Broken Tap Woes, Well kinda....

Ulma Doctor

Ulma Doctor

Infinitely Curious
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on this episode of how the 1/4-20 tap breaks,

today at work....
due to the original manufacturer design was for delrin, it easily breaks and renders the meat cutting saw useless.
i'm now reproducing a part for a meat saw out of 7075 aluminum. :grin:

i figured if they break that 7075, we got bigger problems.

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here is the 7075 in billet form, it is old and dirty, but there is a guide support hidden inside somewhere!

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i had an example of a working model that i was able to reverse engineer and start chopping away at the billet... :grin:

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here is my copy

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the guide support emerges!

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i felt really good, until i went to tap the last hole.
i have done 1/4-20 tapping in aluminum more times than i wanna remember,
but the problem this time was that i misplaced a drill bit when i filled the index :bang head:

when i drilled the last hole, i only drilled to #13 (.185") rather than #7 (.201"),
that created a problem-
i broke the tap at about 3/8" engagement :clapping::clown:

do i scrap the part because of a broken tap at full depth????

Heck no!!!

i'm gonna save it, like an idiot!!!! :bang head:


i took a couple 1/8" carbide ball endmills and turned the Bridgeport as fast as she could go.
luckily i was able to drill through the tap!!!! :cool 2:

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then -
i, tried an old timer's trick...

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i bought a small crock pot at the local walmart.
i filled the small crock pot with 32oz of Hydrogen Dioxide, and added the Alum.
when the mixture neared boiling point , i added the victim of my idiocy.

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the alum goes to work quickly, especially in high concentration.
it is reminiscent of electrolytic rust removal, in that you actually see the reaction happening rapidly.

i'll see in the morning if the trick worked!
wish me luck!

stay tuned for part 2 :grin:
 
Well , well ,well ………………..now you know how my life goes every night ! :grin: I get to send carbide ball mills down thru broken bolts and taps every night , and when I DO break the mills , the EDM gets the dies . Heck , I figure I'll just break them all but do it in a hurry to save me time and the company money ! :big grin: 3 sets last night , 2 tonight .
 
Now wadja go block off the McCormick alum container and leave the Crock Pot logo for us all to see?:grin:
 
Question what does the peroxide do? Can you explain your process? Good luck with ur part.
 
Did you perchance mean hydrogen peroxide? I have heard of hydrogen peroxide and dihydrogen monoxide, otherwise known as water. There is no known chemical that could legitimately be named hydrogen dioxide (HO2).
 
Ulma Doctor said:
Dang it, I tried to make a joke and got the punchline wrong....:-(
Dihydrogen Monoxide is what my punchline should have read, lol
Click to expand...

OK. I had been under the assumption that alum/water was the recipe so I was concerned that you might have been using hydrogen peroxide instead. You could have called it hydrogen hydroxide (HOH) as well.

That reminds me of a story along similar lines. In my second semester freshman chemistry class, we got a new professor who had previously taught at the Air Force Academy in Colorado. It seems they they had a very high evaporation rate with the ethyl alcohol in the labs. The staff changed the name to ethanol which slowed the evaporation down for a time but it quickly resumed. Not to be deterred, they changed the name to methyl carbinol. The evaporation rate went to zero.
 
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