On 7/9/2010 8:40 AM, Jim Thomson wrote:
> I noticed on DX eng's site that they sell boom material, made from 6061-T8.
> Now this T8 version I had not heard of. It's a full 10 ksi stonger [in
> yield strength]
> VS 6061-T6. That equates to 28.6% stronger..which is nothing to sneeze at.
> The boom material they sell is all .120" wall. Now this stuff is superb.
> It all telescopes
> into each other. IE: 1.50"-1.75"- 2.00" - 2.25" -2.5"-2.75"-3.00"
> I don't know how long the .120" wall has been out for. it appears to be only
> available in the
> new T8 version. T6 has been available in .125" wall for many sizes..
> like above, BUT they
> don't telescope, which is a real pain.
It's a whole lot easier to make a relatively small 3 roller swedge as
you only need to reduce about 6 or 8" of the OD at one end by about
0.003 inch for the next size to fit. Of course the typical reduction of
the OD by the wall thickness plus 0.003 would be a bit much for 1/8" and
3/16" standard size wall. The 0.120 wall actually gives a bit too much
clearance. Use Noalox(sp?) and it'll give a good slip fit with only
about 002" or 003" clearance.
> You have to turn it down in a lathe, etc.. to make it fit
> inside the next size up.
With a lathe make a couple of rollers similar to a knurling tool, but
flat that can move along with the tool post. It does need a back support
though, more like a knurling bar that attach to the tool post, but
float. T-6 is harder than the more common alloys and I assume that T-8
is even harder.
I thought the 0.120" T-6 had been out for some time. Like DOM most of
this tubing can be ordered from the factory with any particular wall
thickness. It's just here in the US the fractional sizes are standard
and most suppliers stock only the standard sizes. I can get all the
1/8" (0.125") tube I want in 24' lengths delivered and for about the
same price as one 6 footer with 0.120 wall. I've never asked what it'd
cost to order the various sizes with 0.120 wall. It'd cost more and I'd
probably need to order a bunch.
> The .120" wall has always been available for steel tubing. Dunno why it took
> so long to do the
> same for AL tubing ?
Regular suppliers probably have had little market for ordering a batch
with that wall thickness. Tell them you want a truck load and they'll
probably be able to deliver it to your door in 24' lengths.
> How long has this new 6061-T8 been available ?? It would be the answer,
> and a quick fix to one of
> my new boom projects.
> Later.. Jim VE7RF
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