Group Buy on Special Taps and Dies

[tonydacrow]

As it turns out, a manufacturer of special taps and dies is just down the street from me. Their website is here. Some have expressed an interest in double and triple lead taps for pen caps and the like. I'm going to be purchasing some and Gerry suggested others may wish to purchase them, also.

 

I don't know the costs yet. They won't be cheap, but I doubt they'll be too expensive. If you're interested in any of these or other taps/dies, let me know by posting to this thread. I'll find out the cost once everyone decides what they want. If there's enough interest, I coordinate a group buy on these things.

 

So... here's a list of what I'm getting.

 

1) standard, 60 degree "v" plug tap, 7mm X 0.7mm (Pelikan nib thread)

2) Acme plug tap, 5/16 x 18tpi x triple lead (For 5/16" cap threads - cap end)

3) Acme die, 5/16" x 18tpi x triple lead (For 5/16" cap threads - body end)

4) Acme plug tap, 1/2" x 18tpi x triple lead (For 1/2" cap threads - cap end)

5) Acme die, 1/2" x 18tpi x triple lead (For 1/2" cap threads - body end)

 

Anyone else want anything?

[cacao]

Hello Tony,

 

 

I would be interested in:

 

 

1) Acme plug tap, 3/8" x 18tpi x triple lead (For 3/8" cap threads - cap end) and

2) Acme plug tap, 1/2" x 18tpi x triple lead (For 1/2" cap threads - cap end),

 

 

of course, depending on the price.

[Gerry]

Hi Tony. Of course, it always depends on the price, but I think I'd be interested in the full range of taps you've considered.

 

Regards,

 

Gerry

[sptfr43]

ditto what Gerry said

[fountainbel]

Hi Tony,

Thanks for the excellent proposal.

I'm also interested in the ones you listed, logically cost is an important parameter.

Francis

[Steve]

Hi Tony,

Make that another "ditto".

 

Thanks

Steve

 

 

(edit for stupidity on my part)

Edited January 21, 2007 by Steve

[Gerry]

Gee Tony, counting yours, you've already got a 1/2 dozen.

 

Thats 36 taps - perhaps you're getting into discount territory....

 

Gerry

[wdyasq]

I'd be interested in some taps.

 

I'm wondering what the 'ACME' taps are for. I have never seen a pen with ACME thread.

 

Ron

[Nihontochicken]

Okay, I'll throw in (but probably some interpretation needed). I want a 3/8" major diameter triple lead tap (and matching die), 48 tpi (16 tpi per lead). I suppose with either the tap or the die, I can make the other, but if the price is decent, I'd rather pop for the pair, otherwise really want the die, shear face (bottoming) on one side. I hope this is only $19.95 on Ronco, with Fast Bass as a no cost addition!!!

[tonydacrow]

wdyasq,

 

As you may already know, acme threads are stonger than standard "v" threads because they are more square. I'm using them to build my own pens. I assume most old pens have very specific threads unto themselves.

 

You can read about acme threads vs "v" threads here.

 

Here's a picture of different types of screw threads...

[Gerry]

I suspect then that more of the older pens might employ Unified, rather than Acme thread profiles - or at least the unified would likely fit better than an Acme, which would have interference problems, most likely...

 

Perhaps we need a little more discussion on the issue of threads before ordering... - or at least I need a little more....

 

Regards,

 

Gerry

[tonydacrow]

Here are my observations and suggestions.

 

I suspect every pen manufacturer utilizes their own screw threads for caps, barrels, nibs, etc. Some (like Pelikan) may be “odd-ball” or proprietary sizes. This will most likely be true for those pens made prior to the '50s. Others will use standard threads but they will not necessarily be the same standard threads between manufacturers or classes of pens by the same manufacturer. Most will probably use a "v" form, but I suspect many will use acme (especially for cap and barrel) due to its superior strength.

 

Let's hold off on the tap/die group purchase until everyone has a chance to determine the screw thread form, size, etc of the pens on which they wish to work. (Since I'm doing my own pens, it doesn't matter what I get because the threads will be whatever I make them).

 

To make this a little more orderly, let’s all measure the pens we want to work on and post our observations here. You will need to make the following measurements:

 

1)Diameter: What is the size of the thing that goes into the hole in the cap or the section holding the nib (barrel, nib, etc). The size will be measured either in metric or SAE. European pens will most likely use metric sizes. Most US pens will probably use SAE (i.e., 1/8", 5/16", etc). You can measure Diameter with a hole gauge, micrometer, etc.

 

2)Pitch: What is the number of threads per unit measure. For metric threads it will be expressed as the number of millimeters per thread. EG -- A metric pitch of .5 means that measuring from the top of one thread to the top of its neighboring thread will cover a distance of 1/2 millimeter. A metric pitch of 2 means that measuring from the top of one thread to the top of its neighboring thread will cover a distance of 2 millimeters. For SAE threads, it will be expressed as the number of threads per inch. Therefore, an SAE pitch of 18 means that it will take 18 threads going around the hole to cover a distance of 1". Pitch can be measured with a screw-pitch tool. The come in metric and SAE. These are a collection of several sheets of metal with different sizes of v’s cut into them. You find the collection of v’s that fit the thread of your screw and read the size stamped into the sheet.

 

3)Lead: This is a measure of how many threads will be cut at one time. Standard taps and dies are "single lead" meaning that they cut one thread with one revolution of the tap or die. "Double lead" means that the tap or die will cut two threads per revolution. "Triple lead" means three per revolution, etc. The reason one uses multiple leads is that you move across more distance per revolution. A single lead 18 pitch SAE tap will take 18 revolutions to move in or out of the hole a distance of 1". A double lead 18 pitch SAE tap will take 9 revolutions to move 1". A triple lead 18 pitch SAE tap will take 6 revolutions to move 1". Each will have 18 threads cut per inch but, as an example, a triple lead cut hole will move up or down the hole 3 times faster than a single lead cut. Multiple lead threads maintain the strength of a high number of threads but allow the thing being screwed in or out to go further with fewer revolutions. It is important to note that a singe lead 18 pitch SAE thread will look exactly like a triple lead 18 pitch SAE thread. To determine whether you have a multiple lead screw requires you to follow a single thread around the hole. One way to do this is to use a colored crayon that touches only one thread and move it around a complete revolution while staying in touch with that one thread. If the all of the threads in that one revolution are colored, you have a single lead thread. If only 1/2 of the threads are colored, you have a 2 lead thread. If 1/3 are colored, you have a triple lead thread, and so on.

 

4)Form: Is the thread a "v" form, Acme, Whitworth, etc. Study the picture above to determine the form.

 

5)Handedness: Is it a right-handed (standard) thread or a left-handed thread. Remember, on a standard thread you turn clockwise to tighten, counter-clockwise to loosen. A left-handed thread is just the opposite.

 

There are other parameters such as tolerance that you don't need to worry about.

 

I have measured Pelikan nib threads for the 600 series and found them to be:

7mm x .7mm x single lead x unified thread x right handed.

 

That means (1) that the hole is 7mm in diameter, (2) measuring from the top of one thread to the top of its neighboring thread measures .7mm, (3) only one thread at a time goes around the hole, (4) the thread form is a unified “v” thread, and (5) the nib screws in clockwise and is removed by screwing it out counter-clockwise.

 

OK, guys and gals: lets get measuring!

Edited January 22, 2007 by tonydacrow

[Nihontochicken]

1)Diameter: What is the size of the hole in the cap or the section holding the nib. This will correspond to the diameter of the thing that goes into the hole (barrel, nib, etc).

 

I'm no machinist, but I was told by my more mechanical friend that the key measurement for taps and dies is the major diameter, which he defined as the outside diameter of the threaded male part. So one would need to measure the outside diameter of the section threads, not the inside diameter of the cap or barrel threads, to get the correct size. The ID of the cap or barrel threads would yield a measurement too small by twice the depth of the threads. Again, just going on what I was told, need confirmation or denial!

[Gerry]

Thanks for the clarification Tony. Very informative.

 

Let's see how many of us measure up then...

 

To be honest though, if there are those of you who 'know' what some common threads are for vintage pens, and correlate that info to the pen type, I suspect perhaps better choices may be made. From my POV, although I'll be as careful as I can with the measurement, there will always be some uncertainty, particularly if the model is older and has possibly distorted a bit. Anyway, all additional information gratefully received.

 

Could we also list the pen/model, and application for clarity - Parker Vacumatic/51/75/, or Sheaffer/Esterbrook etc., Barrel/cap/filling unit/section/blind cap thread etc.?

 

Regards,

 

Gerry

Edited January 21, 2007 by Gerry

[sptfr43]

Tony, you said you are making your own pens? how did you decide on the size threads and do you have a source for the pelican nibs and I assume feeds? thanks.

[cacao]

As I too am interested in the taps to make pens from scratch, I stand by my earlier requested sizes. I am measuring the tap size from the maximum outside diameter of the tap, as is the machinist standard. This will be a measure of the outside of the barrel threads.

[kirchh]

As you may already know, acme threads are stonger than standard "v" threads because they are more square.  I'm using them to build my own pens.

I would recommend Unified threads rather than Acme for pens, particularly for caps. The advantage of an Acme thread form is greater strength for axial loads, but that is not an issue for a pen cap, in my opinion; the risk of having a pen cap pulled so hard that all the threads actually shear off is miniscule.

 

Acme threads are superior to Unified threads for drive applications such as machine tool components as well as for vises and clamps. However, fasteners almost never use the Acme form, and the pen application is essentially a fastener.

 

The thread depth of a Unified thread is greater than the thread depth of the equivalent Acme thread. In my opinion, that provides greater tolerance of wear and, perhaps more importantly, it is more tolerant of machining variations due to the greater available engagement depth.

 

I also suspect that Acme threads may be more difficult to cut in one pass in plastics, though, frankly, I suspect that use of a tap or non-adjustable die for cutting threads in plastics (especially in thin-walled parts) may, in general, be impractical if not impossible.

 

--Daniel

[tonydacrow]

Nihontochicken and Cacao;

 

You're both right. In my rush to try to make taps and dies understandable to those with no experience with them, I mispoke. The diameter is measured at the "major diameter" which is the diameter of the outside of the threads of the thing that goes into the hole. I've fixed that part in my original post. Thanks for catching that.

 

Sptfr43;

 

18 tpi is about standard for holes in the 1/2" range. I chose Acme for the reasons stated although I see Kirch disagrees with me. That's what makes life interesting! Also, I ordered the nibs from Swisher Pens. You can find them here.

 

Kirch;

 

I've had no problem cutting threads into pen bodies and nib sections with taps and dies. You have to be careful not to over torque or twist off axis, but overall they work fine. You may be right about the acme threads, but I note that some pen companies use those instead of "v" threads. Also, Unified may be deeper, but they are also narrower at the top of the form and if they break (or crumble!), they will break there. In addition, most of the load is carried at the root. Besides, I've seen too many cross-threaded "v" threads. I've never seen an Acme cross thread!

 

Anyway, good discussion all. Keep it up and lets start measuring those pens!

[kirchh]

I've seen too many cross-threaded "v" threads.  I've never seen an Acme cross thread!

Cross-threading can occur fairly easily on single-lead Unified threads when they start at the very opening of the female part. However, multi-lead threads (particularly triple-lead and more) tend to level the parts on the approach, and more importantly a pen's cap typically has an unthreaded area for perhaps 1/2" before the internal threads begin, so that the two parts are piloted quite nicely into axial alignment before engagement occurs. It is tilting that encourages cross-threading, and in general very little tilting of the cap can occur once it has been slipped far enough on for engagement to commence. Indeed, I'm not sure I've ever seen a cross-threaded quality pen.

 

--Daniel

[Nihontochicken]

However, multi-lead threads (particularly triple-lead and more) tend to level the parts on the approach ...

 

Bingo! Triple lead threading is the way to go for many (most?) applications. Three points determine a plane, hence the much less likelyhood of cross-threading a three lead set up, not to mention having a maximum of only 120 degrees of twist before catching a thread, as compared to 360 degrees for a single lead thread. The only drawback for some applications is the lower camming action of a triple lead - that is, there is less leverage per unit of rotational force forcing the screw forward. This may be a consideration for high force fasteners, but is not much concern for fountain pen caps and barrels and the like.