Recomendations for 00-90 Tap?

[garethashenden]

I just broke a MTL 00-90 tap and I need a new one. I can get one from MTL but I'm wondering if anyone has any experience with other sources? Is there anything better out there?

[Chris333]

http://www.ebay.com/itm/Gyros-91-10090-00-90-High-Speed-Steel-Plug-Tap-/182236919798?hash=item2a6e2ab7f6:g:5-IAAOSwU-pXqe5l

http://www.ebay.com/itm/USA-00-90-Thread-Form-Tap-BH4-HSS-NS-/252743329822?hash=item3ad8ad281e:g:4q4AAOSw-0xYi33~

I found a whole case of them a while back for like $12.

[Lemosteam]

My take on the MT taps is this.  They are much stronger handling torque than true cutting taps. The cross section of the MT tap has, and I am guessing here, 30% more material at the core cross section than a machining fluted tap.


 Recently, I had Shapeways print a sintered stainless tender frame that had printed holes that I drilled to tap drill dimensions. This stuff is very dense and difficult to machine, IMHO. I broke several fluted 2-56 taps and I was finally able to thread a hole using the MT tap. I was very surprised that I could apply the amount of torque I was, because I ended up grinding flats on the MT tap and used a 4" pair of pliers to twist it.

I have a newfound respect for those taps as a result.

[peteski]

What does the MT tap look like? Any closeup photos?  I have at least 2 different 00-90 taps and each looks different. Neither is from MTL.

[Lemosteam]

HI @peteski, imagine a hardened, tapered screw with three sides ground down to form a three sided (equilateral) tap with approx 30% thread left on the "points" of the triangle (10% at each apex). The result is less of a thread cutting edge and more of a thread forming edge. This leaves a larger inscribed circle of material at the center of the tap than what would be left with two or three ground flutes that are typical of thread cutting taps.  I'll draw a picture later.

[Greg Elmassian]

So, to the OP, better stick to the MT tap and take it more easy.

Greg

[Chris333]

I don't think I've had a MTL tap, but those Hobby-Bits ones seem soft.

[Lemosteam]

What does the MT tap look like? Any closeup photos?  I have at least 2 different 00-90 taps and each looks different. Neither is from MTL.

Like this, sorry for the crude images, grey dotted line is the minor diameter.  You can see how the machine tap leaves a sharp cutting edge down the flute and the MT tap does not.

Note the difference in the core diameter. the extra material at the center lets the MT tap absorb much more torque:

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[wcfn100]

I broke my MTL tap years ago and I like it better.   

Jason

[peteski]

Thanks John. I have one like MT (came from Ho-Bits) and one with flutes (I don't recall where I got that one). Neither should break if lubricated and used properly, but I managed to snap one years ago (I'm sure by doing something stupid). 

So the MT tap seems to be the same as my Ho-Bits one.

[Chris333]

Mine are made by Regal and they look like the MTL drawing, but only 2 flutes instead of 3.

[nkalanaga]

I get mine from the Walthers drill/screw/bolt/nut rack at the "local" hobby shop.  They seem to survive well, but I have a couple spares just in case.  As Peteski said, with a little lube, and right hole size, they should last a long time.  They hardest job I usually give mine is tapping the couler holes in MT boxcar underframes.  That metal doesn't like to tap, but I haven't broken one in years.

[mmagliaro]

Here's a nice write-up I found on "cutting taps" vs "forming taps". 
http://www.natool.com/blog/2016/07/cutting-taps-vs-forming-taps

The MT tap appears to be "sort of" a forming tap, but not quite.

[peteski]

Here's a nice write-up I found on "cutting taps" vs "forming taps". 
http://www.natool.com/blog/2016/07/cutting-taps-vs-forming-taps

The MT tap appears to be "sort of" a forming tap, but not quite.

I think that since both types of 00-90 taps we are discussing here generate chips while forming thread, they are both cutting type.