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  #11  
Old 09-04-2023, 09:18 PM
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mcostello mcostello is offline
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If You have a DRO on the mill and it has a bolt circle function You can make any tooth gear You want. Just use a dowel pin against a stop to do the indexing, DRO adds the precision. I used a precision level, did not think of using a stop till later and it was even numbered.
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  #12  
Old 09-05-2023, 03:40 AM
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Originally Posted by GWIZ View Post
Way back, quite a few import lathes only listed SAE or Metric threading
with the right combination of gears an SAE only lathe is able to cut Metric threads.

IIRC: 127T gear was a key size to get SAE to metric cutting but 127T gear were not available or too large.

programs starting to show up that would try different gear combinations from a list of gears that one would have.
the issue is the calculations are based on a 16tip lead screw, quite a few import lathes have 16tpi lead screws.

I was hoping you had a better selection of drive gears to use one of the programs to figure out 11.5tpi.

If you scroll down you will find some programs and links to software but 16tpi lead screw.
http://www.varmintal.com/alath.htm#Cutting_Odd_Threads

Bear in mind the programs do not check if the gears can physically mate or clear obstacles/mounts in a lathe.
so a gear in the list may be to big or to small.
Idea would be once you figure out what gear you need, have one 3D printed.


When I first got my mini lathe I purchased a few sets of gears so the software would have a better chance of finding a closer metric match for cutting metric threads. but that was when a set of gears cost $12.00.
gearsvb61.zip (29Kb)
Looks like there is an up dated program and added a lead screw pitch option.
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  #13  
Old 09-05-2023, 09:48 AM
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I would be willing to cut the threads for you. I have both
the taper attachment and can cut 11.5 tpi.

How long is the pipe/fitting?
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  #14  
Old 09-05-2023, 03:21 PM
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Just curious what you actually need? With all the BS around trying to cut a single thread is there no place local with a pipe threader that could cut a thread for you? What about just buying a 2" pipe nipple, cutting it off and welding it in place? Before we got our Rigid pipe threader years ago if we needed, say, a ten foot long pipe with a thread on one end I'd buy a nipple, cut it in half and weld it to a longer piece...
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  #15  
Old 09-05-2023, 07:34 PM
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Quote:
Originally Posted by LKeithR View Post
Just curious what you actually need? With all the BS around trying to cut a single thread is there no place local with a pipe threader that could cut a thread for you? What about just buying a 2" pipe nipple, cutting it off and welding it in place? Before we got our Rigid pipe threader years ago if we needed, say, a ten foot long pipe with a thread on one end I'd buy a nipple, cut it in half and weld it to a longer piece...
That's what I like, cut to the chase. Spoken like a job shop/flat rate guy
Time is money.
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  #16  
Old 09-05-2023, 08:58 PM
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Quote:
Originally Posted by Shade Tree Welder View Post
I would be willing to cut the threads for you. I have both
the taper attachment and can cut 11.5 tpi.

How long is the pipe/fitting?
Thanks, Ron. After stewing on it for a while, I have figured out a way to cut the threads I want. I'll clue everybody in when I get some photos. I meant to take pics today but totally spaced it out.


Quote:
Originally Posted by LKeithR View Post
Just curious what you actually need? With all the BS around trying to cut a single thread is there no place local with a pipe threader that could cut a thread for you? What about just buying a 2" pipe nipple, cutting it off and welding it in place? Before we got our Rigid pipe threader years ago if we needed, say, a ten foot long pipe with a thread on one end I'd buy a nipple, cut it in half and weld it to a longer piece...
Like everything I do, I try to keep it in house. Why? Just my way, I guess.

One of many reasons is that it gives me an excuse to leave the ladies at home and head to Dad's old shop and make chips. I love my wife, her sister not so much.
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  #17  
Old 09-06-2023, 01:11 AM
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Quote:
Originally Posted by MotorDoctor View Post
...Spoken like a job shop/flat rate guy...
From 1969 till 2022. Still have a shop but I've downsized. When my Bro and I closed our business I kept my lathe and mill and all the tooling and moved in with another business that was in our complex. I can be as busy as I want but don't have to bust my ass to pay rent and all the other overhead costs. I mean, I still pay rent but now it's $375 a month instead of $2000. That plus insurance and a few incidentals is all I have for overhead - 8-9 hrs. a month covers that; anything else is mine...
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  #18  
Old 09-06-2023, 08:15 AM
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Quote:
Originally Posted by LKeithR View Post
From 1969 till 2022. Still have a shop but I've downsized. When my Bro and I closed our business I kept my lathe and mill and all the tooling and moved in with another business that was in our complex. I can be as busy as I want but don't have to bust my ass to pay rent and all the other overhead costs. I mean, I still pay rent but now it's $375 a month instead of $2000. That plus insurance and a few incidentals is all I have for overhead - 8-9 hrs. a month covers that; anything else is mine...

Work just enough to keep your mind going, and gives you something to help other people. And a lot less stress. I like it. Someday I plan the same.


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  #19  
Old 09-06-2023, 08:56 PM
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After stewing on this problem for a couple of days, I hit on the idea of another gear to choose from to insert into the gear train.

The number 11.5 has multiples of whole numbers, namely, 23 and 46. Since there are two 40 tooth gears supplied with the lathe, it made sense to cut a 46 tooth gear.

How does that work? Substitute the bottom 40 tooth with the 46 tooth and set the lathe to cut 10 TPI. In case you're confused, 10/11.5 is the equivalent of 40/46, namely 0.8696. The 40 at the top of the train is the driver and the 46 at the lower end is being driven. Once you have started, the half nut must be left engaged, power in and power out, same as if you were cutting metric threads.

Now the pics.

The gear blank is 10mm width at the teeth with another 10mm shoulder, 18mm bore and 2.4" diameter for a 46 tooth 20PD gear. Setting up to punch a 5mm keyway in the blank, so squaring up the bit.

First pass of the keyway bit.

Arbor with the key installed. Went a bit deep with the keyway, but too much is better than too little in this case.

Cutting on tooth (gash?) #6. DOC is 0.108". Since I didn't have a cutter, I hand ground a 5/16" tool bit and stuck it in a fly cutter. Makes a chattery mess but it gets the job done. Taking easy cuts of .025, .050, .075, .100 and .108 since this one bit has to complete the job.

Another view of the setup.

More than 3/4 of the way around.

Final piece after clean up. I will have to hand file a few burrs tomorrow, but that's another day.



Almost lost my spacing when there were 2 cuts left to make. The nut holding the blank came loose and it started jumping a bit. The key held it in position but the arbor slipped in the chuck just a bit when I tightened the nut. I backed up to the last known gash just shy of DOC, made sure the bit cleared, and adjusted the sector arms for the new position. The bit barely touched when I went into the first gash. Next time it might be wise to have the cutter engaged full DOC before tightening the nut.


A later project may be to build a taper attachment for this lathe, but it's not high on the priority list.
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  #20  
Old 09-07-2023, 10:25 PM
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Made a scratch test today. Gear works like it should and it's not noisy.

Pic of the 40 on top, 46 on the bottom.
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