# Does anyone ever need to thread anything finer than 56 TPI?



## qualitymachinetools (Oct 3, 2017)

Hey guys, working on some updated models of some small lathes, and every once in a while, I get people who ask me why a lathe does not thread any finer than 56 or 60 TPI. 
 What would anyone make that would be finer than that, anything common? 

I never remember cutting anything in my life finer than that, but I just wanted to see how important it was, if maybe I was missing something.


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## pdentrem (Oct 3, 2017)

The finiest I have done is 40 tpi to date. Likely model makers are using finer as some kits are using 0, 1, 2 sized machine screws.
Pierre


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## Bob Korves (Oct 3, 2017)

The lathes probably will already cut much finer threads, even using the feed setup instead of the threading setup.  There is not much room on the charts mounted to the lathes for TMI (too much information.)  Until you need it.  Only the most common and useful threads are shown on the charts, MANY more are usually possible using the stock gearing.  A comprehensive chart of them sent with the new lathe, and a downloadable file online would solve the issue for those willing to look it up.


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## Dave Paine (Oct 3, 2017)

After reading this thread I opened the manual for my Grizzly G9249 thread.   This illustrates Bob K's point.
The inch thread chart goes up to 112 tpi.  I never paid attention, only for the thread I needed at the time, which may have been up to 24 tpi.







The other chart in the manual is for metric and additional inch thread which is also greater than 44 tpi


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## pstemari (Oct 3, 2017)

Optical stuff also has very fine threads. I haven't taken a thread gage to my old Unihex, but I'm guessing it's around 80 TPI and 1.25" major diameter.

One of my backburner projects is to make an adapter so I can use it on my Meade LX50.

Sent from my Pixel XL using Tapatalk


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## Kernbigo (Oct 3, 2017)

i used to make taps and thread gages, i threaded 140 pitch 1 time, 00 80 was very common


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## British Steel (Oct 3, 2017)

Toolroom lathes also have a wide range, mine has:






It does need a couple of gears swapped for Metric, though, and some I don't have for DP and Module pitches (the same ones), a hatful for BA threads which don't adhere to anything in the QCGB...

Dave H. (the other one)


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## wrmiller (Oct 3, 2017)

I have done up to 80 tpi, but typically don't use anything finer than 60 tpi. Mostly for telescopes and small stuff requiring precision movement like that.

For most of my stuff I don't get beyond 40 tpi.


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## Cobra (Oct 3, 2017)

I did some 72 tpi for a microscope eye piece on the little EMCO Compact 5 I started with.


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## ttabbal (Oct 3, 2017)

Not even a tease of what you're working on?


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## qualitymachinetools (Oct 3, 2017)

Reason I am asking is that I am working on a smaller machine and trying to eliminate change gears.  But there is only so much room.   So if we just left off anything 60 or higher, wanted to see if there was anything common that I was missing.  The 1340GT and others we have go up to 112TPI without a change gear, but I am trying to simplify for a smaller machine.      Its nothing too fancy, working on maybe a 10" to 12" smaller hobby lathe with a better gearbox.             The hard part is that it has to fit on the machine, these lathes are not that big.


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## ttabbal (Oct 3, 2017)

qualitymachinetools said:


> Reason I am asking is that I am working on a smaller machine and trying to eliminate change gears.  But there is only so much room.   So if we just left off anything 60 or higher, wanted to see if there was anything common that I was missing.  The 1340GT and others we have go up to 112TPI without a change gear, but I am trying to simplify for a smaller machine.      Its nothing too fancy, working on maybe a 10" to 12" smaller hobby lathe with a better gearbox.             The hard part is that it has to fit on the machine, these lathes are not that big.




Very interesting. I've been seriously considering a 1030 from you guys. For what I'm thinking to use it for, I don't see topping out at 60 TPI to be a big issue. Things like telescopes can use finer threads, but if I couldn't get a die for that I could also look into gearing or just farming that part out. As someone that might be considered part of the target market, I don't think I'd look down on a machine that couldn't go finer, particularly if it gets me no change gears for the rest and other features/equipment/price were in my range.


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## Doubleeboy (Oct 3, 2017)

I would think for the market you are after Matt 56 tpi would be fine.  I know watchmakers and telescope makers use finer threads, but compared to how many of those people you would loose a sale to you could afford to loose those if you could make a great little lathe that would appeal to the larger market.  I think something the size of a Myford with a good gear box, rigid ways and VS would be a great seller, especially if you could get good quality from China factory to keep price down compared to Taiwan machine.


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## Ulma Doctor (Oct 3, 2017)

personally, i haven't cut threads finer than 32 tpi, but i work on industrial equipment.
IMO a lathe that switches easily from metric to imperial threading easily would be a major plus.
my shenwai 1236 cuts from 4 to 112 tpi without any gear changes-
metric threading i gotta change gears.


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## pdentrem (Oct 3, 2017)

I know that there are some lathe that have a simple gear box and with a simple gear change that cuts the feeds by half with a compound gear. That would work for most users perhaps?
Pierre


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## whitmore (Oct 3, 2017)

qualitymachinetools said:


> Hey guys, working on some updated models of some small lathes, and every once in a while, I get people who ask me why a lathe does not thread any finer than 56 or 60 TPI.
> What would anyone make that would be finer than that, anything common?



Not really.   #1-72 and #0-80 are down in the eyeglass-hinge size range.
Used taps/dies and off-the-shelf hardware, but never a lathe, on those.
If a real need for smaller adjustment screws came up, a differential screw with
20  tpi and 25 tpi generates a virtual 100 tpi  effect, and is a LOT less difficult
to cut.   Except that '25 tpi' apparently isn't available in standard taps/dies.


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## rzbill (Oct 3, 2017)

Would this machine have change gears in addition to a gearbox? If so, alternate threads might be available to the specialized user by buying a couple of gears extra.  Others would use the range up to 56 or 60 as suggested.

EDIT>Ah, I see that was already suggested 2 post above. Sorry about that.


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## jim18655 (Oct 4, 2017)

I made a "center dot" adapter for an Ambo adjustable iris" that was very fine threads. I forget what size thread but I had trouble getting a fine enough point on the treading bit to make a nice cut.


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## RandyM (Oct 4, 2017)

jim18655 said:


> I made a "center dot" adapter for an Ambo adjustable iris" that was very fine threads. I forget what size thread *but I had trouble getting a fine enough point on the treading bit to make a nice cut*.



I have been wondering about this. Seems it could be quite fussy.


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## mksj (Oct 4, 2017)

qualitymachinetools said:


> Reason I am asking is that I am working on a smaller machine and trying to eliminate change gears.



I think there would be have a significant market in a smaller lathe without/minimal gearbox change gears, I can't see needing anything beyond 56 TPI in this size lathe. As others have pointed out, it is possible to sell a set of change gears, or possible flip the input and output gears for a different set of ratios. But the market for anything beyond 56 TPI is very limited, and I believe there is much greater value to not having to deal with change gears for the most common threads.  Below is an example of a 11x26 lathe which covers up to 56 TPI, but a major disadvantage is that you need a pile of change gears.   I often suggest to small lathe buyers going with the next size larger lathe, so they do not have to deal with a mess of change gears, and it also gives them more feeds without flipping gears. The other day I was cutting metric threads, and just dealing with re-gearing to 120/127 and back to imperial reminded me of what a PTA it is to deal with gear changes. Really made me appreciate a full range imperial gearbox w/o change gears. Other wish lists would be variable speed with 2 or 3 speed ranges, so something like the PM1022V or PM-1127VF-LB with a full range gearbox I think would be a killer combination, but the latter would be very similar to the PM-1228VF-LB.


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## qualitymachinetools (Oct 4, 2017)

OK Thanks guys, yes thats what I am going for, no change gears for inch threads from 4-56 TPI or so.    I just wanted to make sure I wasnt missing anything obvious thats finer than 56TPI.  A few cases came up, but nothing that I see thats too common.  Just checking my thinking against others for a bit.      I've done a lot of difficult things in a machine shop, worked on some pretty difficult jobs. But I am not sure if I would be able to make a #1 screw. Heck even a 4-40 is tiny. 

   There will be change gears for Metric, the gearbox to do that without change gears is just way too big for these smaller machines.   We are just working on shrinking down a gearbox like the one from the 1340GT that cuts them all without a change gear, so it can fit on a smaller machine.      My goal is a 10/11" Lathe with a quick change gearbox, no change gears for any common inch threads. At a reasonable price. None exist that I've ever found.


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## ttabbal (Oct 4, 2017)

That sounds great! Any idea when something might be available? I'm likely a couple months out, but I suspect this project of yours might take longer than that.


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## woodchucker (Oct 4, 2017)

RandyM said:


> I have been wondering about this. Seems it could be quite fussy.


They do make micro threading tools. I have seen them in the catalogs at one point. I imagine they are pricey, as I don't remember anything other than seeing them. You put that in the back of your brain for reference if you need it... ya  know.


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## qualitymachinetools (Oct 4, 2017)

Depends on the factory, but I'd say about a year or so, it takes some time. Nothing is 100% yet, if its going to cost as much as a 12", then there is no point, but we will see.


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## dave2176 (Oct 4, 2017)

Just one guys opinion but if a 12x36 costs $3,000 plus and a high quality feature rich 10x22 could be had sub $2,500 I think you would have a winner. I don't think it needs to be in the $1,500 range like other 10x22 machines that are lacking features. The features I would go for include larger bore than normal for this size, say 1.25" or more. Extend the spindle just enough to drill it for spider screws. An apron with the features of the 1340GT. QCGB like the 1340GT minus a couple gears. With gear changes the 1340GT can likely get in the 250TPI gear range anyway. If this little guy could do 4-40 TPI without a change that would be great. Change the drive and driven gear from 40-40 to 30-60 and you double the capability and get 80TPI. Use 120/127 for the idler gear instead of the 86/91 used by many lathes to get dead on accuracy with metric threads rather than close enough. Thread the mounting holes for adjustable feet for use on a bench. Throw in a little extra mass so it is rigid for its size. Sorry, now I'm just rambling. Sounds like a great lathe that would fit on a work bench.

Best of luck in your pursuit,
Dave


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## bretthl (Dec 1, 2017)

qualitymachinetools said:


> Reason I am asking is that I am working on a smaller machine and trying to eliminate change gears.  But there is only so much room.   So if we just left off anything 60 or higher, wanted to see if there was anything common that I was missing.  The 1340GT and others we have go up to 112TPI without a change gear, but I am trying to simplify for a smaller machine.      Its nothing too fancy, working on maybe a 10" to 12" smaller hobby lathe with a better gearbox.             The hard part is that it has to fit on the machine, these lathes are not that big.



If it is a smaller lathe, why not eliminate some of the coarse thread pitches.  I don't know much about lathes but if someone were to purchase a smaller lathe perhaps they would be doing finer threading work.  If I were working on instruments and needed a lathe I would want one that is super smooth and quite with tollerances to handle fine work.  Is it practical to thread 8 TPI in steel on a 1 HP lathe?


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## pdentrem (Dec 1, 2017)

I threaded 8 tpi on my Atlas with 1/2 hp. What you likely cannot do is take a .100" for a total of .200"!
Pierre


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## woodchucker (Dec 1, 2017)

bretthl said:


> If it is a smaller lathe, why not eliminate some of the coarse thread pitches.  I don't know much about lathes but if someone were to purchase a smaller lathe perhaps they would be doing finer threading work.  If I were working on instruments and needed a lathe I would want one that is super smooth and quite with tollerances to handle fine work.  Is it practical to thread 8 TPI in steel on a 1 HP lathe?


If you need that high find a watch lathe.  Generally the swiss make watches on lathes that have no power, they hand turn the spindle.
Consider that most of the lathes old and new fit what is generally needed for the size.  And the higher threads might be considered fine, or super fine.


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## rwm (Dec 1, 2017)

Is 60 TPI possible? What is the diameter of an iron atom? 
Robert


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## Dabbler (Dec 2, 2017)

I've had to do 40tpi a bunch, but never finer in 38 years.


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## tq60 (Dec 4, 2017)

A high feature good quality machine in a smaller package would be attractive to many with limited space.

Cannot have everything so if change gears will be considered for metric then possible change gears for fine threads.

We do not consider doing that work but having super fine feed is a must.

Make the spindle same as larger model to allow interchangeable parts to reduce product lines.

3 phase motor with vfd single phase input and gear head to allow better speed control.

Fastest rpm possible.


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## sjg (Dec 24, 2017)

Threaded spindle nose is the main turn off for most small lathes, that said I used to have an ancient - flat bed! myford


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