Thread Gearing on a BT800

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TechTony
Posts: 54
Joined: Wed Aug 31, 2016 7:11 pm

Re: Thread Gearing on a BT800

Post by TechTony » Tue Nov 01, 2016 7:39 pm

...and the challenges continue.

I'm trying to cut a 13 TPI...
What number on the indicator do I need to use?

Behold my stumbling block!
20161101_193722.jpg

TechTony
Posts: 54
Joined: Wed Aug 31, 2016 7:11 pm

Re: Thread Gearing on a BT800

Post by TechTony » Tue Nov 01, 2016 8:57 pm

I set it on 1 just to see and it worked, so now I know. Should I assume it's a 1 anytime is not listed in the chart?
20161101_204127.jpg

Torch
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Location: Muskoka

Re: Thread Gearing on a BT800

Post by Torch » Tue Nov 01, 2016 9:13 pm

TechTony wrote: All is working well now.
Hurray! Have fun!

Torch
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Joined: Wed Mar 17, 2010 7:58 am
Location: Muskoka

Re: Thread Gearing on a BT800

Post by Torch » Tue Nov 01, 2016 9:34 pm

TechTony wrote:I set it on 1 just to see and it worked, so now I know. Should I assume it's a 1 anytime is not listed in the chart?

20161101_204127.jpg
Ok, if I recall correctly, you can engage the half nut on any number if the thread pitch is a) inch and b) divisible by 3 (eg: 6tpi, 9tpi, 18tpi, 24tpi, 27tpi, etc.) You can engage on either 1 or 4 for other inch thread pitches. Finally, you cannot use the thread dial at all for metric threads.

For metric threads you have to stop the motor, back the tool out of the cut, reverse the motor until the tool has cleared the start of the thread, stop the motor, reset the tool, set the motor in forward and start the next pass, leaving the half nut engaged at all times until the thread is complete.

TechTony
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Re: Thread Gearing on a BT800

Post by TechTony » Wed Nov 02, 2016 5:52 pm

that's concerning (about the metric threads)..... since I really like running my threads with the motor in reverse and the tooling mounted upside-down..... guess i won't be doing too many metric threads.... hopefully....

Torch
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Joined: Wed Mar 17, 2010 7:58 am
Location: Muskoka

Re: Thread Gearing on a BT800

Post by Torch » Wed Nov 02, 2016 6:29 pm

TechTony wrote:that's concerning (about the metric threads)..... since I really like running my threads with the motor in reverse and the tooling mounted upside-down..... guess i won't be doing too many metric threads.... hopefully....
Ok. So do the same thing except wind the tool post away from you and put the motor in forward to the left side of the thread then. It doesn't really matter, so long as you do not disengage the half nut from the leadscrew until the thread is completely finished.

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SteveM
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Re: Thread Gearing on a BT800

Post by SteveM » Thu Nov 03, 2016 11:28 am

Keep in mind that when you are threading, the thread dial WILL NOT TURN.

That is normal.

The carriage movement and the speed of the leadscrew exactly offset each other.

You will see it turning if you move the carriage manually, and it will turn when the leadscrew is turning but the halfnuts are not engaged.

If you don't know how to use the thread dial, google for a pdf of the book "how to run a lathe" by South Bend. There are older out-of-copyright versions available on the web, and how to use a threading dial probably hasn't changed since the Cubs won the world series.

Oh, yea, they just did.

Since the PRIOR time the Cubs won the world series.

Steve

TechTony
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Joined: Wed Aug 31, 2016 7:11 pm

Re: Thread Gearing on a BT800

Post by TechTony » Thu Nov 03, 2016 9:10 pm

Last post of page 1 of this thread.... got the dial rotation issue figured out. The hole wasn't machined out enough to allow the thing to rotate, so I fixed it. It was practically press fit into that block. Works as it should now. Thanks though.

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