Hi Phil,
Pieces of tool steel are good as parallels as well. Not thought about using ball races... Nice one.
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Only if you grind them so they are parallel, or selectively assemble them into sets. Or your requirement for 'parallel' is looser than mine because there's no guarantee 2 pieces of tool steel of nominal 1/2" are going to be exactly 0.5000".
They generally are pretty close and I have a couple sets I keep for parallels myself, but it pays to mike them first.
PDW
I use HSS tool blanks for parallels also: You have to pair them up and mark which sides to use though as they aren't perfectly square. Generally if you order from the same source the branding is the same as are the sizings - never square though.
To set your tool post reasonably square to centre line of your lathe when using a 4 way post or quick change place a parallel or piece of tool steel against the face of your chuck or the end of your job, bring tool post to touch and lock in position.
This works well enough for threading and parting from my experience.
Sometimes when setting long or heavy work in the lathe chuck use a piece of timber held by the tailstock and centre to support it.
I use key steel as cheap paralells. Varius sizes are available.
Roger
As far as a tip goes, although not strictly machining related - whenever you're cutting aluminium, a cheap candle makes an excellent stick of lubricant. If hacksawing, just take a couple of shallow cuts into the candle, then have at it. If using an angle grinder with a 1mm cutoff wheel, start the grinder up and rub the end of the candle against both sides of the disc - you'll see it impregnate into the disc as you do it. Would also probably help those using bandsaws with no coolant, could start it up and hold the candle gently onto the teeth. Doesn't take much, I've had the same 20mm diameter candle for about 5 years, plenty of life left in it.
Not sure about the ball with flat,but you could change it for a length of round bar with no flat on it.
I have never used a piece of stock with a flat on it when squaring material in a vice. Cant comment on that.
I have only ever used round bar and generally a little longer than the vice jaws just to make it easier to hold when setting up.
Diameter of the bar is usually between 1/4" to 1/2".
Tool height can be fine tuned to somewhat compensate for taper due to bed wear.
A Harold Hall tip
setting your tool height is critical for fine finishing cuts
if the tool is even a tiny bit above centre it will rub the work and not cut
It is OK if the tool is a fraction below centre, to check this, take a facing cut and look for the pimple left behind to see if your tool is below centre
Mike