PM1236 QCGB - Complete Thread Pitch List

darkzero

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This was originally posted in post #16 here. Posting the information here to find it easier.

I have a PM1236 & it also doesn't list 27 TPI or 11.5 TPI. A while back I wanted to figure out how to cut 11.5 TPI. Looking at the chart on my lathe I figured that I simply needed a 23T gear which was not included with my lathe. I never ended up trying to locate one cause I found something else.

Member ftl on HSM (I wanted to mention to give him credit) created 2 documents that listed every single possible thread that could be cut on a PM1236 with the stock gears. Sadly the DL links were expired so scouring the net for those 2 PDFs, to my surprise someone had uploaded them here on H-M in a post.

I haven't verified if the PDFs are accurate but they seem to be. And if they are (hopefully) they are absolutely invaluable to anyone with a PM1236. In the "All_Pitches" PDFs it shows change gears & QCGB combinations that will allow you to cut pretty much any thread pitch you could ever want...and then some. In it shows 27 TPI & most importantly for me 11.5 TPI (if I ever want to make some garden hose fittings or large pipe thread but I don't have a taper attachment).

The docs are in the post that I linked to but I'll upload them here too (I renamed the files though to better describe them)
 

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  • PM1236_ftl_All_Pitches.pdf
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  • PM1236_ftl_Common_Pitches.pdf
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This is interesting. I was shopping for a lathe in the 1236 size range and saw that it would not cut 27 or 11.5 TPI. I sent PM an email asking if any other of their other small lathes would do these pitches and was told that the 1440GS would do 11.5 but none would do 27. I may go back and look at these machines again. Do all the gears listed in these charts come with the lathe?
 
It all about the gears. The 1236GT and 1340GT will cut a 27 TPI and would be able to cut an 11.5 TPI if a 23T gear was made. The smallest gear I am aware of is 30T. The combination of gears 23-120 and 120-32 when using using C1 gear selector gives 11.5 TPI. Usually lathes come with a fixed set of change gears, sometimes there are optional gears that might be available or you can cut your own gear. The thing about playing with gear charts, is often you can come up with combinations and pitches not listed, or ones that are very close that they might be usable.
 

Attachments

  • PM 1340GT Gear Chart.pdf
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Do you know what pitch and pressure angle the change gears are that are used in the 1236GT and 1340GT?
 
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