The Tap Dance, or The Secret Life of Drills

The Tap Dance, or The Secret Life of Drills

Postby Mopar 151 » Tue Jan 04, 2011 6:51 pm

Image

Continuing an Ascutney campfire discussion - Walter told Steve and I that this Elcheapo (Harbor Freight) tap and die set worked pretty well for occasional use. I mentioned at that time that I'd pass along some "professional secrets" of drilling and threading - stuff that works much better than "hardware store" grade, for comparable prices. MSC direct is a great source for this stuff, but the search is very nomenclature-dependent. I'll list Catalog page #'s, as the print catalog is readily available online.

Drills - Albro Patten got me started on split-point screw machine drills years ago - the split point cuts far better in steel than the common chisel point, and the short length is much less prone to "walking".Image
chisel on the left, split point on the right
Check 'em out on pp. 42 and 43 - The Triumph Thunder Bit works great, but is only available in fractional sizes. I've used the Precision Twist Drill (PTD) brand a lot, and they're good, too.
If you use a drill with a keyless chuck, You'll LOVE Triumph Trinado's - they have 3 flats on the shank, so as not to spin in the chuck. pp265
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Re: The Tap Dance, or The Secret Life of Drills

Postby Rabbit Farmer » Wed Jan 05, 2011 1:07 pm

Good information... thanks John. I have had on my wish-list for quite some time a good (or at least good enough for me) tap and die set. I have a few that I purchased in the past when I needed them for a particular project.

Liking the three sided shanks.

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Re: The Tap Dance, or The Secret Life of Drills

Postby Mopar 151 » Fri Apr 06, 2012 10:39 am

OK, LONG past time for an update. A simple thing or 3 that saves many pains in the posterior - pilot drills, transfer punches, automatic punch.
http://www1.mscdirect.com/cgi/nnsrhm?cm_re=tpnv-_-home-_-home updated link
Image Page 50 This is a "rivet drill", sold for drilling sheetmetal to use blind (Pop) rivets. They are cheap, and are double ended for twice the use. I also use them as a starter or pilot drill while using a handheld drill. They start very easily from a punch mark, or without a mark if your hands are steady and square to the work. And they make drilling a larger hole much easier, particularly in structural steel. I like to keep an "el cheapo" drill handy, deadicated to pilot drilling.
Image page 2340 lets you "transfer" a punchmark dead center from another part, making matching up mounting holes much easier. Nice sets are $$$, but the "Cheap Jack" versions are around $10/set, and they work pretty well.
Imagepage 2338 Put the punch tip on the mark and push! A little snap, and they will leave a nice little punch mark. Also makes a good layout scribe. The larger sizes
Image
are also popular with EMT's and stereo theives, as 1 "pop" in the corner of a tempered glass window will make it shatter & fall out.
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The Tap Dance, or A journey to the root of the thread

Postby Mopar 151 » Mon Apr 09, 2012 10:56 pm

The science of threading is a lot like art, but its progress is relentless. So as with many such things, the forms and dimensions were "Unified" as "National" specifications, or to "Society of Automotive Engineers" spec. , especially in the retooling of the country before/during WW2. What was made standard was the most widely used at the time - like for TAPS and DIES. So, have I been drinkin' the Tap Magic? Nope!
Cuz' what was standardized were multi-flute, straight flute taps with 3 different "starts" - taper, plug, and bottoming. What matters in our current discussion is a "next level" thing - chip management. The straight cutting edges of the standard designs curl the chip, and pack them into the flute - thus the frequent need to turn the tap back and break the chip, so that it might fall out. This ain't no way to make money!
The big technology step- up is nearly free - what you need is in the big-boy catalog under "spiral point taps" {as Wikipaedia} tells the tale:
plug tap (also referred to as a "gun tap"), whose cutting edges are angularly displaced relative to the tap centerline. This feature causes the tap to continuously break the chip and eject it into the flutes, preventing crowding. Another version of the spiral point plug tap is the spiral flute tap, whose flutes resemble those of a twist drill. Spiral flute taps are widely used in high speed, automatic tapping operations due to their ability to work well in blind holes.
Image Page 333. Now for us gararge dogs, what this means is that your cordless drill is a power tapper. Dip the tap in the oil, line up square, run in at low speed. When the tap has either a) cut through, b) cut deep enough, or c) gently bottomed, reverse out. The chip will have "shot" ahead in the hole, thus the term "gun" tap. Don't bother with less than an M4 or 8-32, as doom and broken taps lie ahead. And if you feel the tap twisting up/springing, with any tap - that means the tap is starting to dull or bind up, and it'll break on the sudden side of NOW. If the tap breaks, you can often drive the broken pieces through/out with a punch.
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Re: The Tap Dance, or The Secret Life of Drills

Postby Rabbit Farmer » Tue Apr 10, 2012 12:33 pm

A few months ago I dug up this post looking for a tap/die set as I recall the price was really good. Looks like I should not have waited as the price went way up again.
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Re: The Tap Dance, or The Secret Life of Drills

Postby Mopar 151 » Tue Apr 10, 2012 3:50 pm

Sadly, there is no good way to make tool steel without expensive alloys - like chrome, molybdenum, nickel, and cobalt. And the whole world market in metals is pretty crazy these days, and some of the players ain't nice.
This is Harbor Freight's current delux set.Image
fer $50 clams before whatever discount you can scam up (check magazine ad's and online)

According to MSC Online, a similar US made carbon steel set is $190, (page 389, 390), and comprable in high speed steel is around $800(!) :o
Best plan for most is the cheap set to cover emergencies, carbon steel taps from the "special thread taps" pages for any oddball stuff, and hit the MSC or similar sale flyers (out monthly, available online) for high speed steel, spiral point plug taps for taps you use all the time.
Look up this month's "metalworking" flyer - there are "deals" on most of the stuff I've posted about here every month.
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Re: The Tap Dance, or The Secret Life of Drills

Postby Rabbit Farmer » Tue Apr 10, 2012 4:17 pm

Thanks John, I'll check it out.
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Re: The Tap Dance, or The Secret Life of Drills

Postby Pascal » Tue Apr 10, 2012 4:47 pm

Some good information John, thanks for posting. Those transfer punches look very useful, I'll have to check those out.

I have had really nice results from these dewalt "pilot point" drill bits. http://www.dewalt.com/tools/drilling-ac ... w1956.aspx I bought a set when I needed a 1/2in bit on a sunday and had to head to Lowes. The set with up to a 1/2in bit was only ~$20. They have lasted and cut nicely, I mostly use them drilling through steel. The pilot point is nice for accurate starts.
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Re: The Tap Dance, or The Secret Life of Drills

Postby Rabbit Farmer » Tue Apr 10, 2012 10:24 pm

"INSURE20" gives you 20% off one item at Harbor Freight
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