I thought I'd mention this short cautionary tale in case anybody else finds themselves in a similar position.
My tools have little chance of getting rusty - I use oil on my sharpening stones and there is no source of water in the workshop. The only time that I seem to end up with spots of rust is through drops of sweat getting onto tools. Obviously I wipe sweat away whenever I see it but sometimes I miss the odd drop.
Yesterday I was checking some mitre angles using a 12" and a 6" combination square on the basis of whichever was nearest to hand. I noticed that I was getting marginally different results. I looked closer at the squares and spotted a patch of rust on the mitre face of the 6" square right up against the ruler. It had "bubbled up" in the way that rust can and this was inducing the inaccuracy. It took no more than 20 secs of gentle rubbing on a diamond stone and then it was bang in order and I was getting the same from both squares.
The point is that I hadn't been aware that it was there and I discovered it by chance. I think I will make a point of visually checking steel reference surfaces for rust from now on.
My tools have little chance of getting rusty - I use oil on my sharpening stones and there is no source of water in the workshop. The only time that I seem to end up with spots of rust is through drops of sweat getting onto tools. Obviously I wipe sweat away whenever I see it but sometimes I miss the odd drop.
Yesterday I was checking some mitre angles using a 12" and a 6" combination square on the basis of whichever was nearest to hand. I noticed that I was getting marginally different results. I looked closer at the squares and spotted a patch of rust on the mitre face of the 6" square right up against the ruler. It had "bubbled up" in the way that rust can and this was inducing the inaccuracy. It took no more than 20 secs of gentle rubbing on a diamond stone and then it was bang in order and I was getting the same from both squares.
The point is that I hadn't been aware that it was there and I discovered it by chance. I think I will make a point of visually checking steel reference surfaces for rust from now on.
