Cutting a 1 1/4 inch radius for Home build.

Just started my second Homebuild gun. Part of making the top rail and the trigger housing is mating these parts to the 1.25 inch tube. On the first gun, I cut the 1.25 inch radius the hard way — standing the part upright in the vise and comming down from the top using a boring head.
Today, I built a 1.25 radius milling cutter. Started with a 7/8 inch piece of drill rod. Cut a 1.25 radius in the end using a grinding wheel radius cutter that was adapted with a cutting tool. The piece I am cutting is chucked up in the mill.

Then you cut away half of the round:

Now heat it up with a torch and quench it in a bowl of water. Check out the “RED HOT” color! Comes out rockwell 65 — very hard!!

Now to try it out on a scrap piece of aluminum.

Here is the trigger housing, cut with a 1.25 radius to match the 1.25 inch tube.



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quote :

MB is that a router bit?

Yup, cheap Chinese carbide strikes again! I think it would be wrong to use the proper tool for a job so I try to find something that is only marginally capable of functioning and press it into a totally unintended situation 😆


no wonder it takes so many years to learn how to be a master machinist back in the manual days

id seriously be lost on a manual setup

Whatever it takes! MB is that a router bit? Thats about the same size vice on my drill press. Nice job! Like they say “Don’t let the tools outshine the man”

I just wanted to offer a quick thanks to everyone for the ideas on how to do these cuts.

I tried the Angle method last night and it worked out great. I only had a 3/4″ bit to work with and trial and error led me to an angle of around 32.5 degrees.

While not perfect it’s “close enough for me. Since my cross slide vice has limited travel I have to make long cuts with multiple setups. A little cleanup is necessary and I have to re-cut my first pass a tiny bit deeper to mate cleanly with the second pass.

I was dreading this step of the build and it turned out to be easy and damage free to my drill press 😀

Thanks again

P.S. …yes, I need to clean my shop…

You were lucky here the goverment just does it without peoples input like our GST your VAT type goverment money grab!!

The European Union tried to make us (the UK) change over to metric and totally abandon Imperial units.

I was in the states at the time, but I remember there some legal action if things were marked in imperial units after a deadline, like butchers and deli’s and british pubs not being allowed to sell “pints”.

People were rather annoyed at the idea that EU (especiallu France and Germany) were going to say what we could do, In the end the EU pretty much gave up..


My bad!

When I was growing up they tried to convert us to the Metric System. Then they wised up and remembered….”We are the USA” screw everyone else. So far that is our policy on just about everything
Adam aka WalkonKing

It wasn’t screw metric. 😥

Me I love metric for working on cars, still use inches, feet, yards, onces, miles per gallon for living life day to day. Celcius, kilometers, no problem but snow to me is still measured in inches/feet. 😆


Well, I did, but after he said that. I remember back in school we were gonna change to metric as a standard in the US. Spent a good portion of a school year learning it. The next year, metric was gone and forgotten. Either we were to dumb to change over or someone pissed someone off and we said screw it. I guess it could have been industry crying about tool changes as well.

quote Randyhub:

Question if the US said screw Metric…

I dont see anyone above saying that the US said Screw metric.

Yup technology made the world alot smaller.

I have been fortunate to have heard the truth from both sides as I am somewhat cautious in what I read without having input from different sources to validate facts.

Dad grew up in Germany in the 30s and 40s and cautioned me on trusting the goverment and my Mother was never taught about all the facts of European expansion to other continents in the 1800’s, yup history tends to be rewritten.


quote WalkonKing:

Gotta love those Nazi rocket scientist.

You mispelled EVIL Nazi Rocket Scientist. ;P

I don’t know why but this immediately brings good’old Castle Wolfenstain 3D back in -92 to my mind 😀

Not that I have anything against Germans. Afterall they and especially squadron Kuhlmey with their Stuka’s helped to save our ass during massive Russians attack at the end of WW2.

No I am Canadian of German and British descent with lots of family in the US. In reality the border is culturely very fluid I went to school in the States and the cultures are just so much alike Goverment is different but work habits, education, TV, food pretty much the same. I just moved back up here as my family immigrated here from Europe in the late 40’s while others settled in California and the Central US.

I really view the US and Canada as more of melting pots as opposed to Europe and Asia where they have been around alot longer and were not built by immigrating Europeans over hundreds of years. Most have also forgotten the Chinese built most of the US and Canadian Railway systems in the late 1800’s.

My wife is British and her culture is much different then both ours. Just never bring up Capital Punishment, Guns, the War, or man shit hits the fan. She has a deep hatred for all my handguns, black guns and War views.

Other then Muscle Cars I have owned all my US built cars have been metric for years.

Randy, aka a Family Guy, Lays Potatoe Chips, driving US cars, shooting US guns fan, or maybe just an confused Canadian, eh. 😆

My point don’t really know just didn’t feel like watching with the wife’s show and felt like typing, she taped Coronation Street.

All that and yes the U.S. basically says screw metric. The U.S. is the biggest importer in the world, of technology and products. Its no big mystery that the products we import have metric parts in them. Hell, most the stuff we stamp made in the USA are only assembled here but we buy the parts from somewhere else. Your Jeep was most likely made in Mexico or Canada or a good portion of it was.

Dont forget that the U.S. is made up everyone from around the world. What can we say, the best stuff ends up here ).

Im really not sure what your point is here. You wouldnt be from Germany would you? )

Question if the US said screw Metric why does my Jeep TJ have metric nuts and bolts?? Why does my engine say 4 Litre instead of 232 cu inch???

Why is my M4 stamped 5.56 mm not .223???

And if the Germans didn’t help advance the space race why did all those V2s end up at White Sands??

What technology was used for Sputnik by the Russians?

Why does the M1 Abrams use a German designed 120mm smoothbore cannon?

Why does the Abram use reactive armour the Brits invented?

And if the Germans didn’t have much to do with the space race why did half the German technology end up on different sides of the ocean like liquid fuel for the US and heavy lift solid fuel boosters for the Russians??

Funny how much a AK looks like A German MP44? Or how the US M60 shares the same concepts of the German MG34?

Fiber Optics invented in North America?? Nope Europe, just depends what article one reads and where it is from.

Did I get something wrong from reading history and technology articles??

Seems like we all got todays technology from many different places just not one country or one people. 💡


quote Buba b:

Used both metric and imperial , and metric is just so dam easier ……the only draw back is it was started by the French……….uhhhh!!!!!! 😯

Same here.. English schools taught both during the time I was there. I beleive its Metric now thanks to the EU (or whatever name it goes by now…)

I studied engineering at college and we used Metric (THANK GOD)… but I still ordered my beer in pints at the Students Union bar and wouldnt have it any other way. Other than maybe I’d order less and actually have a degree now….

Its funny how the imperial units are now defined using metric measurements, lol.

All we need to do is tell the Americans that the British came up with “SAE” as they call it…. and they will make up their own screwed up system just to be different – Same as they did with sports.

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