# A couple more tips/transfer screws



## DICKEYBIRD (May 10, 2008)

These aren't earth-shattering revelations but they were new to me and worked well.

Minor revelation #1: When I was tapping the mounting holes in the 5C collet fixture in the XY table/grinder tool sharpening project, the tap was binding up and was about to break due to the hard metal the fixture is made of. My Ace tap set was bought in the early 70's and the 3/8 UNC tap has tapped many a hole back when I was turning wrenches for a living. I looked at the tap under a strong lense and could see that the leading edges of the flutes were galling and had some work-hardened swarf bonded on. I decided to freshen the edges and see if it would help.

I chucked it into a 5C square collet block to hold it securely and used a 1/4" square Eze-Lap diamond stick to work on it by hand. The square block allowed a consistent view of the 4 flutes as I worked on them and a magnifying visor and bright light really helped to see what was going on.  The diamond lap dipped frequently into water with a drop of dishwashing liquid added worked really well to remove a little metal from the leading edge.







The difference was amazing! I was able to cleanly tap the other 3 holes with far less effort. The 1st one required a fresh resharpen and a lot of patience due to the work hardening. 

Minor revelation #2: Once the holes were finished, I realized I didn't have any store-bought transfer screws so I made a couple in the 3/8" U.N.C. size.

I drilled and parted off a couple 1/2" lengths of 3/8" all thread rod; then chucked them in a 5C hex collet block. That was clamped in the mill vise with a work stop on the other side to insure consistent positioning. Since my trig skills are non-existent, I sketched it up in CAD to compute how deep to mill the flats to end up with a socket that would fit into the threaded hole.






I was in a hurry so I used a couple of short pieces of drywall screw for the points. They were available and are pretty hard so they should be durable. I chucked them in my drill and regound the tips to roughly 60 deg. and which also reduced the runout. I glued the the points in with super glue and they ended up plenty accurate.


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## BobWarfield (May 10, 2008)

You gotta luv collet blocks eh? Made short work of the hex you needed to make on your transfer screw. Another tip I got from a machinist while we're on the subject of taps. He never likes to put them in a drill chuck. Prefers ER11 collet chucks for that purpose. If I ever get around to a hand tapper, I'll be tempted to adapt one to work with an ER11. 

Also, if you've never tried a "real" tap, meaning a nice US made one purchased separately and not part of a set, you're missing a treat. I often try to add a couple to my Enco or other orders whenever I have a larger order from one of the suppliers that has everything. Since I have standardized the hardware I keep on hand, that gives me a focus for which taps to order. I really like the spiral flute jobs that through the chips up and out of the hole. Forming taps are nice for aluminum too. I got to try some brand new taps purchased this way against my "kit" taps and was amazed at how much less force was required by the new taps. My only regret is I don't have more of them, especially for really small holes where breakage is more likely.

That grinding setup is going to be really nice. I'm watching to see how it all turns out so I can make one for myself. When I first started out, I had little in the way of "abrasive" capability. As I've gotten an HF Tool grinder and built my disc sander, it has really made a lot of tasks easy and I love the look of ground steel for a finish. I'm thinking you'll be able to use that rig as a little surface grinder and it'll be nice.

Cheers,

BW


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## te_gui (May 10, 2008)

I'll second the post about quality taps, worth every penny. I try and avoid 4 flute taps like the one in the picture as well, especially in the smaller sizes. I can't help but think the extra material they have to remove to make the 4 flute must weaken the tap especially when you are power tapping. I also think power taping is easier overall on the tap, since you are guaranteed proper alignment. Trick I was shown to sharpen taps was a small piece of round stock, charged with clover compound applied in the flutes along the hook of the cutting edge.


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## DICKEYBIRD (May 11, 2008)

Yup, most all of the 5/16" and smaller taps in the set have been replaced with either Champion or Greenfield "real" ones due to chipping & wear. I've been lucky through the years I guess; I've broken very few taps. Now where's that piece of wood to knock on....


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## chiliviking (May 11, 2008)

te-qui....I'd like to hear a full description of your sharpening method. Don't want to hijack the post so perhaps you could share your method on a new post.


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