# 11.5 Threads Per Inch Possible On Pm1236?



## Lynrob (Aug 18, 2015)

I have a PM1236 lathe and I need to make a part with 11.5 threads per inch.  11.5 is not listed in the threading chart on the side of the lathe but I was wondering if there is a way to do it?  Also, the change gears on my lathe are so tight that I need to use a gear puller to get them off.  Is that normal?


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## roadie33 (Aug 18, 2015)

If it will do 2.2 in metric, that might work if it's not too long of a thread. Test it out on a piece of scrap and see if it matches.


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## springer (Aug 18, 2015)

Not sure about the thread pitch question, but my change gears are extremely hard to get on and off as well. I don't need a gear puller, but still hard. I took them all off, cleaned them dry and lubed them as well as the shafts they go on and that helped a bunch.


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## blaser.306 (Aug 18, 2015)

Is what you are looking for a "measured thread" or a listed one (  cannot go to my Machinery's handbook) to see if it is noted there? Perhaps it is as simple as a metric thread


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## Lynrob (Aug 19, 2015)

I hadn't thought of trying a close metric thread... I'll check into that.  I have also removed, cleaned and lubed my gears and shafts without any noticeable improvement.  Luckily I haven't had to change the gears too often.


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## T Bredehoft (Aug 19, 2015)

Yeah, metric 2.2 might work. It comes out to 2.208. That's well under 1% error,  turns out to be .oo4% ± one decimal place.


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## RJSakowski (Aug 19, 2015)

T Bredehoft said:


> Yeah, metric 2.2 might work. It comes out to 2.208. That's well under 1% error,  turns out to be .oo4% ± one decimal place.


Tom, 

It's actually .4% but with a short enough thread engagement and perhaps a slightly undersized thread, it should work.

Bob


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## Lynrob (Aug 20, 2015)

Thanks everyone!  I'll give it a try this weekend.


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## lpeedin (Aug 25, 2015)

Are you working on a garden hose fitting?  I just made a water balloon filler adapter for my kids and I believe that was what the actual garden hose thread is.  Since I only need a few threads, I went with 12 pitch since that was the closes my PM1127VF-LB would do.


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## Andre (Aug 25, 2015)

3dshooter80 said:


> Are you working on a garden hose fitting?  I just made a water balloon filler adapter for my kids and I believe that was what the actual garden hose thread is.  Since I only need a few threads, I went with 12 pitch since that was the closes my PM1127VF-LB would do.


 I believe garden hoses and pop bottles are 11.5 TPI. So are M1 barrels strangely enough.


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## John Hasler (Aug 25, 2015)

Andre said:


> I believe garden hoses and pop bottles are 11.5 TPI. So are M1 barrels strangely enough.


It's also an the NPT thread for 1", 1.25", 1.5", and 2" pipe.


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## falconer (Jan 20, 2016)

I'm new to the machining world so this might be a simple answer for some of you more experienced guys , but can a PM1236 be modified to cut finer than 60TPI?


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## John Hasler (Jan 20, 2016)

Lynrob said:


> I have a PM1236 lathe and I need to make a part with 11.5 threads per inch.  11.5 is not listed in the threading chart on the side of the lathe but I was wondering if there is a way to do it?  Also, the change gears on my lathe are so tight that I need to use a gear puller to get them off.  Is that normal?


11.5 TPI is NTP standard for 1", 1.25", 1.5", and 2" pipe.


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## T Bredehoft (Jan 20, 2016)

falconer said:


> can a PM1236 be modified to cut finer than 60TPI?



I don't know what you're after, but my lathe right is set up for chasing 400 TPI, (.0025 per rev feed)  I'm not threading, just turning a diameter, but with a sharp enough threading tool, I could be chasing threads.


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## dave2176 (Jan 20, 2016)

falconer said:


> I'm new to the machining world so this might be a simple answer for some of you more experienced guys , but can a PM1236 be modified to cut finer than 60TPI?



The answer is in what do you have for change gears? Most lathes are capable of far more feed rates  (aka thread pitches) than they list. So if you set up for 60 tpi, do you have additional gears in your set that can create a finer feed? I don't have access to the specs to give a better answer so start with what you know and do the math by inserting other gears into the equation. 
Dave


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## carlquib (Jan 21, 2016)

I don't know how similar your qc gearbox is to the one on my pm1440 but I ended up using the formula, standard driving gear x gearbox  setting(in tpi) divided by standard driven gear x desired tpi and came up with 48 driver/46 driven, then set the lathe to cut 11 tpi. This setting and the above mentioned change gear combination produced the desired 11.5 tpi  threads.

Hello, my name is Brian and I'm a toolaholic!


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## Lynrob (Jan 21, 2016)

Thanks! I'll give that a try!


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