Making your own specialty taps. Bock 5 mm

[More4dan]

I needed a tap for a Bock 5 mm triple nib unit and didn't want to spend $40-$50. So I chucked up some 3/8" drill rod (W1) and turned it down to 0.253" and cut threads at a 0.6 metric pitch. Heated with a MAPP torch until it was no longer magnetic and quenched in water. I then ground a taper on the tip every 90 degrees. Works great in aluminum, brass, 304 SS, acrylic, and ebonite. Worked so well I made 8.5mm x 0.6, 9mm x 0.75, and 11mm x 0.75. Those worked for aluminum and brass but struggled in the 304 SS. Also much stronger than traditional taps with most of the cross-section milled away.

 

[More4dan]

For making Taps I found this page to be invaluable.

UN imperial screw thread calculator

For metric threads you have manually enter the diameter and tpi then change units to metric to check pitch. Trial and error or convert pitch to tpi for the input. For a tap use the dimensions for the female thread and go for max diameter and depth of cut that allows for the tap drill you are using. Convert back to inches for lathe settings in the US.

 

[Paul in OKC]

Kind of like those thread form taps. Nice idea!

 

[More4dan]

Kind of like those thread form taps. Nice idea!

If you look close at the ground end you see partial threads progressively getting deeper. These actually cut the material forming chips. Because it doesn't have the deep grooves you normally see in a tap you have to be careful when tapping blind holes without room for the chips. An advantage is your aren't likely to break one with the greater cross section.

 

[magpens]

Dan,
I must be missing something. . How does 0.253" relate to 5 mm ?

I calc that 5 mm would be 0.197"

I needed a tap for a Bock 5 mm triple nib unit and didn't want to spend $40-$50. So I chucked up some 3/8" drill rod (W1) and turned it down to 0.253" and cut threads at a 0.6 metric pitch. Heated with a MAPP torch until it was no longer magnetic and quenched in water. I then ground a taper on the tip every 90 degrees. Works great in aluminum, brass, 304 SS, acrylic, and ebonite. Worked so well I made 8.5mm x 0.6, 9mm x 0.75, and 11mm x 0.75. Those worked for aluminum and brass but struggled in the 304 SS. Also much stronger than traditional taps with most of the cross-section milled away.

 

[darrin1200]

Morning Mal

The 5mm does not refer to the thread, it is the diameter of the feed that the nib fits over.

Here is a decent post I found on FPN
Nib # Size ? - Of Nibs & Tines - The Fountain Pen Network

 

[Charlie_W]

Can you explain how your drill rod stock became magnetized?
I didn't know heating would remove magnetic properties....interesting!

 

[More4dan]

Can you explain how your drill rod stock became magnetized?

I didn't know heating would remove magnetic properties....interesting!

Sorry I left the wrong impression, the drill rod isn't magnetic. Tool steel will stick to a magnet when cool. When it has been heated high enough it will not stick to a magnet. The crystalline structure has changed. At or above this temperature if you quickly quench the steel it will harden. It's a poor boys way of heat treating tool steels. After quenching a file should skate across the rod without biting in. Do this after threading and before grinding the tip.

Danny


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