# Carbide Taps



## Eyerelief (Sep 15, 2021)

I've never used a carbide tap prior to this past weekend.  I purchased a couple of press plates online with the idea of adding a ring on the bottom to captivate them on the press while allowing them to rotate if needed.  I soon discovered that the 1" thick plates were also hardened.  To what level I do not know, but a new cobalt drill bit would not make as much as a filing.  No problem, I have an 1/8" carbide drill bit.  I drilled a hole .700 deep, my idea called for a blind hole.  I then opened the hole with carbide end mills, 1/4", then 5/16" (.3125) for a 3/8" cap screw.  Then I discovered my tap wouldn't scratch it either.  I wasn't having fun anymore. OK!  Lets give the guy with anger issues a hardened plate, a blind hole, and a brittle tap and set him alone in the corner and watch what happens!  My wife thinks this is hi entertainment when self quarantining.
I chose a WIDIA TiN coated carbide tap thinking it would look very nice broken off in the hole.  $30 later, I had my eminent failure in hand.  First thing I had overlooked was the fact that the tap had no flats to use with a tap wrench because your not supposed to use carbide taps for hand tapping apparently.
Wouldn't let that slow me down so I ground some flats on it using the universal grinder.


By now I've determined that this project was riding a bullet train, destination disaster.  After consuming a little thinking juice (I usually have pretty good success with Miller Lite) I put a tap guide in the collet on the mill and decided to get started.


Resistance was high and cutting fluid seemed to provide little help. With 1/8 turns and then breaking the chip, I finally made it to the bottom.  The bright threads happened as I believe the hole was flooded with sweat and cutting fluid.



The resistance was present all the way down, so much that I had to keep checking to see if I had hit bottom of the blind hole.   I would be really nervous using a carbide tap 1/4" or smaller.  It did work though with a little patience and a lot of thinking juice.  The ring on the bottom of the press plate allows for free rotation but most importantly can be removed if needed.  I did both plates and surprisingly still have the tap.


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## WobblyHand (Sep 15, 2021)

Well that was entertaining!  Glad you made it through to the end without disaster.


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## brino (Sep 15, 2021)

Success! 
Congratulations.

I always approach such tasks very pessimistically also.
Sometimes I get pleasantly surprised too.

In this case you had already thought about all the ways it could go wrong, so I suspect you were extra careful.

-brino


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## Ulma Doctor (Sep 15, 2021)

Sounds like the story of my life.
I’m very happy to see that I’m not the only one swimming upstream even when going downstream is so much easier.
Your results are well earned and you learned things that aren’t in any textbook.
Some lessons teach us what not to do

Congrats on a job well done


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## Eyerelief (Sep 15, 2021)

Yes brino.  I come up with these ideas and the glass is half full. Once a couple of facets are not as expected, in this case, hardened plate and a tap that isn't designed for hand tapping, suddenly the glass is half empty.  One of my biggest weakness is being in a hurry.  Not because Im in a hurry, but because I cant wait to see how it turns out.


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## Eyerelief (Sep 15, 2021)

Thanks Ulma Doc.  I guess that is why we do this.  Half of the things I do happen because I didnt know I wasnt supposed to do them.


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## extropic (Sep 15, 2021)

Congratulations on achieving what you wanted.

Was the blind hole significant beyond cosmetic/your desire? In other words, why not a through hole?

Secondly, what are the details of the tap type? What thread? Looks like 4 straight flutes. What point type? Taper or Plug? Spiral point or? A picture would resolve the questions.


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## Aukai (Sep 15, 2021)

Things like this is how they developed the TV show "MacGyver", and the saying Get-R-done.


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## macardoso (Sep 15, 2021)

I can't remember if they were carbide, but a shop I interned in had to special order some ~M10 taps for parts that came back from HT slightly warped where the threads were not usable. The taps were AlTiN coated and had like 12 flutes. Scary sharp. I think they were like $300 each. Anyways, they did work great for bringing the tapped holes back into tolerance in some HRc60 steels.


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## pontiac428 (Sep 15, 2021)

When you decide to surface those press plates, come back here and let us know how it goes.  I've got a few that I'd like to face or fly cut square, but I don't have much carbide to spare.


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## Eyerelief (Sep 15, 2021)

Extropic, good questions.  You are correct, I could have done a through hole with no significant consequences.  I did want to retain a smooth plain on the top of the press plate so that if I was forming metal it would not flow into any indentations such as the through hole.  For the most part, that excuse is not worth its weight in dog food but I figured that since I only had 2 holes to do, the time expended to remove the tap and clean out the hole was not significant.  The tap was a 3/8-16, 4 flute bottom tap.  Why?  Other than needing to finish with a bottom tap, my decision was mostly driven by price.  This tap was $30 delivered, I saw many others that were close to $200.  Also, I didn't think I was going to get very far with a 3/8" taper tap or gun tap since my depth was .700 (even if I ground off part of the tip).    I expected a massive change in cutting performance like switching from HSS to carbide when drilling the hole.  The carbide produced a beautiful chip with both the drill and the end mills when drilling.  Thought the tap was going to do the same.  It did not, the swarf it left behind was more like dust instead of "C's" and "6's".  However, the threads were very smooth and polished.   I wasn't hobbled by starting with a bottoming tap, I had the luxury of not moving the part after drilling the hole so my tap guide was directly over center allowing me to apply force straight down into the hole until the cutting threads could pick up the feed.


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## hman (Sep 15, 2021)

OOF!  Starting  hole with  bottom tap is not a happy way to go ... but I guess I can understand the $$$ motivation for your choice of which one to purchase.  Glad you got it done without mishap!


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## extropic (Sep 15, 2021)

@Eyerelief 

Thanks for the details.

I've never started with a bottoming tap. I thought that was a no no.
It seems to have worked for you in less than ideal circumstances.
I guess it's an option, in a pinch.


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## Eyerelief (Sep 15, 2021)

I hear you Ex.  Seems like half the things I do happen because it was never made clear enough for me not to do it.  

"Hold my beer, I'm gonna try sumpthin"


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## B2 (Sep 15, 2021)

???  I thought you were suppose to "tap" a keg ... or was it ... with the juice in one hand use the other to tap the bar with a single finger.   

Seriously, I have been wondering who buys carbide taps.


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