Broken Tap Woes, Well kinda....

Ulma Doctor

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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:
 

mmcmdl

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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 .
 

cathead

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Now wadja go block off the McCormick alum container and leave the Crock Pot logo for us all to see?:grin:
 

Cadillac

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Question what does the peroxide do? Can you explain your process? Good luck with ur part.
 

RJSakowski

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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).
 

RJSakowski

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Dang it, I tried to make a joke and got the punchline wrong....:-(
Dihydrogen Monoxide is what my punchline should have read, lol
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.
 

Ulma Doctor

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well, everything worked out!!!
the alum/water mixture did the job overnight!
i was able to re-tap the hole without going oversize!

below:
here is the finished part
as always thanks for reading!

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ThinWoodsman

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Had to look up what you were doing with the alum.

In the words of the wookie:
"Alum in the form of potassium aluminium sulphate or ammonium aluminium sulfate in a concentrated bath of hot water is regularly used by jewelers and machinists to dissolve hardened steel drill bits that have broken off in items made of aluminum, copper, brass, gold (any karat) and silver (both sterling and fine). This is because alum does not react chemically to any significant degree with any of these metals, but will corrode steel. When heat is applied to an alum mixture holding a piece of work that has a drill bit stuck in it, if the lost bit is small enough, it can sometimes be dissolved / removed within hours".

That's a relief. I thought, "no way is he rebuilding the aluminum wall of the hole by sticking it in some boiling alum" :confused 3:
 

C-Bag

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Good job Doc! I've never heard of this process before so the old dog learns a new trick.

Couple of things on the original piece......why Delrin? Because of wash down on the meat saw? And if so, why was the sample piece so dirty? Or do I want to know......ewwww.
 

Ulma Doctor

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Good job Doc! I've never heard of this process before so the old dog learns a new trick.

Couple of things on the original piece......why Delrin? Because of wash down on the meat saw? And if so, why was the sample piece so dirty? Or do I want to know......ewwww.
Hi C-Bag,
i'm happy i was able to share a trick!
i believe the piece was made of delrin for ease of manufacturing, and low cost- not for longevity.
the sample pieces were bouncing around in the back of my truck for a couple months.
in operation, the guide support is kept clean by scrupulous operators :grin:
 

C-Bag

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Had to laugh when I saw "on this episode of how the 1/4-20 tap breaks, "

I could totally hear Don Pardo saying that. Then, "will the good doctor save the part? Is this a recipe for good or disaster......tune in tomorrow".

My adventure with 1/4-20 taps was more about getting schwangle in the hole doing it by hand than the wrong size hole. After going through the cluster of getting it out I decided that looking ahead at the many 1/4-20 I was going to tap it was a good investment to buy a manual tapping machine. Best $130 I ever spent and best of all no more broken taps(knocks on wooden head).
 

Ulma Doctor

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Question what does the peroxide do? Can you explain your process? Good luck with ur part.
i'm sorry Cadillac, i was trying to make a witty joke, but failed miserably! :black eye:

here is the method i was taught years ago...
use a nonreactive vessel, like Pyrex or Stoneware (Alum will eat your steel pots and pans)
( i have not tried aluminum cookware for this process, but i imagine it would render the cookware useless for cooking food after)
the alum is added to hot/boiling point water until the alum precipitates from the solution.
(in my situation, i used a little over 100 grams of Alum for 32 Oz of water)
since you have a saturated solution, it will have the greatest effect on dissolving iron/steel.

i left my project submerged overnight and it was sufficient to dissolve the tap in about 12 hours

since aluminum is a major constituent in Alum, the aluminum is not harmed during the reaction
the alum/water acts as a corrosive agent, eating away at the steel.
there is a thin coating left on the part after treatment, but it polishes off easily with a stainless brush
 
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Ulma Doctor

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LOL!
i love tapmatic and the old tap magic with 1,1,1 TriChloroethyleyne , was the best.

as my eyes get older,
i'm finding that i can't tell a thousandth like i used to, so now i gotta be way more careful when i put my bits away! :rolleyes:
 

RJSakowski

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I wish that I could find some of the old trichloroethylene based Tap Magic. I had both varieties, the one for steel and the one for aluminum without the TCE. Both were excellent. The TCE based stuff would smoke if you tried to tap aluminum with it.
 

markba633csi

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Now, when alum gets to 20$ / oz you'll have to buy it on the corner from the shady guy:
"Hey want to buy some alum- cheap!?"
 

Tom1948

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I learned my lesson. Anytime I pull a drill out of my index if I am going to tap a hole I throw the mike on it. I then check and double check the chart. Some charts give a differant bit size when tapping steel or aluminum. An ounce of provention is worth a pound of cure.
 

Toolmaker51

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Rarely do small format charts publish what percentage of thread is generated by suggested drill sizes, and huge portion of tapping goes on with users not regarding the "GH" [mainly pitch diameter, then root, then crest configuration] of tap used. It also depends on intended audience. I'd bet a HF tap and die plate of carbon steel steels probably hover ~ 66%. Charts for mechanics run about mid-range, aircraft higher yet, high-stress products...well, they monitor every feature of a thread including the surface finish for positive engagement and applicable torque.
I build industrial machinery [day gig] and we never tap lower than 72%, ferrous or not and regardless print call-out for depth, we go 2.5 diameters of full thread or maximum allowable thickness of feature concerned.

When I post, consider it a gift....not that I'm so awesome, but you go along for the ride that I'm really offering to my friend C-Bag. But that's what community is about.
 

Toolmaker51

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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.
I'm no chemist, but know a handful worth admiring...
Anyway, for the crowd in general, Ulma Doctor & RJSakowski in particular; ever hear a song with lots of chemicals in the lyrics? Read and/ or listened to, might will be quite some time to forget.


 

Toolmaker51

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Where's the smiley with the head exploding.............!
Waddy ya want, The Walking Dead?
Can't think of another show needing a lecture hour to review details; says something about the viewership. Not me. There are two where I spend Sunday evenings. We are working, TV in next room, so a lot of chitchat filters through.
 

Toolmaker51

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brino, you on Spotify?
I'd gladly PM user name, holding kind of vast library all manner of great finds. Meanwhile, some posts beg for a certain bit of music, being self assigned Dispenser of Merriment and Deeper Messages.
Loss of Mr. Zevon also marks loss of one incredible wordsmith. He knew end was near, with album such as My Ride's Here.

Enjoy Every Sandwich
 

hman

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But I have heard this one:
-brino
... and then there's a much shorter "earlier" version, which he attributes to Aristotle, that I found on an obscure recording: "There's earth and air and fire and water."

Are we off-topic, or what? :)
 
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