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Turned my first pen....
Darren:
This was on another forum, I don't claim to understand it, just passing it on.
When using the threading dial, there are three things that come into the equations -- thread pitch, or TPI (as set by the gearing), leadscrew TPI and teeth on the thread dial. There's no one size fits all... you need to calculate if it's not all in the book.
For example, on my 618 I often do 4 lead 36 TPI threads, so I set the gearing to 9 TPI, use a 16 tooth thread dial with a 16 TPI leadscrew so each quarter mark on the dial is a different thread start.
But once I tried to do a different setup that was impossible with the thread dial. I think it was 32 TPI four or three lead.
Using a bit of trig you can always set up for multiple starts in any setup. If you can do one thread start with the thread dial, you can do other thread starts by simply resetting the 0 positions of the compound and cross slide by moving the compound by twice the pitch and moving the cross slide by square root of three times the pitch. Just move them in opposite directions. Then use the thread dial the same way as the previous start. It's really not that hard once you've done it.
John Hill:
Darren, I would have to read that a few more times before I could claim competance!
What would be the chance, especially for soft material, to make a multi point tool? For example, the 36TPI 4 start thread, start with a short length of 36TPI male thread which you braze at right angles across the end of a square steel bar then grind down the round threaded bit until you have a multi point tool. Set the feed to 9TPI and presto! 36TPI 4 start thread! :med:
You could also use a bit of a 36TPI tap or a broken die nut.
BTW, were not the earliest threads cut with such multi pointed tools? Is that not the form of the original 'thread chaser'? Maybe such things are still available? :scratch:
[Bogs probably has a set of them!]
[Still thinking, maybe a fragment of 36TPI hacksaw blade? :coffee:]
John Hill:
OK, here is a thread chaser, for wood though.
sbwhart:
That is spot on John :thumbup:
That is what I was on about using a chaser for I probably didn't explain it well :scratch:
Cheers
Stew
Darren:
I get the gist of it John, he's saying cut 4x 9tpi threads using the dial indicator to give the correct positioning for each start.
Ending up with a 36tpi thread with four starts...if I understand it correctly. It doesn't sound that hard to do?
But then I haven't tried it :lol:
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