quote:

Originally posted by J.D.Steele:

From what I remember, the nitric acid serves to erode the steel at the tap-hole interface, allowing the tap extractor to work. Supposedly.
Regards, Joe

This comment caused me to go back 60 years and check my copy of "Gunsmithing Simplified" by Harold MacFarland, A.S. Barnes & Company Inc., New York, October, 1950.

According to that book, we both have faulty memories. There on pages 28 & 29 of Chapter 2, Shop Practice and Supply, it says

"Another method is to apply a drop of nitric acid to the broken tap.

"This seems to act faster on the hardened steel of the tap than it does on the softer gun steel. In a very short time the tap will be eaten by the acid until it will practically fall out.

"The quick method is to get mad at it and shatter the tap with a center punch, and then pick out the pieces.

"I always have some center punches around that are made from high speed lathe tools. they are harder than the tap, so one sharp blow usually breaks the tap into bits. I've seen this method go wrong, however, and the result was a Model 70 Winchester receiver bridge split full length."

Has anyone ever tried, (assuming its right handed thread, otherwise just reverse what I m saying), your tapping with a right handed thread and brake the tap. Have you tried using a tap slightly smaller then the one broken with a left handed thread to try and work it out? That way when turning it you tighten the bond between the 2 while backing to old tap out.
When I was in the army swapping out parts on any of the fire arms that came tough our shop we sometimes would put a small nick, ding, or notch on the offending item. From there we painstakingly tap it with a punch round and round until it popped out. But i dont think that would apply here.

Some simple advice, it may or may not work.
Hope this helps, if not for the problem it may down the road.

James,
I guess that I am a dumbass, I can't see any way that you are suggesting could work. How can a LH tap thread into a rh threaded hole?
Butch

quote:

Originally posted by butchlambert:
James,
I guess that I am a dumbass, I can't see any way that you are suggesting could work. How can a LH tap thread into a rh threaded hole?
Butch

With the broken tap/bit inside the hole, you would simply drill the pilot into the tap/drill and add the threads into the broken bit(bit for simplicity) now using the revurse threads you are able to screw in a lefthanded screw bolt or setscrew enabling you to back the right handed thread bit out. The left handed threads would only tighten when backing out the right so you know it wouldnt slip only tightening the threads together vs losing them as would be the result for the broken bit or tap.
Sorry about the word soup.
long story short, if you have a right handed thread that broke off drill and tap into the broken bit of the opposite direction. in doing so you will crate a workable mode to back the bit or tap out if possible.
Feel free to correct me or call me on bs so we can solve where I went wrong.

Sir,
I would say you have never drilled a tap in a #6 hole before. I suppose you are saying after doing that, you would tap the tap LH to screw it out. As I said I'm a dumbass, but that is what I am understanding from your post.
Butch

quote:

Originally posted by James Kain:
With the broken tap/bit inside the hole, you would simply drill the pilot into the tap/drill and add the threads into the broken bit(bit for simplicity) now using the revurse threads you are able to screw in a lefthanded screw bolt or setscrew enabling you to back the right handed thread bit out. The left handed threads would only tighten when backing out the right so you know it wouldnt slip only tightening the threads together vs losing them as would be the result for the broken bit or tap.
Sorry about the word soup.
long story short, if you have a right handed thread that broke off drill and tap into the broken bit of the opposite direction. in doing so you will crate a workable mode to back the bit or tap out if possible.
Feel free to correct me or call me on bs so we can solve where I went wrong.

quote:

I can see my machining classes already paying off in my everyday life, let alone my hobby's particularly reloading!
Precision Machining Technology Student - Grad year 2011

James, it is only 2009. Perhaps they will have a way to do as you suggest with a broken tap by the time you graduate from your machining technology school in 2011. In the mean time, it ain't gonna work. Good luck though.

didnt mean to step on any toes or insult anyone, and sorry if it did.
I was just trying to help.

quote:

Originally posted by James Kain:
didnt mean to step on any toes or insult anyone, and sorry if it did.
I was just trying to help.

No problem here.

You didn't step on any toes, we just think it can't be done as we see it. We also don't want you discouraged either.
Butch

Get a can of computer keyboard cleaner, put on some leather gloves, turn the can upside down, lightly trigger and flood the tap with the liquid refrigerant(-270 F). This should contract the tap enough for you to turn it out with the tap extractor or make it brittle enough to easily shatter. It's also a neat way to kill cockroaches.

Well, I called a friend W/a pretty well equiped (industrial) machine shop.

As I suspected, he does not have any endmills that small so I ordered 4 ea 3/32" end mills to make the $25 minimum. He will do the removal for $25. (1/2 hour minimum charge)

Since I will have the endmills in hand, I'm still contemplating trying a go @ this W/my drill press. I ordered a dual 8" travel vise that will bolt down securely to my drill press table. I have always wanted one of those anyway.

I see 2 possible outcomes.

1: I am sucessful @ the endevour & I will have the knowledge & tools to do this again if it happens.

2: I really bugger it up & have to have the hole tigged up & re-drill/tap the hole.

I know I can locate in within a few thousandths. I can now secure the work to the table. My biggest concern is getting the top of the broken tap square & flat @ the outset W/O breaking an endmill.

Meamwhile, I'm working on getting the VZ500 project nearer copletion.

The 98K action is being left to simmer. awaiting tooling.

quote:

Originally posted by wildcat junkie:
My biggest concern is getting the top of the broken tap square & flat @ the outset W/O breaking an endmill.

Lay a punch against the side of the portion of the tap that is protruding out of the top of the hole and whack it with a hammer. This should break the tap off fairly flush with the top of the receiver. The carbide endmill will make it flat and square provided you feed the cutter slowly. High speed, slow feed.

I stayed out of this mess Because it would take to much time to explain. But it seam that everyone else did it for me.
For all those that suggested a machine shop, milling machine, and center cutting carbide end-mills Congratulation you win first prize.
For all of you that suggested tap extractors and EZ outs YOU LOSE.
EZ out's are for bolts not taps. and tap extractors never work unless the tap is still loose and there are no chips in the flutes.
And attempting to mill it out in a drill press is asking for four new BROKEN carbide end mills.
See it's not the vise or the fixture that we are concerned with being rigid, it's the spindle.
A drill press is designed to operate up and down. with no side load. Well trying to cut out a busted tap is going to side load the spindle and then you'll find out just how unrigid your drill press is.
The spindle of your drill press has side play in it and that's what will cause chatter and cause your endmills to break.
Now the procedure for milling out a tap is as follows.
Get a four flute end mill that is smaller then the drill size used to drill the tap hole.
Cutting oil is not needed with carbide.
Center endmill over what's left of tap.
Run the endmill on the fast side of the cutting speeds For something like a 3/32" endmill 2500 to 3000 RPM.
If you have a good feel for the machine and you have been machining part for a long time go a head and use the quill. If not crank up the knee.
The knee moves slower and won't jump when it contacts the tap saving your tooling and cutting the tap out.
Once through the tap blow out the hole and chase the threads with a NEW tap.
check threads with a screw if loose bump it up to 8-40.

Please heed the advice of Gunsmiths and Machinist's on this board. We're not trying to tell you how to do something. We're trying to tell you how to do it right And save you some frustration
You said you need to "learn how to deal with this situation with the tools at hand"
Well you for got one tool.... the one between your ears. Sometimes things are beyond our skill, knowledge, equipment, what ever and we need to farm stuff out to someone with the skills equipment etc. to get the job done. and sometimes you farm stuff out cause you don't have time to futts with it. Believe me I've run into more stuff that was beyond our shops skills and equipment capabilities. but we figured out a way or we ponyed up and bought the tools to do it right. EDM included. That shop now has to EDM sinkers which is just about the best at burning out a tap. If you think this one is hard to get try it in an aluminum part. Like Part of a mold that is so damn expensive you can't just start over. aluminum is very unforgiving and for some reason it like to eat taps.

Now what you should do is get your self a set of safety glasses and go over to you machine shop buddy and watch him do it. then you'll see what we mean, you'll learn and be better for it in the long run. then the next time this happens you'll have the since of satisfaction of know you can handle it.

You are right KC. I would hate to put an endmill, especially a carbide one, in a chuck to do work. Your are going to break it sure as hell.
Butch

Well if you've never done it before it sounds fine then the chuck jumps all over the place and snaps the end mill and then you're really pissed.

Or you could do like I did a build one of these. it's a copy of a forester sight jig built when I had more time then money Complete with V block, clamps all fully adjustable, Drill and tap bushings for 6-48 screws. T slot on back for gage and overarm.
It's made from a chunk of 1.5 aluminum with round stock pressed in. All made from scratch Including the bushing that are heat treated O-1

Well that project has been on the back burner for some time.

I bought a cross vice for my drill press a while back so I could be more precise when locating work for drilling.

I also picked up some 3/32" end mills.

Tonight I got the urge to give this try so I secured the receiver in my scope drill/tap fixture sans the top of the fixture. I was able to secure the receiver straight & square W/the fixture.

I used the traverse cranks on the cross vice to locate the 3/32" end mill over the center of the broken tap. I then fed the mill into the tap W/very little pressyre to allow the end mill to square up the end of the broken tap. It was pretty flat to start wit.)

Once I got the end mill cutting square into the broken tap I slowly increased the downforce all the while watching the progress of the end mill as it cut.

I took my time, and eventually the end mill went through the tap W/O touching the threads.

I ran a fresh 6-48 tap into the hole & all is well.

After securing the rear base & checking W/a flat edge I found that the rear base is @ the right elevation to be in plane W/the front base, but the left side of the bridge needs to come down a bit. The raer base is rotated just a bit to the right.

I get @ it tomorrow W/some spotting black & the mill file to true up the raer base W/the front.

Good to see you got it.
Carbide is worth it's weight in gold

I would still burn it out.....but I have 4 EDM's at my disposal.

quote:

Originally posted by kcstott:
Good to see you got it.
Carbide is worth it's weight in gold

I was lucky that the end of the tap was pretty flat.

I watched the end mill closely & it was trying to side load a bit so I didn't apply any downforce..

I took my time & allowed the end mill to slowly square up the end of the tap. Once I got it where I could see that it was no longer trying to side load & was cutting square I was able to put a bit more pressure on it.

yep that's the way to finesse it.

I trued up the rear bridge today.

Here is what I had to start.






Here's what I have now. I know there is a bit of crown in the center, but that is a moot point as the base does not contact the bridge there. I concentrated on getting the flats where the base rides true & flat. The contact pattern looks pretty good to me in these PIX.






The rear base is now true W/the front base.







Seems the camera is distorting this shot. That safe file on top of the base is staight, not curved as it looks.




I know this is the hard way of doing it, but it's the only way I can afford to keep working being as poor as I am @ the moment.