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 No.214[View All]

Just wanted to post some preliminary progress regarding my AR18 build
i dont have any access to any examples of these because i live in a commie faggot state, but i've started to at least make progress on constructing an upper receiver flat.

im doing this with some knowledge ive deduced and some simplifications as such:
- an AR18 tubular receiver has internal dimensions of 1.25" x 1.25"
- an unbent flat will be approximately 5 inches across
- relative proportions from pictures will be close enough for function

using that i performed progressive rudimentary visual perspective correction for image 1 using GIMP and gridlines to get image 2. i then imported it into autocad and corrected for any rotation. i then visually mapped out the outline to get a general proportions. with this done i scaled the drawing to my 'known' dimension of 5 inches and examined the other dimensions. I then went through them and rounded up or down to units that are convenient to imperial system, and radiused select corners

This would be an iterative process of refining the flat given i dont even have access to an actual rifle. the only dimensions i can think of that will require being really close would be overall length and width. Width i know isn't going to be accurate, given that when bending sheet metal flat dimensions like that wont directly translate to the finished dimensions, but it think its a good starting point. length would be easy enough to change.

71 posts and 25 image replies omitted. Click reply to view.


all right and what happens if you're done early


i'll post pictures of all the stuff i have backlogged


ok it didn't happen today because the gf wanted to make a pie so i had to stay home and do that instead. maybe i can do it tomorrow? idk this fucks my schedule up ngl


so why did you stay at home dealing with some bitch instead of working on your project


wtf retard, ask me if it happened so i can respond "ok it didn't happpen today" then you can ask why, then you can ask when i might do it next, then you can ask if it messes with my schedule
ugh way to fucking ruin everything


what kind of pie was it


we made a pie with pizza filling
so i guess basically deep dish with a crust?
red sauce, pepperoni, italian sausage, green bell pepper, lots of motz


did you save me a piece? haha


all gone.
finished the rib forming die yesterday, if im not lazy i'll post picture


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Ok so updating the thread.
So before I made the new bending jig/vise, I had done a semi-successful rib forming and bend.
The rib forming tool was just a pice of wire on a plate, with an accompanying cutout. It didn't work well, at least partially because the pressure required is way too high to do both ribs at once, but also because of material strength issues and alignment problems.
Because of those, during the bend there was some tearing problems
The bends on the old bending jig weren't great either. Pressure required exceeded what what the press could provide, and the bends could only be completed 80ish percent. The remaining amount I cludged out by squeezing it in a vise. The results were not satisfactory, but the best so far


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So to resolve the bending jig issues, I came up with a bending jig/vise/alignment frame concept for future bends. A thin sheet of rubber will be used stop it, and a bend goal of about 70-80% with the press. Then the piece will be bolted down, press removed, and the vise used to bring them the rest of the way in a controlled manner.
The other thing was building a new better rib forming die. I designed it then machined it in a couple sessions the other day. Today I tested it.
Results were good. Some minor nitpicks, but the depth is consistent, alignment acceptable, and edged fairly crisp. Forming the linger rib seemed to require slight more pressure then was available, however, because it didn't flatten the sheet back out at the end of forming.
The forming tool itself is kinda cool. Inserts held in place with setscrews, and in this case the inserts can be flipped around and combined with each other for different lengths/end positions etc. Is sort of slick


i lik burgr kang


>we made a pie with pizza filling
how'd it taste?


pretty good, the mix of pepp, sausage, and green bell peppers was pretty godly tbh
those bell pepps really add a lot when they get cooked


stopped by yesterday and attempted a bend without the UHMW pads
blocks still slipped, so going to have to do something else.
probly just make a "positioning" plate that has the purpose of putting everything the right distances, and will keep the blocks in place by putting the bolts in shear.
definitely not ideal loading, but i'll do some math to make sure nothing gets too crazy


nothing is worse than slippery blocks shorkcel


ya its kinda crazy how little lubrication is needed to bring steel on steel down to a relatively low static friction coefficient


I know right. me and you have a lot in common we should be friends


wow really maybe we can read a LN together


ask your MAL friends to read it with you


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big progress– did the math to see if the positioning plate would work, numbers were close but it looked good
made it and did the bends
good results. ribs survived. fairly consistnet. actually bent it too tight on the second bend so its trapezoidal, but i can just break my tacks and adjust.
one weird thing is its actually lightly curved like a banana (maybe about 1/16" of an inch?). im still trying to figure out exactly how that happened
big step forward, though


>day skin

we need to talk about your 23andMe results


whats day skin?


notes for next attempts:
- prevent mid beam deflection by making a 1/8" steel flush pressure pad along with some flat head retaining screws
- make a section profile spacer plate to prevent overbend during second bending (in the future, combine this with the punch)
- adjust flange length for a perfect seam upon final bend (for fusion butt weld with TIG)

also adjust 1 & 2 for existing bent flat before moving on to next steps


some other stuff ive noticed
radius on the rib side is slightly crimped
tube is not square, especially on the front (its like a parallelagram). this likely happened because the bends happeed unevenly, and one side got overbent significantly
the guide rod base has a cutout at the bottom to accomodate overpen from the weld seam
i might have to increase the size tolerance for my tube to account for manufacturing defects


also after measurement, opening still isn't opened the same, in the middle inch, over .01" difference in width


yah we know you love increasing size tolerances for tubes


oh wow just wow




i opened it up a little more, but it still wasn't square (needs to open more)
i might go tonight and do that, i'll bring my calipers and actually measure one side to the other


ok i've got updates, will post later sunday


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Latest developments
I opened it up until square, actually significantly larger than I was expecting. Not sure if when I made the tooling I did that intentionally? But everything fits perfect, so doesn't matter either way. I just tacked it maybe 8 places evenly before machining
The issue with being out of square mostly disappeared, it turned out that only one side wasn't bent all the way on the front, and that was enough to throw it out of square when welded.once the pocket up front got machined it spring open on that side (that's why I have it clamped.
3d printed trunnion is in, guide rod and bolt carrier installed. Fits on the lower well but the fire control pocket is a little too small and it hits on the bolt hold open.
Gave a good lesson on work holding, glad I decided to take this one as far as I can, the 'production' one will be nice as a result.
Receiver is still slight banana shaped, but I think that will resolve by adding anything flat and rigid on top along with proper welding procedure
Next will be the cutouts for the bolt handle and holes for the cam pin rail


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oops sorry posted some image thumbnails on accident
also the camera/lighting did some weird shit, they look surprisingly decent considering i did all this on the fly
especially the last one with the clamp looking head on, the pic gives the illusion its not square, it is it looks p. clean IRL


looks great, can't be too far off now right?


nope its gettin real close.
still big hurdles ofc, but the bending stuff is the hardest and most involved.
the other stuff is just tedious machining (machining trunnion, machining front sight block, etc)
i'll 'finish' this one (i'll make simplified components with the critical features on it) so that when i do my next one, i'll have everything figured out and it'll be nice


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milled out the charging handle slot and the plug holes for when you weld the cam rail in.
noticing some unintentional differences with my stiffening ribs, namely the top one should be closer to the cutouts and a tad longer
can adjust on the final one.. kind of annoying though i'll have to mill a new female die
also fucked up milling the front of the charging handle slot, accidently grabbed an 11/16" with a 5/8" shank instead of a 5/8", so the front is 1/32 too big all around
really sucks, even though this is just the 'test' flat, it would have been nice to have a good looking one


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Slightly better one of the upper
My camera sucks


Can you reuse any of the material you goofed on?


I can reuse some of the tooling, if you mean this receiver nah not really but that's ok
I have a pretty good feel for what not to do, so chances for the next one to be near production quality will be good


Thats cool. Making mistakes is a corner stone of learning. Its pretty impressive what youre doing.


its been a really long time doing this project on and off
tonight, i will try to machine the trunnion


ugh nvm wont happen tonight
tomorrow, if im lucky


ok well i went sunday, almost got it done but accidently scrapped it
unfortunate but i know what to avoid next i suppose


What happened that made you have to scrap it?


so i did the press fit stuff perfect
when i was cutting the features on the bottom my endmill slipped in the collet and i lost some Z without realizing it
it was probly because its a pretty dull end mill, the collet may have been dirty too
anyway i broke through the press fit wall of the trunnion
also snapped the shit out of my 1/4" endmill on a plunge lel
i'll probly post a pic at some point


trying again tonight


FUCK this is gay
tire blew out on the way
so bad the mexican shop in the bad part of town wasn't even willing to patch it
gay gay gay gay gay


>not even the Mexicans will patch it


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got the trunnion made
went mostly ok, made a single mistake that resulted in damage to the front of it (not pictured) that was completely avoidable and I'm retarded
this one is good enough to test, tho


sir STOP lelling..

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