: If you think on it, you'll see that the center of a rotating disk moves much : less abrasive against the work than the outer edges.
With you so far.
: The beveled edge evens out the contact.
I'm not seeing how.
If you push a piece of work against the entire surface, the : parts of the work in contact with the outer edges of the disk will have more : material removed than the center.
Only if you're pushing hard enough to bend the wood, or to deflect is away from the right angle of pproach to the disk,
On a bench top sander??? Table does tilt but does not elevate or lower so that the dirrection of disk never gets close to the grain dirrection. On a TS that is a different matter.
I think we are still talking about the OP's bench top disk sander, Not all jointed edges are used for a glue joint. Jointed edges are often the exposed edge.
I have never seen a bench top disk sander capable of raising or lowering the table, only tilt.
When the disc is tilted so the taper is vertical at the center line of the disc, the outside edge of the disc is farther away from the fence. That allows you to feed a board along the fence without hitting the edge of the disc. If the disc is flat and you want to remove, say, 1/32 along the board edge you would not be able to feed it without hitting the edge of the disc. Get a kitchen plate and play with it, you'll see what I mean.
If the disc is flat it is mostly sanding across the grain; when tapered, it is only contacting the wood at one point and is moving *with* the grain. Cutting with the grain with anything always gives smoother results.
For removing 1/32" from the edge of a board, my first choice would be a hand plane -- but before that, I'd ask myself if it's really necessary to remove such a trifling amount.
You're going to have to explain that one, I'm afraid.
You mean about cutting with the grain? What's to explain? If you use, say a router, and cut a rabbet both with and cross grain, which is smoother? Ditto any machine I'm familiar with. Moreover, any tool marks less obvious with the grain and are easier to remove since they can be removed in the same direction as the natural wood grain.
I'll try. I'll start where I was confused and see if that helps. Because I was imaging the wrong tilt to stuff.
Take this tapered/cone disc mounted on a table saw (figure that's the bast setup for visualizing -- familiar to all here).
With the arbor horizontal, you have a cone pointing at the fence.
Now, tilt the arbor until the disc directly above the arbor is vertical. You have a cone pointing somewhere below the fence. Everywhere *except* that vertical line is sloping away from fence. That line is parallel to the fence.
Turn on the motor, and the grit is all going in (slanted) circles. But on that vertical line, as each grain passes for that mathematically short time, they are moving horizontal. By the time they are moving down, they've moved away from the wood and are no longer in contact.
That's the ideal, where the contact is infinitely narrow. With real materials, you have a narrow contact (1/8 or 1/4 inch) and a nearly flat arc.
Now, I was puzzled because I was picturing sanding along the "down meets table" part of the disc with the taper meaning that the outfeed (where the disc is going up) isn't in touch. That could have a benefit (I imagine), but it isn't what was being talked about.
:> I'm confused. Why is this better than a plain flat disc?
: Two reasons...
: 1. When the disc is tilted so the taper is vertical at the center line of : the disc, the outside edge of the disc is farther away from the fence. That : allows you to feed a board along the fence without hitting the edge of the : disc. If the disc is flat and you want to remove, say, 1/32 along the board : edge you would not be able to feed it without hitting the edge of the disc. : Get a kitchen plate and play with it, you'll see what I mean.
Got it, and thanks for the explanation. The plate analogy was excellent. (And thanks to Lobby downthread).
Dunno. The back of the plate is covered by the housing of the unit.
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blue "ring" around the disk extends in a bowl-like manner down to the motor housing, where it appears to be welded right to the motor housing, so the back of the plate is not accessible .
There may be a bolt under the sandpaper itself that allows the plate to be removed, but if so, I think I'd have to remove the table and dust collection housing before the disk could be removed. Not sure, but I'm not into tearing the unit apart right now.
Maybe if I decide to return it, I'll take it apart just before I do.
I asked because I thought your plate might have one cone side, one flat and could be reversed. Why they would make it that way for a disc sander, I have no idea. The plate is being driven directly by the motor so I suspect it is held on to the motor shaft by a nut.
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