2014 POTD Thread Archive

[toolman]

Not much of a job since it only took about 2 min. of cutting plus another 10 to dial it in in the 4 jaw (brought it in at 0.0002 total runout and that'll probably never happen again! ), but here's an 11 degree crown on a brand new AR-15 pistol barrel. The guy applied for the SBR license and ordered the barrel, but the barrel was pretty dang sloppy IMO. It wouldn't pass the Q-Tip test and the flash hider threads were really rough at each end. Being a shorty, it really didn't need a "target" crown, but I like them on AR's for ease of cleaning and it'll give the owner bragging rights, for whatever that's worth.





Sorry for the sorry pics, I'm a gun wrench, not a photographer.

 

[RWL]

It wouldn't pass the Q-Tip test

I had never heard of the Q-Tip test. I assume that's to check for microscopic burrs at the mouth of the bore. Is that correct? What do you look for / find acceptable with the test? I'll have to check some of mine to see if they pass. .... and if one doesn't, the next question is what to do about it.

 

[toolman]

I had never heard of the Q-Tip test. I assume that's to check for microscopic burrs at the mouth of the bore. Is that correct? What do you look for / find acceptable with the test? I'll have to check some of mine to see if they pass. .... and if one doesn't, the next question is what to do about it.

Yep, just run a Q-Tip into the bore and pull it across the edges of the crown and see if it snags. If it does, you can either completely recrown it, or use a brass screw in a drill with a bit of fine lapping compound to clean it up, but you have to be really careful not to get it off-center.

 

[xman_charl]

Made some indicator brackets.
5/15 18 stud through hole on magnet, held by 1/4 20 set screw
slots to align magnet. back stuff covers aluminum
pressed magnet into slot, just a tight fit, as dimensions are not a uniform along
magnets sides.

works okay on small mill and lathe




Charl

 

[jocat54]

I am in the on going process of making gears for my SB 9A to cut metric threads (7 stud gears and a 37/47 compound gear) and wanted an easier way to cut the keyway in the stud gears so made this homemade 1/8" broach with shims. It works really well in aluminum. The cutter is made out of 1/8" 1084 with hand filed teeth and I hardened it by heating until a magnet wouldn't stick to it and quenched it in old motor oil. Didn't temper it though. A file just skates across it.

 

[melsdad]

That will work o.k. in aluminum. But probably not in steel. Any hardened steel should be tempered before use. I am guessing it worked out for you because you probably did not get to full hardness of 1084 with the motor oil quench.

 

[omni_dilletante]

I have started a basic machining night class and needed some way of hauling some tools to class and back.

I did not like the idea of all my tools sloshing around in a tool box. So I cleaned up an old Craftsman 2 drawer box I bought in 1979 before heading off to college and added some dividers and custom holders for important tools.

It is not exactly Gerstner but I feel better about how the tools will travel and that I can get to them.

 

[Marco Bernardini]

It's not in the shop and I started the project long time ago, but ten minutes ago I (almost) finished it: my wind breaker mesh retainers made with hammered iron wire and copper gutters scraps.




(sorry for the quality, photos were made with the phone under the rain)
Today the family who rented the apartment (garden included) for July will arrive, and in August I'll have other guests, so I have to wait until September to finish this job.

 

[Charles Spencer]

I have started a basic machining night class and needed some way of hauling some tools to class and back.

I did not like the idea of all my tools sloshing around in a tool box. So I cleaned up an old Craftsman 2 drawer box I bought in 1979 before heading off to college and added some dividers and custom holders for important tools.

It is not exactly Gerstner but I feel better about how the tools will travel and that I can get to them.

Dag nabbit! What beautifully simple idea that totally escaped me!

I use plastic silverware storage trays and other shallow trays in my Craftsman stacking boxes, but they wouldn't really fit in my workbench box.

D'ya think it'd occur to me to make dividers? Noooooo...

I see a woodworking project in my near future.

Thanks a bunch for the idea.

Charles

 

[Don B]

I am in the on going process of making gears for my SB 9A to cut metric threads (7 stud gears and a 37/47 compound gear) and wanted an easier way to cut the keyway in the stud gears so made this homemade 1/8" broach with shims. It works really well in aluminum. The cutter is made out of 1/8" 1084 with hand filed teeth and I hardened it by heating until a magnet wouldn't stick to it and quenched it in old motor oil. Didn't temper it though. A file just skates across it.

Very nice job on the broach it looks like it's doing a great job, you should really throw that in the kitchen oven though, 450 degrees for about an hour, it should come out a nice dark golden straw color, possibly even 470 degrees for about an hour to get a light straw color, if you heated it until a magnet wouldn't stick then quenched, it's just a mass of tension waiting to release, it will be as brittle as glass, one wrong move when broaching and it will shatter)
This is not a criticism in any way, I know how much work they are to make and I'd hate to see you lose your work.)