Carbide Taps

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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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!
 
@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.
 
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"
 
??? 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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