Thread Tapping Question

donnercruz

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I have a Delta drill press (17-965) with a stop rod for a depth stop. It's a lousy set up that I want to upgrade for better precision.

The current set up is a 1/2" 16tpi rod. I want to change to 1/2 20tpi.

The current rod measures at .45" (28.8/64)

Do I -
A) cut off the current rod or get a replacement bolt to cut off and have the new rod welded to it.
B) drill out the current threads and tap for 1/2 20 (recommended bit size is 29/64)?
C) tap without redrilling?
D) drill out over size and just capture the rod with nuts on either side?
 
I have a Delta drill press (17-965) with a stop rod for a depth stop. It's a lousy set up that I want to upgrade for better precision.

The current set up is a 1/2" 16tpi rod. I want to change to 1/2 20tpi.

The current rod measures at .45" (28.8/64)

Do I -
A) cut off the current rod or get a replacement bolt to cut off and have the new rod welded to it.
B) drill out the current threads and tap for 1/2 20 (recommended bit size is 29/64)?
C) tap without redrilling?
D) drill out over size and just capture the rod with nuts on either side?
Why not move up to a 9/16" or 5/8" rod?
 
A) Yes
B) Would Not Hurt to drill to 29/64
C) you may be able to simply tap w/o drilling- the threads are not going to be high strength
D) is the easiest, you can use an aircraft nut or steel lock nut on the bottom side and a regular hex on the top side to capture

a piece of all thread, a few 1/2"-20 nuts would go a long way :)
 
I'm not familiar with Morton quill stops, and if they're what you want to use, go for it! (maybe post some details, it you would, please)

I've been using push-button hex nuts on my drill presses for quite a while.
https://www.mcmaster.com/#push-button-nuts/=14z0aei
They're very fast to slide up or down the rod, and once in position, the hex flats assist with fine adjustments. My stop rod is threaded ⅜-16, so one hex flat makes a change of about 0.010". That's good enough for my purposes. YMMV.
 
I'm thinking that I'll drill and tap it, if possible, just to keep it tight, but still use lock nuts either way.
 
Last edited by a moderator:
Thanks to the both 'o yuz! I can definitely understand how this would be the hot setup!
 
1/2 16 threads offer one advantage If you turn the nut 1 turn you get 1/16 of an inch deeper hole. if it doesn't matter to you then oh well bill
 
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