Friday, 7 September 2012

Belt Sander

I've been after a bench mounted belt sander to sand down a Bamboo backing and my Oregon Yew heartwood billets.
There was a good solid one on E-bay but the price escalated beyond my target.
In the end I bought a cheapo one, like many cheap tools, it does a good job if tuned up a bit. I modified the guard and end stop to allow me to sand long parts and I modified the dust extraction spigot to work with my dust extractor..
It's amazing how strong atmospheric pressure is.
My dust extractor (standing on the floor behind my bandsaw) has a long flexible hose 4" in diameter.
I connected it to the sander via some old plastic plumbing fittings and switched it on... whaaaa! It dragged my bandsaw across the garage!!! What was going on???
Effectively it was trying to suck through such a small hole it was creating a partial vacuun and the flexible hose was collapsing concertina fashion.
But how come it pulled the bandsaw (on it's castors)?
I did some quick sums:-  4" diameter hose has a cross section of pi x radius squared. That's about 3 x 2 x 2 square inches. Atmospheric pressure which is almost 15 pounds per square inch so, that comes out to 180 pounds, which rather explains it.

So, I opened up the silly small holes in the sander spigot to make it full bore, but I could still see it trying to concertina the hose, I then added some 3/8" holes around the periphery of the adaptor which joins hose to sander, to allow more air to bleed into the hose.
That stopped the bandsaw marching across the garage.

Cautiously I cleaned up the belly of the Maple bow a bit using the belt sander, the rounded pulley end of the belt was good for following the undulations in the bow where there are knots.
I was very careful as power tools enable you to screw up in the blink of an eye.
The bow has had a good few days to stabilise after it's steam bending. It's beginning to flex now on a taut string and looking more symmetrical.
I'll take some pics over the weekend as it comes back to brace height. At the first hint of any set I'll heat treat the belly. I want to get it moving first as there's no point heat treating and then taking off the heat treated timber as it's worked down.

1 comment:

  1. I also plan to buy a belt sander on E-Bay. That's good when I read your article. I think that old belt sanders are not maybe value. Perhaps, i need to change my mind. Thanks the author!