Here's my story about finishing an 80% lower... and some of the tips I noticed along the way. This little project started life as a H2 Targets billet 80% lower and their jig/drill bit kit. I'm happy to say that I didn't need to modify their jig kit to fit the billet lower (i.e. around the flared mag well). However there were some fit issues when putting the jig on the lower. That's one of the big tips I've got for a person with no machine experience. The second big issue I had with the kit is the drill bits. Go ahead and plan on buying a good quality drill bit in each size- particularly the 1/8" and 3/8". I noticed that the 3/8" bit in my kit was slightly out of round- a pretty big issue if you're trying to drill 3/8" hole.
Ok- so first thing is the kit and lower:
The lower looks OK overall. There's some funk on the finish on the right side of the mag well and the first thread on the buffer tube was broken. Not a big deal because I'm going to finish it after it's drilled and a file will clean up the broken thread. Overall, looks pretty decent.
The side plates on the jig fit nice and tight against the lower with the installed dowel pin and the socket head cap screw that goes through the lower. However, I'll talk about the drill plate to side plate alignment a little later.
Now for the first pitfall... Pay close attention to the jig/lower alignment. Just having the jig doesn't quite mean you're on autopilot. I had to play with the jig to get it lined up with the top of the lower. I finally ended up holding it down agaist a flat piece of bar stock and then tightening the screws through the side plates.
Jig misaligned- too high at front:
Now that the side plates are on, it's time to drill the safety, hammer, and trigger pin holes. This isn't bad at all really. Nothing to comment on- just use tapping fluid and cut slow. Well, there is one thing to note- there are only holes in one side plate. You'll have to drill into the other side plate to get true through holes. You can definitely feel the difference when the drill bit is through the aluminum and into the steel side plate.
The next installment will cover the holes on the drill plate/side plate that don't line up worth a crap. Three screws are no problem, but the fourth wasn't close to going in. But there's a way to make it work.
Ok, so now I've gotten to drill a few holes and it's all going pretty good so far. I'm excited. Following the sparse instructions, next you simply bolt on the drill guide plate and drill enough holes to make your shoulder sore from operating the drill press. So let's bolt on the drill plate (the one with the crap ton of 1/8" holes).
Do those holes look right to you? Three screws, no problem. But number four wasn't having any part of this.
Ok- so what the hell? I ended up putting the drill bits through the hammer pin and selector holes to help maintain alignment and loosening only the upper rear screw that holds on the side plates. This allowed me to get the fourth drill plate screw in. Then I re-tightened the side plate screw. So good to go, right? No. Now the drill plate isn't quite lined up with the side plates on the jig.
So loosen the screws again and align it using the flat plate, then tighten everything down again- now the plates are all nicely aligned. So now set the depth on your drill press. Lower the bit until it just touches the top of the drill plate and use a caliper to set the depth stop.
I'd recommend breaking this step up into two different days... but that's just me. It's easy to get excited and anxious and start rushing things. You know you're drilling too fast if it's hard to get the bit going in the hole after bringing it up to clear the chips and add tapping fluid. If it feels like you're breaking through when you start to drill deeper, slow down because you're making too much heat. Anyway, drill about a 1/4" deep and then bring the bit up to clear the chips. Add fluid, keep drilling until the depth stop bottoms out. And repeat. And repeat... repeeeeeaaaat.
Oh- and I left out a heart stopping monent when drilling all those 1/8" holes. I should probably let you find this out for yourself.... but what the hell- you're going to break through the hammer/trigger/selector holes you've already drilled. Sounds like common sense, but I never thought about it when I started drilling that hole pattern. The first time the bit broke through one it was a serious oh **** moment. I thought I'd screwed something up and drilled through the bottom of the lower.
Ok, so now more drilling to open up the middle of the lower. This went quite fast compared to all the 1/8 inch holes. I did notice the 3/8 bit flexing when drilling adjacent holes because there wasn't enough material left to the open side to support the bit. I ended up with slightly sloped sides, but that's going to get fixed with a file later.
Time lapse is a wonderful thing... so here's the lower with the chips cleaned out- pretty even drilling so far.
Now, finally it's down to the last through holes for the trigger. You've got to go slow on these holes because they don't really line up with anything that has been drilled before. Let the drill bit get started and then it will track straight. And here's where I made another mistake (probably because it's been a week since I last worked on this thing). When drilling the trigger holes, I started drilling and then the bit just wouldn't go any farther. So I did what you're not supposed to do and pushed harder. I figured the bit was toast, so I went to a smaller size and was going to drill up from there. Not the problem- the depth stop was still set. As usual, the problem was operator error and not the machine. Move depth stop up and finish drilling.
Not perfect, but not bad. I'm going to clean the sides up with a file to make them more even.
Ok- so first thing is the kit and lower:
The lower looks OK overall. There's some funk on the finish on the right side of the mag well and the first thread on the buffer tube was broken. Not a big deal because I'm going to finish it after it's drilled and a file will clean up the broken thread. Overall, looks pretty decent.
The side plates on the jig fit nice and tight against the lower with the installed dowel pin and the socket head cap screw that goes through the lower. However, I'll talk about the drill plate to side plate alignment a little later.
Now for the first pitfall... Pay close attention to the jig/lower alignment. Just having the jig doesn't quite mean you're on autopilot. I had to play with the jig to get it lined up with the top of the lower. I finally ended up holding it down agaist a flat piece of bar stock and then tightening the screws through the side plates.
Jig misaligned- too high at front:
Now that the side plates are on, it's time to drill the safety, hammer, and trigger pin holes. This isn't bad at all really. Nothing to comment on- just use tapping fluid and cut slow. Well, there is one thing to note- there are only holes in one side plate. You'll have to drill into the other side plate to get true through holes. You can definitely feel the difference when the drill bit is through the aluminum and into the steel side plate.
The next installment will cover the holes on the drill plate/side plate that don't line up worth a crap. Three screws are no problem, but the fourth wasn't close to going in. But there's a way to make it work.
Ok, so now I've gotten to drill a few holes and it's all going pretty good so far. I'm excited. Following the sparse instructions, next you simply bolt on the drill guide plate and drill enough holes to make your shoulder sore from operating the drill press. So let's bolt on the drill plate (the one with the crap ton of 1/8" holes).
Do those holes look right to you? Three screws, no problem. But number four wasn't having any part of this.
Ok- so what the hell? I ended up putting the drill bits through the hammer pin and selector holes to help maintain alignment and loosening only the upper rear screw that holds on the side plates. This allowed me to get the fourth drill plate screw in. Then I re-tightened the side plate screw. So good to go, right? No. Now the drill plate isn't quite lined up with the side plates on the jig.
So loosen the screws again and align it using the flat plate, then tighten everything down again- now the plates are all nicely aligned. So now set the depth on your drill press. Lower the bit until it just touches the top of the drill plate and use a caliper to set the depth stop.
I'd recommend breaking this step up into two different days... but that's just me. It's easy to get excited and anxious and start rushing things. You know you're drilling too fast if it's hard to get the bit going in the hole after bringing it up to clear the chips and add tapping fluid. If it feels like you're breaking through when you start to drill deeper, slow down because you're making too much heat. Anyway, drill about a 1/4" deep and then bring the bit up to clear the chips. Add fluid, keep drilling until the depth stop bottoms out. And repeat. And repeat... repeeeeeaaaat.
Oh- and I left out a heart stopping monent when drilling all those 1/8" holes. I should probably let you find this out for yourself.... but what the hell- you're going to break through the hammer/trigger/selector holes you've already drilled. Sounds like common sense, but I never thought about it when I started drilling that hole pattern. The first time the bit broke through one it was a serious oh **** moment. I thought I'd screwed something up and drilled through the bottom of the lower.
Ok, so now more drilling to open up the middle of the lower. This went quite fast compared to all the 1/8 inch holes. I did notice the 3/8 bit flexing when drilling adjacent holes because there wasn't enough material left to the open side to support the bit. I ended up with slightly sloped sides, but that's going to get fixed with a file later.
Time lapse is a wonderful thing... so here's the lower with the chips cleaned out- pretty even drilling so far.
Now, finally it's down to the last through holes for the trigger. You've got to go slow on these holes because they don't really line up with anything that has been drilled before. Let the drill bit get started and then it will track straight. And here's where I made another mistake (probably because it's been a week since I last worked on this thing). When drilling the trigger holes, I started drilling and then the bit just wouldn't go any farther. So I did what you're not supposed to do and pushed harder. I figured the bit was toast, so I went to a smaller size and was going to drill up from there. Not the problem- the depth stop was still set. As usual, the problem was operator error and not the machine. Move depth stop up and finish drilling.
Not perfect, but not bad. I'm going to clean the sides up with a file to make them more even.
