Tapered thread, expanding to lock

A

AMMASHOOTA

Gary Gruber
I may not be using the correct terminology, so bear with me. I need to drill / tap a hole into the end of a steel bar, split the bar about an inch through the hole lengthwise, and then thread a set screw so as the screw sets, the split end of the bar expands against the hole it is in, locking it in place.

How do I do this?
 
You need to be more specific.....what do you mean "how do I do this?"

You drill and tap the end.
You slot it.
You drill and tap for the setscrew.

What's the problem?
 
If you split it first, and wedge it open a bit, you can then drill and tap, remove the wedge, and the hole will be tapered and threaded. As you advance the set screw in the tapered, threaded hole, the split will be forced back open expanding the end of the bar. Did I visualize what you were trying to draw with words correctly?
 
Problem with this method Boyd will be that it'll not tighten as you advance the screw, it'll just flare up once and then drive forward. I think to make your idea work one would have to wedge the rear and then run the flaring screw clear thru from the other end......

??

al
 
Boyd Allen said:
If you split it first, and wedge it open a bit, you can then drill and tap, remove the wedge, and the hole will be tapered and threaded. As you advance the set screw in the tapered, threaded hole, the split will be forced back open expanding the end of the bar. Did I visualize what you were trying to draw with words correctly?
Click to expand...

your analysis is correct.
 
simply use a pipe thread in the ID of your bar and then use a pipe plug for your set screw -- pipe threads are tapered and the pipe plug will expand the OD quite nicely --- I've used this many times to make an expanding mandrel for holding work

Drill and tap first --- split the bar last

Good luck
 
TSI243 said:
simply use a pipe thread in the ID of your bar and then use a pipe plug for your set screw -- pipe threads are tapered and the pipe plug will expand the OD quite nicely --- I've used this many times to make an expanding mandrel for holding work

Drill and tap first --- split the bar last

Good luck
Click to expand...

Simple and elegant. I will give it a try. Thanks
 
done this many times back in the printing machinery business.......
drill and tap end of shat with pipe threads (.75 taper/ft.)
slot shaft
clean out threads with tap...
VIOLA.......loking shaft
bill larson
 
For small diameter rods, I did a starting tap run in the hole partially, then sawed the split past the end of the threads. The set screw will force its way past the threads enough to spread the rod. Good way to make an expandable lap.
 
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