[How-To] Tap styles and their uses?

[Eddyde]

I have successfully used a ⅜-16 thread forming tap on ¼" thick 6061 Aluminum. I used lots of lubricant/coolant, the slowest speed on my mill (60 RPM) and a lot of feed pressure. They supposedly make stronger threads, used a lot in aviation.

 

[Brento]

https://www.newmantools.com/keysert/Keysert_BrochureNT.pdf

That could be a possibility but i would need to see if the tap size the use is like a regular 3/8 tap however. Bc as i said the thread pitch is definitely 16 and the shank does say 3/8-16. Ill try and get a picture tonight of it.

 

[BGHansen]

Here's a link to a post I had about over-sized 10-24 Morse taps. Brino pointed out in the very next post that my taps were designated as "STI" taps. Their application is to thread an oversized hole for a same thread per inch thread insert (Heli-coil). Not the same as your DTC nomenclature but maybe a clue? My 10-24 STI taps measured 0.2465" to a "book" of 0.19". Curious what the OD is on your 3/8" tap in question.

Bruce

POTD- PROJECT OF THE DAY: What Did You Make In Your Shop Today?

Adjustable stop for my press brake Question... What are the proper terms for the upper movable part and the lower, fixed "V" part??

www.hobby-machinist.com

 

[Brento]

I figured also that it is for an insert as well but just not sure

 

[Brento]

Here is the shank of the tap. The shank is measuring at .380. I cant measure the threads bc it is a 3 flute and i do not have a 3 point mic. It appears that the cutting threads are at the same diameter as the shank but it just feels really hefty like it isnt right? I dont know maybe i am going crazy.

 

[projectnut]

Here is the shank of the tap. The shank is measuring at .380. I cant measure the threads bc it is a 3 flute and i do not have a 3 point mic. It appears that the cutting threads are at the same diameter as the shank but it just feels really hefty like it isnt right? I dont know maybe i am going crazy.

A quick internet search reveals there's a cutting tool company in the UK named Direct Tool Company that manufactures cutting tools including taps & dies for the automotive and machining industries. The tap may be mismarked, but from the information on the shank it appears to be a standard 3/8-16 tap. The NC stands for National Coarse. The HS means it's made from High-Speed Steel, and the GH3 means it's Ground to an H3 tolerance which is .0015" over the nominal size of 3/8". H3 is the most common tolerance for fractional taps between 1/4" and 1".

As for tapping speeds most manufacturers recommend 1.5 times the speed used for the same size thread cutting dies. That's one reason why they're more popular in commercial and industrial shops where the machines have considerably more horsepower than the average hobby shop.