Oeno Posted April 12, 2011 Report Share Posted April 12, 2011 So I go to in stall my Geissel Hi speed trigger on my MA-TEN and the pins wont fit into the holes :'(. I measured and the holes are .153 and the pins are .154. The kicker is I went and got a #23 drill bit to clean the holes out and the bit measured .152, WTF. So did anyone out there have the same problem? Also does anyone have a solution for this?Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted April 12, 2011 Report Share Posted April 12, 2011 I would try stoning a slight taper onto the ends of the pins, if they will start try to gently tap them through. If that fails, try a second set of trigger pins. I would try the drilling dead last. I'm not sure if you're concerned that the drill is undersized, but I can assure you it's going to leave you with a larger bore than .152". If you do drill, it'd be wise to use a low speed and cutting oil to try to keep the bit as cool as possible. Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 12, 2011 Author Report Share Posted April 12, 2011 Thanks for the info. The drill bit was for cleaning out by finger twisting it in the hole. I am no way going to drill it due to not having the proper equipment. Quote Link to comment Share on other sites More sharing options...
Jgun Posted April 12, 2011 Report Share Posted April 12, 2011 You could take some fine emery paper and you can carefully mount the pins in the chuck of a variable speed electric drill. Wrap the paper around it and polish the pins slightly. You should finish with extra fine 1000 ,1200 grit paper for a smooth finish. Look at it this way, It would be far better to screw up and have to replace the pins if you decide the fit of the hammer and trigger is too loose, than to do any damage to the $600 receiver. The KNS non rotating pins aren't a bad idea either. Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 12, 2011 Author Report Share Posted April 12, 2011 This sounds like a good idea. Ruining the pins is better then the receiver. Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted April 12, 2011 Report Share Posted April 12, 2011 Ive done the polishing trick before, but with much larger parts. I can only imagine the headache of fitting a trigger pin into the chuck of a makita, and keeping it from falling out. It might just be easier to hold the pin in vise grips and run a modeling/jewelers file over it a few times. You can also try the freezer trick. Put both the receiver and the pins in the freezer for a few hours. As metal gets colder it shrinks. The pins will be ever-so-slightly thinner, and the pin holes will be ever-so-slightly wider. When the metal comes back to room temp, the metal will go back to normal. They will be in there TIGHT. WD40 is cheap, and your gun can't drown, so don't be afraid to spray!It doesn't hurt to have a freezing agent to help keep the temp down while you work. Maybe try applying dry ice? I don't suggest using a Co2, an upside down duster, or propane, because they collect moisture really easily. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 12, 2011 Report Share Posted April 12, 2011 The freezer trick is good & you can always oil the pins before they are put in the freezer. I believe the pins already have tapered (rounded )ends (maybe not the ones that come with the Geissel ). The pins should be tight (snug )in the receiver. That's whats keeps them from rotating with the moving parts(hammer ,trigger ) Polishing may help , as said. Quote Link to comment Share on other sites More sharing options...
Jgun Posted April 12, 2011 Report Share Posted April 12, 2011 I used the polishing method with the electric drill to fit the .1555" oversize pins I ordered from KNS, in my MA TEN receiver. As stated by survivslshop, I found that I didn't have to polish them down the full length of the pin, mostly on the ends so they fit through the receiver without damaging the holes. I had no trouble mounting them in the drill, I just had to use my 3/8" drill vs the 1/2" that doesn't close small enough. If you have an electric drill that will tighten on a 1/8" drill bit you should have no trouble. The freezing idea sounds pretty good also. One final thing, if you do decide to polish your pins, you need to clean them thoroughly so there is no abrasive grit left or you will prematurely wear out your trigger/hammer/pin fit. Also if you polish them you have to make sure that they feel cold to the touch when you measure or try the fit, as they will measure about .001" bigger when hot than when cold to the touch. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted April 12, 2011 Report Share Posted April 12, 2011 Yep, I didn't think of the freezing but that should work perfectly, it would also be my first choice because it doesn't involve any metal removal. Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 12, 2011 Author Report Share Posted April 12, 2011 Thank you everyone good ideas. I will try the freezer method first. I did sent an email out to Mega, to see what they had to say. So tonight the freezer method.Cheers,Oeno Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted April 12, 2011 Report Share Posted April 12, 2011 what are you gonna do with the ice cream? <munch> Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 12, 2011 Author Report Share Posted April 12, 2011 Eat it of course. Hey I was think that the lower should not be placed in the freezer. This would cause the constriction with the holes. It should be heated up, like with a hair dryer to cause it to expand. This is what I have done in the past with parts on my cars. Anyways will findout later. Mega got back to me. They said the holes are in spec and offered to put the pins in for me. I see their point on the specs but its cool they offered to put the pins in. Quote Link to comment Share on other sites More sharing options...
imschur Posted April 12, 2011 Report Share Posted April 12, 2011 Good to hear they respond <thumbsup> Quote Link to comment Share on other sites More sharing options...
imschur Posted April 12, 2011 Report Share Posted April 12, 2011 BTW In general I keep a can off this and or this around. The one without lube is also good for getting poop and gum off of stuff as well as freezing flies in the air. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted April 12, 2011 Report Share Posted April 12, 2011 Eat it of course. Hey I was think that the lower should not be placed in the freezer. This would cause the constriction with the holes. It should be heated up, like with a hair dryer to cause it to expand. This is what I have done in the past with parts on my cars. Anyways will findout later. You need to consider that carefully one more time, you are right in that heat will cause expansion, but it will go in the direction of least resistance, ie into the bore which is the free area, making the hole itself SHRINK. Freezing both parts causes both to shrink, which causes the bore to GROW (ie more free area, larger bore) while the pin still shrinks. Is it making sense now? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted April 13, 2011 Report Share Posted April 13, 2011 Hey I was think that the lower should not be placed in the freezer. This would cause the constriction with the holes. It should be heated up, like with a hair dryer to cause it to expand. This is what I have done in the past with parts on my cars. Anyways will findout later. You are 100% correct. Other people are overthinking this, but you're right in your thought process. For a living now, I build motorcycle engines ALL the time. If you want bearings out of the lower crankcase halves, heat it to 200 degrees for 30 minutes (not gonne work on a firearm part, but that's not a motorcycle engine, and vice versa). Heat those biotches up, smack them on the table, and out pop the bearings - because the machined bearing areas have expanded. So did the bearings, but not as much as the bearing areas. Before I put bearings into a case half, I heat the case halves, freeze the bearings a couple days prior, and literally drop the new bearings right in there, fully seated. Small, light tap to ensure, and all is good. Anyone that tries to apply physics to this will get it wrong - they'll think heat will expand a hole, and close the diameter. Anyone who has done it knows that it doesn't work that way. Just sayin'... <dontknow> Quote Link to comment Share on other sites More sharing options...
98Z5V Posted April 13, 2011 Report Share Posted April 13, 2011 The one thing that bothers me about this whole affair is this: small-pin trigger standard is 0.154" diameter. On ALL ARs. Not some, ALL. How did Mega make something that doesn't even conform to the standard of the common trigger group? Why did they make something tight, for something that really IS an industry standard?!... Quote Link to comment Share on other sites More sharing options...
imschur Posted April 13, 2011 Report Share Posted April 13, 2011 Well without knowing the state of calibration and type tools the posters measuring with and my not being able to do math this late when Im not feeling well I dont think we have the true measurements. His number 23 drill bit is measuring undersize. How is he measuring the hole in the lower? Caliper is not going to be accurate in a tiny round hole. Hell I have seen import drill bits that arent the correct size.Is it too tight or just a tighter than he anticipates? I have only built a few AR's and my experience was the DPMS took a bit of hammering. Two CMMG's took a little bigger hammer. My Colt was just right JP anti walk pins are .156. Perhaps Geiselle takes a similar approach.Ill measure my lower by the weekend Quote Link to comment Share on other sites More sharing options...
98Z5V Posted April 13, 2011 Report Share Posted April 13, 2011 I know, I know. I even gave the lecture about the "suspect your measuring devices" if you suspect foul play... :-[I will say this - there are different types of "fits" when you're talking about precision parts. If the real size was 0.002" under what the 0.154" trigger pin size is, that's an "interference fit." Most of those are only 0.001" under, and trying to make something 0.002" under work is gonna be a problem, fight, issue, etc. <dontknow>"Precision fit" is what this should be, here - 0.001" or 0.002" over sized on the hole. Based on the size of the hole/pin in the first place, 0.002" would be sloppy for what we do and know. If that true size of that hole is 0.152", something ain't right. Sanding and filing pins isn't the answer. Quote Link to comment Share on other sites More sharing options...
Jgun Posted April 13, 2011 Report Share Posted April 13, 2011 My MA TEN receiver took a .154" precision pin. I ordered the oversize KNS anti rotation pins because I thought the Jard hammer and trigger felt a little sloppy on the .154 pin and liked the way a .155" check pin fit in them better. Besides which the pins weren't includes with the trigger. If I hadn't been trying to get the better fit on my hammer and trigger, I could have used .154" pins in my receiver with no fitting. Maybe he got a "tight" receiver. Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 13, 2011 Author Report Share Posted April 13, 2011 Well I got the pins to fit. <thumbsup> Did the freezer trick.I have to admit I am new to AR building and not familiar with how tight things should be. I always go by the advice you shouldn't"t have to force things together. If you have to double check the info and ask questions before you break it. Forcing things can be costly and I know that one. My measurements were taken by a digital caliber. I do not think it is very accurate but it is consistant with its repeatable measurements. So it did show there was a difference in size between the pins and holes. I was shocked that the drill bit was so under size but it was a cheap OSH brand. Once again, thank you all for your input. Cheers,O Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted April 13, 2011 Report Share Posted April 13, 2011 Well I got the pins to fit. <thumbsup> Did the freezer trick..Score one for Robocop! Glad no damage had to be done. Quote Link to comment Share on other sites More sharing options...
imschur Posted April 13, 2011 Report Share Posted April 13, 2011 Glad it worked out. I like these types of threads to keep the crew thinking. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 13, 2011 Report Share Posted April 13, 2011 You also have to remember that they put a finnish on the lower/upper when it is done with the machining & cleaning process. Quote Link to comment Share on other sites More sharing options...
Oeno Posted April 13, 2011 Author Report Share Posted April 13, 2011 This is the beauty of forums. Have a problem, get more then one brain working on it. 98z5v; That example of bearing fitting is why I rethought the freezing trick with the receiver. That's exactly what I do to fit bearings. Jason at Mega was helpful with the problem and supportive. He also was very fast with responses. This is always good to know. Definitely shows me they are a good company. Quote Link to comment Share on other sites More sharing options...
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