Ok, I will be the first to call myself a dumbarse.....and you all have permission as well, just know we have already established this! :-[ <thumbsup>
Soooo, a while back I was preparing to put together one of my two KD lowers. I had my set screws and tap from previous attacks on lowers. Only a couple times, but this wasn't going to be a first attempt. Now for a side note **I make zero claim to be mechanically competent. It's sad, but my skills aren't what they should be. Back to the lower. I drill the rear take down hole out with the recommended bit for the tap I had. I won't be giving those numbers because this was probably a year ago and I don't remember them. I start to tap the hole. Slow and steady, take her in a little and back her out. Oil? Naw...didn't need it the last few times...why use it now?? I get about halfway in and she binds on the way out....SNAP!! Insert a good handful of words we can no longer say on the forum right....here. At this point there was still a small piece sticking out. "Sweet...where are my pliers?" I grab onto the nub and give her a little twist...SNAP!! This happens a couple times until there is no more to grab onto. "Well that sucks...where's my drill?" Now...not being the most mechanical, I am also not the most well equipped for projects like these. I clamp the lower to a table (due to lack of a vise) and grab the hand drill....
Shhhhhh. Can you hear all the hands that just slapped foreheads?
As most of you have already guessed...that was a terrible idea. We will skim over that one and just say it didn't help. At all. In fact, now we are just making it worse. At this point, in went back on a shelf for a few months until I decided I really needed to take care of it. I took it up to my dad's where we have a few more tools available and this time tried my luck in the drill press(with oil this time too). No luck. Those taps are friggin hard! Though extremely brittle...which gave me another idea....lock it in the vise and beat it with a punch. Nope. Nothing moved, broke. On to what I thought was my last tool to attack this thing with. "Bring me the dremel!" Tried digging at it with a few tips...still no go. Put the cutting wheel on and just gave in to the fact that I was going to have to do some damage to make this work. I cut a slot in the tap along with a slot into the lower receiver itself. It'll get covered and it will be OK I tell myself. Now that I have a nice slot I destroy a screwdriver to make a perfect fit. Don't worry...I destroyed a crappy screwdriver....and that was a mistake. The tip broke off that little bastard right away. So then I destroyed a good one..... ::) Annnd....SNAP!! There goes the tap....again....along with another string of non 308AR approved words. I kept my cool though. I managed to override the beast on my shoulder who thought I should chuck that hunk of metal across the shop. After all...it was my dumb fault I was in this mess, not the Aluminum.
Which brings us to now. With the start of these couple of builds...it was time to fix this. I resorted to the internet. I hate Google...she can find anything and with the first search of "how to remove broken tap from aluminum"....she had a million answers. Apparently model engine builders get this a lot. Chemistry is your friend. The answer is an old household product that was used in everything from pickling to athlete's foot treatment.
ALUM. Aluminum Potassium Sulfate.
Boil water, add crystals until she wont take no more, back it off to just below boiling...they say 200degrees, insert part....wait. The Alum acid will attack ferrous metals and rapidly oxidize them while leaving the non-ferrous metal alone. It basically rusts away right before your eyes. Length of time will vary depending on the size of the tap you need to "erase".
I was a little concerned about the anodizing....and pretty sure it was going to be destroyed. At the 15 minute mark...my concerns were confirmed. Damn, guess I'm gonna have to Cerakote this one. Shucks >:D
So, took it out every 15 minutes to check. It was looking pretty good at 45 and was GONE at one hour. Looks like I crossed up a little as I was backing out and that's what seized it...well that, and the lack of OIL...please...use OIL if you are gonna tap your lower. Save the hassle and embarrassment. The only reason I am sharing this is to hopefully save one of you the trouble someday...and I don't really care if I get laughed at. I screw up a lot...I can admit it. :banana:
So here she is...ugly, but sans-broken tap <thumbsup>
