Jet 9X20 lead screw ?

I just got around to noticing a table for using the threading indicator. The table is the usual listing of indicator readings versus thread pitch.
However I just noticed that the thread pitch column is labeled TPI and the threads listed are all imperial threads.. I have reason to believe that the lead screw is metric.
So my question is, where is the error? Is my lead screw wrong and I should have a Imperial or is the label wrong and no 9X20 was ever shipped with a imperial lead screw.
Confused Bill K7NOM
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Based on what?
Btw, it might help if you told us the vendor of your particular 9x20.

I have yet to come across a 9x20 with anything but Imperial leadscrew & threading dial (at least in the US market). I would love to have a true metric leadscrew (and metric threading dials) on my 9x20 lathe. If you really do have a metric set-up, perhaps we could trade parts?
Regards, Michael
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Oops, I guess I get the "reading-impaired award" for the day. Missed the brand name "Jet" in the subject line.
Jet 9x20 lathes definitely have Imperial leadscrews & threading dials.
- Michael
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DeepDiver wrote:

I tried cutting a 8 TPI thread using the 1 on the dial and got three diferent start positions. Just counted the threads and it 16 or nearlu 16 per inch
Bill K7NOM
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Without seeing or knowing what you are actually doing (and without knowing your background or experience), it is hard to tell what the problem is. But I suspect it's a procedural error. If I'm wrong, I apologize.
I have an Enco 9x20, which is essentially identical to the Jet in every way except for the spindle nose threads (for mounting chucks) and the paint scheme. While I rarely cut Imperial threads, I have done so successfully by disengaging the halfnuts and using the threading dial. It worked exactly as advertised.
Regards, Michael
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I have a JET 9x20 and I successfully threaded a new back plate on it for a 4-jaw chuck without any problems. The spindle is 1 1/2 x 8TPI.
Have you checked to be sure the gear on the end of the thread dial is snug up against the lead screw? It could be skipping if it's loose.
Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"I'm not grown up enough to be so old!"
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This is a multi-part message in MIME format. --------------010707080105080902060809 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit
Thanks for all the comments. I must have used the wrong combination of gears even though my threads were close enough to be usable. So I will try again but this time I will double check the gear combination.
Bill k7NOM
Keith Marshall wrote:

--------------010707080105080902060809 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> <title></title> </head> <body bgcolor="#ffffff" text="#000000"> Thanks for all the comments. I must have used the wrong combination of gears even<br> though my threads were close enough to be usable. So I will try again but this time<br> I will double check the gear combination.<br> <br> Bill k7NOM<br> <br> Keith Marshall wrote: <blockquote cite="midRYche.28263$ snipped-for-privacy@twister.southeast.rr.com" type="cite"> <blockquote type="cite"> <pre wrap="">I tried cutting a 8 TPI thread using the 1 on the dial and got three diferent start positions. Just counted the threads and it 16 or nearlu 16 per inch </pre> </blockquote> <pre wrap=""><!----> I have a JET 9x20 and I successfully threaded a new back plate on it for a 4-jaw chuck without any problems. The spindle is 1 1/2 x 8TPI.
Have you checked to be sure the gear on the end of the thread dial is snug up against the lead screw? It could be skipping if it's loose.
Best Regards, Keith Marshall <a class="moz-txt-link-abbreviated" href="mailto: snipped-for-privacy@progressivelogic.com"> snipped-for-privacy@progressivelogic.com</a>
"I'm not grown up enough to be so old!"
</pre> </blockquote> <br> </body> </html>
--------------010707080105080902060809--
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I have a Jet 12x36 IIRC, to cut metric threads, you have to change the "gears" could your lathe have the "wrong" <metric> gears installed
PS Jet is very helpful for info about this kind of stuff
HTH Otto
"I'm not grown up enough to be so old!"
</PRE></BLOCKQUOTE><BR></BLOCKQUOTE></BODY></HTML>
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    Did you by any chance touch the reverse tumbler while doing the thread? That has to remain engaged until the thread is done, or you get as many different start positions as you have teeth in the tumbler gears.
    Good Luck,         DoN.
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Hi Don,
I know you're not familiar with the 9x20 lathe. FYI, it has no factory tumbler reverse. (However, there are a number of people who have added their own. It's on my list of things to do.)
- Michael
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    O.K. Then it is not a possible mistake -- yet. :-)
    Hopefully, one of the other suggestions will have led you to the solution by now.
    Good Luck,         DoN.
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    He did -- but only in the "Subject: " header, not in the body. I know that it is typically quite a while between the time I select subjects to read and the time a given article pops up, so I sometimes have to remember to look back at the headers.
    As for the original question -- others know the machines better than I -- but I think that all in the US have Imperial leadscrews -- at least the longitudinal one used for threading.
    The cross-feed and compound ones may be a near fit metric, especially if you wind up with weird counts on the dial for a full turn, like 127 or 63-1/2. Precise counts of 200 or 100 or 50 are more likely to be true imperial screws.
    Enjoy,         DoN.
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wrote:

Yes Don, I caught that as soon as I posted the first response (and acknowledged my error in an immediate follow-up post).
- Michael
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    Yes -- but one which I did not see until I posted mine.
    But people really need to be careful to duplicate the information in the "Subject: " header down in the body, so as to make this sort of thing harder to stumble over.
    Sorry,         DoN.
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I have one that is called a CT-918 it may be the same as your 920. My manual provides tables to allow cutting of both imperial and metric threads by making some gear changes. Metric threads are from 0.5 to 3 mm, inch are from 8 to 56 threads per inch. Do you have a manual and the change gears?
Jack
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It isn't too hard, Bill. You hold up a ruler next to your lead screw and count the threads per inch and see if you get e.g. 8 for 1" 16 for 2", 96 for 12" .. GWE
Bill Janssen wrote:

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Grant Erwin wrote:

Ok I get 16 or so for one inch.
Bill k7NOM

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According to the manual the model BD-920N has a 9/16" x 16 TPI leadscrew. Usually though there is a metric/inch change gear, or on fancy machines just a selector. I believe the magic gear is a 127 tooth gear (25.4*5 = 127 zero conversion error). I have used Russian made all metric machines that cut beautiful inch pitch threads, and vice versa. It doesn't really matter whether the lead screw is inch or metric as long as the gear ratio is correct you can cut any pitch you want. - where it matters is in the cross slide, if you have a metric dial that sucks.

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Dean wrote:

My Grizzly G0516 is listed as having a 3/4"x10 tpi leadscrew but it is 20mm and 12 tpi. So much for the manual. I had to sort this out so I can build a thread dial for it.
dp
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That reminds me, There is one flaky thing about using a metric pitch machine cutting inch threads (at least the Russian lathes) & it is that the half nut, on some pitches, can only be engaged on the exact same unique point on the thread dial or you might not be in sync with the previous cut. They make it tricky though by marking the dial like an inch machine so you think you can just drop it in whenever your number comes by. A colleague of mine ruined a leadscrew nut for a 5" HBM made from a cu$tom bronze ca$ting due to this.
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