Les Newell wrote:
> Hi David,
>
> As others have mentioned, al on al is bad. It is ok if it is lubricated
> but the lubricant will pick up abrasive dust and turn into grinding
> paste. If you don't lubricate it, it tends to stick and 'gall'. Drill
> rod/silver steel (depends where you are) with plastic bearings works
> well but even large diameter rod will flex an amazing amount if it isn't
> supported.
Yes that's true and ideally the rod should be
mounted via a continuous support or discrete
supports at fixed intervals.
Commercial solutions typically use a continuous
extruded AL support. If I had to fabricate an
approximation I'd probably use sections of 1/4"
AL bar of suitable height and mill the top to
receive the drill rod. It would likely be preferable
to pre-bore the rod mounting holes in the bar
before milling the top relief.
> My favourite is rectangular bright mild steel with roller
> skate bearings running on it. Bright mild steel is obtainable from most
> metal stockists and is cheap. You end up using quite a few bearings but
> they are dirt cheap so it isn't a problem.
What type of tolerances are you able to hold with this
approach? At least with the mild steel of which I take
delivery the surface really can't compare with ground
drill rod.
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