When sanding with the lathe turning, should speed be increased as finer grit is used?
What speeds should be used for sanding according to grit being used?
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2 Answers
Ah an interesting question.
The first part, 'Should speed be increased as a finer grit is used'
Generally once I've finished turning a piece I do increase the speed a bit for the sanding and I sometimes increase it a bit more when I'm getting really fine sanding almost polishing it.
However, hard numbers unfortunately are difficult for several reasons. the first and biggest issue it that as the size of your work piece changes so too does an 'optimal' speed. On top of that some pieces will just fly apart if spun at the faster speed smaller pieces handle with ease.
I have a variable speed lathe and can just adjust the speed with a turn of the dial and I have a habit of moving it up and down as I'm working on it. For me unfortunately it more what is the fastest SAFE speed to turn this piece.
Making it even harder for me to give you any speed ideas is that the eye that monitors the speed on my machine comes loose quickly and give me no reading, and I have long since given up trying to keep it set.
If you have a lathe like a 5 speed, then my recommendation is generally bump it up one gear after you are done turning.
The single biggest thing I have found for speeding up the sanding process on a lathe is actually not the speed it is turning but the direction. My second lathe I vowed would have a reverse, and it does, it's my favorite feature closely followed by the dial variable speed.
By being able to sand it in reverse you are sanding against the shearing action of the chisels and when you have some tear out it really does sand faster. I tend to switch the turning direction as I sand, I generally let it run both ways for each grit to get the nicest fastest finish out of the piece.
answered Sep 9, 2022 at 17:33
There's no definitive answer to either of these.
It's not just that you'll get differing opinions from various turners on a question like this but that the other variables such as species and abrasive type matter hugely.
Additionally is the often-hidden factor in turning, one that is vital to remember at all times: for any given set speed on the lathe the actual surface speed varies with the diameter. So even sanding a single piece such as a bowl or platter at a set speed on the lathe you're not actually sanding at one speed1.
One more factor to bear in mind is that many turners are power sanding, possibly in addition to varying the speed of the lathe, or instead of it. Obviously this greatly complicates the picture.
What speeds should be used for sanding according to grit being used?
What wood are you sanding? What are you sanding with? How big is the piece? Are you power sanding or sanding by hand so to speak? Do you stop between grits to manually sand along the axis? And last but by no means least, what grit progression are you using?
I understand the desire to get some definitive numbers believe me, but you're going to need to determine this sort of thing for yourself.
You might find that for you, as it is for a great many other turners, this is actually a seat-of-the-pants thing and not a numbers game.
1 The inside of a thick-walled bowl is moving noticeably more slowly than the outside, the rim of a platter is moving much faster than closer to the centre, and so forth.
2 This isn't merely laziness or a lack of rigour, wood varies so much you sort of have to vary your approach nearly on a piece-by-piece basis.
