Tapping questions

On Wed, 21 Mar 2007 16:26:24 GMT, with neither quill nor qualm, Gunner


I haven't yet needed to use it, but it was missing some tap sizes if you have extras. If so, I'll figure out what wasn't there.
-- Love the moment, and energy of that moment will spread beyond all boundaries. -- Corita Kent
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$50 Yikes!
Now I know Gunner needs to pay his bills, but that hand tapper I built cost me about 5 bucks in parts... :-)
I bet if I'd have scrounged the pipe it'd been free...
--.- Dave

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My drill press is tall, it is not convenient. I will buy handles for the chuck.

Sounds nice!
i
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Great list of products, Unca George! I can add but little to it. Brownells' sells a nice little tapping block similar to the OMW except the shank holders fit individually into the block. www.brownells.com Taprite Kit (tap guide), item # 357-001-000 $27.15
Bob Swinney
wrote:

http://www.littlemachineshop.com/products/product_view.php?ProductID%71&category=
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On Mar 20, 11:50 pm, F. George McDuffee

George has some really good advice on the depth of thread. I am not sure where to find the information, but as the thickness of the material increases you can decrease the depth of thread and still break the fastner before stripping the treads.
Also on work hardening material as stainless, you really don't want to back the tap up. Use a spiral tap or a gun tap.
As far as using a drill press............ I drilled a hole in the back of a tap wrench and chuck a bit of rod that is the same diameter as the hole in the drill press. The rod goes in the hole in the tap wrench and keeps every thing aligned. Using the tap wrench to turn the tap is easier ( in my opinion ) than turning the drill press by hand.
If I have to drill and tap without using the drill press, I use the drill press to drill a hole thru some scrap 2 by 4. Then use that to guide the drill and the tap. You can just use the tap drill in the 2 by 4.
Dan
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I gotta say it again: VFD! A 3-phase motor & VFD are perfect for drill presses. Being able to dial in the speed in an instant is obvious, but none of the gizmo's mentioned are as good as a VFD for tapping. Put the VFD on 5 Hz, chuck up a tap, and power it in! It's as simple as changing the drill bit to a tap and turning down the speed! Spiral point taps are best, but reversing is something a VFD does also, so regular taps are almost as easy. I have a forward-reverse foot switch that is nice, but not necessary.
V-F-D, V-F-D, V-F-D ....
Bob
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Steve B wrote:

Speaking of breaking taps, the other day I broke a 3/8" tap! This was a 3/8-16 (NC), HSS, H3 fit, almost new, Cleveland brand, spiral point, in mild steel, 5/16 hole. The work was in a vise, so no unusual motion was required, that might result in side force. I finished the job with an Ace brand backup tap without any problems. Do you think that this might have been a defective tap?
I spent the extra bux for a brand name & I shoulda saved my money.
Bob
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On Tue, 20 Mar 2007 09:43:51 -0700, "Steve B"

HSS taps don't break as easily as carbon steel taps. Good taps (NOT found at Ace) cut better and more easily than not-so-good taps. The biggest key to avoid breakage is get the tap started centered and straight, and apply only torque -- never bending moment. Always lightly c'sink a hole before tapping. I haven't broken a tap from 00-80 up thru 3/4 in recent memory. The most fragile of the lot are 6-32, a terrible thread! Others have mentioned lube: always!
Enco makes a cheap device that is enormously helpful: look at #325-5179. $12.06, now on sale for less. It's a spring-loaded guide with a 1/2" shank. Many tap wrenches and some larger taps have a centered dimple in the back. Stick the 1/2" shank into a collet in the mill (need not be tight), or chuck it in a DP or tailstock chuck in lathe. In the case of mill or DP, center the spindle over the hole -- which it already is if you just drilled the hole. I have a chuck on a 1/2" shank so it's easy to drop the chuck used for drilling and insert this device, often without changing any heights. Set the tap in the hole, lower spindle until the point on this dingus engages the dimple in the tap wrench, then lower a bit more to compress the spring. Now you can tap the hole, turning the tap to and fro at will to clear chips. The spring-loaded guide will keep the tap straight, resist bending or side forces, and will "follow" the tap so you need only adjust height occasionally if at all. Result: far, far fewer broken taps. Another advantage of this is that you don't lose the "feel" of the tap because you're operating the (low mass) tap wrench manually.
This is obviously not a "production" setup, but it works great for a few holes.
BTW, I have had this thing longer than I can remember and only discovered tonight that it is reversable! Oy din't knew that! The other end is a recessed hole to engage the pointy shank on some smaller taps, don't know how you turn 'em then. Maybe a small wrench, or perhaps a shop-made shank-grabber of some sort.
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wrote:

using oil also helps.

Don, this is very nice. Thanks for a good idea. I do not have a spring loaded center, but I found a solid center that I can hold in the chuck. Seems to work quite well, though getting it into the right position is not as easy as with the tap chucked in the chuck.
i
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On Thu, 22 Mar 2007 23:36:10 -0500, Ignoramus15474

Some sort of cutting fluid anyway. I prefer the proprietary cutting/tapping juices like Tap-A-Matic, etc. Kerosene works quite well in aluminum. Ernie has reported that limonene works beautifully. I've not tried it simply because I've not yet found any. Oil works well on larger coarser threading, as when threading pipe.
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Don sez:
". . .Oil works well on larger coarser threading, as when threading pipe."
Yep ! Must be why "pipe threading oil" is the balck sulphurized type.
Bob Swinney
wrote:

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SOMEone... (Iggy?) sed:

If the concentration need not be high, I think I recall that "Goof-off" paint error remover is a mix of mineral spirits and A-Limonene.
I'll try some. I'm all the time tapping 6061 in 10-24 or smaller. "Tap-Magic" doesn't really do the trick. I haven't broken a tap in a while, but I'm always feeling like I'm on the verge, taking 1/8-turn cuts and backing.
LLoyd
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Lloyd sez:
". . .I haven't broken a tap in a while,

Careful here. IMO (though not backed up with a great deal of tappping experience) it would appear that the notion of "small turn and backup" can be overdone. Intuition tells me that very small turns might leave fractured metal ahead of the tap's cutting surface. It seems these unbroken chips would be prone to jam between the tap and hole when backing up. ymmv.
Bob (taps like he lives, hard) Swinney

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Yeah, I agree. I only take such tiny cuts when I have the feeling the cutter is "gumming up" in the work. Usually, I'm working about 1/2-3/4 turn per cut, but some slabs of 6061 have a whole different "feel" than others. I think it must be the variations in temper between lots. But it scares me, working on a piece that's got 10 hours of machining in it, and knowing - just KNOWING - that if I break off a tap in it, that will be the very one I can't get back out. And there aren't any EDM shops within 60 miles of me.
LLoyd
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says...

I almost always use spiral point gun taps, which don't require backing up. One exception is when power tapping M8 holes in the ends of extruded aluminum Item framing, which also exhibits the sort of variability you describe. While a gun tap would sometimes seize in a particularly gummy spot, spiral flute taps have taken all the worry out of the operation.
Ned Simmons
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Thanks, Ned. I'm ordering a couple, ASAP.
LLoyd
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On Fri, 23 Mar 2007 11:13:47 -0400, Lloyd E. Sponenburgh wrote:

One cure for this is alter your order of operations. Do the riskier stuff first (if possible), then if you ruin the part, you aren't as invested in it. It's also possible to remove a broken tap from aluminum chemically. I don't recall the liquid you'd use, but I'm sure someone here will know. This has been discussed here in the past. I know vinegar will remove steel, but I don't know if it would bother the aluminum.
Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA
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Boiling in water containing alum.
Wes
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    [ ... ]

    Absolutely the worst! It has too deep a thread for its diameter, thanks to someone deciding to keep 32 TPI through three consecutive common sizes. (Perhaps too lazy to change the gearing in their lathe. :-)

    Also -- yes.

    [ ... ]

    I've got one of these (came in an eBay lot of tools in an old machinst's toolbox). But I haven't used it yet.

    Yep -- the reversible feature is documented in the "manual" which was still with this one -- suggesting that the original machinist had not used it much either. :-)
    I did recently drill and tap for 42 1/4-20 holes in some 1/4" thick mild steel plate. I used the drill press, and for the tapping a TapMatic tapping head. I also used some "TapMagic" original formula (thanks Scott) as the tapping lube.
    If anyone cares -- it was to make a new "apron" for a DiAcro 24" bench shear. The apron and the back stops were both missing. I adapted the stops from a much smaller (8", IIRC) shear, and had to make the apron from scratch. I had to guess at a reasonable grid for the threaded holes -- it was obvious that the pattern from the much smaller shear would not work.
    FWIW -- I can also say that the Acme threaded rod from MSC machines nicely. I had to machine a 7/8" long 1/2-13 thread on one end to fit the holes in the casting -- much larger than those in the tiny shear, and I had to drill and tap the other end, to install stops to keep the backstop adjusters from sliding off the end of the rods.
    The finish on the Acme rod from MSC is black, FWIW.
    Enjoy,         DoN.
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On Thu, 22 Mar 2007 22:33:29 -0500, Don Foreman

I busted a brand new 1/2-13 Sossner tap last weekend while tapping a 1" piece of 6061 in my Lassy Tapper.
Sossner is one of my preferred brands so I was extremely surprised. Inspection under a micrscope showed it had been cracked prior to me getting it and I simply finished it off.
Gunner
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