Author Topic: 00-90 cutting tap versus forming tap  (Read 1430 times)

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peteski

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Re: 00-90 cutting tap versus forming tap
« Reply #15 on: November 09, 2021, 09:57:56 PM »
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I'm no expert but with such a small cutting area, Rods tap looks to me like a forming (not a cutting) tap.
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BuddyBorders

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Re: 00-90 cutting tap versus forming tap
« Reply #16 on: November 09, 2021, 11:46:22 PM »
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That's a spiral point tap (aka - Gun Tap) Should work just fine if used carefully. Recommended tap drill is #62 (.038" dia)

Regards,

Buddy

peteski

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Re: 00-90 cutting tap versus forming tap
« Reply #17 on: November 09, 2021, 11:51:10 PM »
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That's a spiral point tap (aka - Gun Tap) Should work just fine if used carefully. Recommended tap drill is #62 (.038" dia)

Regards,

Buddy

My mistake. On second look I see that there is a groove along the entire length of the threads.   Barely visible in the photo.
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Lemosteam

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Re: 00-90 cutting tap versus forming tap
« Reply #18 on: November 10, 2021, 06:08:55 AM »
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A forming tap would only work in very soft material. Cutting taps are all I use .

This depends on the tap drill size used.

In my example I was tapping 2-56 thread in a 3D printed steel tender chassis after using the proper tap drill (which also wore very quickly).  The steel is mush harder that mill steel, aluminum or hard brass. The prints were $30+ each and I could not get the broken tap out no matter what I tried.

The MT tap dulled too quickly and the "chips" it produced would bind in the grooves and would eventually snap.  Cutting taps were worse because of the reduced cross section (A below) at the center of a fluted tap (B below, a little better with two flutes) as compared to the MT Tap:



In the end I went with a true forming (plug) tap which is primarily a hardened threaded rod and the cross section is simply the rood diameter of the thread.  But instead of using the "proper" tap drill size I went with a larger size that still left a reasonable amount of thread, especially since the forming tap is designed to displace metal into the threads.  Let's face it; in our scale a full thread depth is not really needed as we will never need to apply full load on the thread anyway, nor will the operational load be enough to pull those threads out. 

It's still tough to tap, but I haven't broken a tap since and as far as I know no customer has complained to me of a stripped thread or loose joint in the kit.

I use these but unfortunately I do not see a 00-90:


Chris333

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Re: 00-90 cutting tap versus forming tap
« Reply #19 on: November 10, 2021, 06:14:23 AM »
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I've seen kits to remove broken tabs that fit into the 3 flutes to grab the broke part, but I suspect the smaller the size the further up the creek you are.

When I tapped all those hole in aluminum for my printer...   :scared:

Lemosteam

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Re: 00-90 cutting tap versus forming tap
« Reply #20 on: November 10, 2021, 06:16:23 AM »
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Yeah I even tried a diamond burr to grind the remainder out of there.  No dice.

rodsup9000

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Re: 00-90 cutting tap versus forming tap
« Reply #21 on: November 10, 2021, 06:34:06 AM »
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This depends on the tap drill size used.

In my example I was tapping 2-56 thread in a 3D printed steel tender chassis after using the proper tap drill (which also wore very quickly).  The steel is mush harder that mill steel, aluminum or hard brass. The prints were $30+ each and I could not get the broken tap out no matter what I tried.

The MT tap dulled too quickly and the "chips" it produced would bind in the grooves and would eventually snap.  Cutting taps were worse because of the reduced cross section (A below) at the center of a fluted tap (B below, a little better with two flutes) as compared to the MT Tap:



In the end I went with a true forming (plug) tap which is primarily a hardened threaded rod and the cross section is simply the rood diameter of the thread.  But instead of using the "proper" tap drill size I went with a larger size that still left a reasonable amount of thread, especially since the forming tap is designed to displace metal into the threads.  Let's face it; in our scale a full thread depth is not really needed as we will never need to apply full load on the thread anyway, nor will the operational load be enough to pull those threads out. 

It's still tough to tap, but I haven't broken a tap since and as far as I know no customer has complained to me of a stripped thread or loose joint in the kit.

I use these but unfortunately I do not see a 00-90:



 Is this stuff harder than A2 tool steel??? I've used American made 2-56 gun taps with TiN finish to power tap 1/4" thick A2 (in the Bridgeport) and never had a problem with breakage.
Rodney

My Feather River Canyon in N-scale
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mmagliaro

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Re: 00-90 cutting tap versus forming tap
« Reply #22 on: November 10, 2021, 12:42:42 PM »
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Lemosteam,
Some of the 00-90 taps I just bought are "bottom forming" taps, and they look as you describe:
just a piece of 00-90 threaded rod in hardened steel.  They are made by Regal in the USA and
were available on eBay very cheaply (about 8 bucks).  They are not tapered, which would make them tricky to
start in a hole to make a new thread.  You can find them by looking for:

USA 00-90 Thread Form Bottom Tap GH8 HSS NS