You asked if your barrel index pin being slightly undersized is a problem. Everyone stated no and some offered explanations or solutions. You obviously will not accept those replies. You should either take it up with the manufacturer or replace the pin yourself. They're not expensive and easy to replace.
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Index pin undersized by .0002 should it be concerning?
- Thread starter URGILOVERR
- Start date
Sorry man didn’t mean to come off rude or anything I just prefer stuff measuring within the TDP Besides a few dimensions like buffer tube cross face, receiver face diameter, carrier 3 bore and trigger pin cross face’s. I am rejecting this barrel anyways because of rust inside the bore even after soaking it in WIPEOUT for 24 hours and then placing it In an ultrasonic cleaner for a few hours thank you all for the replies.
Did you know that the TDP is not a public document and is considered Intellectual Property? There is also no requirement for a particular manufacturer to follow the TDP (not to mention how they legitimately came into possession of it) unless they are supplying the .mil or .gov.
Yes and no the company I purchased the barrel from will remain unnamed, but I have three other barrels from them that measure well within the TDP spec, as well as everything else on the barrels being within TDP . I believe the company I purchased it from follows prints off the TDP.
So, you wrecked your barrel by leaving a strong base in it overnight, and now it's the manufacturer's fault?
You also ignore the answers that are trying to help you and explain why the tolerance is what it is....machining probably isn't for you.
You'd make an okay operator, but not understanding the why in tolerances is going to limit you.
Do some research on @msgriff 's reply you quoted here. Very few companies have been given access to the AR15/M4 Carbine TDP and none of them have posted any of it online because all of it is IP owned by Colt. Only with specific permissions from Colt, can the gov't release the TDP to other companies for special contracts. And that comes with a whole host of NDA's for those companies. Most of the prints you find online are either reverse engineered or copied old manufacturing documents from the civilian market. What you find online as AR15 TDP's are just an assemblage of old prints that didn't come from Colt. Any "part print" you find online for an AR15/M4 should only be used as a reference. As others in this thread have stated, what matters most is how your parts fit and function with each other.
That little "slop" means nothing in the real world of an AR.
Honestly, I am not entirely sure what the concern is... and how that would effect anything.
Honestly, I am not entirely sure what the concern is... and how that would effect anything.
No I used the bore scope and it was in there before I applied any wipeout, wipe out can’t cause rust. maybe not a full 24 hours but still that’s safe to do with wipeout, The rest of the barrel is literally spotless but the rust/pitting that was originally on there, I didn’t “ruin” anything.
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I don't want to thread drift too far, but here is an interesting recent development concerning Wipe-Out/Accelerator. Post #126. I'm not implying any correlation to your situation. I've also seen corrosion inhibitors, like CRC SP400, applied to barrel extensions and bores, which can sometimes look like rust and needs a solvent to remove.
SH thread: For the Love of God, GI Joe and John Wayne.... cleaning and abrasive cleaners
If you were smart, you'd keep the slop and blame all of your misses on it. At least that's what the professionals would do.
I’ll take a look at it, I don’t use the accelerator with the wipeout just wipeout I make sure to get any excess oil/Lube the company may put for storage out before I apply the wipeout due to potential incompatible mixing, all of my experiences with the wipeout with my chrome lined barrels have come out spotless I have very good experience with wipeout on another note I don’t know everything about chems but after a lot of research and staying away from ammonia I decided to go with wipeout due to great reviews and being chrome lined friendly but I’m always willing to learn more .
The dudes over at Practical Machinist have about the same level of patience as everyone here. Most there have the experience to state something meaningful the first time, and that is a good thing. It would not do him well to over there and start questioning them either. Most machinists have a very low tolerance for constant questioning of their decisions or opinions on how to approach a thing. That’s the benefit of experience, but it is up to the questioner to be humble enough to listen. That’s what is missing at this moment.
This. It gets even more interesting when you start to get into it from the QA and calibration side of things.
I would love For you to explain how I’m using my tools incorrectly I’m measuring in a 68°F room i listen for the two clicks on my micrometers clutch for the reading, I use a stand for my micrometers and use a vise fixture for my barrel.
But what if that pin is on the high end of its tolerance? Say it’s actually 0.07195 or 0.07200? So that isn’t really a valid way to get the precision you need. Is the pin in question concentric?
I make a living manufacturing custom cutting tools, often with 0.0001” tolerance, and that isn’t how we verify our measuring tools.
@LeftyJason , and others here pretty much covered what you need to know.
Lmfao the 0 on my sleeve matches with the 0 line on the thimble these micrometers go to the 5th decimal place as well, I’ve measured .155 minus gauges, .176 gauges 1.0002 gauges 1.0004 gauges they are all SPOT ON!! each and every gauge that I have read was determined at its lowest point I also double check with digital calipers and dial calipers and dial micrometers with the vernier scale this is what I did with the index pin as well please tell me more.
Have you considered what the actual function of the pin is and what the affect of being 0.0002" under is going to affect? What if it was 0.0002" over, what would that affect be? Do you really think that that amount of dimensional difference would affect the function or accuracy of the rifle? These are not benchrest firearms and even if they were I doubt that 0.0002" would have any real work affect.
Calipers???
Ok cool. I’m not saying the pin is not undersized. It probably is. But does it matter in the application? Absolutely not, provided it doesn’t fall out, beyond that it only provides rotational positioning, calculate the angular deviation at the diameter the pin is located, and I’m positive you don’t have the tool to measure that angle.
Or replace the barrel and pin. ?
So keep studying in school. Sounds like you desire excellence, and we need more of that in this world!
But, there are correct and incorrect ways to calibrate things, we send mics and guages in to have them “certified” and they actually come with a stamped and signed certificate of exact size. We calibrate from those when specs get tight.
I’m over the 0002 carap just want this gentleman to let me know how I’m measuring wrong
I know it’s not the most accurate reading but the lowest point was spot on again I’ve checked the pin gauges for concentricity and runout at the shopCalipers???
Ok cool. I’m not saying the pin is not undersized. It probably is. But does it matter in the application? Absolutely not, provided it doesn’t fall out, beyond that it only provides rotational positioning, calculate the angular deviation at the diameter the pin is located, and I’m positive you don’t have the tool to measure that angle.
Or replace the barrel and pin. ?
So keep studying in school. Sounds like you desire excellence, and we need more of that in this world!
zz pin guages are a good way to check mics. But they do have a tolerance.
When the allowed tolerance of the guage pin equals the amount the part is out of spec, you need to go to another level of accuracy to verify the part is actually out of spec.
The question of concentricity was regarding the pin in the barrel, but I’ll assume you can’t measure all directions on that pin due to the barrel extension?
Is the pin hole axis perpendicular to barrel axis and is it on center?
Are the lugs of the barrel extension also rotationally aligned to this locating pin?
Is the slot for this pin in the receiver the correct width and also aligned properly to the gas key slot?
Are the bolt lugs located rotationally correct in relation to the gas key on the bolt carrier?
All connected dimensions that work together, maybe there are others as well. Most are hard to measure with average tools.
Not trying to nitpick, sounds like you are doing well on measuring things, but this is like complaining that one strand of bailing twine is frayed on one bail on the entire load of hay. Or some other applicable analogy.
Assemble the gun and have fun!
Are the lugs of the barrel extension also rotationally aligned to this locating pin?
Is the slot for this pin in the receiver the correct width and also aligned properly to the gas key slot?
Are the bolt lugs located rotationally correct in relation to the gas key on the bolt carrier?
All connected dimensions that work together, maybe there are others as well. Most are hard to measure with average tools.
Not trying to nitpick, sounds like you are doing well on measuring things, but this is like complaining that one strand of bailing twine is frayed on one bail on the entire load of hay. Or some other applicable analogy.
Assemble the gun and have fun!
I know it’s not the most accurate reading but the lowest point was spot on again I’ve checked the pin gauges for concentricisty and runout at the shop inCalipers???
Ok cool. I’m not saying the pin is not undersized. It probably is. But does it matter in the application? Absolutely not, provided it doesn’t fall out, beyond that it only provides rotational positioning, calculate the angular deviation at the diameter the pin is located, and I’m positive you don’t have the tool to measure that angle.
Or replace the barrel and pin. ?
So keep studying in school. Sounds like you desire excellence, and we need more of that in this world!
mate I’m not looking for sub 10 micron accuracy. My pin gauges all read within the .00020 spec. I don’t know what you’re trying to say. And My bad thought it was about pin gauges.
Ok cool. 10 micron is 0.000394”. That’s twice the amount you are concerned with.
Use the part, build the gun, and have fun!
Not sure if you read my comment earlier, but I’ve already returned the barrel because I found rust even after cleaning it out yes I have done all the proper checks on my upreceiver index slot up receiver, gas tube, hole yada yada ya anything you can think of I’ve checked.
thanks mate forgot to put the . In front of “10 micron”
This is the most autistic thread I've read here in while.
He has zero idea what he is doing, other than his super duper fine exact precision measurements. He will argue all day and do absofuckinglutely nothing. This is much worse than just mental masturbation. This is the epitome of the definition of an askhole. He is worse than a troll, because at least a troll is easier to spot.
Trust me this thread should die. There is not a person on this world that will make one difference to this know-nothing know-it-all.
Never claimed to “know it all” I even stated the thread was dead don’t careHe has zero idea what he is doing, other than his super duper fine exact precision measurements. He will argue all day and do absofuckinglutely nothing. This is much worse than just mental masturbation. This is the epitome of the definition of an askhole. He is worse than a troll, because at least a troll is easier to spot.
Trust me this thread should die. There is not a person on this world that will make one difference to this know-nothing know-it-all.
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Buy one of these pin clips and machine the upper to the tolerance that you want,
Wow that’s pretty amazing thank youBuy one of these pin clips and machine the upper to the tolerance that you want,
For this purpose waste of time.Buy one of these pin clips and machine the upper to the tolerance that you want,
Pulled up a barrel extension print. Barrel extension Dia of 0.9987 +0 - 0.0008. Hole size 0.1235 - 0 +0.0015. Taking the pin and having it undersize by 0.0002 gives an extra 0.0057° of rotation each direction. Doesn't matter. How aligned are you getting all other parts of the gun? Can you tell an extra 0.0057° of rotation?
Let's do some quick comparisons.
Starrett machinist level. $302. From Starrett site description. "Main level vials have graduations that are approximately 80-90 seconds or .005" per foot (0.42mm per meter). "
Starrett master precision level. $1188. "Ground and graduated main vial of 10-second accuracy; one division equals 1/2 thousandth (0.0005) of an inch per foot, or 0.04mm per meter."
Converting that 0.0057° to seconds equals 20.52 seconds.
The 0.0002" undersize for assembly DOES NOT FREAKING MATTER as long as it fits properly in it's hole. That's it.
I think that you're using the wrong conversions. By my calculations, using an index pin clip to resolve a 0.0002" undersize pin equals two, maybe three weeks of peace and quiet.
Why are you guys arguing with him. Just let him and his OCD be inconsolable, right?
@Makinchips208 and @LeftyJason Mind if I quote some of this for helping some of our interns? its very succinctly put compared to some other explanations
I’m telling you right now the OP will be a prime candidate for receiving prank tools that are marked incorrectly or put in the wrong slot in the box, just to watch the meltdown. If he ends up being QC he will be hated by everyone - the production guys and his management for causing issues for them, which will include production stoppages. Much risk in being like that.
Take your liberty. Im happy to know someone actually benefited or found something I said as useful.
