DNP Posted July 22, 2013 Report Share Posted July 22, 2013 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> Quote Link to comment Share on other sites More sharing options...
sketch Posted July 22, 2013 Report Share Posted July 22, 2013 That was painful bro but now we know! Thanks Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 (edited) Man, I can't believe it worked. I also can't believe my wife let me do that on her stove! Editing to add: Total cost of the beaker and a 500g bottle of Alum shipped to my door was just under $30. Could have save about $6 and got the 100g bottle. Didn't know how much I would need. Edited July 22, 2013 by DNP Quote Link to comment Share on other sites More sharing options...
sketch Posted July 22, 2013 Report Share Posted July 22, 2013 Weird science! Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted July 22, 2013 Report Share Posted July 22, 2013 Damn it! I have a tool designed to remove those buggers. You would've been done in few seconds. I had a similar issue a while back happen to me. I bought the tool, used it once, and never ran into the problem again. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted July 22, 2013 Report Share Posted July 22, 2013 Very cool! Quote Link to comment Share on other sites More sharing options...
mineralman55 Posted July 22, 2013 Report Share Posted July 22, 2013 Glad you got it fixed. As you learned, always use tapping fluid... even in aluminum. I got to thinking about how your process removed the anodizing and I'm trying to understand why. Anodizing is aluminum "grown" onto the surface of the substrate. There is no ferrous material involved so why did your "acid" solution take it off? Chemists chime in here. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 I don't know...but if oven cleaner didn't work so well, I would highly recommend this stuff as a stripper. Quote Link to comment Share on other sites More sharing options...
392heminut Posted July 22, 2013 Report Share Posted July 22, 2013 (edited) Dirk, another thing I've learned in all my years of gunsmithing is that taps DO wear out! When they start getting dull you're inviting disaster by continuing to use them. I'm not sure how hard aluminum is on a tap or how many times you used that particular tap so I'm not passing judgement on your actions, just stating what I've learned. When I built my son's STI 2011 I used a slide that already had the Bomar sight cut from the factory, but for some strange reason they don't tap the elevation screw hole! STI slides have a reputation for being some hard steel I found out later, AFTER I broke the tap off in the slide! The tap had been used maybe 5 or 6 times before, and yes, I was using oil. Fortunately my machinist friend in El Paso is also an excellent welder and after a phone call and an afternoon drive to El Paso the problem was solved. The guy literally welded up a nub on the very small part of the tap that was protruding and then just took a pair of pliers and turned the tap out! I ordered a new tap from Brownells and finished the job. I could definitely feel the difference between the old tap and the new one when I finished tapping that hole. BTW, cool solution you came up with! I definitely have to remember it in case I have a similar problem. Taps are evil! Just when you think things are going great they will mess your day up! Edited July 22, 2013 by 392heminut Quote Link to comment Share on other sites More sharing options...
imschur Posted July 22, 2013 Report Share Posted July 22, 2013 I will add my 2 cents. Whenever possible use a tapping guide. #8 and smaller can be quite tricky freehand in aluminum. Make sure you use a lube that works on Aluminum. Brownells smartly carries a lube that is good for everything. It's called Universal Do-Drill. Do not use a lube not designed for aluminum. We use Tap Magic Aluminum and Cool II at the day job The proper Tap type and quality is also important. Spiral point taps work very well in aluminum. The chip will string out and not bind in the hole. Forming taps work well too. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 Great info you guys are adding. This was my hope for this thread. A lot of us non mechanical folk try to attack things we just don't know enough about. Tips like these could help save a lot of time and heartache for the next guy who wants to do it, but has no background experience in tapping. Thanks for all the ifo guys! Quote Link to comment Share on other sites More sharing options...
imschur Posted July 22, 2013 Report Share Posted July 22, 2013 Good point. Sometimes we take some of this for granted. BTW Brownells sells Broken Tap Extractors. This is exactly what we use at the day job. Quote Link to comment Share on other sites More sharing options...
texas30cal Posted July 22, 2013 Report Share Posted July 22, 2013 (edited) As imschur stated spiral point and forming taps, make sure you use a machine shop quality tap made of HSS, NOT a tap out of a tap and die set. Try to avoid anything with more than 2 flutes they are just waiting to break off. Call me stupid but what the hell is making this line ! Edited July 22, 2013 by imschur Quote Link to comment Share on other sites More sharing options...
imschur Posted July 22, 2013 Report Share Posted July 22, 2013 you accidentally clicked strikethrough in the toolbar. Its the "S" symbol Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted July 22, 2013 Report Share Posted July 22, 2013 Good point. Sometimes we take some of this for granted. BTW Brownells sells Broken Tap Extractors. This is exactly what we use at the day job. I've used similar in automotive work, they are a godsend sometimes. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 Lol. Yeah...my Home Depot tap had 4 flutes. It's the little things that make a difference. The right tool saves you money every time. Quote Link to comment Share on other sites More sharing options...
imschur Posted July 22, 2013 Report Share Posted July 22, 2013 There are all different kinds of taps. It can make you nuts. If you dont have Amazon prime places like MSC, Grainger and Mcmaster Carr will have stuff in your hand typically next day. MSC and Grainger have a lot of local branches open to the public. None of those three typically sell crap as far as taps go. Mcmaster has a great selector tool. Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted July 22, 2013 Report Share Posted July 22, 2013 Good point. Sometimes we take some of this for granted. BTW Brownells sells Broken Tap Extractors. This is exactly what we use at the day job. I have this part. It worked when I did the EXACT same mistake as DNP. Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 Well damn do I feel dumberer....lol. Quote Link to comment Share on other sites More sharing options...
392heminut Posted July 22, 2013 Report Share Posted July 22, 2013 <laughs> <lmao> <laughs> <lmao> Just messin' with you brother! Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted July 22, 2013 Report Share Posted July 22, 2013 There are all different kinds of taps. It can make you nuts. Hahahaha, that's a funny bit of machinist humor there. Definitely screwed up the whole way I perceived this thread... Quote Link to comment Share on other sites More sharing options...
DNP Posted July 22, 2013 Author Report Share Posted July 22, 2013 Bazinga... Quote Link to comment Share on other sites More sharing options...
texas30cal Posted July 22, 2013 Report Share Posted July 22, 2013 YA, a home depot tap is definitely a no-no, they are ok at best for cleaning up threads and getting by, once you use a high quality ground hss tap you will know the difference and probably throw the others away. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted July 23, 2013 Report Share Posted July 23, 2013 The ones that really gave us issues were 10-42 taps in some 17-4 stainless. I'd check out several taps prior to doing that operation...they couldn't understand why my scrap rate was 0%. <laughs> Be careful with tapping guides also. I've seen one that was off about 7* from square. That was fun. Quote Link to comment Share on other sites More sharing options...
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