Threading ?s

[Naiveambition]

A part I'm working on requires a one inch thread, and having trouble laying it out so ,

As u can see in pic only the center of the bar is threaded, and mating to the female part. My issue is the chart calls for 8 tpi and 12 is lowest on my lathe , plus With the nut only being a 1/2" this only leaves four threads. No stress on the part so I don't need a deep , large thread.

I would like a more compact thread.. Can I just pick say 12 or 24 tpi and still achieve a fit with the sizing I have now. My parts are sized to what thread limit charts call for.
1" bar for external threads and 59/64 for the nut

 

[bazmak]

Thread form and TPI(pitch ) are the main criterier everything else
forms itself.If you are making the male and female you can do anything you wish.If you want imperial then whit at 55o and tpi for a fine thread BSF
will give charts for any other dims or a non std pitch and you will have to calculate any missing dims.All that changes is depth of thread or cut

 

[goldstar31]

Deleted- Poster gave confusing details

 

[Picko]

If you're making both parts it will not matter what pitch you use.

 

[Naiveambition]

Yes I am making or threading both parts. I know what I want it to look like just don't know what thread I'm looking for. Granted I work in imperial. And topping it of this is my first thread job ever!! Gonna try on a test peice first and hope and pray.

Something similar to the photo is the intended target. As you see they are very shallow threads. Im guessin around 20 tpi . So when I say a 1" thread I mean the outside diameter, not trying to cut the normal thread for a inch bolt per se.
Probably a little deeper and longer but the same style.

How would I know my depth of cut? Just pick a depth and mate the other part?

 

[bazmak]

It depends on the lathe is it metric or imperial. If you want 1" thread
then you can still cut metric pitch at 60o and whatever pitch you want
If metric then each thread is an equilateral triangle ,so depth of cut = pitch
and you would be cutting an M25.4 thread at say 1mm pitch= 25.4 tpi
The thread is best determined by what your lathe will cut pitchwise and if
metric or imperial. Personally it is easier and cheaper to cut metric form at 60o
on any diameter depth = pitch. Make a male piece by eye till it looks rigt then cut a female and check for fit. All trial and error

 

[ShopShoe]

Since you are creating a thread of your own, what others have said above is true. Make one thread and then make the matching part.

The pitch of whatever thread you make will depend on the change gears (either manually set or with your lathe's threading gearbox). Use a chart to choose a pitch and set the gears for cutting.

If you use a 60-degree cutting tool, then you are OK for either metric or imperial thread forms.

The diameter of the part you are threading really has no relation to the pitch, other than when making standard fasteners or fittings. If that is an issue, consult a reference source like Machinery's Handbook.

If you want to measure a known thread, you can buy inexpensive thread-pitch gauges. They might not be a bad investment if you will be wanting to know about other threads later. If you are thinking of buying a tap and die set to add to your shop it may include one. Useful little tools.

You can attempt to measure your TPI with a ruler (also called a scale). If you have a magnifier that may help you.

--

My first attempt a thread-cutting was making a brass barrel for a ballpoint pen. I used a ruler and guestimated a thread pitch to use based on my lathe's change-gear chart. It was a strange "kinda-square" thread form, so I ground external and internal toolbits to make the form and went from there. The whole pen, with two internal and two external threads to be cut, took less than three hours, including the toolbit grinding. One aborted attempt.

--ShopShoe

 

[Sansspaceship]

Hi,
Not sure if you are aware, but given your description of the problem thought that I would mention a common tool ‘thread gages’ you can buy them pretty much at any tool store they allow you to check threads to on say a bolt or part like in your photo. They will only set you back a few bucks, and give you a better idea of the tpi you are looking for visualaly.

Sorry if you know about them, wasn’t trying to be a smart ar*e :hDe:

You haven’t talked about trying to cut the thread yet, but if it’s your first one don’t don’t get disappointed if you make a meal of it. It will seem like more art than science for the first few you cut. If you run into problems I picked a lot of tips up from the gunsmith forums, when starting out theading .... as to get them right it’s not quite as simple as just plunging in a 60 degree threading bit.

Hope it does well, and please share your finished parts with the forum.

edit - shop-shoe posted just before me :thumbup:

Cheers,
.adrian

 

[Edke6bnl]

I have only done a dozen threads myself but I like to experiment on pvc first to get the motion and moves down.

 

[john_reese]

It sounds like you have the freedom to choose your pitch and thread form. Make your decision then start in on it.

You may scrap a couple parts but you will become proficient in short order.

A suggestion for the female part. Leave it a bit long. Bore that excess length to the major diameter of the thread. When the threading tool just marks that diameter your thread is on size. Cut off the excess length after threading. If using a sharp V tool instead on a truncated V, be sure to calculate the major diameter based on the sharp V.

 

[mfrick]

If your really into threading you can use thread wires to get a correct depth them make the mating part to fit.

 

[Wizard69]

Im wondering what this part is for. Everybody is saying you can use whatever pitch you want which is true to a limited extent. However 8 TPI has me wondering if there was a specific reason for the pitch. It comes down to what the part was designed for.

By the way your machine may or may not be able to cit the pitch. If you get creative with the change gears you can often come up with many other pitches.

Perhaps the most important suggestion here is to get a copy of Machinery's Handbook and study threading. If you learn the formulas involved you can do threads in any size or form you want. Probably the second most important thing to do here is practice on cheap materials PVC was mentioned above but others will do.

One other thing i noticed, one of your pictures had a ring with graduations. If that is your nut or part of it you cant change pitch and expect that the graduations will work. It would help a lot to clear up what you have here and what it does.

 

[Chiptosser]

You can make it to the thread that you choose, and you machine has available.

 

[pp2076]

Perhaps the most important suggestion here is to get a copy of Machinery's Handbook and study threading.

Google has an old version for download at https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwj92a3KyMTXAhWLF5QKHdM4DXoQFggoMAA&url=http%3A%2F%2Fwww.woodworkslibrary.com%2Frepository%2Fmachinery_handbook_for_machine_shop_and_drafting_room_1914.pdf&usg=AOvVaw2Iv-I-fWAoLI4ZjQmMjcOC

Newer version here: https://www.google.com.au/url?sa=t&..._Edition.pdf&usg=AOvVaw1EVKaLZxinM4PjoUGeoTvJ

 

[Naiveambition]

Well tried to do my threads today. Started with I'm guessing acetal rod or something similar and came out great. Was amazed I got on first try. So now I'm feeling confident and went to my metal pieces.

Here's where it all went to s@&t Broke every carbide tip I used(3 different kinds) for various reasons, Hss blunted Fast as usual for me. Machine kept kicking out of gears when it would jam losing its spot. And ruin my peices. With all theses issues I don't ever want to thread again, I love taps!!

Even though I will try again since I have to have these parts. But:wall: I still can't really figure out what went wrong The minor diameter would not produce a nice valley being flat. The nut was okish but the the rod was terrible . This was where all my issues were. may go to alum. I'm pretty sure that they were stainless of some sort, and may be part of why :fan: I got a load of it from a guy that worked on space station parts and have no idea what hardness it is or if I work hardened it

As for the part use. I'm making a half scale ma duece .22 (from ccs on the web)and the piece I'm on is the barrel ring that holds the cooling pipe. The threaded peices are purely cosmetic and have no real job. This is why I can choose any thread that will work vs what my tap chart was at 8tpi. The peice I'm holding will thread into the collar around the barrel..

 

[ShopShoe]

Anybody else please chime in.

My Guesses:

1. Trying to cut thread in one pass? You need to make multiple passes.

2. Too big a cut on each pass?

3. Rigidity of the tool at the workface?

4. Speed too fast? Some ( Me included) have made a hand crank to turn the lathe for really slow operation (Small lathe, and of course the lathe is unplugged.)

5. Maybe still not the right cutter (or sharpness) for the Stainless or exotic metal you have.

6. Maybe not the right lube for the metal, cutter, and speed you are using.

It would really help if your friend could tell you exactly what the metal is.

Perhaps it's academic at this point, but if the metal is difficult to thread on the lathe, it would probably be a problem with a die or tap, unless you are looking at specialty dies or taps (read as expensive.)

--ShopShoe

 

[Hopper]

...
... I'm pretty sure that they were stainless of some sort, and may be part of why :fan: I got a load of it from a guy that worked on space station parts and have no idea what hardness it is or if I work hardened it

...

You are fighting an uphill battle there. Stainless can be a real pain to machine. Well worth buying some nice mild steel bar that you know is a standard grade and should machine well. Using scrap and offcuts is always a bit of a lucky dip.

 

[Sansspaceship]

Will add a few thoughts, in addition to the comments from shopshoe:

A) Run a file across your stock, if it skips or doesn’t scratch .... I would be looking for new stock! How does it turn down in normal operation with a normal cutter, test number 2?

B) are you plunging straight in i.e is the cutter engaged on both sides of the V. If so You might want to have a look for some gunsmithing videos as mentioned In my earlier post. But in short setup you cross slide at 59 degrees (may be different on some lathes). Then setup the cutter ensuring it’s central. Start cutting using the cross slide, so you are engaging only one side of the V at anyone time, that is after your initial cut.

Cutting, threads takes practice and some skill - but once you have it down, believe me a tapped thread isn’t anywhere near as nice for mateing two parts... especially if you are cutting both threads.

If you have a ridged machine - don’t baby the carbide bits, but your speed must be slow... I cut threads on the slowest speed available on my lathe.

Good luck - don’t get disappointed it just takes a bit of research and some practice.

Cheers,
.adrian

 

[Sansspaceship]

You are fighting an uphill battle there. Stainless can be a real pain to machine. Well worth buying some nice mild steel bar that you know is a standard grade and should machine well. Using scrap and offcuts is always a bit of a lucky dip.

Agree with this comment from hopper, as will be easier than learning on SS, I would go with 12L14 over 1018 in your generic CRS.

 

[Sansspaceship]

Hi - just thought I would ask if you had any further luck with your threading adventure?

Cheers,
.adrian