A miniture tap and die for steam engine pipe threads

I was building a PM Research No. 7 steam engine and needed to tap and cut male and female pipe threads in 3/16-40. These taps and dies are available but are far from cheap. I was looking at over $90 for a set.

Since a coworker needed a set for an engine he was building, I told him if he bought the drill rod, I would try my hand at making a tap and die set for both of us. He agreed that even if I wasn't successful, I would still get tpo keep the W1 drill rod he bought.

Here are some photos with captions showing the operations:

Setting the taper by offsetting the tailstock and verifying it:
Attachment 264

Turning the tapered thread for the tap:
Attachment 262

Cutting the threads:
Attachment 263

Hardening and tempering happens... Heat to cherry red, quench. Heat to pale straw, quench again...

Cutting the flutes. That's a dremel with a diamond coated form grinding tool held in my mill vise. Notice the grinding tool is NOT located on the vertical centerline of the tap... This gives positive rake to the cutting edges. The mill spindle was indexed by eye to give 4 flutes. With the mill tunred off (and UNPLUGGED), the quill was plunged down onto the grinding wheel to cut (and sharpen) the flutes.
Attachment 265

I hit my four picture limit, so I will show more pics in another post...

John

Using the newly made taps to cut the threads for the die:
Attachment 266

Cutting the rake holes:
Attachment 267

Hardening of the die now occurs the same way as the tap. The rake holes are afterwards cleaned up with a cylindrical diamond cutter in the dremel to return the edges to sharpness.

Some test threads:
Attachment 268

Test fit:
Attachment 269

John

Finished tap and die:
Attachment 270

That's it! You can make straight taps the same way (but without the taper)

John

Thanks jgedde! This one has been added to our Drilling and Tapping and Metalworking categories, and to your homemade tools page: jgedde's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"><div class="bimg"><div><a href="/miniature-tap-and-die"><img src="/images/thumb/bc/bc155378ffa8b3d8d5849e49692ea32d-20121019130556.jpg" alt="Miniature Tap and Die"/></a></div></div><div class="head pngfix"></div><div class="left pngfix"></div><div class="right pngfix"></div><div class="blockover b1 pngfix"><div class="title"><a href="/miniature-tap-and-die">Miniature Tap and Die</a><span> by <a href="/builder/jgedde">jgedde</a></span></div><div class="tags">tags: <a href="/tag/steam">steam</a>, <a href="/tag/engine">engine</a>, <a href="/tag/dremel">Dremel</a>, <a href="/tag/tap-die">tap & die</a></div></div></div></div>

very nice and well documented

Quote:

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Originally Posted by jgedde

I was building a PM Research No. 7 steam engine and needed to tap and cut male and female pipe threads in 3/16-40. These taps and dies are available but are far from cheap. I was looking at over $90 for a set.

Since a coworker needed a set for an engine he was building, I told him if he bought the drill rod, I would try my hand at making a tap and die set for both of us. He agreed that even if I wasn't successful, I would still get tpo keep the W1 drill rod he bought.

Here are some photos with captions showing the operations:

Setting the taper by offsetting the tailstock and verifying it:
Attachment 264

Turning the tapered thread for the tap:
Attachment 262

Cutting the threads:
Attachment 263

Hardening and tempering happens... Heat to cherry red, quench. Heat to pale straw, quench again...

Cutting the flutes. That's a dremel with a diamond coated form grinding tool held in my mill vise. Notice the grinding tool is NOT located on the vertical centerline of the tap... This gives positive rake to the cutting edges. The mill spindle was indexed by eye to give 4 flutes. With the mill tunred off (and UNPLUGGED), the quill was plunged down onto the grinding wheel to cut (and sharpen) the flutes.
Attachment 265

I hit my four picture limit, so I will show more pics in another post...

John

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What material did you make the tap and die set from?