Threading cleanup with the indexer

[dana_swift]

I needed to clean up nearly a box of bolts with badly degraded threads. I decided to re-cut the threads, and with that many bolts doing it by hand was not a good idea.

Wanting a way to turn the die a known number of turns, then go in reverse the same number of turns it occurred to me the indexer was ready-made for the job.

I whipped out a SBP file to control the indexer. Mounted a 5/16x18 die in the chuck. And after my third bolt things were running very smoothly.

To see more I posted a video on youtube:

http://www.youtube.com/watch?v=M1_xu9MQ_cw

This is so typical of my ShopBot use, I never imagined using the machine to re-cut threads when I bought it. However it works wonderfully for the purpose.

Because using the indexer while mounted on the ShopBot would not work for this project, I just removed the indexer and clamped it to my bandsaw table (that is getting to be a common trick now) with two standard glue clamps.

Enjoy-

D

[billp]

Dana,
That's a new one, and a good one.....

[jdervin]

Love it! Does your .sbp file have a means to adjust the number of rotations for different bolt lengths or do you use different cutting files?

[myxpykalix]

Wouldn't it be easier to just go buy some new bolts? lol

Actually that is very clever. Keeps you from having to turn, turn, turn the die ands goes much faster. Good job...

[dana_swift]

Bill P- thanks!
--------------------------

John- here is the entire SBP file:
ZA ' Wherever the indexer is at the moment define that as 0
VR,.4, .4, .4, .4, .4, .4, .4, .4, 10, .2, 100, .10, 65, 3.0, 1.75, .8
MS,,,90 ' Make the first half turn slowly so I can detect cross threading
MA 180 ' Command the first half turn
MS,,,120, ' Pick up the speed. I have tried several values.
MA 360*27 ' Command the number of threads to cut
PAUSE 1 ' Wait before backing up so I know its finished forward
MS,,,360*3, ' Back up real fast
MA -360*3 ' Back up far enough to always clear the bolt.
VR,.4, .4, .4, .4, .4, .4, .4, .4, .4, .2, 100, .10, 65, 3.0, 1.75, .8
END
Note, my indexer is on my A axis, most of them are on the B, so make appropriate changes if you indexer is on B.

Note the 27*360 is determined by the number of threads that can be cut before the bolt penetrates so deep into the chuck that it pushes the die out of the jaws. It seems to be about 1.5" deep. I have tried 30 and 28 as alternative values. 28 "usually" works, but when I thread the bolt in the first turn or two by hand it can be too much, so I ended up with 27.

I have measured the mounting holes on the Talon jaws, they are 1/4x28 tapped and spaced on 0.4 centers. When I do this next time, I will make an attachment (on the main SB table) that bolts to the jaws and holds the die "out in the room". Then I can cut more threads before hitting bottom. And have a nice hex pocket to hold the die securely.

Also for cutting new threads on round stock, I will change the SBP file to turn forward 180, then back up 90, then forward 270, back 90 etc until the threads have been cut mimicking the way I cut threads on a vise. That will be trivial also, probably I will use the move relative commands to make it easy to code.

The 4 jaw chuck is just right to hold a tap. I am thinking that when I am tapping threads on aluminum or steel plate stock I can see the same trick with the tap mounted directly in the chuck jaws.

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Jack- One of the reasons I bought the indexer is you made it look like fun. I originally had no business reason for it at all. But like everything else about the SB it has found its way into applications unimagined before I owned it.

Thanks! I have enjoyed reading your many posts on the indexer.

D

[myxpykalix]

Jack- One of the reasons I bought the indexer is you made it look like fun

If thats the case then your next assignment is to make a hollow spiral!

[curtiss]

Could you clamp the die in a vice properly and use a variable speed electric drill to turn the bolt as needed ??

Are you needing to just clean up a few inches of thread on each bolt ?