Parallels - what are the differences?

[Rickabilly]

If we are going to go into bearings as parallels, one that very few think of, is using the actual rolling elements themselves, if you can get a hold of an assortment of different large-ish bearings and knock out the cages not only can you use the inner and outer rings but you can use the rollers on end as fixed length spacers which is very handy when you are bolting down directly to the table and the work is an odd shape, within my capability to measure, all the rollers in a given bearing will be the same length, It is possible to use cylinderical rollers laying down also but only in the bottom of a vice. My favorite rolling elements are the Barrel shaped ones from self aligning roller bearings, they are just nice in your hands for some reason but the tapered ones out of tapered roller bearings are the most practical as one face being larger gives better stability while the smaller top face means that you've got less chance of the tool bumping into them as you break through.

I am partial to the use of HSS section too but I suppose my favorite set of parallels were a set made as a shaper exercise at tech college then hardened and ground, as it would happen the set I made were taken by mistake (or stolen) so as a form of compensation the teacher gave me the pick of the sets that weren't collected, while the ones I had made were really good (I came top of the class on that exercise) the two sets I ended up with were poorly machined before hardening and grinding, so the side reliefs and through holes are uneven but they are parallel and square and I have been using them for more than two decades and now they are just a part of my little collection of stuff, I can't imagine not having them around.

Regards
Rick