Lathe chuck slippage

According to Techniks, the torque specification on a ER40 nut is 140 ft-lbs. ER torque specs The dinky wrenches that are typically supplied are not very long. If your wrench is 1 foot long you need to apply 140 lbs of force. If only 9" long then even more force is required. If you just snug it with 30 lbs or so, you are nowhere near the spec. I get lazy and don't torque it down for many items, but if I want it to hold, I crank on it.
 
For a normal thread (hardware store tolerance) I would turn the bar down to 0.368".
If I would thread this bar using a die on the nominal diameter of 0.375" I to would have a hard time getting it done. The threaded bar would have zero play, not something you really want.
 
Here's my trick. You won't see it anywhere else, it's proprietary. You sweep up a little bit of carbide dust from around your grinder, mix that with a dab of silicone grease, and smear a little of the resulting dope on your slipping work with a finger. Place back in collet, tighten, and it will never slip again. My dad came up with that trick, and the company he worked for had carbide dust as a waste product, so they patented it and put it in tubes. Also works on stripped cross-tip screws and hex sockets too.

Interesting. The railroad uses special lubricants to increase (not decrease) friction on the rails. Not sure what's in there, but probably not an abrasive like this :)

Based on an earlier suggestion, I degreased my part, and the bore of the collet chuck (q-tip). This seemed to help.

Kevin
 
Turn down to major diameter and cut the threads to near finished size before attempting to run the threading die and use some sort of threading oil.
Pierre
 
According to Techniks, the torque specification on a ER40 nut is 140 ft-lbs. ER torque specs The dinky wrenches that are typically supplied are not very long. If your wrench is 1 foot long you need to apply 140 lbs of force. If only 9" long then even more force is required. If you just snug it with 30 lbs or so, you are nowhere near the spec. I get lazy and don't torque it down for many items, but if I want it to hold, I crank on it.
wow, I am nowhere near that value. my dinky wrench is 6" center to end, and maybe 4" where I apply force. Then 420 lbs to get 140 ft-lbs at 4".

I see a wrench mod in my future :)

Thanks !!
 
wow, I am nowhere near that value. my dinky wrench is 6" center to end, and maybe 4" where I apply force. Then 420 lbs to get 140 ft-lbs at 4".

I see a wrench mod in my future :)

Thanks !!
The ER40 wrenches I have are 11" long, so I do have to really work at it to tighten. Surprisingly an ER32 is spec'd at 100 ft-lbs. But my ER32 wrench is only 6" long. Basically, for these short wrenches, you need to put a bit of effort into them to even get to 1/2 torque.
 
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I used diamond lapping compound when I was using an ER chuck for pullbtestimg MP25N wire to failure. I had it set up so that the pull dragged the collet tighter, ball bearing nuts, lubed threadbare cone, but I just couldn't pull it to failure without the diamonds

That stuff can reach 300 ksi, so the 1/4" diameter wire was almost 15,000 pounds of pull... good-stuffium!

Sent from my SM-G715A using Tapatalk
 
Here's my trick. You won't see it anywhere else, it's proprietary. You sweep up a little bit of carbide dust from around your grinder, mix that with a dab of silicone grease, and smear a little of the resulting dope on your slipping work with a finger. Place back in collet, tighten, and it will never slip again. My dad came up with that trick, and the company he worked for had carbide dust as a waste product, so they patented it and put it in tubes. Also works on stripped cross-tip screws and hex sockets too.
Craftsman sold a “friction aid” for applying to worn screw heads to give the driver more bite. I’ve got a little bottle of it somewhere, if I can find it I’ll post a photo.
 
Craftsman sold a “friction aid” for applying to worn screw heads to give the driver more bite. I’ve got a little bottle of it somewhere, if I can find it I’ll post a photo.
Found it:

Grip Doctor.jpeg
Unfortunately, it's dried up. However, while searching for "Craftsman GripDoctor dried up" I found several current replacements on Amazon, all with the same label:

Screw Grab.jpeg Bondhus.jpeg

Screw Grab Inst.jpeg
In addition to the uses listed above, the Craftsman label suggests using it on wrench jaws to prevent slippage.

Also found a larger container with the same description:

EZ-Grip.jpeg
Makes sense that this would find use in aircraft with the thin Phillips head screws that are commonly used on access panels than don't have quick-turns.



And unfortunately also found this as a recommendation:

Grip-It Spray.jpeg
Some day I'll tell you about the chemist I worked with in the 90's in the composites industry: he was looking for a magazine that he had read years before called "Rubber World:" you can imagine what came up online.
 
Wow, the Craftsman grit is only good for 400% grip, while the Bondhus grit is good for 800%.

As for the girl, if she provides the grip, I'll supply the pole.
 
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