# 11.5 TPI



## Just for fun (Sep 14, 2022)

I had the desire to cut a 11.5 TPI thread the other day.  Found out my 1236T does not cut 11.5 TPI.

I have read through quite a few threads on the subject and have concluded that I either need a 23T or a 46T change gear before my lathe will cut that thread.  I have reached out to PM and neither one is available.

I have a friend that has a 3D printer, I haven't asked him yet but I'm thinking if I had a drawing, he could make me one.

So, my question is does anyone have a drawing and/or the file needed for him to make me a gear?   Or another solution so I can cut 11.5 TPI. 

Tim


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## Janderso (Sep 14, 2022)

I had to check, my lathe has the 11.5 setting. Never had a need, yet.

Smart people will be along to help you....


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## Funbact (Sep 14, 2022)

Just for fun said:


> I have a friend that has a 3D printer, I haven't asked him yet but I'm thinking if I had a drawing, he could make me one.



Do you have any change gears at all for the machine? If so, measure the outside diameter of one you have (preferably one with an even number of teeth) and report that number and the number of teeth. That will allow us to identify the specification of the gear. You can then download GearDXF and produce an outline of the 23t or 46t gear for 3DP. You will have to measure and draw the centre detail of the gear yourself, but if it is complicated, you can bolt or pin the new gear concentrically to one of your existing gears as long as the one you use is smaller and does not get in the way.


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## DAT510 (Sep 14, 2022)

Looking at the PM manual and supplemental Thread chart (PM 1236T And 1340GT Thread Chart) it appears your lathe has the same quick change gear box ratios as my Jet 1024.  I'm attaching an excel spreadsheet I made, based on the 30t, 32t, 40t and 46t gears I had, that calculates additional pitch combinations that weren't included on my threading placard.  What Change Gears do you have?   My table also shows you can also achieve 11.5tpi with a 32t/40t combo or 40t/46t combo.

A couple of options:

My change gears have an ID of 0.710 or ~18mm.  If your machine uses the same ID, Grizzly has the 32t and 46t in stock (Items# 1117, 1118) for $25.58 & $39.60 respectively.  https://www.grizzly.com/products/g9249/parts  If the DP is the same you could try and order them from Grizzly.













Then there's Rush Gears:  https://www.rushgears.com/tech-tools/part-search/build-custom-gears

You can input your gear requirements and it will output a DXF file that you can use to 3D print your gear.

Hope this helps.


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## mksj (Sep 14, 2022)

The 1236T/1340GT do not cut an 11.5 pitch which is a standard pitch for hoses. Some people have had decent success with 3D printed gears if for occasional use, but there are a number of companies that will make them as a single item.
Two other links for custom gears.


			Any Gear Made Quickly Inexpensively & Perfectly Al Meekins GearsMade.com. --Delrin gears Plastic gears Bevel gears Worm gears Spur gears Helical gears Phenolic gears Stainless steel gears Cast iron gears Machine gears Steel gears Metric gears Bronze 
		






						Gear Making | American Machine & Gear Works
					






					www.thegearmaker.com


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## DAT510 (Sep 14, 2022)

Funbact said:


> The ID of a gear tells you nothing about the spec. of the gear.



The reference to the ID was so that "Just for Fun" could see if the Grizzly Gears might fit the shaft of his Lathe.  No need to even consider ordering the gears if the ID is different.  A call to Grizzly could then help determine the DP of the Gears.  


As mentioned........


DAT510 said:


> If the DP is the same you could try and order them from Grizzly.


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## darkzero (Sep 14, 2022)

I have heard if you single point a 12 TPI thread on the sloppy side, it will fit garden hoses fine since garden hose ends don't have a really long thread. I have no idea if that's true though, haven't needed to try myself yet.


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## MrWhoopee (Sep 14, 2022)

Funny, my SB cuts both 11.5 and 27 tpi, threads that haven fallen out of favor with many lathe manufacturers but not with hose and pipe makers.


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## Ischgl99 (Sep 14, 2022)

Maedler Gears makes metric gears and might have something suitable.  You might need to modify it, but since you have a lathe, that won’t be a problem.









						Drive-train specialist - Large metric inventory - Maedler North America
					

Maedler North America offers an extensive range of industrial transmission components for sale. Huge inventory / online store!




					maedlernorthamerica.com


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## WobblyHand (Sep 14, 2022)

An ELS is not limited to standard threads.  Just an option.


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## jocat54 (Sep 14, 2022)

Some one made a PDF file that pretty much covers all the TPI. Have used it a couple of times and was accurate for me. Don't remember who or I could give them the credit


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## Just for fun (Sep 14, 2022)

Thanks for the responses and the links.  The ELS system would work but it's not that important to go to all that work.  I believe I have seen all of the charts that have been produced and there are some combinations that come close, but not exact with the gears I have.

@Funbact I checked out the program GearDFX, that pretty cool.  And I do have some other change gears I just didn't get any measurements yet.

With all the question that have come before mine, I was hoping that someone would have a file for a 3D printed gear that they would be willing to share.

I Grizzle one is 10 thousand to large on the bore.  And I still need to learn what DP is and how to measure it.


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## Ken226 (Sep 15, 2022)

Just for fun said:


> Thanks for the responses and the links.  The ELS system would work but it's not that important to go to all that work.  I believe I have seen all of the charts that have been produced and there are some combinations that come close, but not exact with the gears I have.
> 
> @Funbact I checked out the program GearDFX, that pretty cool.  And I do have some other change gears I just didn't get any measurements yet.
> 
> ...



I'd be more than happy to model a gear for you and provide a .STL file for 3d printing,  but it isn't possible with what little info has been provided so far.

Awhile back @Chewy was needing a thread dial gear for his pm1226









						While we are on gears
					

We have had several recent posts about gears, so I thought I would add this one.  I have a PM 1228 lathe and the thread indicator gear is toast.  I did some work on the carriage and noticed the thread indicator was not turning.  After taking it off I found that the shaft was seized and the gear...




					www.hobby-machinist.com
				





Assuming yours uses the same gear spec as his thread dial,  it's a .91 module (diametral pitch 28) , and 20° pressure angle, but thats just a wild guess.   With some luck, maybe he would know if his change gears are the same spec as his thread dial gear.

If you can measure one of your gears and give me the tooth count,  outside diameter, thickness, bore diameter and keyway size,  it would be easy to calculate module/pitch diameter and produce a .stl file for your 23t/46t change gears.


I sketched one right quick, using  0.91mm module and 23 teeth,  but without knowing the thickness, hole diameter and key size,  it won't help you much.









Just an FYI,   if your gears fit an 18mm shaft with a 4mm key,  then a 23T gear isn't going to work for you.   I'd recommend going with the 46T instead.










This is the online calculator I use to get the info needed to model gears using Alibre Design:








						Gear Dimensions Calculator | Evolvent Design
					

Calculator to make the right dimensions for a gear or gear blank: calculate gear pitch, outer diameter (OD), root diameter, and clearance.




					evolventdesign.com


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## Ischgl99 (Sep 15, 2022)

The gears are module, so you will need to use the formulas for an M1.25 gear to determine what size will fit and not the DP formulas .


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## RJSakowski (Sep 15, 2022)

Diametral pitch is calculated by measuring the o.d. of a gear, and dividing that number into the number of teeth + 2.  Module is calculated by dividing the o.d. in mm by the (number of teeth + 2).  Diametral pitch x mod = 25.4. 

When calculating either d.p. or mod, the numbers will be slightly off, due to the o.d. of the gear being slightly less than theoretical but they will be close enough to determine the correct value.  The calculations can also help to determine whether a gear is metric or inch.  One of the calculations will be significantly different from standard d.p.'s or mod's  to make that determination.  Asian gears are typically metric while  USA old iron gears are inch.


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## RJSakowski (Sep 15, 2022)

https://www.sdp-si.com/products/Gears/Index.php is a good source for gears at a reasonable cost.


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## RJSakowski (Sep 15, 2022)

I have used gear generator.com to create gears.  Gears can be downloaded in various file formats.








						Involute spur gear generator and simulator
					

Gear Generator is a tool for creating involute spur gears and download them in SVG format. In addition it let you compose full gear layouts with connetcted gears to design multiple gears system with control of the input/output ratio and rotation speed. Gears can be animated with various speed to...



					geargenerator.com


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## RJSakowski (Sep 15, 2022)

One last point and then I'll quit.  You also have to know the pressure angle of the gear set in order to purchase or make a gear.  Gears are either 14.5º or 20º.


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## Just for fun (Sep 15, 2022)

Thanks guys,

I will get some measurements of the 40T gear today and post them on here.

@Ken226  Thanks for the offer.  And I will scratch the 23T gear off the list.

@RJSakowski  How do I know what the pressure angle of the gear is?


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## Ken226 (Sep 15, 2022)

From the manual on PMs website.

Double check your own manual.


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## Ischgl99 (Sep 15, 2022)

Ken226 said:


> From the manual on PMs website.
> 
> Double check your own manual.


That’s a typo, the change gears are M1.25.


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## Ken226 (Sep 15, 2022)

Ischgl99 said:


> That’s a typo, the change gears are M1.25.



I thought 2.25 sounded a bit, off.  

So, it's a M1.25,  20 degree PA  46 teeth.  That should be everything needed to sketch and model the teeth. 

OD Reference:      60.0000    mm    2.3622    in
Pitch Diameter:    57.5000    mm    2.2638    in
Base Circle:       54.0323    mm    2.1273    in
Root Diameter:     54.3750    mm    2.1407    in

Addendum:           1.2500    mm    0.0492    in
Dedendum:           1.5625    mm    0.0615    in
Working Depth:      2.5000    mm    0.0984    in
Whole Depth:        2.8125    mm    0.1107    in
Circular Pitch:     3.9270    mm    0.1546    in



All thats lacking is the info on the thickness, axle diameter and key size.  Once i have that, ill create a model and upload the .stl here for the OP, and anyone else.


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## Just for fun (Sep 15, 2022)

Oh Man,  Thanks guys.  All this gear stuff is a little mind boggling.  Something new to learn every day.

Thickness is 10 mm
Axle diameter is 18 mm   (I measured the gear)
Keyway 5 mm

I'll go measure the shaft just to make sure.


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## Ken226 (Sep 15, 2022)

Just for fun said:


> Oh Man,  Thanks guys.  All this gear stuff is a little mind boggling.  Something new to learn every day.
> 
> Thickness is 10 mm
> Axle diameter is 18 mm   (I measured the gear)
> ...



3d printers tend to print holes about 3%   undersize and external features about  3% oversize.  I'll adjust the dimensions of the model accordingly, unless you'd like otherwise.

Also,  it's easy to adjust the tooth count while doing this,  so if you'd like models with different numbers of teeth,  let me know and I'll post them up as well.


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## Just for fun (Sep 15, 2022)

Thanks Ken,   Is it a problem to do both incase I want to have a metal one made?  

I haven't asked my friend with the 3D printer yet, but I can't see where that would be a problem.   What would be the best materal to use for a gear like that?


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## Ken226 (Sep 15, 2022)

Just for fun said:


> Thanks Ken,   Is it a problem to do both incase I want to have a metal one made?
> 
> I haven't asked my friend with the 3D printer yet, but I can't see where that would be a problem.   What would be the best materal to use for a gear like that?




It's no problem,  but I need to know the tooth count.  Remember, 23t is smaller than the keyway diameter.


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## Ken226 (Sep 15, 2022)

Here is the .stl file.  I scaled the outside down and the hole up, about .15mm to acct for the amount most 3d printers tend print over/under sized.


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## Just for fun (Sep 15, 2022)

Ken226 said:


> It's no problem,  but I need to know the tooth count.  Remember, 23t is smaller than the keyway diameter.


46T is what I'm looking for.


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## Just for fun (Sep 15, 2022)

Ken226 said:


> Here is the .stl file.  I scaled the outside down and the hole up, about .15mm to acct for the amount most 3d printers tend print over/under sized.
> 
> View attachment 420470


Very cool....  Thank You


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## Ken226 (Sep 15, 2022)

Just for fun said:


> Very cool....  Thank You



If you able to print one and make sure it fits,  I'll keep the part model file in case you need changes,  or a different tooth count.


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## MikeWi (Sep 15, 2022)

"3d printers tend to print holes about 3% undersize and external features about 3% oversize. I'll adjust the dimensions of the model accordingly, unless you'd like otherwise."

You can't assume a specific percentage, and if the owner has properly calibrated the printer, they already are taking that into account. All slicer software allows you to adjust for the error, even accounting for the different filaments you use. You just have to determine what those adjustments are for that printer/filament (gross generalizations being committed here).


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## Just for fun (Sep 15, 2022)

Ken226 said:


> If you able to print one and make sure it fits,  I'll keep the part model file in case you need changes,  or a different tooth count.


Sounds good thanks.


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## Ken226 (Sep 15, 2022)

Just for fun said:


> Thanks Ken,   Is it a problem to do both incase I want to have a metal one made?
> 
> I haven't asked my friend with the 3D printer yet, but I can't see where that would be a problem.   What would be the best materal to use for a gear like that?



Sorry,  I missed your question earlier regarding the best material.

a 3d printed gear isn't going to last with a thread as coarse as 11.5tpi regardless of which plastic is used.  Nylon would probably be strongest, but most consumer 3d printers aren't likely capable of doing nylon.  I would just use PLA,  and expect the gear to be a consumable than needs frequently replaced.

If you want one that will last, consider the 3d printed gear as a temporary stopgap and order a metal gear.

I have some PLA gears I printed for infrequent weird pitches.  They have actually surprised me at how long they have lasted, but i'm mostly doing finer pitches that involve lower cutting forces.


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## Ken226 (Sep 15, 2022)

Here is a .stl for the same gear, but modeled to actual dimensions with no offsets.

In case your friends 3d printer is adjusted/calibrated such that the offsets aren't needed.


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## Just for fun (Sep 15, 2022)

Ken226 said:


> Here is a .stl for the same gear, but modeled to actual dimensions with no offsets.
> 
> In case your friends 3d printer is adjusted/calibrated such that the offsets aren't needed.


Thanks, I'm getting ready to check some of the web sites on having a metal gear made, I might just go that route and call it good.  I appreciate all your help.

Tim


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## RJSakowski (Sep 15, 2022)

Just for fun said:


> Thanks guys,
> 
> I will get some measurements of the 40T gear today and post them on here.
> 
> ...


That's actually a tough one, especially for smaller gears.  Without a known gear or gage for comparison it comes down to a visual thing.  

The gear generator in the link above can be useful as you can change from 14.5 to 20 and back and see the difference.  Generate a  gear with the same number of teeth as one of your gears for the most accurate comparison.


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## B2 (Sep 15, 2022)

Just for fun said:


> I had the desire to cut a 11.5 TPI thread the other day.  Found out my 1236T does not cut 11.5 TPI.
> 
> I have read through quite a few threads on the subject and have concluded that I either need a 23T or a 46T change gear before my lathe will cut that thread.  I have reached out to PM and neither one is available.
> 
> ...


Check this out.  It provides lots of possible things plus approximate tpi settings.


Just for fun said:


> I had the desire to cut a 11.5 TPI thread the other day.  Found out my 1236T does not cut 11.5 TPI.
> 
> I have read through quite a few threads on the subject and have concluded that I either need a 23T or a 46T change gear before my lathe will cut that thread.  I have reached out to PM and neither one is available.
> 
> ...


Check out the following thread to find ALL possible tpi with all possible gears and gear box settings.   You should be able to get close to 11.5 if not exactly. 









						TPI Feeds X-Feeds: Generalized Excel file for your Lathe
					

TPI Feeds X-Feeds: Generalized Excel file for your Lathe  Hi Folks,  My PM1440GT lathe manual only showed a few of the possible threading values and it appeared to me that the Feed rates were incorrect.  They were.   Hence, I set about to figure out what all possible TPI could be achieved via...




					www.hobby-machinist.com
				




Dave L


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## Ischgl99 (Sep 15, 2022)

Just for fun said:


> Thanks, I'm getting ready to check some of the web sites on having a metal gear made, I might just go that route and call it good.  I appreciate all your help.
> 
> Tim


It looks like you will have to go the custom route, I didn’t see any 46 tooth M1.25 gears from the suppliers I know of.  I checked on having a couple gears made last winter that were half the size of what you are looking at, I never went through with the quote when she told me it would be very expensive for a one off.  That’s when I found Maedler had something I could modify to work.  It might be cheaper to find two stock gears of different tooth counts that will work rather than having a custom gear made.  You  could also post a request on the can you make me something forum and see if someone can do that cheaper for you then from a gear supplier.


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## Just for fun (Sep 15, 2022)

Ischgl99 said:


> It looks like you will have to go the custom route, I didn’t see any 46 tooth M1.25 gears from the suppliers I know of.  I checked on having a couple gears made last winter that were half the size of what you are looking at, I never went through with the quote when she told me it* would be very expensive for a one off. * That’s when I found Maedler had something I could modify to work.  It might be cheaper to find two stock gears of different tooth counts that will work rather than having a custom gear made.  You  could also post a request on the can you make me something forum and see if someone can do that cheaper for you then from a gear supplier.


That's what I'm thinking also.  My friend said he would make one for me with his 3D printer.  I don't really have that much of a need for one that would justify an expensive gear.  It's going to be interesting how long a plastic gear will last.

I was going to make a custom hose end for my wintertime stock tank hose.  It's kind of a long story but basically every time I add water to the stock tank I have to connect and disconnect a hose.  With the currently available hose ends it gets a little tough with gloves on.  So, I thought I would make one that was glove friendly. 

Another option would be for me to learn to make gears and make my own.  That might take a while though since I'm still trying to learn all the nomenclature as it is.


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## Ischgl99 (Sep 15, 2022)

Which part requires 11.5 TPI and can you design around it?  Since you are making custom fittings, might as well make it with what you have unless the 11.5 TPI goes into something you can't make yourself.  If this is for NPT, those are tapered as well, will you be able to do a tapered thread?


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## Ken226 (Sep 15, 2022)

Just for fun said:


> That's what I'm thinking also.  My friend said he would make one for me with his 3D printer.  I don't really have that much of a need for one that would justify an expensive gear.  It's going to be interesting how long a plastic gear will last.
> 
> I was going to make a custom hose end for my wintertime stock tank hose.  It's kind of a long story but basically every time I add water to the stock tank I have to connect and disconnect a hose.  With the currently available hose ends it gets a little tough with gloves on.  So, I thought I would make one that was glove friendly.
> 
> Another option would be for me to learn to make gears and make my own.  That might take a while though since I'm still trying to learn all the nomenclature as it is.



If you can't find anything else and don't mind ordering from the UK:

It's 13mm thick and has a 12mm bore.

You'd have to face 3mm off,  bore the hole to 18mm then cut a 5mm keyway.

26 Euros + whatever shipping from the UK.

And of course, not currently in stock. but it says "manufactured within 7 days of order".









						R5180 - Spur Gears - Module 1.25
					

R5180 Spur Gears - Module 1.25; Free CAD models available online.




					www.automotioncomponents.co.uk


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## Ken226 (Sep 15, 2022)

DAT510 said:


> Looking at the PM manual and supplemental Thread chart (PM 1236T And 1340GT Thread Chart) it appears your lathe has the same quick change gear box ratios as my Jet 1024.  I'm attaching an excel spreadsheet I made, based on the 30t, 32t, 40t and 46t gears I had, that calculates additional pitch combinations that weren't included on my threading placard.  What Change Gears do you have?   My table also shows you can also achieve 11.5tpi with a 32t/40t combo or 40t/46t combo.
> 
> A couple of options:
> 
> ...



I'm not sure if it matters to you or not,  but in my boredom today I was browsing internet forums and came across this thread.   In the 2nd and
 3rd pages, it looks like it was decided that the Jet 1024 change gears have a 1.75 module and 20° PA.

In case you ever find that info useful.



			Jet 1024 lathe change gear pressure angle -  		 		The Home Shop Machinist & Machinist's Workshop Magazine's BBS


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## Just for fun (Sep 15, 2022)

Ischgl99 said:


> Which part requires 11.5 TPI and can you design around it?  Since you are making custom fittings, might as well make it with what you have unless the 11.5 TPI goes into something you can't make yourself.  If this is for NPT, those are tapered as well, will you be able to do a tapered thread?



I just wanted to make a new end for the poly pipe that goes up the hill to the stock tank.  It's just a female hose end that attaches to the poly pipe, I would still have to use the NPT part of the fitting, as I can't cut tapered threads.


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## tq60 (Sep 16, 2022)

They do make NPT to hose thread adaptors in common 1/2 and 3/4 NPT male and female to hose thread male and female for just a few bucks.

We use them for making lawn sprinklers.

Sent from my SM-G781V using Tapatalk


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## Just for fun (Sep 16, 2022)

Yeah, I know they do I have a bunch stuff like that.  I just wanted to make a custom hose end for my wintertime stock tank hose/pipe. It's kind of a long story, but the water line is in the air over the driveway, grape vineyard and compost piles. So, in the winter every time I add water to the stock tank I have to connect and disconnect a hose. With the currently available hose ends it gets a little tough with gloves on.  I thought I would make one that was glove friendly.

Anyway, that's how it all started.......  And now I am learning what makes gears work and how to talk the lingo.  LOL


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## Just for fun (Sep 16, 2022)

Here's my solution for the time being.


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## Ischgl99 (Sep 16, 2022)

I would get something like this and spend the money for a gear on something you would use more often.









						Quick Connectors for Water Hoses & Fittings | Gilmour
					

Our Quick Connectors let you switch tools in a snap. Find the garden hose Quick Connectors you're looking for today at Gilmour!




					gilmour.com


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## jwmelvin (Sep 16, 2022)

You might consider a handled sleeve that secures over the ring of a stock connector. Secure with loctite or epoxy.


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## Ischgl99 (Sep 16, 2022)

jwmelvin said:


> You might consider a handled sleeve that secures over the ring of a stock connector. Secure with loctite or epoxy.


That’s a good idea, just like fire hose connections.  Then he doesn’t have to worry about the quick connects I recommended failing in the winter if they freeze.


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## Just for fun (Sep 16, 2022)

jwmelvin said:


> You might consider a handled sleeve that secures over the ring of a stock connector. Secure with loctite or epoxy.



That is probably the best idea of all right there.


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## Firstram (Sep 16, 2022)

These are extremely glove friendly
https://www.amazon.com/Gloxco-Alumi...+Fittings&qid=1663348556&s=industrial&sr=1-24


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## Just for fun (Sep 16, 2022)

It's a frost-free hydrant that I still need to use to water the chickens.  And in the summer, I hook up a manifold system that feeds several water systems. 

The summer manifold system.


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## Ischgl99 (Sep 16, 2022)

That looks like a good application for a cam lock fitting.  McMaster-Carr has them in water hose sizes.


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## B2 (Sep 21, 2022)

Hi Tim,

I was traveling when I posted  the link to my Threading spread sheet, so could not run it for you at that time.   However, I just ran it.   Anyway, if you have not found a gear solution yet here is an alternative to the 11.5TPI gearing for the 1236T, which according to the PM web site is the same as the 1340GT.

I think the gears that came with the lathe were 30T, 32T, 40T plus the 120/127T change gear so I used these as possible combinations.  If so and my spread sheet works for the 1236T then:

The following gear set up should get you to 11.5175TPI , which is only 0.15% off from the exact 11.5TPI.

Set your gearing as follows:  Norton gear box to Seven and B, at the spindle output put the 32T gear in contact with the 120T of the change gear, at the gear box input put the 30T gear in contact with the 127T of the change gear.  Make your cut using the lead screw drive.

Let us know if this works for you.  

I will attach two pdf copies of the entire set of possible TPI that I think you can make with your machine.  They are the same numbers, but one is sorted by increasing TPI values and shows the search for the ~11.5 TPI.  The second appears to have random TPI order, but is actually sorted by the gears that are being inserted.    There are some duplicates in the spread sheet and there are some places where it calls for you to use the same gear in two positions, but ....  It also provides all of the metric threads that are possible plus it also calculates the TPI values you would get if you used the feed bar to drive the saddle rather than the lead screw.  (I do not know if that is physically possible on your lathe model but it is on my 1440GT.)  The spread sheet macros that is posted allows you to sort the table in various ways as well as to search for TPI values that are close to the one you may want.  If you have additional gears you can change the sheets to include these then regenerate the table. (By the way, the feed values that are printed on some of the lathes are not very accurate!)

Including these possible redundancies, the table indicates that there are 1442 possible TPI values that you can cut using the lead screw and if you add the feed drive then the number goes to 1622.



B2 said:


> TPI Feeds X-Feeds: Generalized Excel file for your Lathe
> 
> 
> TPI Feeds X-Feeds: Generalized Excel file for your Lathe  Hi Folks,  My PM1440GT lathe manual only showed a few of the possible threading values and it appeared to me that the Feed rates were incorrect.  They were.   Hence, I set about to figure out what all possible TPI could be achieved via...
> ...



Hopefully this is useful sometime!

Dave L.


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## Just for fun (Sep 22, 2022)

B2 said:


> It also provides all of the metric threads that are possible plus* it also calculates the TPI values you would get if you used the feed bar to drive the saddle rather than the lead screw.*  (I do not know if that is physically possible on your lathe model but it is on my 1440GT.)  The spread sheet macros that is posted allows you to sort the table in various ways as well as to search for TPI values that are close to the one you may want.  If you have additional gears you can change the sheets to include these then regenerate the table. (By the way, the feed values that are printed on some of the lathes are not very accurate!)
> 
> *Including these possible redundancies, the table indicates that there are 1442 possible TPI values that you can cut using the lead screw and if you add the feed drive then the number goes to 1622.*
> 
> ...



Thanks Dave,

I'm not sure what you're talking about using lead screw vs the feed drive?   As far as I know when threading I can only use the leadscrew.

My friend made me three gears one of the gray one is a little too small, the black one fits the shaft really well and seems to mesh with the gears really well.  (I need to get one of those 3D printers, that's some cool stuff) I haven't tried anything other than that so far.  Thank to @Ken226 for the stl file.

So, after lots of discussion on this subject of cutting 11.5 tpi and the fact that I can't turn a taper.  I have decided that @jwmelvin has the best idea and will probably go that route.

I will check out the gears and see if I can cut 11.5 tpi but to implement my plan would not work well considering I need to drain the water out of the pipe as quickly and thoroughly as possible when it is only single digits outside.


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## Just for fun (Sep 22, 2022)

I gave it a little test run today, running 40-127 and 120-46 with the Norton gear box in B2.   I took a few light cuts of .005 and then a couple .002.  It looks like 11.5 TPI and the gear still looks like new.   I just grabbed a piece of mystery metal just to see if I could cut 11.5.

@B2  Dave,  I have not tried your gear setup yet, next time I get achance I'll try it and let you know.

Somewhere I read with that gear setup to use B8, but they may have been talking about a PM1340, maybe there is a difference.   At any rate B8 was more like 18 TPI.

Here is a photo of my test piece.


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## B2 (Sep 23, 2022)

Good Morning Tim,

Looks like you have a good solution!  I have never tried the 3D printed gears, but I suspect that they work fine, but maybe wear out after a lot of usage.   I always wanted one to convert to metric threading for my old SB lathe.  Maybe one of these days I will make one on my 3D printer, but I an not for sure why now that I have the 1440GT.


Just for fun said:


> I'm not sure what you're talking about using lead screw vs the feed drive? As far as I know when threading I can only use the leadscrew.



I am not for sure about the 1236T vs the 1340GT, but I think they have the same gear box etc.  In fact, just by looking at the PM web site it appears the 1340 just has a longer bed and the 13 inch swing, plus you get a stand.   The Feed rod runs parallel to the lead screw, and is just below it, but only has a slot in it, not threads.  This slot turns and engages with the saddle gears.  On the spread sheet that I posted to you, if you look at the 4, 5,and 6th columns you will see the feed rates.  Printed labels that come on the lathes are not very accurate as to xfeed rates and in come cases they are just wrong.   If I recall the arrow knob just to the right of your Norton gear box handles determines if the feed rod is engaged.  You will notice that by using the feed to cut threads you can get some very high TPI values.  My old SB would generate these just via the Norton gear box, but the 1440GT is limited.  The only time I ever needed TPI greater than 100 was when I needed make some very precise/delicate devices.  This was for an optical systems where I wanted to move a lens along a threaded rod by only 1 or 2 microns.   (1 turn of a 100TPI thread is 0.01 inch or 254 micron.)

When I was working on the spread sheet  I went through the 1340GT settings with  @Ischgl99 .  He is very knowledgeable about the 1340GT lathe gearing and we worked out the details of the xfeed gears in the saddle.  Anyway, on my PM1440GT the X-feed rod can be used in a manor similar to the lead screw to cause the saddle to move down the lathe.  Hence, it can be used to cut threads.  However, this maybe not be as precise as using the lead screw.    My old SB 10 Heavy does not have a feed rod, one just uses the lead screw to do x-feeds.

I look forward to hearing if my proposed gear settings generates the calculated 11.5175 TPI value, although measuring anything more accurate than 11.5 maybe be very difficult.  

Dave L.


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## Ischgl99 (Sep 23, 2022)

@B2, I have the 1236T, but according to the manual, all the mechanical components are identical to the 1340GT, so the gearbox calculations should work for either machine.


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## Just for fun (Sep 23, 2022)

I found the original thread where the decision was cutting 11.5 TPI on a PM1340.  In post #4 @davidpbest recommended 40-127 120-46 and the Norton box position B8 would get you 11.503.  I was not able to reproduce that.  In position B8 I was getting closer 18 TPI.

https://www.hobby-machinist.com/threads/pm-1340-gt-threading.84388/


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## Ischgl99 (Sep 23, 2022)

I get the same as David when calculating it.  How did you calculate it?


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## Just for fun (Sep 23, 2022)

Ischgl99 said:


> I get the same as David when calculating it.  How did you calculate it?



I didn't do any calculations ....  I had a friend print me a 46 tooth gear and installed it, did a test cut just to see how it worked.  See post #56 above.


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## davidpbest (Sep 23, 2022)

This is very strange.  The original formulas for all my calculations are from Mark ( @mksj ).  The source data is attached.  On the 4th tab ("Master Data . . . . "), note the red arrows/boxes.  It clearly calculates the 11.503 TPI with 40-127 / 120-46 gearing and the Norton box position B8.  My contribution here has largely been to reformat Mark's data into a format I find more useful when actually standing at the machine scratching my head - see the first three tabs in the attached.  I've known Mark to question his calculations, but I've never known him to be wrong.   

I'm wondering if you don't have a cockpit error at the lathe with your new gear.   Have you inverted the positions of 40 and 46?  Mark?????


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## Ken226 (Sep 23, 2022)

If I work out the ratios using the data and charts you guys have posted so far,   position B8 is 14tpi according to PM,  using the 40/127 x 127/40 gear arrangement (1:1 ratio).     I used that to determine the ratio of position B8, which shows to be .57144.    using the indicated  14tpi  (the pitch as indicated in the pm chart) and (.125") 8tpi leadscrew.

To determine the ratio of position B8:
40/127 x 127/40 (.57144) x .125 = 1/14,  where I solved for the parenthesis.

So if I use the same equation, except change the gear arrangement to 40/127 x 120/46,  then solve for the pitch, I get:

40/127 x 120/46 (.57144) x .125 = 1/17.039

 (17.039tpi).

 Isn't that about what @Just for fun got when he tried it? 17tpi


So you can check my work:


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## davidpbest (Sep 23, 2022)




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## Just for fun (Sep 23, 2022)

Ok,  So, I was mistaken on the Norton box I was using B3 not B2.

I tried it again.  I had the gears correct. And I had the Norton gear box in B3.

Tim


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## Ken226 (Sep 23, 2022)

Just for fun said:


> Ok,  So, I was mistaken on the Norton box I was using B3 not B2.
> 
> I tried it again.  I had the gears correct. And I had the Norton gear box in B3.
> 
> ...



Using the equation and method above,  for B3 I get 11.56229 TPI in position b3,  using 40/127 x 120/46:





Close enough that your pitch gauge shows good.


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## Ken226 (Sep 23, 2022)

Just for fun said:


> Ok,  So, I was mistaken on the Norton box I was using B3 not B2.
> 
> I tried it again.  I had the gears correct. And I had the Norton gear box in B3.
> 
> ...




I forgot to ask,

Is the  gear that fit the one I modeled with offsets to accommodate the 3d printers tendency to print oversize?   

Or was it the one I modeled to exact dimensions?


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## Just for fun (Sep 23, 2022)

I don't really know.  He made three gears two out of PLA the gray ones, one was tight, and one was loose, and one out of ABS the black one and the one that fits the best.


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## WobblyHand (Sep 23, 2022)

With 0.5% error, about how many threads can one engage before it binds on a true thread?  Always wondered about that.


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## Ken226 (Sep 23, 2022)

WobblyHand said:


> With 0.5% error, about how many threads can one engage before it binds on a true thread?  Always wondered about that.



A good question.

It would almost certainly depend on the fit and the length of the female part. 

I imagine it wouldn't be an issue on a 1a/1b nut bolt assembly.  

But would likely bind on a 3a/3b assembly, especially if the female part is long.


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## WobblyHand (Sep 23, 2022)

Ken226 said:


> A good question.
> 
> It would almost certainly depend on the fit and the length of the female part.
> 
> ...


Even a 1a/1b would bind if long enough.  Really wondering on a 2a/2b how many threads it would take.  Are we talking 3? 10? 15?  If 100 threads, I'm not going to worry about it.


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## Ken226 (Sep 23, 2022)

WobblyHand said:


> Even a 1a/1b would bind if long enough.  Really wondering on a 2a/2b how many threads it would take.  Are we talking 3? 10? 15?  If 100 threads, I'm not going to worry about it.



A few years ago I 3d printed a batch of gears for my lathe, to allow for alot of weird non-standard  thread pitches.  Like that m16 x 19tpi Whitworth thread  on that old locomotive whistle I posted in the Alibre CAD subforum.

In doing so, I created a spreadsheet that calculated all of the ratios in my QCGB and realized that many of the metric pitches are close approximations anyway, even using my OEM change gears.

Most of us have been cutting threads that are close approximations for years without knowing anyway.

Without searching my old removable drives for that spreadsheet,  I'd wager that some of the pitches we cut with the oem gears are off by at least the same as his 11.56tpi setup.


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## WobblyHand (Sep 23, 2022)

I know at least on my mini lathe LMS published the pitch error.  I don't recall if Grizzly did the same for my 10x22.

I made my own ELS for my 10x 22.  I can hit most of the threads exactly, so the accumulated error is zero.  Well maybe not a pi mm thread, but practically all other threads have zero accumulated error.  (I'm off by 0.0002% for that thread.)  But it is still interesting to think about pitch error and what it means in a practical sense.  If I make parts for my Grizzly using my mini lathe, I do need to know under what conditions I need to be concerned.  It's a math problem that confuses me more than it should.


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## Ken226 (Sep 23, 2022)

Edited to correct an error:

The difference between 11.5 tpi and 11.56tpi is an additional .06 threads per inch.   .06 times the pitch (.06x.0869) is .005" difference per inch of threads.


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## Just for fun (Sep 24, 2022)

B2 said:


> I look forward to hearing if my proposed gear settings generates the calculated 11.5175 TPI value, although measuring anything more accurate than 11.5 maybe be very difficult.
> 
> Dave L.



Dave,

I did not come up with 11.5175 TPI with your gearing options.  Here is what I had.  30-127 and 120-32 Norton box at B7, looks more like 15 TPI.


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## Ken226 (Sep 24, 2022)

Just for fun said:


> Dave,
> 
> I did not come up with 11.5175 TPI with your gearing options.  Here is what I had.  30-127 and 120-32 Norton box at B7, looks more like 15 TPI.
> 
> ...



Doing the math on that gear combo,  30/127 * 120/32 * .125 * .6153848 = .068141 pitch, hence (14.676)


That combination shows B7  should produce  14.676 TPI, which is so close to 15 that the 15 pitch gauge matches up.


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## Ken226 (Sep 25, 2022)

@davidpbest

I opened up your spreadsheet from a few posts back to see if i could figure out why it isn't giving the pitches that Just for funi s seeing when he actually cuts the threads.

It appears that the formulas in the TPI row are the issue.  As they are now, they multiply the gear ratio times the thread TPI count.  To get an accurate pitch,  the gear ratio needs to be multiplied with the actual pitch, then take 1 divided  by the gear ratio*pitch product, to convert the pitch back to TPI.

here is an example.  For 40/127 * 120/46,  in B3 the current formula shown is F15 * R3, which gives 7.806 TPI,  but the OP is seeing an actual 11.56 tpi using that setup.   The formula for that cell should be 1/ (f15*R4).    The same typo appears to exist in all of the TPI cells.

When I edit that cell to show =1/(F15*R4)  it gives the correct 11.562 TPI.





The metric formulas are currently correct and shouldn't need any adjustment.

I went through and pasted the formula adjustments into all of the TPI cells.  I'm using Openoffice, but tried to save it using the current excel format. Hopefully it still works.

@Just for fun
Just to check my work, does the data in this adjusted spreadsheet now match what you've seen so far in test cutting threads?








Edited to add:  Just wanted to point out, according to the adjusted spreadsheet,  35/127 * 120/40  in B3  gets you alot closer to a true 11.5tpi (11.49) tpi) than the other setting.


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## Just for fun (Sep 25, 2022)

Yes Ken,  That looks right to me.

Tim


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## davidpbest (Sep 25, 2022)

Ken226 said:


> I opened up your spreadsheet from a few posts back to see if i could figure out why it isn't giving the pitches that Just for funi s seeing when he actually cuts the threads.
> 
> It appears that the formulas in the TPI row are the issue.  As they are now, they multiply the gear ratio times the thread TPI count.  To get an accurate pitch,  the gear ratio needs to be multiplied with the actual pitch, then take 1 divided  by the gear ratio*pitch product, to convert the pitch back to TPI.
> 
> ...


@Ken226 @mksj 

Ken, thanks for the "new math".   LOL  As I said before, my source data was provided by Mark Jacobs - I didn't check the formulas.  I have updated the files on my system so if this comes up again, I can provide the corrected data.  Lesson learned again: metric rules !!!

@Just for fun   Tim, sorry to have misled you with the 46-tooth suggestion.  Classic case of the blind leading the blind.  Mea culpa!


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## Ken226 (Sep 25, 2022)

davidpbest said:


> @Ken226 @mksj
> 
> Lesson learned again: metric rules !!!



  I know the feeling.



BTW:

Not sure if this is something that you guys would be interested in or even care about,  but since I had the spreadsheet already open I added a couple things that I have in the version I made for my own lathe.

In the first tab,  I added dropdown selections.  You can select the gear from those listed (i got the tooth counts from the "master data" tab.

When you select the gears, in the appropriate positions,  It will automatically display the pitches for the selected gear combo in both the Imperial and Metric tables, for each respective QCGB lever arrangement.










Also, I added the formulas using OpenOffice Calc,  so I'm not certain they'll still work when opened using excel.


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## Just for fun (Sep 25, 2022)

Looks like a good idea Ken,  I'll have to check out the spreadsheet after while though as I'm on my phone now.


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## Ischgl99 (Sep 25, 2022)

I made the same mistake Mark did in his spreadsheet and had my formulas set up to slow the lead screw and not speed it up as would be needed to go from 14 to 11.5.  Once I realized that, I found a combination you can get pretty close with your using your existing change gears.  If you put the 32 gear on the 120 gear in the top position, and the 30 gear on the 127 on the banjo, you will get about 11.57.  For a short hose fitting, that should be close enough to work, at least it’s worth a try since you already have the gears you need.  I verified it on my lathe and it comes out almost spot on to the calculation.


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## B2 (Sep 26, 2022)

Just for fun said:


> I did not come up with 11.5175 TPI with your gearing options. Here is what I had. 30-127 and 120-32 Norton box at B7, looks more like 15 TPI.





Ken226 said:


> Doing the math on that gear combo, 30/127 * 120/32 * .125 * .6153848 = .068141 pitch, hence (14.676)


Hi Tim,
Thanks for the posting. This is helpful and seems to confirm my Excel work book..  Since I only have my lathes to work with I cannot check the other lathe sheets for accuracy with out your contributions.

I think maybe we have miss-communicated as to how the external gears are arranged.  I am sorry if my first posting was not clear. 

Interestingly @Ken226 pointed out that the 14.676 would be close to your measurement.  I think the 30/127 * 120/32 external gear combo is what your photo shows, where the 32T is connected to the Norton gear box and the 30T is at the spindle.  I think he used 1.25*0.6153848=0.80890 as the pass through pitch ratio for all the other gears, including B7 of the Norton box.  My spread sheet also predicts 14.676TPI for this configuration.  So it appears to be in agreement and ok .... atleast for this configuration!

My suggestion for gear arrangement had the 32T/120T at the spindle and the 30T/127T at the Norton gear box input, the opposite of your photo......  again, I am sorry if this was not clear.

Note:
  30/127 * 120/32=.8858    Ken's value,  where as
  32/120 * 127/30=1/.8858=1.1289 and so  .8858/1.1289=0.7847.  (0.7847*14.676=11.5157TPI), better still
Using Ken's equation:
  32/120*127/30*0.125*0.6153848=0.086838 pitch(in/thread)  or 11.5157 TPI

I realize that my Excel workbook is complex.  However, if you open it and select the tab (sheet) uwPM1340 you will have the calculations for the PM1340 which is the same as the PM1236.  The cell at Column "I", line 30 show what Norton gear # has been selected, cell N30 is for the Norton Letters.  These are pull down menus and if you click on it, to high light it, it should give you an arrow to choose from a list of Norton gear position 1 through 7.  If you select a a different number then you should see the new TPI value in cell F24,  (Column F, line 24).  (The thread pitch appears in cell F25.  Metric equivalents are shown at the far right in column W) You can make similar selections in each of the cells I30 to V30 to set up a set of gears.  With each of these selections the TIP value of cell F25 will change.  

The order of these columns (or gears) start at the right, V30, corresponds to the gear at the spindle moving from gear to gear to the input to the Norton Box at "O30".  Below these cells in  the rows in orange color you will find the gears via tooth number available for selection.  If the you want to add to these possibilities you my do so by just typing in the integer number of teeth on the new gear... i.e. 30, 32, 40, 46 etc. and they should appear in the selection list.   The Zzz indicates the last gear available for the macros so do not delete it, just type it farther down if need be.

Thanks again for making the thread cut and the excellent pictures!

Dave L.


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## Just for fun (Sep 26, 2022)

Thanks Dave,

I thought that was probably the case about me mixing up the gears especially after reading @Ischgl99 post about the gearing he has used.

I was just checking out your spreadsheet but I'm not getting it.  On the spreadsheet, I changed the gears to 32-120 and 127-30 then for the Norton box I set to Seven and B.  In position F24 shows 14.675556


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## Just for fun (Sep 26, 2022)

I just got it..... I'm not sure what I changed but I have the right numbers now..


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## B2 (Sep 26, 2022)

Great!  Thanks.  The 14.675556 that you had was the same as the 14.676 that Ken had.  So you may have had the gears at the top and bottom reversed in the spread sheet cell locations.  Anyway, the column names (cells just above the pull down menus) for the gear cells are a little cryptic ... in order to get them to fit in the column width.

"Spindle" gear, 32T, is spread sheet cell V30; 
"A2Spin" (gear A contacting to Spindle gear, "2" => contacting to), 120T, is spread sheet cell U30
"C-C" gear, 127T, is spread sheet cell P30
"Screw2C" gear, 30T, is spread sheet cell O30
and the Norton gear box levers at B7 should yield the 11.5157 TPI

Because in the 1236 (and 1340) there are no other shafts for intermediate gears nor coupling gears, the columns
C2B,    B-B,    B2A,  and   A-A all contain gears or gear ratios of 1.  This then causes C-C to be in contact with A2Spin and so both turn at the same rate.  It is the two halves of the 120/127 change gear. 

These extra shafts columns, C2B,    B-B,    B2A,  and  A-A allow folks with lathes which do not have gear boxes with levers (like the Norton box) to alter the spread sheet to make more complex sets of manual exchange gears.  Be grateful for having a Norton gear Box!  The PM1440GT has a gear box, but not a Norton and it is not nearly as intuitive to use!

FYI:

Attached is a screen shot of the part of the spread sheet of interest with the gear set up just described.  This should look similar to the first lines of the threading spread sheet that I first posted for you the other day.  "TPI PM1340GT-1236 M421_1443 M921.pdf".  It was generated via the macros : Run1  : "GenAllTIP_14" to generate a list of all possible TPI values in the sheet called AllTPI located at the left of the WorkBook Tabs, then Run2 : "SortAllTIP_1Col" to sort each line by increasing TPI, then Run3 : "SearchTPI_At_TPI_Col" .    You do not need to do the sort, each macro runs independently.

By the way, in the file name the M921 means today's date: M=>22nd year (2022), 9=> September, 26=> 26th day.  

Likewise, in the file name M421_1443 is the date and time I last made significant changes to the spread sheet. 2022, April 21, at 1443 hundred hours (2:43PM).  This short hand date-time stamp is how I keep versions of files in order without typing out a long file name.   This should be the same date and time stamp that was on the spread sheet that you downloaded from my posting back in April.  

Dave L.

PS.  It is nice to know that someone else has actually run the workbook.  I got very little feed back on it.  Thanks.


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## Just for fun (Sep 26, 2022)

I tried the gears you recommended and it looks pretty darn close.


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## B2 (Sep 27, 2022)

Hi Tim,

Fantastic!  Congratulations and thanks.  And now you also know how to use the workbook!  What a high quality photo.  

Looks dead-on to me, but then you probably need to turn the spindle at least 11.5157 x100 =1151 times and measure the 10.0 inch length accurately to be completely sure!  I can do that with my digital spindle counter and the DRO pretty quickly.  However, there is something very satisfying about a scratch cut confirmation.

Dave L.


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