Gunsmithing Heard a small snap when snugging up my aluminum forend in a vise

[SuperSneakySniper]

Heyo guys,

This question probably belongs in the Stupid marksmanship questions section, but it doesn't have anything to do with shooting.

Rather, I was snugging up a 6061 anodized aluminum handgaurd in a bench vise last night in order to file some of it down to smoothen out some of the edges. I didn't think I was tightening it all that much, but I did hear a small faint snap/crackle sound and decided to stop tightening. It is a thin, lightweight competition handgaurd. Similair in thickness/feel to say a Samson Evolution or BCM KMR Alpha rail etc...

No visible damage can be seen on the inside or outside of the handgaurd, but it got me thinking: did I just crack this thing? Maybe internally or something? Or does aluminum just do this sometimes when put under a little pressure? I'm hoping I didn't just screw up the structural integrity of the handgaurd. I don't want it cracking on me mid-match.

 

[GH41]

Sounds to me like you cracked it. Probably deformed it as well. That would be pretty easy to verify/eliminate with calipers. Who's rail is it that needs edges filed?

 

[SuperSneakySniper]

Sounds to me like you cracked it. Probably deformed it as well. That would be pretty easy to verify/eliminate with calipers. Who's rail is it that needs edges filed?

Oh i was only filing down the anti-rotation tabs so that they lay flush with my billet receiver, (only way i can get the handgaurd to fit properly) the handgaurd itself is very well machined and deburred.
Geez i hope i didnt deform anything. It looks, fits and feels just as solid as new.
Ill get the ol calipers out and see if the OD changed at all from factory spec.

 

[SuperSneakySniper]

Update: I measured the dimensions of the rail in about 20 different places, and throughout the length of the handgaurd there is a .005 difference in dimensions, in the area i held in the vise there was only a .001 inch difference, which was consistant with the dimension in that section of the rail, even in places that were not held in the vise.
At this point I am feeling pretty confident that I didnt change the structural integrity of the rail.

My buddy who was with me during the encounter said he didnt even hear the tiny "snap" that im talking about. We were using rubber covers on top of that. Im probably just being a worry wart. I am pretty darn anal compared to most.
But if my concerns do have merit, do let me know!

 

[...]

really hard to say without inspecting it......but generally if you hear "snaps".....youre cracking the metal.

is it going to shatter on you mid match?....eh probably not, theyre likely small stress fractures.....but i guarantee you if you do a dye penetrant test, youll find them.

especially if the aluminum is 6061-T6 aluminum, because the heat treat will make it slightly more brittle.


ooooooor it could just be junk and debris grinding in the vise.....


essentially, dont make a habit of it, buuuut this one incident isnt going to ruin your handguard.

 

[SuperSneakySniper]

really hard to say without inspecting it......but generally if you hear "snaps".....youre cracking the metal.

is it going to shatter on you mid match?....eh probably not, theyre likely small stress fractures.....but i guarantee you if you do a dye penetrant test, youll find them.

especially if the aluminum is 6061-T6 aluminum, because the heat treat will make it slightly more brittle.


ooooooor it could just be junk and debris grinding in the vise.....


essentially, dont make a habit of it, buuuut this one incident isnt going to ruin your handguard.

Gotchya... It was just the one tiiiny little snap really. Idk if it was debris or not. We were using rubber plates on the vise. But as long as it doesn't affect accuracy and won't break if I throw it into a dump bucket or barricade it against a wall, I should be fine. I learned my lesson though, that's for damn sure. I do doubt it will have any affect. Now I pretty much just wish I didn't hear anything so that I could rest easy lol.

 

[scudzuki]

Install it on the receiver and tighten the fixing screws.
If it cracks and falls off the rifle, it's safe to say you broke it.

 

[ejg]

I don't know much about alu forends... is the one you have anodized? If so it could be that the alu oxide surface will crack long before the alu base get's into trouble when the alu get's stretched/bent etc.
Maybe that is what you heard. Aluoxide is around 6 times stiffer/brittle than alu.
edi

 

[SuperSneakySniper]

I don't know much about alu forends... is the one you have anodized? If so it could be that the alu oxide surface will crack long before the alu base get's into trouble when the alu get's stretched/bent etc.
Maybe that is what you heard. Aluoxide is around 6 times stiffer/brittle than alu.
edi

Interesting. honestly the "crack" sound was so very faint, that it coulda just been the anodization for all I know. However, Its with Robar right now getting a new NP3 coating so the condition of the finish doesn't matter anymore.

I did install it onto the rifle just to check, and it seemed just fine.