Material selection question.........

RoyB

Member
I will be making a Unertl style rifle scope mount and I need a materials expert.....

The prototype is in aluminum and I used the internals from a set of micrometers to get the hardened threaded shaft and insert

P1020971-vi.jpg


I want to do away with using the micrometer internals so I ordered taps and dies at 3/8-40 and 1/2-40 (not sure what size I'll use as I want a large bearing area on the scope tube.

P1020962-vi.jpg


So help me with materials.

There will not be much wear as the turrets are turned relatively infreaquently.

But I'm thinking about making the entire mount out of some type of bronze.

I've never worked with bronze.........

Questions:

Ease of machining?
Ease of threading / taping?
Bronze against bronze OK?
What type of Bronze should I use? (there are lots of different types)

C510 PHOS BRONZE
C544 PHOS BRONZE
C630 ALUMINUM BRONZE
C642 ALUMINUM BRONZE
C655 SILICON BRONZE
C863 MANGANESE BRONZE
C932 BEARING BRONZE (SAE 660)
C954 ALUMINUM BRONZE
SAE 841 OIL-IMPREGNATED PWDR. BRONZE
SAE 863 POWDERED IRON-COPPER

Full article on the prototype mount I built:
http://rvbprecision.com/

Thanks in advance!
 
... and I need a materials expert.....
Well, I guess I'm not qualified then, so you'll have to accept that you're getting what you pay for.

The prototype is in aluminum and I used the internals from a set of micrometers to get the hardened threaded shaft and insert
I would continue with aluminum. 6K or 7K T6 will work just fine.

I want to do away with using the micrometer internals so I ordered taps and dies at 3/8-40 and 1/2-40 (not sure what size I'll use as I want a large bearing area on the scope tube.
You may end up getting fancy there.

So help me with materials.

There will not be much wear as the turrets are turned relatively infreaquently.

But I'm thinking about making the entire mount out of some type of bronze.

I've never worked with bronze.........

Questions:

Ease of machining?
very, but only when using the right tools, they are set up properly and the setup is very rigid.

Ease of threading / taping?
doesn't get any easier than this

Bronze against bronze OK?
Any metal against a like metal is never ok.

What type of Bronze should I use? (there are lots of different types)

C510 PHOS BRONZE
C544 PHOS BRONZE
C630 ALUMINUM BRONZE
C642 ALUMINUM BRONZE
C655 SILICON BRONZE
C863 MANGANESE BRONZE
C932 BEARING BRONZE (SAE 660)
C954 ALUMINUM BRONZE
SAE 841 OIL-IMPREGNATED PWDR. BRONZE
SAE 863 POWDERED IRON-COPPER
Aluminum...
 
That is one nicely made mount. I would think any easy, machinable material would be fine. The Unertl mount appears to be die cast aluminum. It is the internals that count. You have already found that. Nice work, and that should be what this board is about.
 
Bronze against Bronze and Bronze against Aluminum is not ok. Granted, there might be certain grades that are enginnered to be compatible, but you should not have to go there.

Make the mount out of 7075 T-6 aluminum, and the turrets out of Stressproof. Stressproof has a phenominol anti-gall quality, machines great, and has enough hardness to do what you want to do with it.........jackie
 
That is a nice looking mount, that you have started. Are you building in any click/detents, on the adjustments? A pre-hardened 420ss(32-36Rc), should work well for the spindles. The heads will probably need a softer material, to accept the knurling, and engraving. I, have cut a lot of 7075 T651(blow molds)alum. It cuts a lot like 1018-1045crs. Will the caps, be finished blue/black, to contrast w/ the engraving marks? Stay away from the Al. bronzes, for your application. Standard 660 bearing bronze, will wear as long as the Earth survives, for the nuts, and is available anywhere.
What single shot, is your prototype mounted on?
Regards,
Bob
 
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