- Joined
- Feb 1, 2015
- Messages
- 9,605
Persuant to completing the lathe tool height gage made last week (, I needed a 4-48 jam nut to lock my custom dial indicator tip. I could buy a box of nuts from McMaster but what would I do with the other 99? Fastenal has them as well but I would feel foolish walking in for just one nut. Besides, it's a fifty mile round trip. But damn, I'm a machinist (sort of). Why not single point the internal thread. Now, I' haven't done that much internal threading and certainly nothing a small as 4-48 but I thought,"nothing to lose except some time, hey".
First on the list was to make an internal threading tool. I have a bunch of 1/8" tool bits. Using my Dremel with an abrasive wheel and my diamond disk, I managed to make something that resembled a threading tool. As for stock, I could have cut the hex bar but I cheated and used a 1/4" threaded standoff. I selected one which had not been threaded through and chucked it in the 3 jaw chuck. Checking for runout, there was about .003". A paper shim under two of the jaws brought it down to under .001" which was close enough.
I drilled a through hole with a #42 drill and set up for threading.For setting the tool height, I put a 1/4" spacer under the tool. A few adjustments and I was ready to thread. I used WD40 for cutting fluid. and threaded inward using the compound for engaging and disengaging and the compound set at 29.5º for advancing the cut. I threaded in at 170 rpm about 1/4", using the tool itself to gage the depth. After disengaging the half nuts, I turned a bit further to ensure that subsequent passes would run into virgin territory. I checked the progress after each pass using a 4-48 indicator tip as a gage.
When threading was complete, I parted off the nut. A little deburring with a file and the nut was finished. I'm sure that the threads aren't perfect but then who's going to inspect the internal threading on a 4-48 nut. Here is a photo of the the threading tool and the nut mounted on my custom indicator tip.
First on the list was to make an internal threading tool. I have a bunch of 1/8" tool bits. Using my Dremel with an abrasive wheel and my diamond disk, I managed to make something that resembled a threading tool. As for stock, I could have cut the hex bar but I cheated and used a 1/4" threaded standoff. I selected one which had not been threaded through and chucked it in the 3 jaw chuck. Checking for runout, there was about .003". A paper shim under two of the jaws brought it down to under .001" which was close enough.
I drilled a through hole with a #42 drill and set up for threading.For setting the tool height, I put a 1/4" spacer under the tool. A few adjustments and I was ready to thread. I used WD40 for cutting fluid. and threaded inward using the compound for engaging and disengaging and the compound set at 29.5º for advancing the cut. I threaded in at 170 rpm about 1/4", using the tool itself to gage the depth. After disengaging the half nuts, I turned a bit further to ensure that subsequent passes would run into virgin territory. I checked the progress after each pass using a 4-48 indicator tip as a gage.
When threading was complete, I parted off the nut. A little deburring with a file and the nut was finished. I'm sure that the threads aren't perfect but then who's going to inspect the internal threading on a 4-48 nut. Here is a photo of the the threading tool and the nut mounted on my custom indicator tip.
