Marlin Firearms Forum banner
1 - 20 of 22 Posts

·
Registered
Joined
·
3,260 Posts
Discussion Starter · #1 ·
I have a 50 336A 35 that is in nice shape except it has been D&T'd. It had a scope mounted which I removed & the front screw was broken off. I put it in the mill & used a small end mill to get a flat spot to be able to drill for removal. That's when I realized that it was a tap because of it being so hard.

If I could figure out some way to cut a slot for a flat screwdriver, I'm pretty sure that it would come out. It's deep enough so that I can't get anything to it for a slot. Any good ideas?

I thought about pulling the barrel, but I don't think it would help. When a carbide end mill won't cut it & a high grade punch doesn't scratch it, you know it's hard!
Thanks, trad
 

·
Read Only
Joined
·
488 Posts
You are sort of in one of Dante's levels of hell. The only thing I can think of is getting it under a magnifying glass and see if you can see any gaps where the fluted part of the tap is, and if there is a slight gap (should be 3 of them 120 degrees apart) maybe you can get something in there and rotate the broken piece.

You know it's not a long piece, and it should be an end / blind-hole tap (piece of tap). Or maybe you drill & tap two holes on each side of the broken tap for one piece of a two-piece base set.....
 

·
Premium Member
Joined
·
2,333 Posts
I don't have an easy answer, and as you are witnessing, that kind of fix is beyond a nightmare. But.. I did pull off a similar adventure a while back. it took a long time and I wiped out 2 small end mills doing it, but it worked.. your results may vary.

I fished out a broken tap that snapped off flush, chucked it in the mill and started with the smallest end mill that I could get to fit that wouldn't hit the threads. 2 flute end mill 1/16" or 3/32" if memory serves.. and took it really, really slow, like 400rpm. and a lot of oil and slowly let it chew with steady pressure, but not enough to deflect the bit. slow RPM and lots of oil-coolant was really the key in the process

I didn't go directly bullseye center on purpose so it would chew into the area partially over the fluted area essentially making 2 - 3 loose ragged pieces that i could chip out in the next process (basically drill off center so I could collapse the sidewall of the remaining bit in on itself)

It took a while and was very slow going, but it slowly started to dig in and cut, I wiped out the first bit about half way thru, then switched to a new bit and finally got thru.
Once I got thru, the flutes were compromised enough that the extra pieces just kind of chipped and flaked out of the threads with a little persuasion from a small metal scribe i made by grinding a point on the back end of a dead 1/16" drill bit. and a few light taps with a small hammer... took a few minutes to pick out the little remaining pieces, but once that process got started, it went pretty fast from there...

Hope this made sense. Good luck with it, I feel your pain.
 

·
Registered
Joined
·
7,411 Posts
Depending on the size of the tap and how buggered up it is, broken tap removal tools are available down to No. 4.

Left hand carbide drill? Not the best solution either unless you can get dead centered on it.

If desperation has set in, here's a (semi) crazy way of getting them out I ran across in Volume I and II of Gunsmith Kinks. YMMV. I've never tried this....



 

·
Registered
Joined
·
3,260 Posts
Discussion Starter · #7 ·
"I know, stupid question but what size tap?" \ 8 - 40

I thought about a Dremel. I have a precision router base for it, but I would have to find a small hard cutter to grind a slot in the tap.

Being that it is the front, I doubt that the hole goes through unless they drilled into the barrel threads. I may pull it to see if I can't get it out from the top.

I could just get over it & leave it. I would put 8-40 plugs in it anyway because I am not going to scope it.

I need a rear sight for it as well. It has a dovetail filler in place.
 

·
Super Moderator
Joined
·
12,713 Posts
Eric that sounds like a Bubba special. With that in mind I would be concerned that the tap extends into the barrel threads and trying to remove the barrel would either be difficult or screw up the threads during removal. If it doesn't work out you could always see if Andy @ Skinner could make a peep sight that will cover it. Kind of like the Alaskan but to move the front mounting hole back to screw site #2, presuming Bubba drilled the holes where they are normally supposed to go.
 

·
Registered
Joined
·
2,706 Posts
I have removed small taps broken below the surface of the material by carefully centering a prick punch on the broken tap, then smacking the punch with a hammer. Since the tap is considerably harder and more brittle than the material, it will shatter and leave you with several pieces to pick out of the hole. I've done this successfully with up to #8 taps, am told by the machinists at work that it works fairly well up to 1/4"
 

·
Registered
Joined
·
3,503 Posts
Sadly, I have some experience with this. Years ago I broke a tap off in a water pump for my car, short boring story but this is what I learned. Whatever they make the tap out of is hard as hell and nothing I had would even scratch it. The plan was to drill a hole in the broken tap and use one of them reverse thread backout doohickeys. I was told the only drill that could even put a dent in it would have to be diamond tipped.

The solution.... I took the water pump to a machine shop that had an ultrasonic drill. It basically disintegrated the tap. They got the busted tap out, then they tapped the hole, installed sleeve and I was good to go. It wasn't cheap.
 

·
Registered
Joined
·
267 Posts
Sadly, I have some experience with this. Years ago I broke a tap off in a water pump for my car, short boring story but this is what I learned. Whatever they make the tap out of is hard as hell and nothing I had would even scratch it. The plan was to drill a hole in the broken tap and use one of them reverse thread backout doohickeys. I was told the only drill that could even put a dent in it would have to be diamond tipped.

The solution.... I took the water pump to a machine shop that had an ultrasonic drill. It basically disintegrated the tap. They got the busted tap out, then they tapped the hole, installed sleeve and I was good to go. It wasn't cheap.
I've taken stuff to a machine shop and other stuff to a welder and they always refused to work on it because it was part of a gun. "We are not licensed to work on firearms.".
 

·
Registered
Joined
·
3,260 Posts
Discussion Starter · #12 ·
The holes are in line & in the correct position. I think it was done by a professional, but I believe that the tap bottomed out & broke.
I guess he cut the front screw off so it would thread in part way.

If a diamond tipped Dremel bit will cut a slot in it, I believe that I can get it out.

I hit it with a high grade punch & the tip flattened out a bit without a scratch on the tap.
 

·
Premium Member
Joined
·
25,367 Posts
I know this is not the solution you are looking for, but I have a
waffle top 35Rem I've been shooting and hunting for 6 years now that
has 3 screw holding the scope base on...because one of them is off
a little and won't line up.
It's the very front one too.
The guy didn't charge me since he messed up, though.
I never worried about it. Put the other three in and carried on.
It's never budged and I haven't babied it either.

I can tell you this, though...
The post about heating up the broken tap and letting it
melt out of the hole will work.
I worked in welding and metal fab for 20 years.
The broken tap is a seperate piece of metal and will
heat up way faster than the surrounding metal.
I have even done this with a broken screw on a
Rem 600 once. It didn't even harm the bluing.
I have also done this with broken bolts on car parts
and on heavy equipment.
 

·
Registered
Joined
·
3,260 Posts
Discussion Starter · #14 ·
Thanks navajo. I'm not going to scope it. I just wanted to remove it & put 8-40 plug screws in.

How would be the best way to heat it up in such a small hole? The barrel would absorb some heat also. Don't want to remove the barrel since I don't know if it is thru & into the threads.
 

·
Premium Member
Joined
·
25,367 Posts
You need to use a small brazing tip like a plumber uses
on copper line.
If you aren't familiar with this sort of thing, have a welder do it.
But as soon as you start to heat it up, that broken tap will
turn bright red and start to melt. Like the earlier post says,
turn the gas off, and blow it out of the hole.
I don't think you will get enough heat on that action to
cause any damage. If you're worried about it have a wet
wrag handy.
But I will tell you this, I've removed quite a few barrels on 336's,
and most of the time, that front hole goes into the barrel some.
All four holes go all the way through.
Not sure how much that would help though.
 

·
Registered
Joined
·
3,260 Posts
Discussion Starter · #16 ·
Plumber! I'm a HVAC guy & electrician. I've got brazing tools, but how do you get the heat into the small hole? Heat a small piece of steel to transfer the heat to the tap? I'm not going to heat the receiver itself.
 

·
Premium Member
Joined
·
25,367 Posts
Plumber! I'm a HVAC guy & electrician. I've got brazing tools, but how do you get the heat into the small hole? Heat a small piece of steel to transfer the heat to the tap? I'm not going to heat the receiver itself.


Well, that's what you'd have to do...so if you're not comfortable doing so,
this won't be an option for you.
 
  • Like
Reactions: Owen49

·
Registered
Joined
·
14,566 Posts
I don't think I would do that torch method myself. Never herd tell of it before. I have removed a few broken taps with a punch. The
trick is to do it with one solid blow with a heavy hammer. To many guys are peck hammer jockeys and do nothing but tear up threads.
Sometimes there is clearence to punch flute CW, which will back it out or snap off a chunk of tap. If you get it moving you can usually
worry it out by tapping on the flutes. I've had some in BA rifles that were already Bubbaed from attempts to get the tap out. It has to
be retapped to larger thread anyway so you just drive it out, it will break during the process. I'm a pretty fair hand with soldering
- silver braze and have fixed a gun or two. I am very careful about applying heat and flame to any gun.
 

·
Banned
Joined
·
4,646 Posts
Have the holes TIG welded up, dressed, and touched up.
 

·
Registered
Joined
·
2,400 Posts
This is on the receiver of the gun.... And that receiver is rectangular..... If you torch on it - it will warp and possibly draw the heat treat.

Take it to a pro gunsmith who has a good machine shop on site with good credentials and pay him to deal with it. It won’t cost much and they won’t mess it up.
 
1 - 20 of 22 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top