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A bottoming tap is flat on the bottom and is able to thread deeper than a regular tap because it does not have a tapered tip on the bottom. If you are needing to know this for a screw build you can buy a regular tap and grind down the tapered section at the end until it is flat. Hope this helps.
 

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You can try a broken tap remover but to be honest, I haven't had much success with them. What I do is get a screw driver, cut and grind a fork in the tip (using a Dremel Tool Cutoff Wheel) so it fits into the flutes of the broken tap (it ends up being very small). I then harden it using Kasenit, insert the fork into the flutes and back out the broken tap. I might lose the screwdrivew but I get the tap out.

I don't know if it's your picture but it looks like there is still some rivet material left in the hole or is it the countersink?
 

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Depending on how deep it is will depend on how easy or hard it is to get out. As a machinst I have had to deal with broken taps many times. If you can get the tap to turn by one of the methods above or useing a punch and a hammer is the easiest. If it is in there very deep you may have no luck and you have two options bassicly try to break the tap up with a punch. Taps are very brittle and can be shattered since it is a through hole you can smack it from the other side and force it out this option will most certainly destroy your threads and you will either need to go up a screw size, weld the hole and redrill it or use a Helicoil to repair it. The next option is to find a machine shop that has a tap burnout tool. It is a machine that will use a electrode to disintegrate the tap the same process basicly as a EDM machine.
A little advice for future tapping is don't use 4 flute taps especially when they are under a quarter inch they require more effort to turn and will break very easily. Another sugesstion don't grind the tip off a tap that is what cuts the thread once thats gone you are trying to roll form the thread. You can get away with that with bigger taps but not small ones like 10-32's. Another thing I would suggest for tapping holes is to make yourself a tapping guide block out of a piece of aluminum block or anything that has flat sides. Drill a hole in the block just a hair over the tap diameter. This will keep the tap straight and square with the hole and will lessen the chances of it breaking. Another way to make a tap straight is to use a drill press. Line up the hole in the part with the drill in the chuck and clamp it down. Put the tap in the chuck and turn it by hand until its in enough to make sure its straight then you can finish with a tap wrench.
 

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Discussion Starter · #6 ·
Thanks for all your suggestions but the tap was broke off very near the face of the trunnion pretty close to 1/2 an inch in so I cut it in half longwise through the trunnion and pounded it out with a bolt and hammer. As Toten Kopf notice the hole was countersunk but the top two still have rivet left in them so I tryed to drill them out but cant find a #3 bit worth a sh*t. So here is what I have, 1 hole fit for 1/4 x28 ,2 fit for 10-32, and 1 I could probably loctite a 10-32 in if I am lucky.
Is there anything else I can do or is my trunnion junk?
 

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JW762x39...

I did a tutorial about removing rear trunnion rivets. It's a word document but I hope to get software that allows me to convert MS Word to .pdf format. If you can't read the Word doc. you will have to wait till I convert it. Hope this helps

http://www.gunco.net/forums/showthread.php?t=2564
 

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Did you get the tap out yet?

One of my taps broke off into the front trunion. I took my handy dandy dremel tool and used a lawn mower blade sharpener bit. I was able to grind a lot of the tap out down through the middle until it finally all came out. If you dont have a dremel I suggest buying one.
 

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I suggest that anyone doing screw builds purchase a table mounted tapping tool from Enco.It is the best tool for under $100.00 (actually $84.95) that you can buy. I have yet to break a tap using one.
 

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gtbehary said:
I suggest that anyone doing screw builds purchase a table mounted tapping tool from Enco.It is the best tool for under $100.00 (actually $84.95) that you can buy. I have yet to break a tap using one.
Thats the tool you were trying to tell me about. Wish I would of taken your advise and got me one.
Just after you told me about it, I broke a tap in the front trunion hole. Man.....I was pissed. It took me about an hour and a half of dremeling, but I finally removed it. Pain in the ass it was. Im done with those screw builds....Im going with the rivits for now on.
 

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Discussion Starter · #12 ·
What kind of bits do they use to drill out the trunnions?
I tryed using a cobalt bit to drill out the holes but just killed
the bit and didn't even get anywhere with the hole.
Is this tunnion junk?
 

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Bzrkr21 said:
Depending on how deep it is will depend on how easy or hard it is to get out. As a machinst I have had to deal with broken taps many times. If you can get the tap to turn by one of the methods above or useing a punch and a hammer is the easiest. If it is in there very deep you may have no luck and you have two options bassicly try to break the tap up with a punch. Taps are very brittle and can be shattered since it is a through hole you can smack it from the other side and force it out this option will most certainly destroy your threads and you will either need to go up a screw size, weld the hole and redrill it or use a Helicoil to repair it. The next option is to find a machine shop that has a tap burnout tool. It is a machine that will use a electrode to disintegrate the tap the same process basicly as a EDM machine.
A little advice for future tapping is don't use 4 flute taps especially when they are under a quarter inch they require more effort to turn and will break very easily. Another sugesstion don't grind the tip off a tap that is what cuts the thread once thats gone you are trying to roll form the thread. You can get away with that with bigger taps but not small ones like 10-32's. Another thing I would suggest for tapping holes is to make yourself a tapping guide block out of a piece of aluminum block or anything that has flat sides. Drill a hole in the block just a hair over the tap diameter. This will keep the tap straight and square with the hole and will lessen the chances of it breaking. Another way to make a tap straight is to use a drill press. Line up the hole in the part with the drill in the chuck and clamp it down. Put the tap in the chuck and turn it by hand until its in enough to make sure its straight then you can finish with a tap wrench.
Nice post bzrkr21, good info.
 

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I bought a set of tapping guides from MSC, works on flat and round stock. No space shuttle but it was cheap.
 

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Bzrkr21 said:
Depending on how deep it is will depend on how easy or hard it is to get out. As a machinst I have had to deal with broken taps many times. If you can get the tap to turn by one of the methods above or useing a punch and a hammer is the easiest. If it is in there very deep you may have no luck and you have two options bassicly try to break the tap up with a punch. Taps are very brittle and can be shattered since it is a through hole you can smack it from the other side and force it out this option will most certainly destroy your threads and you will either need to go up a screw size, weld the hole and redrill it or use a Helicoil to repair it. The next option is to find a machine shop that has a tap burnout tool. It is a machine that will use a electrode to disintegrate the tap the same process basicly as a EDM machine.
A little advice for future tapping is don't use 4 flute taps especially when they are under a quarter inch they require more effort to turn and will break very easily. Another sugesstion don't grind the tip off a tap that is what cuts the thread once thats gone you are trying to roll form the thread. You can get away with that with bigger taps but not small ones like 10-32's. Another thing I would suggest for tapping holes is to make yourself a tapping guide block out of a piece of aluminum block or anything that has flat sides. Drill a hole in the block just a hair over the tap diameter. This will keep the tap straight and square with the hole and will lessen the chances of it breaking. Another way to make a tap straight is to use a drill press. Line up the hole in the part with the drill in the chuck and clamp it down. Put the tap in the chuck and turn it by hand until its in enough to make sure its straight then you can finish with a tap wrench.

I agree, very very good info!
 
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