Visit our Popular Forums

St. Elsewhere · 22-08-2014, 15:42

I have accumulated a collection of 3/8" and 1/2" brass pencil zinc plugs that have zinc stuck in the threaded hole. I have found about 30% of the zincs that I remove break off when trying to unscrew the used pencil zinc from them to reuse the brass plug.

Have any of you found an effective way of getting the remaining zinc out of them without damaging the brass plugs. Is there is some kind of chemical solution that eats zinc and would leave the brass alone?

Jd1 · 22-08-2014, 15:46

Carefully drill out the center of the zinc and then the thread part is easy to remove.

**StuM** · 22-08-2014, 16:44

Quote:

Originally Posted by St. Elsewhere

Is there is some kind of chemical solution that eats zinc and would leave the brass alone?

Salt water seems to do a pretty good job of it

Blue Stocking · 22-08-2014, 17:02

Most engine zincs are threaded 1/4-20 or 5/16-18. I keep both bottom taps in my toolbox.

**Jim Cate** · 22-08-2014, 17:19

Dilute HCl will attack the zinc faster than the brass. If you mechanically remove as much of the remaining mass of zinc as is convenient (drilling, etc) and then drip some HCl into the threaded hole, a great fizzing will commence and the scraps of Zn will soon be gone. Rinse and neutralize with bicarbonate of soda, and you will be ready to install the new anode. I found that using some metallic based anti-seize on the threads made removal without breaking easier, BTW.

Jim

St. Elsewhere · 04-09-2014, 20:42

Quote:

Originally Posted by Blue Stocking

Most engine zincs are threaded 1/4-20 or 5/16-18. I keep both bottom taps in my toolbox.

This tip plus JD1's suggestion to carefully drill out the old zinc, has been some of the best advice that I have received here. I needed two bottom taps a bit larger than suggested. If bottom taps were not suggested, I might have gone for ordinary taps that would not have reached the "bottom" of the internal threads in the plugs. I was able to salvage all of the brass NPT zinc plugs that I have accumulated without a great deal of effort.

Thanks CF! What a great resource!

HopCar · 04-09-2014, 21:34

While I'm sure the method you used worked fine, it wasn't nearly as much fun as what Jim suggested. You could have played with acid and made hydrogen gas!
When I was a kid I'd pick up old zincs from a boat yard, put them in a bucket, and pour Muriatic Acid over them. I'd cover a bucket with a plastic trash bag and inflate the bag with the hydrogen given off by the reaction. Then I'd tie a sparkler to the bag, light the sparkler with a propane torch and let the rig float up into the sky.

Anybody see a problem with any of that? I didn't either.

**Jim Cate** · 04-09-2014, 21:57

Quote:

Originally Posted by HopCar

While I'm sure the method you used worked fine, it wasn't nearly as much fun as what Jim suggested. You could have played with acid and made hydrogen gas!
When I was a kid I'd pick up old zincs from a boat yard, put them in a bucket, and pour Muriatic Acid over them. I'd cover a bucket with a plastic trash bag and inflate the bag with the hydrogen given off by the reaction. Then I'd tie a sparkler to the bag, light the sparkler with a propane torch and let the rig float up into the sky.

Anybody see a problem with any of that? I didn't either.

My kinda guy! I wish that I had thought of that when I was a kid. I had to make do with acetylene made from carbide for miner's lamps.

Cheers,

Jim

HopCar · 04-09-2014, 22:28

Carbide was fun too! You get an empty paint can, punch a small hole in the bottom with a nail, prop the can up at an angle, pour a little water in, dump in some carbide, let it fizz for a few seconds while you put the lid on the can, hold a lit match to the hole and enjoy the explosion. Sadly I didn't have a steady supply of carbide. I did make a pretty good bomb one time with a CO2 cartridge and match heads. It was supposed to be a rocket engine but it was a much better bomb.

Blue Stocking · 05-09-2014, 04:21

Quote:

Originally Posted by HopCar

Carbide was fun too! You get an empty paint can, punch a small hole in the bottom with a nail, prop the can up at an angle, pour a little water in, dump in some carbide, let it fizz for a few seconds while you put the lid on the can, hold a lit match to the hole and enjoy the explosion. Sadly I didn't have a steady supply of carbide. I did make a pretty good bomb one time with a CO2 cartridge and match heads. It was supposed to be a rocket engine but it was a much better bomb.

Where do you and Jim play ? I'll bring the Saltpetre, charcoal, and Sulphur.

**HappyMdRSailor** · 05-09-2014, 05:08

Oh man...

Acetylene bombs were a hoot as a youngin'.... Amazing we still have all of our digits let alone hearing...

**a64pilot** · 05-09-2014, 05:15

I did most of what you guys describe, except for the CO2 match head thing, I built model rockets as a kid and there was this pledge you took that said you wouldn't shoot them horizontal, or make your own engine etc, so believe it or not I didn't.
You can bite the end of a 12Ga shotgun shell and dump the shot out, fill it with whatever, baby powder is nice, then tape a steel ball bearing over the percussion cap, makes a nice hand grenade when you toss it into the air and it lands on pavement.
Take pure iodine crystals, filter pure ammonia over them with filter paper and a funnel, put one crystal when it is still wet into a gelatin capsule filled with corn starch and you have home made snap caps, no idea of what the chemical becomes but it is pressure sensitive and explodes. Just don't play touch football with a Sucrets box full of them in your pocket, that actually caused a bruise.

Funny thing is we all survived, even without knee pads and bicycle helmets

HopCar · 05-09-2014, 15:46

"... there was this pledge you took that said you wouldn't shoot them horizontal, or make your own engine etc, so believe it or not I didn't."
What a goody two shoes. You never made an Estes Bazooka? Luckily I missed the kid on the bike.

"...no idea of what the chemical becomes but it is pressure sensitive and explodes."
That would be ammonium iodide. I was never successful in making it. I tried.
I think it was used in early percussion caps.

Then there was the Great Gun Cotton Debacle. I snuck into the high school chem lab and tried to mix sulfuric and nitric acid to make gun cotton. I ran when the acid started sputtering and popping. Now were you supposed to add the nitric to the sulfuric or was it the other way?