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Thread: A miniture tap and die for steam engine pipe threads

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    jgedde's Tools

    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:
    A miniture tap and die for steam engine pipe threads-verifying-taper.jpg

    Turning the tapered thread for the tap:
    A miniture tap and die for steam engine pipe threads-turning-od.jpg

    Cutting the threads:
    A miniture tap and die for steam engine pipe threads-finished-thread.jpg

    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.
    A miniture tap and die for steam engine pipe threads-cutting-flutes.jpg

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

    John
    Last edited by jgedde; 10-27-2012 at 07:01 PM.

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    jgedde's Tools
    Using the newly made taps to cut the threads for the die:
    A miniture tap and die for steam engine pipe threads-using-newlay-made-tap-thread-die.jpg

    Cutting the rake holes:
    A miniture tap and die for steam engine pipe threads-cutting-rake-holes.jpg

    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:
    A miniture tap and die for steam engine pipe threads-test-threads.jpg

    Test fit:
    A miniture tap and die for steam engine pipe threads-they-fit.jpg

    John

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    Paul Jones (05-04-2015), PJs (04-10-2016), Toolmaker51 (02-07-2017)

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    Finished tap and die:
    A miniture tap and die for steam engine pipe threads-finished-tap-die-set.jpg

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

    John

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    bigtrev8xl (04-25-2018), PJs (04-10-2016)

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    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:


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    very nice and well documented

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    Quote Originally Posted by jgedde View Post
    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:
    Click image for larger version. 

Name:	Verifying the taper.jpg 
Views:	575 
Size:	41.1 KB 
ID:	264

    Turning the tapered thread for the tap:
    Click image for larger version. 

Name:	Turning OD.jpg 
Views:	547 
Size:	45.1 KB 
ID:	262

    Cutting the threads:
    Click image for larger version. 

Name:	finished thread.jpg 
Views:	564 
Size:	32.5 KB 
ID:	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.
    Click image for larger version. 

Name:	Cutting the flutes.jpg 
Views:	783 
Size:	44.8 KB 
ID:	265

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

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


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