Re: *ist D revisited

[Bruce Rubenstein]

Referring to a metal as aluminum is about as meaningful as saying it's 
made of "stuff". Things are made from aluminum alloys. The alloys can 
have a range of properties from soft and malleable to hard and brittle. 
Some alloys have to be treated after machining to attain their proper 
characteristics (Aircraft alloys like T4 and T6). The lens barrels and 
internals have been made from aluminum alloys for decades. (The lens 
mounts of Pentax lenses are made from a very hard high silica content 
aluminum alloy. It's harder than the stainless steel lens mount on the 
camera.) Brass (which also comes in a range of hardness) has been used 
in focusing helicoids and lens mounts.

BR

[EMAIL PROTECTED] wrote:

On 03.6.7 5:57 PM, "Alan Chan" <[EMAIL PROTECTED]> wrote:

 

If that silver shell isn't soft, I don't know why? Besides, I believe
they used hardened steel on K/M/A lenses (along with some plastic for A),
not brass.
   

I said hard anodized "surface".  Aluminium is inherently a soft metal.  Once
you scratch down to the bare metal, be careful, it's soft.
Re K/M barrels, I thought they were of brass those days.  I cannot think
they use hardened steel as it would be a bit costly to machine.  The metal
barrel does not have to be super strong as it does not bear much structural
stress but should give easier machinability.  But I could be wrong.
Cheers,

Ken