Turning threads off rod fine but now rod advances out of chuck.

[helmbelly]

ou have lots of advice at this point.

good advice too, thanks all. Still no idea about the OP (original problem) but the parts are getting made so no problemo. ;-)

 

[toprecyler]

good advice too, thanks all. Still no idea about the OP (original problem) but the parts are getting made so no problemo. ;-)

My guess as to the original problem, after the first couple you did, you might not have been clamping it tight enough to hold the bolt from turning a little bit. It wore the alum threads a bit, and then wouldn’t hold the bolt again true and tight.


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[helmbelly]

My guess as to the original problem, after the first couple you did, you might not have been clamping it tight enough to hold the bolt from turning a little bit. It wore the alum threads a bit, and then wouldn’t hold the bolt again true and tight.

Right, it would have only taken one loose chucking /hard cut because once it "walked" it would cut a deeper tap and been useless going forward. Makes sense. I'll take a look today and will get back

 

[Al 1]

Cutter may be too small and riding existing threads. Try a wide cutter. Al

 

[helmbelly]

Cutter may be too small and riding existing threads. Try a wide cutter. Al

I'm not sure what you mean by wide, it which direction? No matter the width isn't it really only the pointy end of the spear that is cutting? How does width effect point of contact with the work? How the toolbit is shaped, relieved, raked - yes but width? I'm not seeing it. Do you mean angled? bc yes the tip if it's angled wrong will ride like a sailboat.

 

[tq60]

Here is my input.

The very first photo for reference.

Make it a but shorter

Remove enough to allow for another nut and washer to be added.

Now, put nuton front, tighten against spacer, place washer in front of not, this is optional shield and stop indicator.

Sneak up on final diameter on first bolt, but do NOT go to washer, go just far enough to get final diameter.

Once there, proceed until tip of cutter touches washer, the washer will stop turning and cutter good.

Replace bolt, now do cut in one pass.

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[helmbelly]

Here is my input.

The very first photo for reference.

Make it a but shorter

Remove enough to allow for another nut and washer to be added.

Now, put nuton front, tighten against spacer, place washer in front of not, this is optional shield and stop indicator.

Sneak up on final diameter on first bolt, but do NOT go to washer, go just far enough to get final diameter.

Once there, proceed until tip of cutter touches washer, the washer will stop turning and cutter good.

Replace bolt, now do cut in one pass.

Sent from my SM-G781V using Tapatalk

If it slips again I like the idea of bolting it front and back but trying to keep the change outs quick if I can, right now a few seconds on the grinder just makes the whole thing easy. Also finding the 316 cuts a lot easier than I thought.

Note for others removing threads: unthreaded delrin sliced and relieved is working great - I'm going to make another delrin coupling today with 2 relief cuts to clamp in the 3 jaw better. Gonna try my micro-carbide bit to take a heavy cut w/o pregrinding threads off and see if I can come to dimension in a couple passes today. I'll let you know.

 

[whitmore]

like a 5c collet

A clamping pressure argument applies here; the 'like a collet' item gets good engagement when it is threaded,
and good elastic deformation (locking the workpiece position) when the region of high pressure is only the
tip end, one or two diameters of the workpiece. The tail of the collet helps alignment, but doesn't
press into the work. The long engagement of the three-jaw chuck is hurting the deflection
requirement of the holds-the-work end; this argument says the nose of the colletlike item will
be holding the work, and the tail of the collet-like item should be relieved (lesser outer diameter).

 

[helmbelly]

A clamping pressure argument applies here; the 'like a collet' item gets good engagement when it is threaded,
and good elastic deformation (locking the workpiece position) when the region of high pressure is only the
tip end, one or two diameters of the workpiece. The tail of the collet helps alignment, but doesn't
press into the work. The long engagement of the three-jaw chuck is hurting the deflection
requirement of the holds-the-work end; this argument says the nose of the colletlike item will
be holding the work, and the tail of the collet-like item should be relieved (lesser outer diameter).

Are you saying it's better to pinch just the front of the work near cutter? With a straight rod I would want maximum engagement in the holder wether it's in a jaw, collet or coupling. Standard disclaimer here, I am not an engineer!

 

[WobblyHand]

Do you have any concentricity requirements? If you don't really have super concentricity requirements (you were using a 3 jaw after all), I don't see why using a coupler nut and a top side jam nut wouldn't work. The chuck grabs the coupler nut, the jam nut is external and possibly sacrificial. If you need to flip the part, I'd put on a second jam nut on the coupler (other side) or totally remove that one, so the stud is held near where the turning is.

Threads can be tricky to remove, been burned a couple of times. But locking up the jam nut is pretty effective, as is using a tool with a greater nose radius (at least until some of the thread has been shaved off). Small nose radius tools tend to want to follow the thread. Once the tops of the thread have been knocked down, a smaller radius is fine.