Thread: Greaseless Compound Grit Question

There you have it - it depends on the substrate you use to load the compounds onto.

Sisals are not all equal - some are very, very hard, some are soft. The grit of the compound is nearer the stated grit number on the harder sisals - on softet sisals it sinks in a bit and the grinding effect is less.

You can get hard wool felt wheels - these are in three degrees of hardness, and the hardest one is nearly as hard as the hardest sisal - but, unlike very hard sisal, it adds nothing of its own. A very hard sisal will leave lines.

Stitched wheels are pretty soft, so if you put a blade on a 72 x 2 inch sanding belt of 600 grit, then take it to a stitched wheel with 600 grit compound, it will soften the marks left by the belt.

Thats not the whole story though. If you go to grease lapping compounds of the same grit, the effect is much less. What you see on the metal is much more the effect of the wheel.

Or you can go the other way - using redhead cement you cover the wheel with the cement, then run it through lapidary grit. These wheels are really abrasive - almost like ordinary sold grinding wheels. You also have to let the cement dry, then hit it all over with a hammer to break it into small bits, otherwise the effect will be exactly the same as using a solid grinding wheel.

In the old days, when people were apprenticed to learn this sort of work, they were tested by the instructors. Any evidence of 'smear' - those drag lines that occur with lettering and which soften edges and make everything look 'soft' was heavily penalised. They were taught, especially where metal had been stamped with a mark or logo, to keep turning the workpiece to avoid the draglines. A soft wheel is a prime culprit in producing draglines - it gets into the cavities. To keep things sharp, a harder wheel was used.

The very soft wheels are used in final polishing only - they distort and bend over everything, but the abrasive effect with finishing compounds is so slight that draglines are not a problem. However, if the work is not pristine, then it is best not to use these soft wheels and finishing compounds - all they do is enhance the marks left by previous grits.

Regards,
Neil