Would any of these work?
http://www.mscdirect.com/browse/Cla...agnets/Alnico-Shielded-Magnets?navid=12101494
http://www.mscdirect.com/browse/Cla...agnets/Alnico-Shielded-Magnets?navid=12101494
My AR Lower receiver from scratch
- Thread starter chsnprodigy
- Start date
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Another possibility.. adhesive backed even!
http://www.mcmaster.com/#rare-earth-magnets/=nguwxe
aargh, link won't quite work.. click on the 'adhesive backed ultra high pull'
http://www.mcmaster.com/#rare-earth-magnets/=nguwxe
aargh, link won't quite work.. click on the 'adhesive backed ultra high pull'
chsnprodigy
Active Member
- Dec 24, 2012
- 128
Yup some of those may work. Im going to run to michals with my wife and see if they have anything there.
kalister1
R.I.P.
What would Countersinking the holes for Flat Head Screws do to the structure of the unit? Would it weaken it?
chsnprodigy
Active Member
- Dec 24, 2012
- 128
All of the side plates are 1/8 (.125) thick. If you were to countersink the screw holes and use a countersunk screw it may work, but at the same time it may leave to little material to take the shock and vibration of firing. If you were to countersink it may leave a "knife edge" effect. All of the major aircraft manufactures suggest you leave .005 after countersinking. Without a screw to measure I can only guess how close it would be. This might be an idea for a MK2 design.
This is kind of sexy in an industrial erector set kind of way.
sent from somewhere in the world.
sent from somewhere in the world.
chsnprodigy
Active Member
- Dec 24, 2012
- 128
Thanks Blaster. I know I said it should of been firing by now...but things come up and its on the back burner till next week. I will be making the part that got burnt this weekend though.
I know that feeling... 
Still workin on the CAD drawings so I can do some tweaking.. have most of it modeled, have to finish the last two parts and I can do some actual manipulation with the parts to fine tune the lower. I have already nixed the buffer pin and put the proper hole in at the 6* cant to allow me to use a standard buffer retainer and spring. The other thing I am going to look at is to use thicker stock for the one side plate to allow me to use a selector detent and spring for that and perhaps a few tweaks to put some radii on a few key areas..
Should have the models all done in a day or so, then I can do some engineering..
Still workin on the CAD drawings so I can do some tweaking.. have most of it modeled, have to finish the last two parts and I can do some actual manipulation with the parts to fine tune the lower. I have already nixed the buffer pin and put the proper hole in at the 6* cant to allow me to use a standard buffer retainer and spring. The other thing I am going to look at is to use thicker stock for the one side plate to allow me to use a selector detent and spring for that and perhaps a few tweaks to put some radii on a few key areas..
Should have the models all done in a day or so, then I can do some engineering..
The 'thickness' of a #6 screw head is 0.094, so to set it flush or .005 below flush would leave you about .025 - .030" of hole without countersink. I honestly don't think that would be an issue, I'll look at this when I finish up the drawings and see how it looks. I like the idea of FH machine screws, would leave a neater overall outer appearance imo...
chsnprodigy
Active Member
- Dec 24, 2012
- 128
Agreed! I do think countersunk screws would look more complete.
Here is a 6-32 countersunk flat head machine screw in one of the receiver sideplates... you can see that you have almost .060" from the top of the shank to the bottom of the plate... this would be a little less when you actually drill and countersink the hole for the screw, but I think you will have plenty of meat to serve the purpose. 
(sorry, it plotted sideways... lol)
(sorry, it plotted sideways... lol)A link that is helpful.. to the originator's mirrored webpage. Took me a while to find it, but it does answer a few questions...
http://www.oocities.org/elmgrove1765/project6/project6.html
http://www.oocities.org/elmgrove1765/project6/project6.html
sst4270
Member
Scratch Built Lower CAD files
Hello all,
I've been following this thread with great interest. I finished modeling up the parts last night. And I've reached out to Sticky to offer some collaboration as well, but I thought I'd also drop some screen shots here and make some comments about this design.
I'm gonna try and tackle solving some of the issues with this design.
1. add correct buffer tube retainer hole. (This design uses a custom buffer tube retainer that you have to machine yourself. It shouldn't be much trouble to spend that time on machining the buffer tube hole correctly)
2. Add bolt catch release features back in. (This may be difficult, but we'll see)
3. Add trigger guard features back in to be able to use the wide variety of trigger guards on the market. (Also shouldn't be too hard to do)
I also don't like the boxiness of the front. I'd personally want to add either the orginal slope of the mag well back in or some kind of cool profile similar to some of the billet ones I've seen on the market. And again this shouldn't be too hard to do.
Anyways here's a couple of screen shots.
There is a small flaw in the original design that has a gap on either side of the trigger group bottom plate and the two mag well sides. It's hard to describe, so take a look at the screen shot below that shows a cutaway that reveals this flaw. This is easily corrected.
Anyhow, that's it for now.
Regards,
Steve
Hello all,
I've been following this thread with great interest. I finished modeling up the parts last night. And I've reached out to Sticky to offer some collaboration as well, but I thought I'd also drop some screen shots here and make some comments about this design.
I'm gonna try and tackle solving some of the issues with this design.
1. add correct buffer tube retainer hole. (This design uses a custom buffer tube retainer that you have to machine yourself. It shouldn't be much trouble to spend that time on machining the buffer tube hole correctly)
2. Add bolt catch release features back in. (This may be difficult, but we'll see)
3. Add trigger guard features back in to be able to use the wide variety of trigger guards on the market. (Also shouldn't be too hard to do)
I also don't like the boxiness of the front. I'd personally want to add either the orginal slope of the mag well back in or some kind of cool profile similar to some of the billet ones I've seen on the market. And again this shouldn't be too hard to do.
Anyways here's a couple of screen shots.
There is a small flaw in the original design that has a gap on either side of the trigger group bottom plate and the two mag well sides. It's hard to describe, so take a look at the screen shot below that shows a cutaway that reveals this flaw. This is easily corrected.
Anyhow, that's it for now.
Regards,
Steve
chsnprodigy
Active Member
- Dec 24, 2012
- 128
Giggity giggity!!! Those are some good looking CAD designs. 
I never thought this thread would take off like this and have 3,500 views! Im glad there are others out ther who like to think outside the box to make things. I can't wait to see the end product CAD design you guys are coming up with! Better yet, I cant wait to see a finished product!!!!
I never thought this thread would take off like this and have 3,500 views! Im glad there are others out ther who like to think outside the box to make things. I can't wait to see the end product CAD design you guys are coming up with! Better yet, I cant wait to see a finished product!!!!
chsnprodigy
Active Member
- Dec 24, 2012
- 128
I like it! Function over form, I say... lol (especially with a safety device!)
I have my modeling done, need a couple tweaks (found a pair of holes that don't quite line up, thinkin my dyslexia swapped a couple digits somewhere..
One other thing that has puzzled me, besides the small error that sst found, is why is this cutout going all the way to the rear of the part, leaving a little hole on either side of the magwell???
I have my modeling done, need a couple tweaks (found a pair of holes that don't quite line up, thinkin my dyslexia swapped a couple digits somewhere..
One other thing that has puzzled me, besides the small error that sst found, is why is this cutout going all the way to the rear of the part, leaving a little hole on either side of the magwell???
chsnprodigy
Active Member
- Dec 24, 2012
- 128
There is no function to that cutout. I didnt know that at the time. OR....the cutout is to reduce the overall weight!!!!
Possibly for manufacturing reasons if it doesn't negatively affect anything. Your front block, the well that holds the pivot pin part of the upper, is impossible to machine as drawn unless you have an EDM. You can't make square interior corners w/ a finite diameter endmill. You can get one edge square, but another will be rounded.
Another spot this is done on commercial lowers: the buffer hole threading. It doesn't need to extend past the buffer retaining pin (its as far as you can screw on the buffer tube.) Its easy to only thread it that far when thread milling. But using a tap the threads will extend all the way across the back of the upper. Doesn't hurt anything. You can see that mega probably tapped it. Noveske thread milled it.
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