I recently acquired Glen Zediker's book "THe Competitive AR15 Builder's Guide" and have chosen to use this as my resource for my first build. I have all the parts and tools and am getting ready to start the lower. QUick question though. PRior to starting the build be states that I should ream out the holes with machinsts drill bits. I will be using Cobalt bits, but it's the sizing that's confusing me. How does a #22, 23, and 40 correlate into inches? Are the drill bits labeled as such at the store?
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Machinsts Drill Bits For AR Build Question
- Thread starter RLinNH
- Start date
Here you go. Yes, they are labeled at the store, however you may to find a machine supply shop to find lettered and numbered drill bits.
McMaster-Carr is going to have everything you need. They have a website and their shipping is quick.
Because you're just clearing paint or Cerakote from the holes, high speed stella will work just as well as cobalt, and will save you some coin.
McMaster-Carr is going to have everything you need. They have a website and their shipping is quick.
Because you're just clearing paint or Cerakote from the holes, high speed stella will work just as well as cobalt, and will save you some coin.
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Yes, you can get numbered drill bits from a real tool store, but you won't be finding them at home depot or the such.
if you need to start reaming out holes on a an ar receiver, you are buying parts with really poor qc. I've assembled more than I can count, and can only think of one I ran a bit through a single hole. If its out of spec, send it back.
if you need to start reaming out holes on a an ar receiver, you are buying parts with really poor qc. I've assembled more than I can count, and can only think of one I ran a bit through a single hole. If its out of spec, send it back.
If you need to ream out holes, you should not do it with drill bits.
You should do it with hand reamers (or chucking reamers) if using a power tool.
Drills are for making holes. Reamers are for precisely truing holes. They are two totally different animals and not interchangeable.
And I can start on Pin hones if you want to talk about aligning holes and truing them to tenths.
I don’t know the book or the author. But if I read a book that said “Start by using drills to ream out holes...” I’d get a different book.
Sirhr
You should do it with hand reamers (or chucking reamers) if using a power tool.
Drills are for making holes. Reamers are for precisely truing holes. They are two totally different animals and not interchangeable.
And I can start on Pin hones if you want to talk about aligning holes and truing them to tenths.
I don’t know the book or the author. But if I read a book that said “Start by using drills to ream out holes...” I’d get a different book.
Sirhr
Actually, the book says to use the drill bits by hand just to ream out any burrs and such. And the upper/lower/Rail I am using is an Aero Precision Builders set. So I don’t think I’ll need to ream, but I am a stickler for directions...
Screwdriver: chisel, prybar, punch, awl
Drill: reamer, chamfering bit, deburring tool
Sirhr
I was going to suggest to twist them by hand. This method is suggested is more places than one, that I've seen, in regards to AR building. While I do not think it is the CORRECT method; if the proper sized bit is used, it works great for quick cleaning out of holes. Aluminum is soft though, and a sharp bit, even turned by hand, can oblong the hole you're trying to "correct".
I feel that Aero is in the upper echelon of "budget" - mid tier receiver sets. I have assembled, and own/owned, many of them. You should not need to make any adjustments or modifications to the finished sets. If you do, contact Aero. Best of luck, building gives great reward, and teaches great lessons. Welcome to your new addiction.
You know your going to have to deburr those holes after towing ....
There are very few AR parts that are currently not being made on CNC machines. Do you think you are more precise than those?
I've never reamed a hole either. I usually put a little oil on the roll pins for the bolt catch and trigger guard and drive them in without issues. One thing I always do now when assembling a lower is I thread the hole for the take down pin with a 4-40 tap. Some manufacturers do that when they make them, Aero Precision is one. It makes installing the receiver extension much easier. You just have to trim a little off the spring to account for the set screw length.
If you are having to ream holes than someone’s product needs to be sent back. There is zero reason to need to do that.
I may be wrong, but I think it is possible to buy over-sized pin sets, specifically for building very tight-tolerance lowers.
That said... there is not much 'need' for a very tight tolerance lower. And while the upper-to-lower retaining pins can cause issues if extremely loose, there are camming pins on the market that can lock the upper and lower together.
I am in agreement that after building more AR's than I can count... I have never needed to ream a pin hole.
But if one DOES have to ream a pin hole... doing it with a drill would not by my method of choice!
Sirhr
No need to ream anything on Aero products. I would skip that step. All your pins, doo-dads, and thing-a-ma-bobs will fit in there both fine and dandy.
I personally also use the ol' German method for the castle nut on the receiver extension: Goodntight.
Most Aero lowers have a nylon tipped screw under the grip, that can be adjusted to remove upper/lower "slop". Makes pushing the takedown pin a little tougher, but does remove a little play.
To the OP; there are also "accu-wedge" products for the rear to do the same thing. An O ring around the boss in the upper, for the pivot pin, will tighten up a little also. Again though, I've tried these, and ended up not needing them with Aero sets
Keep the drill bits away from your completed lower, unless you're intentionally trying to make the holes sloppy and loose. There's no good reason to do that, regardless what that book says. IF you find a hole that has a ding in the edge, massage out the ding or send it back. The last thing you want is to cut through the wear resistant hard anodized surface into the soft aluminum underneath.
Keep that crap away from your AR receivers too. See my post right above yours about cutting through the anodizing layer.
We aren't talking about deburring holes on unfinished machining projects. We're talking about finished AR receivers here; they don't need deburring unless someone really screwed up, and if they do, try to massage the burr out instead of cutting or lapping anything.
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