Bandook Makes An 80% Lower!

[JAE]

So a fellow Calguns member came by and made a lower with one of the jigs I have. Pretty sure this was the first one he made. I got bit by the 80% bug awhile back, bought a couple of jigs, posted some results and some amount of debate ensued about the jigs. I challenged the jig makers to send some parts and I would try them on a new guy and see how they worked out. This is what happened.

Here's the workstation. As low tech as possible. On the left is the 80% Arms jig and on the right is the Modulus Arms jig. 80% Arms was kind enough to send along a new drill plate. The jig on the left has made about a dozen lowers the one on the right two. Bandook chose to use the 80% Arms jig.


These are the first holes that he drilled. I deviate from the instructions here and drill the rear shelf first. Since you have to remove the rear bolt for this I figure a dull bit would make you press harder and might move the lower around (push it down). So why not start here first with a nice sharp bit, put the bolt back, then do the FCG holes? Couldn't hurt.


After drilling all the holes and vacuuming it out looks like this.


More in next post.....

[JAE]

I want to point out another tip before continuing: notice the vacuum? I can't understate the value of attaching a wet/dry vacuum here like this. There is really no mess. Once in awhile while drilling you have to reach in there and push the chips toward the vacuum because they tend to clog (especially if you use cutting oil). If you don't do this the milling process with the router will literally make a cloud of chips. What a mess! This way the vacuum just sucks them right up. I happen to have a power tool triggered wet/dry vacuum with a hose that is about right but any vacuum will work. That and some PVC pipe and fittings from the hardware store and good to go.

As for lubrication it was only used for drilling and that can you see is a cheap Home Depot oil can filled with even cheaper no name ATF.

One thing you DON'T see here is that there is a little slop in the jig and in order to compensate for that we pushed the jig away from the buffer for the rear shelf holes before snugging it down, and towards the buffer for the FCG holes before snugging it down. Ever see a picture of a lower finished with a jig and there's a little piece of a drill hole left after milling? You won't with this one and that's why. Just a nature of making a tight jig that needs to be bolted together: there will be a little slop. With a little thought you can eliminate this.

More to come....

[JAE]

Now that our holes are drilled he's ready to start milling with the router! See in this picture we are pushing the template away from the buffer before we snug it down? Remember: he pushed the drill block the other way when he drilled it. So just follow the instructions they give and do a bit at a time. Bandook got the hang of it pretty quick.


And after some milling this is what it looks like.


Now for the rear shelf! Remember: push drill block away from buffer for drilling and toward buffer for milling (for rear shelf; opposite for FCG).


See any little left over drill hole edges? See? Told you so! Take a look around at pictures of lowers made and you'll see them. Does it affect function? Hell no. Just for grins. Because we can.

But I forgot something! As we approached the end of the two milling processes we had to make sure.....

[JAE]

Digital calipers are cheap (and so are we!). We expect the best tolerances we can get using cheap tools that can't hold any tolerance really at all. What to do? Buy a caliper and measure BEFORE you remove the template. If you take off the template and try to put it back you'll screw up the width (remember previous discussion on inherent bolt up slop?). So use the depth function, stick that sucker in there and creep up on those last cuts. The jig makers would like you to think you can just use the marker they give you but the truth is most guys are all thumbs and will screw it up. The answer is measure as many times as you need to be sure. Stop a little short and get a feel for the tools, measuring between cuts. Yes? All about results so here are some....

The FCG depth specification is 1.249" plus or minus 0.010". We got 1.247"! Not bad, huh? Here's a picture of our second to last measurement.


And here's a picture of the final measurement before we took the template off.


Here's the rear shelf measurement picture. Spec is 0.630" plus or minus 0.010". We did pretty well.


Next up a little personal triumph of mine: the perfect trigger hole!

[JAE]

Both jig makers have you drilling the trigger hole and then milling it out. This is fine if you have a press, but getting a 90 degree angle by hand is just impossible (Hey, some get lucky. You feel lucky? Well DO YOU PUNK?). Add to that the width of the trigger hole in relation to the drill width and it won't take you long to realize you only have to be off a couple degrees and you get one of those funky trigger holes you see OTHER guys make. So throw away the drill bit for this. Flat out don't use it. Let's do something else....

With the trigger hole template setup place the router on there and bottom the end mill in the FCG. Then, using the fine adjustment on the router, adjust the end mill so it tilts it just a little. Like this.


Lock it in to position, tilt it a little more so it's not touching, start the router and mill out the trigger hole. It's a real shallow cut. It may chatter a little on start but nothing more than milling out the FCG or rear shelf. By the time you get here it'll be child's play. Hard to see in the picture but you get the idea. A few passes later and you'll be through.


And viola! A trigger hole that looks like one.


This is the picture that counts. What you'll see on the finished product.


Anybody comes up with a better way let me know. Let me tell you: doing all that other work only to have a buggered trigger hole at the end SUCKS. That's why I came up with this alternate method.

Not done yet.....

[JAE]

Drilling the side holes (safety and hammer/trigger) is a little different. At this point you have drilled some pretty deep holes and leaned into the thing pretty hard. You need to hit your mental reset button here. Go SLOW and apply steay and even pressure. Use a new bit for the safety holes if you can. Clear chips often. Remember: if you aren't making chips all your doing is ****ing up the jig and dulling your bit! Bandook did just this by going maximum speed with the drill and alternately leaning on the jig heavy and then light. Even at that, the safety holes were perfectly salvageable with a little bit of filing and you'll never see it unless pointed out. With an ambidextrous safety you would never see it.

Drilling the safety.


There's no space for the chips to go here except through the jig. Make sure you clear them by getting the drill out of there periodically. Bandook didn't do this and it destroyed the side walls of the jig. He said he would send me replacements but I just got word from 80% Arms that he asked THEM to send me parts. Let's be clear: I don't work for jig makers and don't get free parts! This is a public service to my fellow 2nd Amendment advocates and BY LAW I can not do the work, charge for the service, or provide lowers or gun parts. It's like hackerspace for programmers..... Get it? So don't poop on it folks or I'll have to bail on it.

Okay rant over.

Here's a picture of the FCG width. Specification is 0.690". We got 0.6895". Damn good. We also checked hammer and trigger fitment before he left. Good to go!


Of an interesting side note, and not mattering one bit, I measure the wall thicknesses at the end. Both of the jigs I tried the wall thickness was different. Looking at the pics of ones made by others; they are too. You would have to be way off, like mill out a side wall, to make a weapon that wouldn't fire. Nonethless interesting data.
Right wall.

Left wall.


So that's all I've got on this one. Soon as I get the jig wall issue squared away I'm ready for the next guy. Would be nice if Modulus Arms sent me a new jig as promised so we can do a write up on that one as well. I think it may still be in process but we shall see. Meanwhile if I continue to host these I may require a deposit for damaged parts. I'm not going out of pocket. This is my hobby and I'm already donating my time and space. Just got a new copy of some ATF rules on the rules.... will do some, er, light reading.....

[Lingwendil]

what router did you guys use for the milling?

[bandook]

Thanks JAE.

@lingwendil, Router is a Bosch Colt - Variable speed. Setting between 4 and 5.
One thing I would add is that it would be a good idea to get a light shining over your shoulder during the milling process. Its no fun running blind while milling. If you do end up running blind - especially when you're almost at the end and the mill end is buried in debris - keep the top drilling template near you so you can see how to run the mill to 'join the holes' when you can't see them.

Drill was Milwaukee cordless 18V. Ended up using both batteries on the top holes.

I did get a message back from 80percent on the offset (one side slightly thicker than the other) Their suggestion was to trace the FCG pocket on the receiver with a pencil first to see if it lined up. It adds a step but I guess it would work.

[golfish]

what router did you guys use for the milling?

Looks like a Bosch

http://www.homedepot.com/p/Bosch-5-6-Amp-1-HP-Colt-Palm-Router-Kit-PR20EVSK/202242735

[JAE]

Any variable speed router about the same footprint will work. I think the DeWalt comes with an LED built in. That would be handy.

As for the FCG this topic came up with another jig maker as well. Much discussion ensued. They pointed something out: look at the print and give me a spec for it. I did and couldn't find one. Curious. Let's think about this in a real world sense though: what does this dimension control? Center of the FCG right? Which controls where the hammer will land right? Now think about the target (hammer to pin) and the size of it. See what I mean? In order for the hammer not to strike the firing pin the FCG would have to be outside the lower. So measure all you want, mark the lower, etc, etc.. And in the end it won't make a difference. Just build them. Buy them cheap and stack them deep....

[sigstroker]

JAE, I don't get at all what you mean by saying there''s slop in the jig. Doesn't the jig bolt go through the pivot pin holes?

I also don't get what you mean about moving something towards or away from the buffer. Isn't it all bolted up?

The jig has those bit depth grooves. Why the need to measure if you use those? The chances of me screwing up a measurement is far greater than sticking a drill bit into a groove wrong.

edit: Also wanted to ask about how big a drill press vice I should get. I see 3", 4", 5", etc sizes.

[JAE]

JAE, I don't get at all what you mean by saying there''s slop in the jig. Doesn't the jig bolt go through the pivot pin holes?

I also don't get what you mean about moving something towards or away from the buffer. Isn't it all bolted up?

The jig has those bit depth grooves. Why the need to measure if you use those? The chances of me screwing up a measurement is far greater than sticking a drill bit into a groove wrong.

edit: Also wanted to ask about how big a drill press vice I should get. I see 3", 4", 5", etc sizes.

OK. Let me try to explain.... If all the parts were in a perfectly temperature controlled environment, both at manufacture and assembly, you could machine them with a perfect fit. If you never ever had any dirt, grit, chips from the process, or anything else ever get in there you could have a perfect fit with no play at all. Had enough of fantasy land?

In the real world stuff needs to bolted together by folks with an average IQ. And no tool experience. You do know the average IQ is 100, right? The definition. OK. Let's just say the shallow end of the gene pool is very... broad. Right.

So there's a little play in there. If you get that little bit of play all one way in the drill process, and all the other way in the mill process, you COULD have the edge of a drill hole left over.Could. Look for pics of lowers made by guys and you'll see them. I've done it. On the first ones. I figured out how to take it out that's all. Looks nicer. Why not? Does it MATTER? Not_one_bit. Just me being picky. If it bugs you ignore it you'll be fine.

Measurements.... Look if you want to use the go/nogo method that's cool. I just like my **** perfect because I can. No other reason. It will work just fine for you. You'll be fine. Just wanted to show folks what you CAN do if so inclined. Dig?

Not sure what size vice that is. 6" I think. That and the two clamps at Harbor Freight were like $30.

[biglou]

Good job I really like the method you used to finish the trigger hole.

[Dano3467]

Thanks JAE...nice write up, & good pic's, also good service/hobby

I see your in Los Gatos, awesome town...

[80% Arms]

Great work guys! Keep in mind that JAE doesn't work for us or the red jig company. He volunteers his time teaching and giving tips to first time builders because he believes in your 2A rights and wants to promote it. It can take a few hours of his time with a first time builder. Just because he doesn't charge anything doesn't mean his generosity can't be reciprocated.

Remember, you don't need to overthink things. Our Easy Jig is designed to simplify and speed up the process compared to traditional jigs. The built in depth gauges tell you how far to go. Read the directions and watch the videos. Go slow on your first one so you don't overlook anything and you'll get great results.

After doing a couple you probably won't even look at the end mill in the template when joining the holes. You simply work from the center out until you make your finishing pass with the end mill gliding against the template. Your end mill should be cutting smoothly the full time. You can feel it and it will tell you if you are pushing it too fast.

Keep up the great work and remember to have fun in the process.