Boring a D mag for 4-AA... hand tools only

I wanted to build a 2D mag with an MT-G2 as a present for some in-laws. Only hitch was, they didn't want to get into fancy lithium ion batteries. So, inspired by Old-Lumens and kyfishguy ( https://budgetlightforum.com/t/-/26363 ) in particular, I figured a bored out 8-AA mag was in my future.

Justin's excellent thread is here: https://budgetlightforum.com/t/-/9451 ... it covers just about everything you'd need to know, but problem was, I don't have a drill press. (If I'd thought long and hard about it, I probably should've tried harder to find a drill press, but what-cha-gonna-do?)

Anyway, I figured a hole saw with a dowel stuck out of the end would keep the saw centered in the mag body.

That pic might be all you need to move forward on this project. What follows is a bit more of a step by step, with some of the quirky things I discovered along the way.

Justin mentioned getting a hole saw off ebay. I figured I had a 35mm saw already waiting in the garage, but unfortunately, the mandrel the saw attaches to is bigger than 35mm. So, off to ebay for a Morse TAC22 1-3/8" hole saw. This had an attached arbor, and the welds didn't need to be knocked down because they were within the 35mm diameter. The other happy bonus was the arbor was 3/8", which matched the extension I already owned. The hole saw didn't come with a pilot bit, which was okay because I didn't want one anyway, but odd nonetheless.

To find a suitable dowel, strip your mag down and take the tube to your favorite big box construction retailer. I found one that was a little loose at 1-5/16". If you can find a perfect friction fit, then go for it, but I had to pad mine out a little with iron-on wood veneer. (Note that I used wood, rather than plastic... I doubt plastic would work well with all the friction.)

After I set the glue (the blue thing is a heatgun), the fit was a tiny bit loose, but not too bad. Another layer of veneer would have been way too tight. I'm not sure if it mattered, but I wound it so that the drill action in use wouldn't try to unroll the veneer.

To get the dowel seated inside the holesaw, I made a right mess and had to make up for it with masking tape. Next time, I'll either do it precisely with a router, or whittle a bit of a point on the dowel and run the hole saw onto it. Either way, you want it centered and snug.

Now it's just time and effort. I went in through the head end to avoid ruining the threads in the tail. I'm reluctant to admit it, but I didn't use any lube... just slowish with lots of cool-down breaks and repeated clearing of the swarf. I turned the mag tube occasionally while drilling, to offset any bias to one side or another. I was surprised and pleased that the cutting was extremely even all the way down. (I tried taking pics to prove this, but you'll have to take my word for it.)

Once I got close to the tail end, I pulled the dowel off so I could watch the saw cutting the last bit and not wrecking the tail threads. As it turned out, I only scuffed them a little.

The interior looks like it's been scratched to death by zombies. I'm not sure I'd drive a truck over the light now, but I think it'll do fine as a yard sweeper.

And it fits 4- Duracell Ion Core AA batteries. Yay!

So, next I need a battery carrier. (FT is out of stock, so I'll have to diy it.) If I discover a magic way to make one, you'll read about it here.

Questions?

I think you can Oshpark the carrier if nothing else works. Some good ideas here too. I like the veneer.

Looks like a lot of hours were put in already. If you want a smoother finish inside a bet some adhesive backed emery cloth or sandpaper put onto the dowel would work great.

And for the battery carrier, just run a 1/4” SQUARE dowel up the center of the tube. You could cut off a piece of that same large dowel you used, center drill a hole, then chisel/file it square, then just glue in the square dowel. Put a large donut shaped contact ring at the front and run a wire to your switch. You could build up the O.D. of the large dowel with a veneer first, then whatever tape that’d work to make a good friction fit, and jam it into the tube to the proper depth. The negative end gets a little tricky but it’s not too bad. You can use the square dowel as a key and make a PCB yourself out of full faced copper ones at Radioshack (hurry before they’re gone). Solder on four springs on the one side, then a big one on the other. A P60 drop-in ground spring comes to mind here. Remove the ano from the bottom of the tail cap and you should be good to go. Heck, you might even be better off modifying the stock tail spring like many other people have demonstrated before since depending on the spring rates you use for the 4 little guys (I’d recommend a relatively stiff spring) then the P60 spring might be too soft to not bottom out.

Just my 2 cents.

Would a brake cylinder hone with a bit extension have done something similar? Not sure if anyone has tried it.

I have, but it takes time, I was thinking in gluing pieces of metal files or coarser stones to make it cut faster

Hmm, I could see putting some cheap harbor freight diamond stones on there and making it cut quicker

A brake cylinder hone would take forever. The method I’ve used is to take a smaller hole saw or drill bit and build it up with tape then a final wrap with sand paper. It still takes a long time but turns out very clean. For Mininags it’s start with a 3/4 step drill bit to establish the 3/4 hole then 3/4 hole saw to get a flat bottom to the hole then tape and sandpaper on a 5/8 bit to smooth it out. Using the dowel to stay centered is a great idea and you probably only need a short bit sticking out instead of the long piece used here. If the dowel slips then the inward set teeth might wear a ring in the dowel and get sloppy towards the end so it might help to bend or grind them out but that’s a trial and error thing.

Love the dowel idea! If you use cutting lube, the cut will end up being a lot smoother. It's messy, but it does make a nicer cut. To smooth the one you have, you might try using a piece of metal rod stock and cutting a slit, so you can put several strips of emery paper in the slit and make your own flapper sanding wheel. You might even find one in one of the automotive stores.

Nice. 10 out of 10 for effort and achievement.

Hey, thanks for all the good ideas and positive vibes.

I’m going to try wrapping the dowel with sandpaper for a bit of smoothing… we’ll see how that goes.

And I hadn’t seen the oshpark/helios carrier before — thanks for that link. Still trying to decide if I want to get the minimum order of 3 sets. (Though if anyone had one set gathering dust, drop me a PM…)

Great job using your head to get it done. The dowel method may be superior to using a drill press in terms of keeping the cut straight. Might try it next time. I will be following this thread to see how you deal with the switch diameter in the over bored tube. More veneer perhaps?

Hmmm, hadn’t given that much thought until now. My initial thought was that I could just wind the switch tighter with the mounting screw… except that means there’s no lip for the rubber switch cover to seat under.

So I think you’re right that there’s more veneer in my future. (Or maybe masking tape. Shhh!)

In other news, I spun some 80 grit sandpaper inside the tube, and it looks a ton better. My self respect is intact.

now that's a neat way of doing it! Using a dowel to guide the holesaw was an excellent idea, well done. To be honest, even on a lathe boring that depth would be hard, so it's a technique that I'm going to squirrel away in case of future need.

Do it again with 220 and you’ll be really happy…