Using an air-powered belt linisher to clean before welding

When I got my air compressor I was very delighted with the air tools. They were much smoother and quieter than electric tools. They are not very powerful and find their use for fine jobs. You need about ten times the power at the compressor which you would use directly to do the same job with an electric version of the power tool. But for these fine jobs, they are just the ones to use...

Saw and responded this question on sci.engr.joining.welding ("sejw") newsgroup. When doing high-quality welds, you want your preparation to be very clean. This question is about getting rid of mill scale on metal stock. I had experience of this, finding that my air tools gave me a way to have lovely "prepared to silver" steel preparation.

In the kit of air tools which I got with the compressor, there was a pneumatically powered "belt linisher". Playing around with it, I found this very useful application. It involves turning down the air pressure to about 50 p.s.i. (normal operating pressure for most air tools is 90 p.s.i.). Power will be about proportional to the square of the air pressure, so this is going to vastly reduce the power of the tool. But it has this interesting effect...

acrobat-ants  writes:
> what do you guys preffer for metal cean up when hot rolled metal are
> used?

> this would be before fit up and welding and as well as before
> painting.

> knotted wire wheel using angle grinder
> or sand blasting?
> what are the advantages and disadvantages?

> also as far as sand blast media:
> garnet or glass?

> thanks

Hi

My little contribution - definitely not an expert speaking:

For small neat stuff like eg. 1inch / 25mm square tube, with thin
black scale, I find that a little pneumatic hand-held linisher ("power
file", "belt-sander"?) works well. But used with a little difference.
I turn down the air pressure so that I press on firmly and the belt
just creeps round, scouring off the oxide while not removing much
metal (an angle-grinder is a bit indiscrimate, making narrow deep cuts
and not covering the whole surface). Furthermore, I preferably use a
highly-worn belt for this purpose. If I want to dig out a groove,
like where there is the resistance-weld, I ease off the pressure and
let the belt speed-up, plus draw back so that the end-wheel is trying
to press into the feature, so that it actually starts grinding into
the metal a bit and gets to the bottom of the groove.

Air pressure - tool is designed to run at 90 p.s.i.. For 1inch-sq tube,
about 50 to 55 p.s.i. does nicely. For 6inch diameter pipe, the full
90 p.s.i. does the trick. Power would be expected to increase as about a
square of the air pressure, by the way (?).

I have been told these belt-linishers are expensive to use because
they use a lot of belts, but used this way, I have yet to find out how
much a belt costs because you hardly use them up.

This tool I refer to, this belt-sander. It has a belt which runs
about 10inches (250mm) forward from a drive-drum just forward of a
handle which you hold in the palm of your hand.

If there were an electric variant of this tool which you have, don't
choke-down its speed in this way - it would certainly not like it!

Richard Smith

(Richard Smith, June 2005)