so I should be okay. The parts machine I have works very smooth but the project machine does not. There is some kind of damage that will have to be corrected. I have the apron off the machine but have not taken it apart yet. Too cold in the shop!

Benny
The Orphanage Never Closes
Click to expand...

Hello, I've got a 13" LeBlond regal , just did a quick test with some hot rolled steel and managed to do about 125th doc at the slowest feed which is 2.5th per rev, surface finnish was a bit rough but i think the rpm was a bit low for the diamitor.

Best way to find a good balance for the cut depths is probably to start somware reasonable and work up, their should be a good cross over where you stop getting clean results and it all starts becoming a little scarry :)

I generaly back off the depth if it all seems a bit stresed, sometimes I push the feed harder, I can do 2x 50th doc passes at 6th feed vs one cut at 100doc and 0.0025 feed.

Slinkier work pieces normaly require shalower cuts as the part starts to bend. Tail stock or between centers help with that.

I was using a HSS tool with a basic knife edge grind, carbide users might be able to go faster deeper feed'ier but I live in HSS tooling land for cost saveing ;)

Do you think the damage to your worm drive was from too much force or binding on stuff stuck in the keyway?

Might be worth disasembling the clutch and checking for burs or damage if you think it's had some abuse during it's life.

I've taken a quick video of the test cut I will post it when I get a chance.

Stuart
 
Hello,

video finished doing the u tube thingy,


I had given the tool and work piece a little vegetable oil for coolant/lubrication.

The tool was zeroed on the od of the rough bar and I just did a little bit to demonstrate.

The center hole is gnarly as it was a blank for a bolt that I snaped a centre drill in, whoops. :)

Stuart
 
Stuart your leblond sounds a bit rough/loud starting up--kind of a pulsating sound- do you have a bad bearing or belt?
Mark
 
markba633csi said:
Stuart your leblond sounds a bit rough/loud starting up--kind of a pulsating sound- do you have a bad bearing or belt?
Mark
Click to expand...

Might be the chuck making a fan like wosh noise ? all seems fairly smooth in the bearing department. does have a little bit of a rumble to it when running but doesn't sound bad when your using it.

Stu
 
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