Making multi start tap and die

[soligen]

I know the multi start taps and dies are special orders and cost a lot. More than I can justify spending right now.

So, my question us, if someone local had a multi start tap and die already, couldn't those be used to make another multi-start tap and die?

I understand the quality would not be the same, and the metal would need to be softer, but for use on acrylics, I wouldn't think this would matter all that much. An inexspensive cabon steel die smaller than the target could be modded into the multi tap die.

Is this feasible? I have to wonder since no-one is doing it.

 

[BRobbins629]

If it were that easy, we wouldn't need taps and dies, we could use nuts and bolts. I have used my taps and dies to make mandrels in brass and mild steel, but would never consider them to cut threads. The threads are not as sharp as the taps and dies and they would still need some machining to provide room for the metal being cut. I think Skiprat made a post on how to make multistart taps and dies on a metal lathe. That would be a better approach.

 

[workinforwood]

I disagree and say the answer is yes. Back when I first started making threads in aluminum, I made them at whatever size they came out to be and did not have a matching tap for the threaded aluminum rods I made, so I used part of the threaded aluminum as taps to tap the plastic cap section and it worked out just fine. Those pens still work great a few years later. You can simply mount a dremel with a cut off wheel on it and run that across the threads 3-4 times around the pen to create a slot for debris to go into while tapping. The Aluminum taps I made did not last long, only for a few pens, but they did work. Brass is certainly easy to die and is much stronger than aluminum, so you would get a lot more life out of that, but still nothing compared to real tool steel.

Now I ask..why do you even care about triple threads anyhow? I think many of us don't do anything like you are saying because we don't even want the triple thread action. The only benefit of triple threading that I know of is that you are able to screw the pen together faster because of the difference in angle of the threads. Forgive my threading lingo, but if you compare threads to stairs, the steeper your rise, the faster you get to the top. A triple thread is this way, the rise has to be steeper in order to fit more threads into the mix. But..because the rise is steeper, the hold when it is closed is weaker...it's like now you imagine your staircase is coated in ice, and if that was the case, being on a steep staircase will be harder to hold on. This is why you pack your JR kit pens and go to a show and when you get there, some of them the lids are a bit loose from the vibrations of travel. So now as a customer you walk around with your fountain pen in your pocket and the lid vibrates loose and you get ink all over your shirt. Single threads hold strong..yea it takes an extra turn or too to close it, but it stays closed. There are ways to make single threads with a steep pitch too, like acme threads, but then you are back to the holding power issues, and so I rather the person has to turn the pen one more time than have the cap come loose in their pocket.

 

[soligen]

The answer Jeff, is that the multi start threads are simply my paradigm of what is "correct" for capped pens. All the kits I see have triple start cap threads, and I see past group buys for the taps and dies too.

My first true kitless will be with single start threads, probably only 20 TPI since I is what I have, but I figured getting into multi start is "doing it right". Maybe I need a paradigm shift!

If I'm working in PR, how many threads are needed for a secure hold that will stand up to use over time?

Bruce, I figured on cutting relief into the threads for the waste. I saw a video of a guy making a tap from a bolt

 

[workinforwood]

Taps made of bolts are nothing new. I've seen video's of guys hooking a hose up to a spark plug hole to generate air to fill their tires. You do what you need to do to get by. I have a few vintage pens here and there laying around and some of them are triple thread, some are double thread, some are single thread, there is just no rules regarding how it has to be. There will be some positives and negatives regardless how you do it. I do not know what 20 teeth per inch looks like. I use metric, I just find it is much simpler to do the math. If parts are really tiny, like the nib feed, then .5 is what I use, and I like .75 threads the most, but those are going to be your medium sized parts, like a nib coupler and if the pen is relatively small in size, like a bit smaller than a baron, a .75 set up will run the cap threads too, but otherwise, anything larger, like once you get up in the 10mm range, the finest logical threads are 1mm. And those look fine in my opinion. The number of threads I generally keep on the pen portion to screw into a cap would be about 7 or so..whatever looks good to me at that moment. Those will hold plenty strong. You can also move the threads back towards the pen body, or further up towards the nib. There's positives and negatives to each way. threads closer to the nib will be less comfortable because you might touch them when writing, but you have a more solid hold on the cap because you are further inside which is less stressful on the cap if the pen is dropped or side pressure is applied to the cap for any reason. So threads closer to the body will be more comfy and can often look better, but harder on the cap..yet you can use a metal centerband over the cap to give some strength back to it. Many of the vintage pens that have the threads furthest back, the ends of the caps are broke because the caps is just plastic only. Look at all the old pens on ebay..great place to study different joining techniques and see the positives and negatives of them...making a pen from scratch is engineering and no one way is the "perfect" way.

 

[ldb2000]

I have to disagree about the lack of need for multi start threads . The amount of turns to cap a pen is only one of the reasons for using multi start threading . I have made several pens with single start threading and found them to be unacceptable for sale for reasons related to strength and aesthetics . There is a reason that almost all of the major pen companies use multi start threading . Strength is very important in the threading of the cap and for a single start thread to be strong enough to stand up to years of use , you have to have as many threads in contact as you possibly can to spread out the stresses that the joint is subjected to . It has been said that just 3 threads are needed for a strong threaded connection but after allot of experimentation I have found that 3 threads will not stand up to the stresses of a pen cap and the joint will fail , in most cases the cap cracked . This means in general at least 8 to 12 threads for a normal acrylic pen cap . That many turns to tighten the cap would be totally unacceptable , I normally try to have at least 9 threads in contact on my pens made of acrylic to provide a strong joint . This is easily accomplished with just 3 turns of a triple start thread .
The other reason , aesthetics , is just as important . A strong single start threaded joint just looks and feels fugly . The large size of the threads feels very rough and uncomfortable for long writing sessions . Threads of that size also break up the flow of well made pen and distract the eye from the look of the rest of the pen .
As for cutting your own triple start taps and dies , very few are doing it because it is a PITA to do and to do it for sale would not be cost effective . I make my own taps including triple and quad start , out of brass on my metal lathe and they work very well for acrylics but they are not usable for other metals so making dies with them is out and I have had no luck with internal threading on the metal lathe yet , so when I need body threads I do as Skiprat does and make a longer threaded piece and cut off a section to make a threaded insert for the body and use the rest of the threaded rod to make a tap for the cap .
Making taps and dies from taps and dies won't work very well due to errors that creep in from the machining process and while I guess it could be done , again it wouldn't be cost effective to do them for sale .