Delrin Dustcover

[Brett248Vista]

Only trouble is...these parts are pretty small.

I'd personally prefer to use a Dremel with a roundover router bit.

They make an attachment for a Dremel so you can use it as a router.

STEWMAC.COM : Precision Router Base

My router table could handle parts that small, but that dremel setup would likely work much better, easier to control the parts and the dremel!

 

[Xapalambos]

STEW MAC

Thumbs up to Stewart Mcdonald for making an appearance here. Great source for guitar building/repair tools and products.

 

[TwistedCreations]

Thanks!

I used a plain old combination blade. If you've ever worked with a very hard hardwood like Beech or Rock Maple, this stuff behaves about the same. I didn't have any melting problems while cutting. It's important to go slowly. This stuff is really hard.

I have worked with Delrin before (for my RC hobby) and have a bunch of pieces of it around here. I had just never used an actual circular saw to cut it. So wasn't sure if you had melting problems or not...Looks like I will go the saw route, as it looks to cut very well...

Thanks for the info on it and the magpul rail covers

 

[CPTBeaker]

I took the plunge and secured my dustcover with machine screws. The 3M tape worked well, but something bugged about using tape.

The hardest part was deciding to drill my receiver.

Steps

1 - using a #43 bit, drill two holes in the boss and countersink the holes with a larger bit.
2 - using a #43 bit, drill two holes in the receiver using the boss as a guide.
3 - tap all 4 holes using a 4-40NC tap.

I used two 1/4" 4-40NC screws.

Note: I recommend using a new tap & drill to ensure the holes and threads are crisp.

- 4-40NC Tap was ~$4.00
- #43 drill bit was ~$1.50

If I ever decide to remove the dustcover, all I have to do is put two small cap screws in the holes. They should not look too much out of place.

[/IMG]

 

[Brett248Vista]

Or you could just buy a new upper for less than $30 delivered.. So it's no big deal. The counter sunk machine screws turned out nice. How well did the Upper take the threads? I am guessing fairly well, it's a fiber impregnated plastic.

 

[CPTBeaker]

Or you could just buy a new upper for less than $30 delivered.. So it's no big deal. The counter sunk machine screws turned out nice. How well did the Upper take the threads? I am guessing fairly well, it's a fiber impregnated plastic.

It took the threads really well.

 

[Brett248Vista]

This thread needs to be added to the notable thread index! You put a lot of time and effort into not only making this part, but also documenting the process with fantastic CAD work to support it.

 

[FIDDY3]

Man, this is the way these covers SHOULD be done! You really should consider taking these plans to a manufacturer and having them knocked out in bulk and selling them. There is a huge market for these.

Fiddy

 

[kj2082]

Awesome work guys, I'm definitely interested! Would there be any way to make it conform to the curves of the gun better? I know nothing about working with plastic but it would be cool if a guy could make it curve to the shape of the upper for a tighter fit.

 

[Foxtrot]

I took the plunge and secured my dustcover with machine screws. The 3M tape worked well, but something bugged about using tape.

The hardest part was deciding to drill my receiver.

Steps

1 - using a #43 bit, drill two holes in the boss and countersink the holes with a larger bit.
2 - using a #43 bit, drill two holes in the receiver using the boss as a guide.
3 - tap all 4 holes using a 4-40NC tap.

I used two 1/4" 4-40NC screws.

Note: I recommend using a new tap & drill to ensure the holes and threads are crisp.

- 4-40NC Tap was ~$4.00
- #43 drill bit was ~$1.50

If I ever decide to remove the dustcover, all I have to do is put two small cap screws in the holes. They should not look too much out of place.

[/IMG]

I figured you'd get around to deciding on drill/tap/screws before long.

Looks good.

 

[CPTBeaker]

Here's my latest dustcover. Sandblasted to match the finish of the rifle.

Here I used a 3/4" x 1/8" black epoxy coated Neodymium magnet. It's countersunk flush with the inside surface.

 

[PainterlyShotgroup]

Really nice work! Now with this stuff you are able to use wood working tools?

 

[CPTBeaker]

Really nice work! Now with this stuff you are able to use wood working tools?

Yep.

- Table saw, Chop Saw, drill press, belt sander, etc..

Delrin is pretty easy to work with. It's really hard so you have to go slowly if you are ripping it on a table saw. It's seems to me about as hard as Maple, Beech, etc. but not quite as hard as Ebony. I used a standard combination blade on my table saw and chop saw. Using a finer tooth blade would just melt the stuff I think. Also it will melt if your drill speed is too fast.

I used a belt sander to shape the radius areas on my first couple of prototypes. The last one I made, I used a radius router bit for my Dremel and it worked really well.

The Delrin sands and files really well also. Same idea behind sanding wood, start out rough, progressively get finer.

The Delrin takes to sandblasting well also. If you don't have access to a sand blaster / air compressor, no worries. I got an aerosol sand blaster from a local Michael's craft store. It's basically a replaceable air can, and a plastic attachment that holds the blasting media. The kit costs ~$45. It will work in a pinch for small jobs. Obviously it's not something appropriate for mass production. A higher pressure, real sand blaster and an appropriate stencil could be used to approximate the ridges stamped into the surface of a real AR dust cover. By applying a stencil to the face of the cover and blasting away areas that are not the 'ridges' you will be left with an approximation - if you get my drift. I've used this technique on 1911 pistol grips to add logos and grip textures not possible by checkering.

I know you didn't ask about my magnet, but I ordered mine at http://www.kjmagnetics.com/. They sell tons of different sizes, shapes, colors (i.e. black).

Hope this info helps in your endeavor.

 

[CPTBeaker]

Awesome work guys, I'm definitely interested! Would there be any way to make it conform to the curves of the gun better? I know nothing about working with plastic but it would be cool if a guy could make it curve to the shape of the upper for a tighter fit.

Thanks for the compliment!

Reference the fit, if you notice the side of the receiver surrounding the ejection port, it's raised and angled back towards the top rail. The majority of the ejection port seems to be completely sealed by my dust cover because to sits flat on this raised angled back area. There is a little open space at the bottom of the ejection port where the receiver begins to curve.

Can the dust cover be shaped to completely seal the ejection port?...Sure. It would just take more work to do so and would probably make the shape too complex to produce en-mass by hand. Since the Delrin isn't mold-able it has to be shaped/machined. With the appropriate CNC equipment and proper shape programmed, these things would be cake to make, however access to this equipment is not easy to come by for most of us. (Hint..Hint... Tacti cool22 )

Ref. the open space on my cover, it's not visible from the exterior without turning the rifle upside down and peeking in underneath. I would categorize this current design as a 'crud cover' and not necessarily a dust cover, however I do think it fits tightly enough around the majority of the ejection port to keep most dust and dirt out.

...On a side note, unrelated to your question, I have tried firing this from a closed cover and I get ~50% failure to eject w/stovepipes. My current design has the magnet located in the center of the dustcover. With the magnet there, the cover does not flip open early enough. The magnet has to be forward more so the bolt clears it sooner. Something to keep in mind if anyone is planning to make one of these.

 

[jpoz5856]

I'd just like to mention that I thought you did a good job on this. I'd also like to mention that you should have actually filed a patent on it too.

I know it doesn't seem like much, but i've a little bad experience with things like this. I like to design and build my own suppressors. In 1999 I had designed and built a suppressor for use with a 9mm handgun I had at the time. It was a great suppressor, lab measured at 40db reduction with regular off the shelf ammo, a little first round pop but so muted as to be ignored and I could have probably refined it a little more and gotten rid of that, and all you really heard was the metal parts of the gun from any angle. I told a guy at a dealer I had dealt with several times at gun shows over the years about it in general conversation, he seemed interested in wanting to build his own as he had the same handgun. I gave him a copy of the design plans. He turns around and patents the plans, and today his company has made more than a few million selling one of the top of the line suppressors based on that design to the commercial consumer and government markets. I made nothing off it. Its also the reason I don't post pictures of my weapons with suppressors on them so as not to give away clues to another design. Once its in the public domain, its fair game for anyone to rip off and patent.

Ya never know when something like this could make a buck for you. I'm sure there are more then just in this forum that have been wanting a dust cover for their rifle.

A little refinement (the magnet is OK but need firmer more perm attachment and could be smaller - and a better attachment to the weapon other than tape - i'd look into adhesives if I were you if your really going to stick with a no mechanical attachment system) , and you could sell these for about $10.00 each minimum. There are places that will fabricate these for you in thousand piece production runs for probably less than $3.00 per unit.

That's what's wrong with people today, no dignity. Your version indicates you were trying to help a friend and he totally turned around and screwed you! Hopefully you design another stellar product and your able to capitalize financially off of it.

Good luck!

 

[CBR240]

Excellent thread!

CPTBeaker - Outstanding thread! Great idea, awesome pictures, excellent work, and CAD drawings too. I am truly impressed.

 

[2TALLTARY]

Great job!

Great job on the post. I like the whole step by step process. I was also trying to make a dust cover out of delrin I bought at Delrin Sheet, Delrin Rod, Acetal Sheet and Acetal Rod | Industrial Plastic Supply, Inc.. Now with the help of your post I think I can finally complete it. Hope it works.

 

[hakr100]

Wow! I wear loafers because I have trouble tying good knots on shoestrings, so the OP's contributions to the knowledge base and the additional comments just blew me away.

 

[photoracer]

And the final question is, why?

 

[Brett248Vista]

The only logical answer to "Why" is.... Why Not?