Sunday, August 29, 1999

Dimpled Swell Neck Rivets VS Flat Non-countersunk

Here's the deal with dimples in an AK:

The "front trunnion" has one hole - each side - that is countersunk drilled. The "receiver sheet metal" is drilled to the center hole size. And then smashed around the edges to match the countersink in the trunnion hole below it. So that you then have a countersunk trunnion hole and a matching countersunk receiver hole. Then instead of using a rivet head that is flat at the bottom neck (opposite side of the head from the top). You use one that has a corresponding countersunk or "swelled neck" to match the countersink in your receiver/trunnion. Make sense? The rear trunnion/tang holes are the same way - countersunk.

Here is a pic of a normal "flat" neck rivet:

Here is a pic of a "swelled" neck rivet - although the ones we use on AK's are less complicated. Ones we use have the same round top as above with a full "countersink" bottom on the head. But this is the best pic I could find. You get the idea:

The raging debate is whether or not this countersinking or "dimpling" of these rivets/holes add any strength to the build. Or if it was originally just used to line up the holes in the receiver to the holes in the trunnions - when the went to line them up in their rivet machine. Meaning the Russians or whomever.

So the simple question is - does "countersinking" (or dimpling) rivets make a build stronger? And if so, by how much? Enough to go to the added trouble? Cause it's a b**ch to get the dimple in the receiver sheet metal. Or at least an added step. Most of the time it works but sometimes it doesn't. And your left with a hole that just won't seem to take a dimple. If you end up with a bad rivet head it's usually one caused by having to deal with the dimpling. Whereas a flat neck rivet goes in smooth every time. Alot of the later model Yugo's don't even use the dimple and swell neck rivets.

The area around the hole in the receiver sheet metal that is dimpled (or countersunk smashed) is very tiny. Less than a MM wide around the hole(?). IMHO countersinking swell neck rivets are not that necessary. Flat heads will work fine.

Saturday, August 28, 1999

Trunnion Jig Recommendation

Drilling your own trunnion holes (especially if your trying to do an underfolder without a template) can be a real pain. But I'll tell you what is making this a breeze now. I bought a trunnion drilling jig a couple months back. (It's not the one shown below. But the same idea.) I threw it in my build tool box. And forgot I had it. Had never used it before. It's basically like the one below. Except it expands more with what looks like a big concrete bolt hole holder thing. You know those things you put in a hole in concrete or cinder block to hold a screw or big bolt? Like that. Except BIG. You screw the bolt in and out to make it expand or retract to the size hole you need.

The jig is meant for the front trunnion barrel hole. But I fiddled around with it and got it to hold the rear uf trunnion. Which is kind of odd shaped to get ahold of and still be able to slide the receiver on all three sides.

The jig holds the trunnion in place so you can center your bit perfectly in the drill press. Then slide the receiver on and drill the hole. PERFECT placement. No measuring. No tape templates. It's a pretty common jig but mostly used for front trunnions and AKM full stock rear trunnions (has screws to hold those in place).  I don't know if the one below would have big enough couplings to work on the UF rear trunnion. But even if this thing saves one $100 Nodak receiver from getting mangled with bad placed holes it's worth it's money. It's definitely worth it for the time it saves you. And the underfolder has some pretty non-typical holes to be drilled. And this things makes it so you can place them perfectly without any measuring or guesswork.

Friday, August 27, 1999

Careful Cosmoline Removal

This has probably been read before. But I found this nice section of the Cosmoline Removal post on It pertains to removing cosmoline if you don't want to also remove the original finish. Like what happens when you use brake cleaner or put it in the dishwasher:

"The stock is a different matter. Water and harsh chemicals are simply poor choices for cleaning wood. Chemical companies have been working for many years to develop cleaners for wood, only a few of which are water based. Murphy's Oil Soap is one such product that can be used in reasonable quantities on wood. The heavy duty "green" and "orange" cleaners are simply not appropriate for cleaning wood stocks. They contain harsh chemicals that are absolutely not necessary for cleaning cosmoline. So if your objective is to do nothing damaging to the wood while simultaneously removing the cosmoline, do NOT use any water based cleaners and avoid "grease cutters" like oven cleaners. They are extremely harsh chemicals (like, why else are you supposed to wear gloves if they aren't harsh?) and are NOT GOOD FOR WOOD.

So, let's explore the correct way to remove cosmoline. As mentioned above, gentle heat is by far the best way to liquefy and remove cosmoline. If your oven is big enough you can put it in there at "warm" (lowest possible oven setting) and it will bleed the cosmoline out from the pores of the wood. Wipe it down every 15 minutes with old toweling until the weeping has stopped. If that won't work due to size or domestic issues you can put it outside in a plastic bag, some people like black because it absorbs the heat of the sun better and some prefer clear because they opine that the direct sunshine generates more heat. This will take a little longer but it's important that whenever it starts to cool down that the stock be removed and wiped dry. I kind of like the creativity of the "dashboard" process which is a sheet of tinfoil bent up to hold liquefied Cosmoline and set on the dashboard of your vehicle. I haven't done it but it sounds like a great plan to me if you have a place where you can do it without tempting someone to "borrow" your stock. The latest method is a wrap in rags, VERY tightly sealed in a plastic bag, and a bath in the hottest water you can get. Haven't tried that one but it sounds pretty reasonable to me. Word has it that you can add boiling water from your stove to the hot water from your heater and get pretty satisfactory results.

I am going to build a "cosmo coffin" that uses light bulbs for heat but haven't done it yet. It's one of those projects that I'll get to when I get a round to it.

Word of warning - When baking your stock make absolutely sure that it's positioned in a way that will keep it from close proximity to the coil. I understand that modern gas ranges have plates above the burner so they should be fine as well. Also, if you are using a rag to remove the stock and/or hand guard from the oven, and the element is in the heating mode, if the rag touches the element it WILL begin to smolder, virtually immediately. (Please don't ask how I know.)

The point is, GENTLE heat will melt cosmoline away from both wood and metal with NO ADVERSE AFFECTS on either the wood or the blued or bright metal. After a couple of hours of 15 minute heating cycles, wiping between cycles, just let it cool and wipe off any remaining surface cosmoline with mineral spirits.

It's also a good idea to keep ANY solvents or cosmoline out of your drains. They are petroleum based and float on water. This means that they are not going to flow easily through the traps and are likely to gum up and/or clog drains. Everybody has to figure out the best disposal method in their particular circumstances.

So, that's about it. If you want to put your mil-surp rifle back into the condition it was in prior to going into storage, be patient, be gentle, and be thorough. You will ultimately be very, very glad you took the time to do it right, the first time. And if you are going to refinish you will not be disappointed by having the cosmoline seep up into and/or through your finish of choice. When you do it right you will find that the stock will take just about any finish that you like."