Why Doesn't My Tap Work!?

[watch_art]

I have a 3/8 x 36 tpi tap for - supposedly - threading sections to take Pel M1000 nib units.

That's what I read here:

http://www.fountainp...post__p__614715

 

Just tried it - doesn't work. Doesn't even almost work.

What the heck tap do I need for the Pel M1000 nib unit?

 

Thanks for any help guys.

 

Cheers!

Edited July 18, 2012 by watch_art

[Rich L]

You don't say what the problem is . Too tight? Too loose? ??

 

I don't mess around much with Pelikan nibs but I just measured the one P1000 I have and the major diameter is a touch over 3/8" (.377 - .378) so I would guess that your nib won't go in - too tight. That difference is enough to bind against the minor diameter of the threaded hole as the thread form on the nib is around 70%.

 

The pitch gauge says 36 tpi or .75mm over the short distance. Either will work as far as thread pitch goes.

 

Try over drilling the hole a bit.

 

Cheers,

Rich

Edited July 18, 2012 by Rich L

[watch_art]

Will do - thanks!

 

As for the problem, it won't even start. Holding the nib unit up to the tap, comparing threads, it looks like a dead match but...

 

I dunno.

 

I'll try a larger bit before threading.

 

Thanks

[Rich L]

What size hole are you drilling?

[watch_art]

9.3mm and the tap is about 9.54mm - so yeah - no way it's going to work --

 

a while back you said that I could make my own tap. How do you mean?

https://www.fountainpennetwork.com/forum/index.php?/topic/201237-cutting-threads/page__view__findpost__p__2057864

 

Would I be able to find a bolt with the same threads and cut it all up and make a tap out of it?

[Rich L]

a while back you said that I could make my own tap. How do you mean?

http://www.fountainp...ost__p__2057864 Since you asked, I'm happy to share...

 

Would I be able to find a bolt with the same threads and cut it all up and make a tap out of it? I seriously doubt that you'll find a bolt, but, who, knows, maybe there's something out there. Like I said, I don't mess with Pelikan much but I do find it curious that they would use an Imperial size. My estimate of the thread is M9.6 x .75

 

So ... making a tap. I posted this a while back in another forum ::

 

-------------------------

 

If you're just needing a tap, that's not too hard especially if you're tapping soft stuff - brass to plastics. I know it's not trivial but here's what I'd do (and I've done it):

 

Examine a tap closely first ...

 

Get some W1 or O1 drill rod and thread the thing so it's a nice easy turning fit where you can barely feel friction. Very little wiggle. This should give you the tolerance you need if it's a small diameter thread. Make sure your threads are nice and clean - no burs. Also, don't try and thread a full profile if you're using a sharp triangular lathe tool bit and not a full profile insert. If you're using a full profile insert then go ahead and thread the full profile. About 80% is fine but no less than 75%. You can almost eyeball this thread form with some 5x optivisor thing. You'll have a little bit of a flat crest on the threads which is fine.

 

Taper the end of the threads so that the taper runs through about 3-4 threads. This will give you a tap that's between a plug and taper form.

 

Now the harder part if you don't have a mill and some setup. You need to mill (don't need to grind) the flutes. You want to get a suitable cutting edge rake and a suitable clearance angle underneath the cutting edge. Run a square edge end mill (doesn't matter what diameter) lengthwise along your threads, with the edge of the end mill slightly over center (say .015"). If the edge of the mill is right on center of the tap you'll get no cutting rake with the tap so move the mill a bit more over center. Depth of cut needs to be greater than the thread depth for chip removal during tapping. If you don't need a really strong tap, twice the thread depth or more should work.

 

The clearance angle is next and you can do this by hand if you have a fine Arkansas stone. Improvise otherwise. You need to grind off (or mill, but the setup may be tricky) the back side, or underside, of the cutting edges. Just look at any tap you have and you'll see that the threads doing the cutting touch the part being cut only at the tip of the cutting edge. You can't have any other non cutting part of the tap at the business end of the tap touching the hole or there will be no penetration - and no cutting. You'll end up rolling your threads if not messing the part up completely. Once you've got the clearance angle ground on each flute you should have a tap that works.

 

Harden it if you want (for tapping metals) and then temper to at least 450ºF for an hour.

 

It's very hard to measure and specify non-standard threads (pitch diameters) without all the right metrology. You may end up buying a special tap that won't be the right size.

 

Have at it!!

----------------------

Pictures show staining which comes from the oxides formed during oil quenching O1 steel. I made this tap for the Parker Centennial internal barrel threads that their section assembly screws into. I advocate O1 or W1 for this application because you can harden and temper if you want and it's easy cutting steel unlike mild steel or some old bolt stock. Also, hardening and tempering is really no big deal for small parts if you don't care what they look like when you're done.

 

Don't hesitate to PM me if you have questions - I can coach you through it if you'd like. It might be hard to visualize some of the directions. I guarantee that by doing this you will gain a good education in "thread science."

 

Cheers,

Rich

[watch_art]

All that is brilliant! Very clear and easy to understand.

 

And some new news. Measuring my M1000 nib unit again I see that it's 9.7mm thick at the threads - so if I tap with my M10x.75 tap...

That's the same thread I used on my smaller pens for the section to barrel connetion -

 

AND IT FITS PERFECTLY!!!!

 

Yeeha!!

I'll post pics in a bit of my tortoise pen with the Pel nib unit!

[watch_art]

Yeeha!

 

 

http://newtonpens.files.wordpress.com/2012/07/83-pel-nib.jpg

[quinden]

WOW! That is awesome work

[djpyle]

Too cool!

 

Well done.

[watch_art]

Thanks!

[drgoretex]

All that is brilliant! Very clear and easy to understand.

 

And some new news. Measuring my M1000 nib unit again I see that it's 9.7mm thick at the threads - so if I tap with my M10x.75 tap...

That's the same thread I used on my smaller pens for the section to barrel connetion -

 

AND IT FITS PERFECTLY!!!!

 

Yeeha!!

I'll post pics in a bit of my tortoise pen with the Pel nib unit!

 

M10 x 0.75?? really? COOL! Thanks for experimenting! I have such a tap, and have routinely declined requests to make pens for Pel nibs because I assumed they were all specialty specs. Awesome. I think I will be ordering me an M1000 nib to make a home for!

 

Ken

 

PS - Now - anyone know the thread specs for M800s and M600s?

[watch_art]

9/32"- 36TPI M400/600 Pelikan nib unit

11/32"-36TPI M800 Pelikan nib unit.

3/8"- 36TPI M1000 Pelikan unit.

 

They're all 36tpi, or .75pitch

Just measure the major diameter of each units threads and go with the closest metric tap.

The M1000 was 9.7, so a 10x.75 worked.

 

I want to get some other nibs to make pens for as well.

 

9/32"- 36TPI M400/600 = 7x.75? The threads are actually 7.14 so this one may not work...

 

11/32"-36TPI M800 = 8.7313 = 9x.75

[drgoretex]

9/32"- 36TPI M400/600 Pelikan nib unit

11/32"-36TPI M800 Pelikan nib unit.

3/8"- 36TPI M1000 Pelikan unit.

 

They're all 36tpi, or .75pitch

Just measure the major diameter of each units threads and go with the closest metric tap.

The M1000 was 9.7, so a 10x.75 worked.

 

I want to get some other nibs to make pens for as well.

 

9/32"- 36TPI M400/600 = 7x.75? The threads are actually 7.14 so this one may not work...

 

11/32"-36TPI M800 = 8.7313 = 9x.75

 

 

Cool. Thanks!

 

Ken

[hari317]

9/32"- 36TPI M400/600 Pelikan nib unit

11/32"-36TPI M800 Pelikan nib unit.

3/8"- 36TPI M1000 Pelikan unit.

 

They're all 36tpi, or .75pitch

Just measure the major diameter of each units threads and go with the closest metric tap.

The M1000 was 9.7, so a 10x.75 worked.

 

I want to get some other nibs to make pens for as well.

 

9/32"- 36TPI M400/600 = 7x.75? The threads are actually 7.14 so this one may not work...

 

11/32"-36TPI M800 = 8.7313 = 9x.75

 

I tried the 11/32" 36 tpi special tap to accommodate a M800 nib unit. The unit threads on, but it is very tight. I had a bad time getting the nib unit off. So in short not recommended. have you tried the 9.0x0.75 tap for the M800? does it work well? wanted to confirm before I spend more money...

[watch_art]

9x.75 for the m800 works wonderfully. I've done it for a couple pens already...

[hari317]

Ok, thanks! I think the 9/32" 36 tpi should work well for the M400 et al. since the nib unit will be a slightly loose fit with this tap. have you tried it?

[watch_art]

Not yet. I will be very soon though.

[hari317]

Ok, I have just now tried the 9/32 36 UNS tap with me. it is as useless as the M800 tap. too tight. I suspect the 7x0.75 is also going to be too tight.

 

I think the easily available on ebay 5/16" 36 TPI tap might work, I think will be just slightly loose. I think same tap is used for the blind cap threads on the vac 51. I threaded a M200 nib unit into a vac 51 blind cap, worked very well! HTH.

[watch_art]

Slightly loose is better than so tight won't fit. At least with a little slack you can use the lip of the nib unit to create tension.