# How to Thread?



## Tiresius (Oct 1, 2012)

I'm stumped. I thought my brother and nephew knows how to do threading on a lathe machine. it turns out that they cheated and used the threading bits. Well, they couldn't weenie their way out of my current project because none of the bits are large enough. I've gone and read the book given to me but it does not tell me how much clearance or thickness of each piece needs to be within each other.

Have tried searching but turned out that I'm sent to just custom made lights built or modified lights. No tutorials, sad to say.

Does anyone have tips of how to do standard "V" shaped cuts both male and female on the lathe? If there are instructions, it'll be even better. Anywhere from the proper thickness of both pieces to properly making passes.

NOTE: I'm using a manual lathe that costed my brother 3,000 USD.

I'm currently working on my first light build but have stalled after completing the head with no threads.

EDIT: I have failed in serveral times to thread and it came up ugly.


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## 350xfire (Oct 1, 2012)

You need a threading tool. You need to decide which threads type to use- NPT, ACME, etc etc... Also decide which TPI you want... Machinist's handbook will tell you the dimensions to use. On the lathe you will need to set the andgle of the cross slide to 29.5-30 degrees. Of course that is assuming 60 degree threads...

You really need to provide more details so you can get specific help. Picture of the parts or a drawing will be best.


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## gadget_lover (Oct 1, 2012)

It's not as hard as it seems. I'll explain a little, then point you to some links. You will need to learn some terminology. 

It sounds like the "threading bits" your brother used was actually a threading DIE or TAP. Die makes male threads (like the top of a water bottle) and the Tap makes female threads, like the cap that goes on the water bottle.

When using a lathe to make threads, it's called "single point threading". Use that term on Google or YouTube and you will get lots of matches. ( click here for a quick start http://www.youtube.com/results?sear...g+tutorial&oq=single+point+threading+tutorial ) . Especially good are the videos by Tubal Cain such as http://www.youtube.com/watch?list=PLC5B620636E4B4C1A&feature=player_detailpage&v=9y0MmvscBzg 

The things you need to know are 
1) The "standard thread" is the Unified Thread. The size of the thread is based on how many threads per inch you use. You can use the same thread on a 1/2 inch diameter rod that you use on a 6 inch diameter rod. The diameter will change but the depth of the thread and the space between threads will be the same. The thread size is based on a formula. There are on line calculators that will tell you the various specs once you specify the diameter of the male thread and the thread pitch.

2) The threads are cut in multiple passes. You make progressively lighter cuts as you go deeper. This is to avoid overloading the tool, since the tool has a triangular shaped tip. A 10 TPI thread is 0.0758 inch deep. Cutting .075 in one pass is a lot. There is a chart somewhere that shows you generally take 8 cuts or so for a single thread. ( http://www.discount-tools.com/techcontents/Threading Tool Speeds & Feeds.pdf ) This one shows that shallow threads ( 40 tpi) being done in 2 passes, but deep threads (8 tpi ) being done in 9 passes.

3) The Unified thread profile is the same for metric and imperial threads. It's just measured in mm per thread (distance between each thread) instead of thread per inch (threads in a set distance). They all have a top (known as a crest) that is flat and a matching flat on the bottom of the groove.

4) You will have to set up your lathe to cut the thread of your choice. This determines how many times the chuck turns for each inch that the tool moves. In some lathes that is done by selecting a combination of removable gears known as change gears. In others you flip levers or knobs. It's common to have lathes with levers AND change gears. Each lathe is different, so you will need to read and understand the owners manual.

5) The thread you choose for a flashlight depends on: a) How many turns do you want the user to have to make? b) How far does the part have to move? c) How thick are the walls that you are threading? Keep in mind that a 40 tpi thread is only 0.018 inch deep, where an 8 tpi is 0.094 inch deep. Obviously you can not use 8tpi on a part that is .050 thick. I tried. 

You now have a lot to look at and read. After that comes experimentation. You should practice until you can make several exactly copies of the same thread. A good way to practice is to start with a nut from the store and try to make a decent thread that will fit it. You have mastered it when you can make one that fits well without having to test fit it.

Dan
P.S. I tried to capture my understanding of threading at http://www.tanj.com/cgi-bin/tpi.cgi I think it's mostly correct.


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## Tiresius (Oct 1, 2012)

Thanks for the information, Dan. I have done the readings and will post pictures of my trial and error when I get the chance to go back and work more on the lathe.


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## Gtamazing (Oct 1, 2012)

I think Mag uses 20tpi on all their tails caps, heads, and bezels. It might be a good starting point.


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## moderator007 (Oct 1, 2012)

This is how I learned to cut threads.


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## h2o (Oct 2, 2012)

:thumbsup::thumbsup:thumbs up for helpful & knowledgeable reply/post


gadget_lover said:


> It's not as hard as it seems. I'll explain a little, then point you to some links. You will need to learn some terminology.
> 
> It sounds like the "threading bits" your brother used was actually a threading DIE or TAP. Die makes male threads (like the top of a water bottle) and the Tap makes female threads, like the cap that goes on the water bottle.
> 
> ...


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## gadget_lover (Oct 2, 2012)

Thanks H2o. I appreciate the feedback. Most of the folks here like to share. 


Daniel


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## 350xfire (Oct 3, 2012)

It's nice to start with a threaded part and build the opposite end to it. Like the Maglite mantioned. You can start with the barrel and build a tail cap or start with tailcap and thread the barrel. This way you get to know how deep the threads are, etc. When you first start, just test fit the part until it works. Then you'll get to know how deep you need to go.

Then move on to custom parts that are threaded together and use charts to make the threads per specification. It's a matter of trial and experimantation.


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## gadget_lover (Oct 3, 2012)

I don't quite agree with 350xfire's statement. When you are trying to match an unknown thread, trial and fit is one way to do it. Maglite is a terrible example to start with because the threads are very inconsistent. Many mass produced items do not have to stick to a standard since they only have to match their own parts. It is for this reason that trying to make a good thread that fits a bad thread is frustrating for the beginner. It takes a lot of trial and error. If you are trying to match a bolt or a nut from the hardware store, it's much more consistent. Once you learn to make them properly it's easier to figure out how to match odd or poorly made threads.

It's a good idea to look at the standards and to try to understand the formula that the thread form is based on. It starts to make sense pretty quickly. 

Assume you will use a cutting tool with a 60 degree tip (triangle) to make a "sharp V" bottomed thread.
The pitch is defined as 1 / threads per inch. 
The "thread height" is defined as pitch multiplied by .86603 ; The "thread height" is a reference number, not one that you use to cut the threads. 
The crest of the MALE thread will have a flat that is 1/8 the width of the "thread height". The thread will be cut to a depth of 7/8 of the "thread height".
The crest of the FEMALE thread will have a flat that is 1/4 the width of the "thread height". This thread will be cut to a depth of 3/4 of the "thread height". 

Cutting to a depth that is only part of the thread height will leave the flat crests. The flat crests keep the tips of the crests from bottoming out in the valleys of the mating threads. If they bottom out, then they quickly gall and jam, often permanently. It is the SIDES of the threads that are supposed to touch, not the tips of the crests. 

Daniel


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## 350xfire (Oct 3, 2012)

gadget_lover said:


> I don't quite agree with 350xfire's statement. When you are trying to match an unknown thread, trial and fit is one way to do it. Maglite is a terrible example to start with because the threads are very inconsistent. Many mass produced items do not have to stick to a standard since they only have to match their own parts. It is for this reason that trying to make a good thread that fits a bad thread is frustrating for the beginner. It takes a lot of trial and error. If you are trying to match a bolt or a nut from the hardware store, it's much more consistent. Once you learn to make them properly it's easier to figure out how to match odd or poorly made threads.
> 
> It's a good idea to look at the standards and to try to understand the formula that the thread form is based on. It starts to make sense pretty quickly.
> 
> ...



No agreement needed... Just the way I learned. I'm sure others have learned using other methods. It's just a way to start...


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## gadget_lover (Oct 3, 2012)

I learned that way too. I started with a 1 AA battery powered Dorcy with 3 LEDs. I replaced it one part at a time. I even posted a thread about it. 

http://www.candlepowerforums.com/vb/showthread.php?65656-Well-it-was-a-Dorcy

Funny to think that the Dorcy was hot stuff back in 2004.

One of the key learnings is that it is difficult to match a thread using trial and error, then make another part to match both. 

Daniel


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## darkzero (Oct 3, 2012)

I learned to thread using Go gages. At home I don't have anything to measure pitch diameters for internal threads. I only have an external pitch mic. I tend to use standard/common threads so I always start with the external first. I thread to within pitch diameter specs & then I do the internal threads & check fitment if I don't have a an Go gage for that size internal thread (I currently only own like 3 sizes). 

I never base my threads by matching a sample cause like Daniel said, some threads can be way out of spec. Copy that part & your threads won't fit anything else. In reference to flashlight parts, if you are making bezel, heads, & tailcaps for sale, you can quickly get emails from unhappy customers saying you part doesn't fit my body, head, etc. Sure you can make it with very loose tolerances to avoid that but I personally hate loose sloppy threads. If I'm making something with a uncommon thread diameter & pitch combo then of course it wouldn't matter or if it is intended to never be used with something else.


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## Tiresius (Oct 3, 2012)

Okay, after reading the information and visiting videos, I went and tried the threading again. This time, I managed to get some type of threading down. The biggest downfall of my threading is that the machine can only thread very fine threads. It's maybe 15-20 T/I". Or that's what I think I'm capable of doing only. I have no idea how to increase the movement of the cutting tool. The instruction manual doesn't tell users how. It only tells us how to do the threading but doesn't tell us how to set the speed of the cutting tool to move left or right.

Linked is my threading attempt. On the 4th pass, the threads start to break apart because of the distance between each thread is so close.
http://i707.photobucket.com/albums/ww77/zeron18/IMAG0341_zpsc324ace1.jpg

Here's the lathe machine I'm using:
http://i707.photobucket.com/albums/ww77/zeron18/IMAG0343_zps2c0dd981.jpg

http://i707.photobucket.com/albums/ww77/zeron18/IMAG0342_zpsa89b3685.jpg


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## darkzero (Oct 4, 2012)

Tiresius said:


> The biggest downfall of my threading is that the machine can only thread very fine threads. It's maybe 15-20 T/I".



That's a nice looking lathe. It looks to be the same lathe as the PM1127VF which is what I originally had purchased before what I have now.

Looking at the chart the lathe is capable of cutting 8 - 56 TPI (just like the PM1127VF) which would probably cover more than what you would ever need. For flashlights, 32, 28, & 20 TPI are the most common (not including metric).

Unfortuantely for that lathe you'll have to change some gears around to get different TPI but it's not hard once you've done it a few times. I assume it's probably currently set up for finishing feeding, you'll have to change gears to for threading, then change back when you want to do finishing passes again. First off & most importantly, do you have all the extra gears that should have came with the lathe?

That chart tells you everything you need to know. When you open the cover it should look something like this:








So to cut a 20 TPI thread, you'll need to look at these:












For 20 TPI you'll need to use gears 70, 40, 50, & 80 as shown in the second red square on the top & put them in the corresponding positions as labeled in the first red square on top. 

I'm just going off what I can see in the pic of the PM lathe so gear 70 should be on top on the right which is the Z2. This is the gear that should be driven by the spindle. Since 70 would mesh with gear 50 as indicated with the line, on the left side of 70 which is labeld as H (Z1), you would need to use a spacer or any small gear to fill in the gap so the nut can be screwed on. So next is 40 (Z4) & 50 (Z3). 40 meshes with 80 on the bottom left so again as marked H, a spacer would need to go on the right side of the 80. Lever needs to be in the A position to get 20 TPI. Once these gears are set, any of the three TPI listed under that column of gear configuration can be used by flipping the lever which would be 10 TPI for position B & 40 TPI for position C.

For reference, judging by the pic of the PM1127VF gears, it looks like it's set for inch feeding: .0025, .005, .01. Look at your gears now & compare it to the chart, that will give you a better understanding of everything I just mentioned.


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## Tiresius (Oct 4, 2012)

Thanks, Will.

I was hoping that I do not have to change the gears around. Yes, there is a box with extra gears and equipments. However, since it is not mines, I will have to ask my brother if he can change it for me. I was hoping that the gears can easily be changed like in the video Dan linked to me. Guess it's back to tinkering with his machine.

Yes, the machine you have is very similar to the one I'm using--right down to the chart. Except, it's not blue 

EDIT: If you noticed, this lathe is almost brand new--aside from *only *me using it three times.


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## darkzero (Oct 4, 2012)

Tiresius said:


> Thanks, Will.
> 
> I was hoping that I do not have to change the gears around. Yes, there is a box with extra gears and equipments. However, since it is not mines, I will have to ask my brother if he can change it for me. I was hoping that the gears can easily be changed like in the video Dan linked to me. Guess it's back to tinkering with his machine.
> 
> Yes, the machine you have is very similar to the one I'm using--right down to the chart. Except, it's not blue



No problem, glad to help. Actually I don't have that lathe. I initially did purchase one but when I found out about still having to change gears I then changed my mind and bought a different lathe to avoid those kind of gear changes. It sounds like a pain & it can be but it's not that bad after doing it a few times.


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## 350xfire (Oct 4, 2012)

Tiresius said:


> Thanks, Will.
> 
> I was hoping that I do not have to change the gears around. Yes, there is a box with extra gears and equipments. However, since it is not mines, I will have to ask my brother if he can change it for me. I was hoping that the gears can easily be changed like in the video Dan linked to me. Guess it's back to tinkering with his machine.
> 
> ...



I have a feeling you will be the owner of a gear head lathe some day! Once you get one you'll never go back.


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## wquiles (Oct 4, 2012)

The good "Will" and Daniel already made great contributions on this thread, but the "evil" Will (me), although late, can perhaps resurrect some old threads on threading:
http://www.candlepowerforums.com/vb/showthread.php?261759-Mag-D-Threading-Videos&highlight=thread

http://www.candlepowerforums.com/vb/showthread.php?204226-thread-on-outside-threading&highlight=thread


Will


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## Tiresius (Oct 5, 2012)

350xfire said:


> I have a feeling you will be the owner of a gear head lathe some day! Once you get one you'll never go back.



Maybe 

I was thinking of making stuff and selling them to fund for my way through tech school. Then again, I may want to make some money along the way  Ultimately, owning my own lathe and shop equipments?


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## sanddan52 (Oct 5, 2012)

wquiles said:


> The good "Will" and Daniel already made great contributions on this thread, but the "evil" Will (me), although late, can perhaps resurrect some old threads on threading:
> http://www.candlepowerforums.com/vb/showthread.php?261759-Mag-D-Threading-Videos&highlight=thread
> 
> http://www.candlepowerforums.com/vb...-thread-on-outside-threading&highlight=thread
> ...



Will,

What kind of lubricator are you using in the videos.

Dan


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## gadget_lover (Oct 5, 2012)

Congrats on the first threads, BTW. Now that you have started, you need a few more tools to make life easier for you.

First is a $3 tool called a "thread gage". You use it to quickly find the pitch of an unknown thread. It's a little bundle of flat plates with a serrated edge that represents all the common threads. You simply press that edge against the thread to see if it fits. There are separate gages for metric and imperial.

You can not cut a thread to the right depth until you know what the pitch is, then you can do the math. 

I really recommend the threads that "Evil Will" (wquiles) posted since he does a very nice job of laying out the process and there is good discussion of right and wrong. 

Daniel


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## wquiles (Oct 6, 2012)

sanddan52 said:


> Will,
> 
> What kind of lubricator are you using in the videos.
> 
> Dan



In those old videos I used a mist-type lubricator. But now-a-days I use the near-dry lubricator from Accu-Lube:
http://www.candlepowerforums.com/vb/showthread.php?257169-Near-dry-machining&highlight=
http://www.atdms.com/exair_stuff.html

Will


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## Tiresius (Oct 9, 2012)

So...here's a fail attempt by me trying to do things manually:






Now here's how it is when I use the machine to do the work. No human errors.


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## Gtamazing (Oct 11, 2012)

Have you made any mating parts yet? Also if the mating parts start to screw together and get tight don't let them lock up. they can become life partners.


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## gadget_lover (Oct 11, 2012)

Tiresius said:


> So...here's a fail attempt by me trying to do things manually:
> 
> 
> 
> ...



That looks good. What do you mean by "Manual" vs "use the machine"?


Daniel


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## Tiresius (Oct 12, 2012)

gadget_lover said:


> That looks good. What do you mean by "Manual" vs "use the machine"?
> 
> 
> Daniel



Sorry to confuse you there, Daniel. I tried to thread by using the dial and timing when to engage the half-nut lever with the machine constantly on. It turns out that the lever won't engage at the precise moment and was off by 2mm on the dial.

It was so much more easier to thread by simply turning it on and turning it off when I get it to the right spot...Then I simply pull the blade back and reverse the sucker. Finally, line up the blade and forward it goes!!! This way, human errors are removed and the thread came out perfectly.


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## Tiresius (Oct 12, 2012)

Gtamazing said:


> Have you made any mating parts yet? Also if the mating parts start to screw together and get tight don't let them lock up. they can become life partners.



This is made to fit in my Crelant 7G5 V2. I designed a solid block to slap on a thrower LED. The pitch is 1.5mm? I have no idea what metric measuring unit is 

Yes, after two attempts, I finally got this thing right. First time was complete fail and the thread didn't screw together. Second attempt was too thick as I forgot to take the measurements from the original.

Thanks to everyone's tips and inputs, I finally learned to thread properly. Except, my fists weren't happy as they are cut from changing gears


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## gadget_lover (Oct 12, 2012)

So glad to hear that it worked well for you. 

Sorry to hear about the hand damage. I seem to contribute a drop of blood to every project. I count that as part of the "blood, sweat and tears" that make up a successful job.

Congrats.

Daniel


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## Tiresius (Oct 12, 2012)

Here's the result of the project: http://www.candlepowerforums.com/vb/showthread.php?345669-Crelant-7G5-XR-C-Thrower

I was pretty happy with the new drop-in I made. Not so happy with the result as the lux did not seem like much compared to the XML on 2 IMR cells--only *slightly* brighter.


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## gadget_lover (Oct 12, 2012)

Good work on that drop in. Something to be proud of. 

Daniel


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