00-90 cutting tap versus forming tap

[mike_lawyer]

With regard to tapping holes in metal locomotive frames, is it preferable to use a cutting tap or a forming tap?  Is one easier to use than the other in metal?  I just broke a 00-90 forming tap, and was thinking that maybe a cutting tap might be better to use in metal than a regular MT forming tap.  Any pros and cons of one versus the other?

[metalworkertom]

A forming tap would only work in very soft material. Cutting taps are all I use .

[robert3985]

...and always use a quality tap cutting fluid...such as Tap Magic.

Cheerio!
Bob Gilmore

[woodone]

I do not think you were using a forming tap. A forming tap has no flutes.
Forming taps are used on soft metals. With a 00-90 you really need to be careful.
00-90 is very small and will break with very little torque, plus you need to keep the tap straight with plenty of l lube.

[nickelplate759]

is the tap that Micro-trains sells a forming tap?  It has 3 flat sides (not really flutes) and three groups of teeth.

I have used it in plastic, brass, white metal (like Micro-trains floors) and mild steel (like the sheet metal weights in the old American Limited N-scale core kits).   It does want to get stuck pretty easily in harder materials.  I always use oil with metals, even brass.

[mmagliaro]

The Micro Trains is kind of a forming tap, in my opinion, because as you note, it doesn't have flutes.  But it is also like a cutting tap in that it does make chips and the 3 flatted sides give the chips somewhere to go. 
I don't personally like it, as I find it makes very shallow threads, especially in metal. 

I don't even know where I got the taps I have.  They aren't marked.  But I orded some Regal forming taps recently off eBay.
I'll let you know how they work when they get here.  They were only about $8.  A good tap will typically cost you $25, and it hurts when something that pricey breaks.  I got lucky and scored a box of NOS Greenfield taps for 2-56 on eBay very cheap, brand new.  But not so lucky with 00-90.

And yes, whatever tap you are using, always ALWAYS use oil, and go slow.  After the first few turns to get it started, just go a half-turn, then back out, brush off the tap, screw it back in, another half-turn of cut, and so on.   It's when it seems to be going so well, that you'll get greedy and figure, "What the heck, I'll turn it a whole turn this time"... and Snap!
 

[Chris333]

I seem to remember the tap Micro Trains sells was kind of soft and easy to break.

[rodsup9000]

 When buying taps, I buy American made "gun" (spiral point) taps. They don't need to be backed out at all, if you are tapping a through hole. With blind holes, it takes some care when tapping. I've tapped hundreds of 2-56 holes in 1/4" and 3/8" aluminum with a power drill and tapping fluid. Most with never backing the tap out at all. I guess the don't make them this small, as I've been searching for some 00-90's and 00-80's gun taps for a long time.

[mmagliaro]

https://www.msdiscounttool.com/catalog/product_info.php?csv=gg&products_id=145657&gclid=Cj0KCQjwlOmLBhCHARIsAGiJg7mM-qBs4r3oyCzXDSaHRDevgxZ8gxNOkli0GFrTurj8aqSDP_pYOskaAoTtEALw_wcB

never thought to look by "gun tap".  Great idea!

[rodsup9000]

https://www.msdiscounttool.com/catalog/product_info.php?csv=gg&products_id=145657&gclid=Cj0KCQjwlOmLBhCHARIsAGiJg7mM-qBs4r3oyCzXDSaHRDevgxZ8gxNOkli0GFrTurj8aqSDP_pYOskaAoTtEALw_wcB

never thought to look by "gun tap".  Great idea!

 Thanks, Max
Just ordered 2 of them.
 More than likely Asian made as is states "MEDA - Superior Import"
Never have had much luck with any Asian made taps or dies though.

[up1950s]

And just to add a bit , When the tapered tip of the tap breaks off it is still useful as a bottoming tap for a hole that does not go all the way through the meterial .

[mmagliaro]

And just to add a bit , When the tapered tip of the tap breaks off it is still useful as a bottoming tap for a hole that does not go all the way through the meterial .

Oh yes!  I have an 0-80 I kept after the tip broke for just this purpose.  I used a Dremel fine grit disk to even up and smooth the broken tip into a nice flat end

[BuddyBorders]

The tap posted above looks like a decent tap for our purposes. I look for the words "High Speed Steel". That tells me it's a quality tool steel and not carbon steel which is pretty poor in my opinion.

Another issue that hasn't been brought up is the tap drill size. Form a thread forming tap, you need a larger tap drill hole since the tap displaces the metal as opposed to cutting it like a hand tap or spiral point (aka - gun tap). The standard tap drill is a #65 or 64 (.035-.036") A roll form tap needs a .042 hole (#58) from what I can find. That should give you about 70-75% thread when done right.

I hope this helps some.

Regards,
Buddy

[rodsup9000]

Thanks, Max
Just ordered 2 of them.
 More than likely Asian made as is states "MEDA - Superior Import"
Never have had much luck with any Asian made taps or dies though.

Got the taps yesterday and they are made in Korea. It took 4 business days to ship and USPS 3 days to deliver.
They look nice and hope the HHS is of quality.

[mmagliaro]

Thanks for letting us know, Rodney.  I suppose you'll know how good it is when you try to tap a hole through some steel or brass.
It does *look* good, though.