M14 Forum banner

1 - 16 of 16 Posts

·
Banned
Joined
·
3,729 Posts
Discussion Starter #1
For those that feel it is important to have a Muzzle Crown kept in excellent condition, here is a Tip I use every time the M1A is give an overhaul.

The M14 combo tool has a swing out handle, on the end of this handle is a round ball like feature. This tool is made of hard steel, harder than the Barrel. Remove this handle and chuck it into a drill with a slow speed control, Coat the Muzzle Crown and Ball with Valve grinding paste, I start with 400 and finish with 800, Secure the Barrel and work the ball into the Crown with gentle pressure at slow speed, Being round you can not get off center no matter, within reason, how out of drive position you may move.

Inspect the Crown frequently to follow your progress, when a complete ring, or surface polishing, is apparent you are finished. Clean the Barrel and you are ready for another range experience. art
 

·
Registered
Joined
·
123 Posts
First off, this isn't intended to be one of those "flaming post". So please don't jump down my throat. Besides, I've been coughing alot lately, don't think you want to get that close anyway.

But actually, your idea of the ball end of the handle being harder than the barrel is completely backwards from the way you want to lap something. Ideally you want your lap softer than the piece your lapping. Like the brass lap in the link bricktop posted, or even casting a lead lap to lap a bore. Reason is, the grit in your lapping compound is going to imbed itself in and be held by the softer material enabling it to cut the harder material. You may not be accomplishing very much the way your doing it. Maybe just a little polishing. Which might be all your after.

If you have a copy of the "Machinist Handbook", there's a section in it that tells alot more about lapping. It's an expensive book though, probably run $75-80 new, I haven't looked. I've got an old edition (194?) I picked up for around $20 in an antique store of all places. But if your interested in alot of mechanical stuff, could be worth looking at.

This does remind me of something I read a long time ago in Roy Dunlap's "Gunsmithing" regarding the same principle. A hard, polished, one piece cleaning rod is alot better than a soft one. Kind of makes you wonder about all these coated rods and pull through's and such.
 

·
Read Only
Joined
·
2,559 Posts
I'll second ExMR2. When polishing glass, as in lens making, the polishing tool is made of pitch or another tar-like substance. The polishing compound becomes imbedded in the polishing tool and polishing action is against the harder glass.

It's probably not a big deal on a rifle crown though, since it's just a hunk of steel hardware. I use brass rod for that function. I also use aluminum to polish (lap) brass items, and soft epoxy to polish plastic (plexiglass). If it didn't work that way I wouldn't do it that way.
 

·
Registered
Joined
·
174 Posts
I'll chime in on this one. The reason you want your lap to be harder than the barrel is because you want the lap and compound to remove the unevenness of the crown. A soft lap would just follow that unevenness and not true it, which is what we are trying to accomplish. This would be comparable to a soft bit used to remove metal in a lathe operation. If you want to true something, the removal or uniforming tool has to be harder than the material it is trying to true or cut.

Kevin
 

·
Banned
Joined
·
3,729 Posts
Discussion Starter #6
Both positions are correct..

This once again is a problem of not reading the Thread correctly. or perhaps I was not clear. I wrote, the ball end, steel, of the handle is harder than muzzle.. This made it clear, to me anyhow, that this combination is not what is usually used to lap. Also the Thread states, the purpose of this labor is to Polish the Crown, A Polished Crown gathers less carbon than an unpolished crown.

This is not intended to attack or belittle anyone, I appreciate all responses, this Gentleman did not, and he states so, indent to made a fuss.

If you recall, the lapping of the bolt lugs to the receiver uses the bolt as the moving part in this lapping-in process, it works, I don't know if the bolt is harder than the receiver, but never the less that's how it is done. Art MCORPS1
 

·
Banned
Joined
·
3,729 Posts
Discussion Starter #7
Thank You Kevin

I'll chime in on this one. The reason you want your lap to be harder than the barrel is because you want the lap and compound to remove the unevenness of the crown. A soft lap would just follow that unevenness and not true it, which is what we are trying to accomplish. This would be comparable to a soft bit used to remove metal in a lathe operation. If you want to true something, the removal or uniforming tool has to be harder than the material it is trying to true or cut.

Kevin
It is been my understanding from Threads that are questioned by members,,, almost always result in all of us leaning something, and that is part of what this Forum is about. It is interesting how two people read the same material and come away at opposite ends.

Your response is helpful and of course correct. I hope everyone reads it and puts it into practice. I'll attempt to make my Threads clearer in the future. Art
 

·
Registered
Joined
·
174 Posts
No worries Art. I knew what you were trying to convey; I was just trying to clear up any confusion.

Respectfully,

Kevin
 

·
Premium Member
Joined
·
16,891 Posts
You done good Art.
I have been using exactly the same tool for 40 plus years to polish the crown on my M14s. Being a 7 digit old corp guy. I learned that this repaired damage done by our multiple part cleaning rods. Works for me. Thanks for what you have done.You explained it perfectly.
Art Banks SGT USMC ret.
 

·
Registered
Joined
·
5,679 Posts
Being a 7 digit old corp guy. I learned that this repaired damage done by our multiple part cleaning rods.
Makes a body wonder how many of those sectioned cleaning rods the U.S. military had left over from the Spanish-American War (?), WW I, WW II, and Korea. Sometimes left-overs (e.g., .30-06 Spg) end up making the best meal, but not always. If we were starting from scratch, the Otis-type kit - essentially the same thing the Germans had - would be a no-brainer for cleaning rifle barrels without ruining them.
 

·
Registered
Joined
·
123 Posts
I'll chime in on this one. The reason you want your lap to be harder than the barrel is because you want the lap and compound to remove the unevenness of the crown. A soft lap would just follow that unevenness and not true it, which is what we are trying to accomplish. This would be comparable to a soft bit used to remove metal in a lathe operation. If you want to true something, the removal or uniforming tool has to be harder than the material it is trying to true or cut.

Kevin
Like I said before, not intending to flame anybody, but your comparing apples to oranges. Lapping is basiclly using an abrasive to polish something that's already been cut very close to finish size to a very smooth surface. Your only meaning to remove a very small amount of material by lapping. Completely different process from turning something in the lathe. Yes your turning tool has to be harder than the material your turning. But in lapping, your cutting tool is the abrasive itself not the lap. As Art say's all he wants to do is polish the crown, and what he's doing might be working for him. But if the crown is untrue, if you start lapping it all your going to do is lap an untrue surface. You would have to have the crown recut to true it up before you lap it.

Also as far as lapping the bolt lugs. Your lapping two parts together to obtain (ideally) 100 percent contact between the two. With both materials being roughly the same hardness, your cutting on both the bolt lugs and the reciever.

Art, from the original post, I didn't realize you knew what you were saying was backwards and just wanted to let you know. I've been machining for 20 years and not trying to claim I know everything, I'm still learning things. All I was trying to do was explain the process. Believe me I've seen and heard some pretty weird stuff from people who have been at this longer than I have and they think it's right just because that's the way they do it. No matter if you can show them and explain to them that's it's not. If what your doing is working for the intended purpose, I have no problem with that whatsoever, carry on.
Same thing with RVPilot76, not inteding to flame you, just wanting to explain the difference.
 

·
Banned
Joined
·
2,325 Posts
proper

Like I said before, not intending to flame anybody, but your comparing apples to oranges. Lapping is basiclly using an abrasive to polish something that's already been cut very close to finish size to a very smooth surface. Your only meaning to remove a very small amount of material by lapping. Completely different process from turning something in the lathe. Yes your turning tool has to be harder than the material your turning. But in lapping, your cutting tool is the abrasive itself not the lap. As Art say's all he wants to do is polish the crown, and what he's doing might be working for him. But if the crown is untrue, if you start lapping it all your going to do is lap an untrue surface. You would have to have the crown recut to true it up before you lap it.

Also as far as lapping the bolt lugs. Your lapping two parts together to obtain (ideally) 100 percent contact between the two. With both materials being roughly the same hardness, your cutting on both the bolt lugs and the reciever.

Art, from the original post, I didn't realize you knew what you were saying was backwards and just wanted to let you know. I've been machining for 20 years and not trying to claim I know everything, I'm still learning things. All I was trying to do was explain the process. Believe me I've seen and heard some pretty weird stuff from people who have been at this longer than I have and they think it's right just because that's the way they do it. No matter if you can show them and explain to them that's it's not. If what your doing is working for the intended purpose, I have no problem with that whatsoever, carry on.
Same thing with RVPilot76, not inteding to flame you, just wanting to explain the difference.
Thats why they make different color of paints too.....people like different stuff.....I assume you see Art's logo at the bottom of his post ?

He has more time in on these rifles than all of us put together....so if i was given the choice, I think I would listen to his ideas.

Not saying you are wrong or trying to cause trouble, because I also use a brass roundhead screw for slight lap/polish procedures....but when its time for more.....I will try this method from Art. If I screw it up...I promise , you will be the first one I contact and tell DI2....Then Art ...and tell him he owes me a golf game !!!....and Lunch!
 

·
Eye Master
Joined
·
3,942 Posts
I think this is a symantics discussion.

Lapping has two different definitions (according to Wikipedia, the fountain of knowlege):

"Lapping is a machining operation, in which two surfaces are rubbed together with an abrasive between them, by hand movement or by way of a machine.

This can take two forms. The first type of lapping (traditionally called grinding), typically involves rubbing a brittle material against a surface with an abrasive such as aluminum oxide, jeweller's rouge, optician's rouge, emery, silicon carbide, diamond, etc., in between them. This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both.

The other form of lapping involves a softer material such as pitch or a ceramic for the lap, which is "charged" with the abrasive. The lap is then used to cut a harder material—the workpiece. The abrasive embeds within the softer material which holds it and permits it to score across and cut the harder material. Taken to the finer limit, this will produce a polished surface such as with a polishing cloth on an automobile, or a polishing cloth or polishing pitch upon glass or steel."

Art
 

·
Registered
Joined
·
690 Posts
Another way to make use of the materials at hand! Thanks for sharing, Art.
Doc
MC1EXPRT1
 

·
Registered
Joined
·
558 Posts
If you are intending to just polish, either way will probably work, and if either does, so be it. If your barrel needs "recrowning" that means cutting. Neither would suffice, if absolute accuracy is expected. Im inclined to think a lap made of brass (not too soft, but softer than barrel steel) is probably the best material to use for polishing. A lathe and a cutter for re-crowning....
 
1 - 16 of 16 Posts
Top