Gunsmithing files for aluminum.

Dan Forrester · Nov 21, 2019

Can anyone recommend to me what file I should be using to adjust fit between aluminum uppers and lowers?

I have an assortment of files that are clearly way too aggressive for use on aluminum. I’m looking for something much finer and more precision.

Thank you,

Dan

earlthegoat2 · Nov 21, 2019

Usually files made for aluminum appear to be quite aggressive. This is so they dont load up as fast and can be carded out easier.

jmorris · Nov 21, 2019

For more precision, with a file, I generally use a less aggressive single cut and make a pass then clean it with a file card so the spoils do not mess up the next pass.

Kp321 · Nov 21, 2019

In addition to frequent carding, chalking the file can reduce the clogging.

Steve762us · Nov 21, 2019

Needle files, or stones, perhaps?

Are you talking filing on AR-type uppers & lowers, to make them fit?

entropy · Nov 21, 2019

Machining is much more precise.

#1buck · Nov 22, 2019

Good quality sandpaper glued to a wooden block can be quite useful for this. Clean it with a wire brush when it loads up. Using rubber cement will allow you to change the paper out. Just make sure to clamp the sandpaper when the glue is setting. Any anomalies in the surface could ruin your parts.

shoobe01 · Nov 22, 2019

Get an aluminum file for sure. Changed my life. They look very aggressive but that is just what they are for soft metal cutting.

Somewhat hard to find any variety in these, but McMaster has three sizes in Aluminum cutting files, that may help also.

Alaskan Ironworker · Nov 22, 2019

What shoobe said. Im not sure what these files are called, but they are the cat’s meow for softer metals that typically clog a standard file. My pedantic uncle told me they were originally made for plumbers to remove excess lead solder off plumbing pipes. Not sure if theres any truth to that, but I got mine in a box of antique plumbing tools, so maybe? It works awesome on aluminum and leaves a smooth finish.

boom boom · Nov 22, 2019

You can often get amazing deals on old name brand files and mechanical tools via Ebay and they are usually better made with better materials than what comes from China nowadays.

Blue68f100 · Nov 22, 2019

I clean the files using a piece of AL following the groves. The AL is soft enough to form to the file pattern. It will pop anything filling the groves out, making it look like new again. I only use this on #2 and finer patterns. Using chalk makes them clean up easier.

Rule3 · Nov 22, 2019

https://www.amazon.com/Nicholson-Aluminum-American-Pattern-Rectangular/dp/B006P2XB4E

SGW Gunsmith · Nov 22, 2019

Kp321 said:
In addition to frequent carding, chalking the file can reduce the clogging.

This is the process I learned and also what most professionals use. For the record, I prefer an 8-inch second cut file, with one row of teeth for aluminum. Use regular chalkboard or sidewalk chalk and you will be pleased as to how the above recommendation saves you cleanup time.

jmorris · Nov 22, 2019

entropy said:
Machining is much more precise.

Depends on the machine, tooling, part and a number of other variables.

There are reasons for many “post machine” operations but they are getting better all the time.

If you are old enough to have ever heard the term “break-in”, that’s referring to a period of time to “condition” a piece(s) of equipment to be better together than the initial machining processes could achieve individually.

JRadice45 · Nov 23, 2019

Wrap a piece of sand / emery paper tight around a file and when it is toast, use a new piece. 180 to 800 grit depending on how much and how fast you want to remove material.

Dan Forrester · Nov 23, 2019

Thanks for everyone’s responses. I learned a lot from this thread.

It turns out I already have one of those aluminum files shoobe01 posted an image of. I also have a file card sitting in my tool box. I honestly never knew what it was. I inherited it from my dad and kept it around figuring it must be something important.

I really like the idea of the sandpaper on the wooden block idea that #1buck suggested. I think that’s all I will need. Most uppers fit the lower great. I just have one or two I need to fine tune a little.

Steve762us: Yes I’m fitting a modern upper to to an old pre 86 M16 lower. CNC machining and standardization of AR15/M16 has come a long way since this thing was originally made 40 years ago.

Thank you for all the help!

Dan

Jackrabbit1957 · Nov 24, 2019

Just to help with your search the files are called Vixen files, remembered the name when I saw the photo from Shoobe01.

Gunsmithing files for aluminum.

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