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Drilling the end of a threaded rod

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oskar

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#1
I have a piece of 1” long steel threaded rod 3/4-20 and I like to drill / tap one end for 1/4-20

First question: which chuck is better for the job; I have 3 jaws self adjusting and 4 jaws independent adjustable chuck

Second question: what should I use to protect the threads when I secure it to the chuck or perhaps there is no need for any protection?

Thank you
 

Cobra

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#2
Depending on the precision you need, the 3 jaw would likely work and is the easiest to use.
I would take a piece of copper pipe, split it length wise and heat it red and let it cool. That will soften the copper.
Wrap your threads with the copper and snug up in the chuck and the threads will be fine.
Without the copper, it is really easy to mar the threads.
 

Reddinr

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#3
I have done something similar with a 3-jaw. In my case, I wound some bailing wire in the threads. The wire was large enough to stick out over the threads. It worked for the accuracy I was looking for. I've used copper wire too.
 

Ulma Doctor

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#4
another method for protecting the threads is to tighten 2 hex nuts on the threaded rod and hold one of the nuts in the 3 jaw

you may lose a little concentricity by this set up, but it works for non precision projects
 

benmychree

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#5
If the chuck jaws are smooth, little damage will be done by chucking with moderate pressure, to my experience; one might think that a collet would be best, but it is difficult to get enough pressure to avoid slippage with most collet setups.
 

oskar

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#6
Tighten 2 hex nuts is a good idea but in my case the thickness of one nut is almost more than the length of my piece so I can’t do this. The next easiest way is to wrap the threads with 12 AWG copper wire.

Many thanks to all
 

francist

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#7
You're well on your way with the above advice, all of which is sound. For the memory bank though, here's a couple of other ways you can keep in mind. One is just to split a nut on one side so it acts like a collet, the other is cut right through a nut and use the two halves like jaws. Both ways work, and I just toss the pieces into a bin for the next time with that particular thread.

-frank
image.jpeg
 

Dabbler

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#8
Francist, great idea! I was going to warn to never chuck a thread in your jaws diectly, but to turn a round collet and split it - but your nut idea is far better!
 

BaronJ

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#9
Hi Guys,

If I get that situation, I just use the correct size split die and clamp it in the three jaw chuck.
No thread damage and self centering. You can use the die face and the jaws face for aligning the work.

Otherwise the split copper tube works just as well.
 

Cadillac

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#10
You're well on your way with the above advice, all of which is sound. For the memory bank though, here's a couple of other ways you can keep in mind. One is just to split a nut on one side so it acts like a collet, the other is cut right through a nut and use the two halves like jaws. Both ways work, and I just toss the pieces into a bin for the next time with that particular thread.

-frank
View attachment 279476
I've come across this acouple times and always had great results with a slit in the nut. You can do two to get more contact area "support" But u said your part is short. Piece of copper pipe about the same diameter with a slit works good too.
 

francist

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#11
Francist, great idea! I was going to warn to never chuck a thread in your jaws diectly, but to turn a round collet and split it - but your nut idea is far better!
Thanks, although I'm sure I saw someone else do it and picked it up there. Not much is really new anymore, eh. The added benefit of the split nut is that it can be easily used in a shop vise as well for those times when you want to saw a fastener off but don't have enough room on the waste side to grab it.

-frank
 

rwm

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#12
I love the copper wire idea. Thanks.
Robert
 

mmcmdl

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#14
Got any soft jaws ? I've never marred a thread in a collet nor a 3 jaw even with hard jaws . Use a little finesse when tightening and don't use a cheater bar ! 1/4 -20 doesn't take much to drill and tap .
 

oskar

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#15
Will give it a try, thanks
 

homebrewed

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#16
For smaller screws I use a section of nylon rod. I chuck it in my 3-jaw and through-drill a hole that is slightly larger than the screw. Insert the screw and crank the jaws down. The nylon deforms around the threads and holds the screw in place, good enough to cut screws down to the size I want. I made several of these for numbered screws (#4-#10) and some metric ones in the same size range. I've also made split collets out of aluminum, but it requires an extra machining step (cutting the slit).

This approach won't necessarily give you a precisely centered screw but it's been "good enough" for most of my requirements.
 

kwilliam

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#17
If you want to drill / tap threaded rod precisely, then use a four jaw chuck with copper sheet wrapped over the threads.
Then arrange to hold a small piece of copper sheet outside of the chuck that rests stationary on the threads while the chuck can be rotated.
Then have your dial test indicator sit on top of the copper sheet.
Adjust four jaws until desired run out is achieved.
Drill and tap aligned hole.
 

RJSakowski

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#18
When modifying threaded rod, I will use three nuts. As Mike stated, I use two jammed together to secure the threaded rod but I also have a third nut on the thread to engage the back of the chuck jaws. This prevents the rod from twisting due to the relatively short contact area of the nut.
 
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