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[6un5_4r3_N347]

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[FatBoy5478]

Tagged

[Germz]

If you needed to open the magwell up, you'd have to file about .015" from either side internally. You'd also have to shorten the grip screws.

Sent from my SM-N920V using Tapatalk

[kcstott]

Figuring hole sizes after anodizing is tough, it pretty much a judgment call.
But I'll give you my rule of thumb. This is for slip fit that can stand up to .001" of potential slop over all on Type III anodizing. Type II just ream to size as a finished part.

Holes <.100", ream on size to +.001" for a looser fit.
.100"-.200" ream .001"-.002" over
.200"-.500" ream .002" over minimum.

This is all guess work and the boys over on caswell don't have the proper tools to measure coating thickness and they are calulating based on time and amperage.
They will be close but far from correct.
If you ask your anodizer for the Milspec process. My numbers will work with maybe a subtle amount of lapping not drilling after the fact to get the proper fit.

[nuggethunter]

Normal to ream/resize after anodize

Going past 4 decimal places little over the top, and.really, given this is alumuninum, going past 3 is silly considering this is aluminum and it will change that much with normal temperature change.

[kcstott]

Normal to ream/resize after anodize

Going past 4 decimal places little over the top, and.really, given this is alumuninum, going past 3 is silly considering this is aluminum and it will change that much with normal temperature change.

Yeah I'm going to to say no.

The parts we made that were anodized had to fit after anodizing, there was no fitting after the fact.

and to say three decimals is over kill due to aluminum's movement due to temp change. Also BS. Aluminum averages about .000013" per degree per inch
which is about double that of steel but really to say that you can round off to the Hundredth of an inch....
a 100 degree temp change over a 5" long part will produce.0065" change over all. that same change over a .375" diameter hole =.00048" over all

OP ream your small holes 1-2 thousandths over size and ream your larger one 2 thousandths over an be done. the pins the fin in there are most likely going to be .0005" under anyway.

[vlady]

You should be more concerned with what to do with the rails as those are the parts of the frame with the most movement across them and where you want to keep the hardcoat anodizing in tact. This has been my dilemma with what to do and how to do it best

[nuggethunter]

Yeah I'm going to to say no.

The parts we made that were anodized had to fit after anodizing, there was no fitting after the fact.

and to say three decimals is over kill due to aluminum's movement due to temp change. Also BS. Aluminum averages about .000013" per degree per inch
which is about double that of steel but really to say that you can round off to the Hundredth of an inch....
a 100 degree temp change over a 5" long part will produce.0065" change over all. that same change over a .375" diameter hole =.00048" over all

OP ream your small holes 1-2 thousandths over size and ream your larger one 2 thousandths over an be done. the pins the fin in there are most likely going to be .0005" under anyway.

Never said a thing about rounding to the hundreth of an inch.

In about the 4th grade we learned: .01 is hundredths (2 decimal places), .001 would be thousandths (3 decimal places) .0001" would be ten thousandths (4 decimal places)
Google "Decimal Places" if you are still confused.

Now that the Elemtary school math lesson is done, you are saying .001" - .002" which is the same thing I said....3 decimal places, thousandths

Who do you have that can anodize to a specific .0001" thickness? Nobody, thats why the parts that had to fit after anodize had slop when they were done.

As for thermals, .0000001" interference can still cause something to stick.

A temp range for a gun in a vehicle can easily swing 100 in California. Where I live 160 degrees every year.

Frame is 6" + long

[ar15barrels]

So, there is the question of whether to re-drill the holes after anodizing or to drill them oversized before anodizing?

The answer is NEITHER.
REAM them oversized before anodizing.
Then you know what diameter the hole really is and that it's pretty round.

[nuggethunter]

Correct answer ^

I ordered appropriate reamers off amazon. $5-20 each

[pklin1297]

Correct answer ^

I ordered appropriate reamers off amazon. $5-20 each

Care to share the links?

[nuggethunter]

Go to amazon and search for 9mm reamer for example. One you need for the sig...take down pin. Mine was tight

[nuggethunter]

Just about and size you could need:

http://www.amazon.com/Alvord-Polk-High-Speed-Chucking-Straight/dp/B003G301GG/ref=sr_1_6?ie=UTF8&qid=1464145252&sr=8-6&keywords=reamer+alvord+polk

Certainly cheaper options as well. Can spend a little more and get adjustable.....

[MosinVirus]

I guess I went the most low tech route... Rolled up sandpaper.

[nuggethunter]

There are no other critical holes on the frame. I'm going to use a 4.5 and 9mm Reamer. I'm going to freeze my frame to -10F, ream, anodize, ream if necessary.

The other option is to ream the right size (or drill for that matter) and plug the holes with plastic. They don't need anodize in the first place.

As for the statement: "For those that want to do it right" - You are assuming you can control the anodizing, and you can't. I've worked with 5, none could control their process to +/- .00025" for type III and even type II we were lucky to get +/-.00015".....and they sure are not going to care or do you any favors for you a single part.

One of my customers had to redo over a half million dollars worth of product in a recall because the anodize was .0002" too thin on a defense project.