METALLURGY

[Daniel Watters]

Actually, some units did remove the Blish lock from their early model Thompsons. In one Australian unit, the trick was that their armorer cut a machine bolt to the width of the Thompson's bolt and then screwed on a nut. The bolt and nut could then be dropped in to replace the Blish lock. I've also heard of armorers machining the locking flanges off of each side of the Blish lock.

Certainly, the Blish lock did not work for the exact reason that Commander Blish had given. And for a SMG, the Blish lock was an bit of over-engineering, just like the roller locking pieces on a MP5. The Thompson 'Auto Rifle' .30-06 used the same locking system. However, like other delayed blowback weapons, it had problems with extraction. For the Thompson .30-06, this was solved by either waxing or oiling the cases. Neither solution was considered to be suitable for military service. One wonders how well the rifle would have worked if it had a fluted chamber like the G3.

 

[James K]

Hi, Daniel,

Of course the actuator and bolt can be fixed permanently together, welding being one way. But that is not the usual picture, in hundreds of magazines and books, of the frustrated "Tommy", in the midst of firing at Rommel's troops, taking out the Blish lock and flinging it out into the wadi. After which, he went happily back to shooting Germans with no further problems.

Jim

 

[Oldspeed]

Nick,
Re: Titanium Nitrite coated parts? I have seen the shiny Gold colored coating which you said is very hard. What about the Black Ti coating that I have seen on a few gun parts and knife blades? Is it as hard as the Gold finish? The Gold looks like it would be more self lubricating and smooth but maybe only because it is shiny instead of flat black color? What process changes the color of the coating? I have read that it is very thin and requires high temperatures to apply?
Thanks,
Bob

 

[Nick19]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Oldspeed:
Nick,
Re: Titanium Nitrite coated parts? I have seen the shiny Gold colored coating which you said is very hard. What about the Black Ti coating that I have seen on a few gun parts and knife blades? Is it as hard as the Gold finish? The Gold looks like it would be more self lubricating and smooth but maybe only because it is shiny instead of flat black color? What process changes the color of the coating? I have read that it is very thin and requires high temperatures to apply?
Thanks,
Bob[/quote]

There are several dark titanium based coating used to improve wear or corrosion resistance. TiAlN (TiN co-deposited with AlN) is usuallybrown to dark brown, TiCN is gray to black in color. These coatings, including TiN, must be applied at a high enough temperature to achieve metallurgical bonding with the substrate, typically 400 or 500 degrees C (roughly 700 to 900 degrees F). There may be newer processes that can be applied sucessfully at lower temperatures.
CrN is silver like chrome. The color depends mostly on the composition and somewhat on processing temperature and other process variables, while the smoothness depends on some processing variables and the texture of the substrate finish, I believe (though you should check this out with a company that provides these coatings, like www.brycoat.com).

Also, a titanium metal coating can be anodized to obtain a black or dark grey titanium oxide finish, which is also hard. I believe this is normally done with a trisodium phosphate solution, but the hard oxide is very thin, and probably much less durable than a TiCN black finish. I doubt this coating is used on knives or firearms, although I think it is used on some writing pens. Plasma coated titanium is a grey color as well, but not black.

Nitride coatings are very hard and wear resistant, and can also reduce the friction between components, but they are not truly self lubricating like molybdenum disulfide or teflon containing coatings. I believe that ORNL (Oak Ridge National Labs) has sucessfully applied TiN coatings containing MoS2, which would be a truly self lubricating TiN coating. I would guess that this coating would be much more expensive to apply than phenolic MoS2 containing resins like Gunkote, which are self lubricating and very tough.

The hardness of these coatings depends on a lot of variables, but they are all much harder than steel. I believe that TiN is the hardest, followed by TiN and then TiAlN, but I could be wrong (TiCN may be harder than TiN).

-Nick19

 

[EQUALIZER]

Nick 19,

I am considering sending out a project to be finished in TiC or TiCN. The slide is steel and the frame is cast Al Alloy. I was told that I can request a "rose" colored finish if I wish, which is supposed to be applied at a lower temp. My question is, do you think that the high temps in which these are applied would cause the frame, (ie. high stress area of slide stop pin hole), to stress crack prematurely? I realize the coating is very hard/durable. I don't know if the strength of the frame in regards to cracks or dents would be positively or negetively affected. Do you know? Thanks.

robert

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