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Old 03-14-2019, 07:34 AM
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Improving the punty knock off

Starting with punty 101. Use a kitchen knife or preferred weapon of mass destruction and tap or poke the joint.
I noticed that while poking the joint I also hit the bottom of the piece.
Is that ok . If not how or where do you tap without hitting the piece? Doesent It fracture the piece a bit.
Franklin
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Old 03-14-2019, 09:32 AM
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If your punty is correctly attached, it does not take much to knock it off. If I can, I turn the piece over and gently press on the punty and use a piece of wood to knock it off. I feel that the shock waves are sent more to the joint if the piece is on the lip...
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Old 03-14-2019, 10:16 AM
Eben Horton Eben Horton is offline
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Knocking off the punty when your piece is too cold will make the bottoms chip out. Sometimes an extra deep reheat before you knock it off will make the difference between a disaster and a high five.
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Old 03-14-2019, 01:57 PM
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This may sound dumb but when I was starting out I had little instruction that was we we might call "correct". So for a long time, when I was knocking off a piece I used a file on the pipe and knocked it towards the piece which resulted in a lot of butt ugly divots or broken pieces. Once I started to knock it off "away" from the base, things really improved.

What you really want is a mediocre weld between two pieces of glass that are hot enough but not ripping hot or stone cold either. As in welding, the result of a mediocre weld would be that it holds until pressure is put on it and then the weld fails. If you tried to apply a lightning hot gather to a room temp piece, it wouldn't stick at all. The same applies in trying to apply a stone cold punty to a molten gather. The desired result is in between. Happy hunting. Based on what you keep saying, I think that everything is a bit too cold.
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Old 03-14-2019, 01:58 PM
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Quote:
Originally Posted by Franklin Sankar View Post
Starting with punty 101. Use a kitchen knife or preferred weapon of mass destruction and tap or poke the joint.
I noticed that while poking the joint I also hit the bottom of the piece.
Is that ok . If not how or where do you tap without hitting the piece? Doesent It fracture the piece a bit.
Franklin
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If the proportions of your actual pieces are at all the same as that drawing, you really need to make the punty smaller.
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Old 03-14-2019, 03:29 PM
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Thanks especially for sharing the story about your early days. The drawing was exaggerated to show the place I tap. But since you mentioned it I will look at my punty size. I noticed no one mentioned that they tap the joint. Can I skip the tapping?
When I hit the pipe itís agonizing for me to keep hitting it and nothing happens then I hit harder to make it happen and I know itís going to bust out a chunk in the bottom. I think about hitting the pipe over a longer time but in the haste I donít.
I am working hotter and it did help. I could still improve. Going to work hotter . Maybe a longer flash before knocking off.
Mark when you say turn the piece upside down how do you press on the punty? Against the table top?
Franklin
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Old 03-14-2019, 04:08 PM
Rick Kellner Rick Kellner is online now
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Could try setting the lip of the piece on a piece of wood, or old paddle. Then while it's partially supported, bonk the punty shaft with another paddle, or your favorite tool. Practice makes perfect!
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Old 03-14-2019, 04:10 PM
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I have a knock-off table that is board covered with whatever that high refractory woven blanket is called... Do not tap the glass on your punty. Tap the rod itself. If you want to cool the punty a bit, you can run your knife flat against the glass and then invert, press, and tap...
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Old 03-14-2019, 04:49 PM
Shawn Everette Shawn Everette is online now
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Does nobody use water anymore?

I was brought up using a tweezer full of water to quench the punty. Get as close as you can to the joint without touching the piece, little tap on the pipe should pop it right off.

I do the knife method too, but am pretty careless when it comes to touching the bottom of the piece since I will usually clean up with a torch. Letting the knife touch your piece is more of a concern the colder your piece is, if you have ice cold glass you risk cracking or checking it.

Again this all depends on the type of punty your using and how your weld is.
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Old 03-14-2019, 07:23 PM
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Longer flash should fix the cold bottom.
Sorry Mark but when you say press do you mean press the lip on the table and then tap the rod?
Franklin
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Old 03-14-2019, 08:19 PM
Eben Horton Eben Horton is offline
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Quote:
Originally Posted by Shawn Everette View Post
Does nobody use water anymore?

I was brought up using a tweezer full of water to quench the punty. Get as close as you can to the joint without touching the piece, little tap on the pipe should pop it right off.

I do the knife method too, but am pretty careless when it comes to touching the bottom of the piece since I will usually clean up with a torch. Letting the knife touch your piece is more of a concern the colder your piece is, if you have ice cold glass you risk cracking or checking it.

Again this all depends on the type of punty your using and how your weld is.
I never use water
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Old 03-14-2019, 08:52 PM
rodman gilder miller rodman gilder miller is offline
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Yes, Franklin: pushing the piece onto the punty helps to make a clean break. This is especially true when breaking of at the neck-line. Push in just as you tap the pipe or punty.

I have never figured why this helps...does anyone have an idea why?
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Old 03-14-2019, 08:56 PM
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Thanks never heard that before.
Franklin
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Old 03-15-2019, 12:31 AM
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Some good advice so far. When I hit the punty to crack off, I make sure I'm only holding the punty gently with a few fingers (not your whole hand) to be sure the shock goes to the glass--rather than be partially absorbed by your hand. For cups, I always take off dry with a bonk from a wood paddle. I always flash frequently and don't work long on the punty, so things are generally pretty warm. A good Boyd trick if you work the piece a bit long is to use MAP gas to warm the bottom and edge of the piece (not the punty) before you crack off--this makes your crack off less likely to crack the bottom of the piece.

That said, I think how you stick the punty on and how you treat it has more to do with how it comes off than the range of methods discussed to crack off (wood, tweezers, knife in the joint, etc). If you jam a hot punty on hard, chances are it won't come off nicely no matter what kind of voodoo you employ.

Most of my work (aside from cane cups) uses sculpture punties--those are as close to foolproof as you can get, but there's always coldwork.
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Old 03-14-2019, 08:55 PM
Peter Bowles Peter Bowles is offline
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I'm a never use water guy too. But I do use a 1 inch paint scraper as my tool of choice to tap into the join.
Another thing to look at is where you are holding the iron when you are trying to tap it off. There's probably some physics to do with wave harmonics or something, but try holding the iron in slightly different places close to the center and try tapping with your wooden stick at different places.....there are a couple of sweet spots where you get more of a ring than a dull thud, try finding those sweet spots and your work will come off easier and cleaner.
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