Lathe disc sander question

[Dale Allen]

With rare exceptions, I see these designs patterned after the dedicated units in that the table is set at the center of the disk.
I use a small 6" one that I made years ago and it is set about 1" below center. Until I started planing a bigger unit, I had not given this much thought.
There are a lot of manufactured ones that even have a guard on the back half of the disk.
Is there a reason they are set up this way?
My though is that on the front half the disk is pushing down toward the table and at the back it is pushing up. So that in fact may contribute to an uneven sanded surface on my small one when I run the piece back and forth across the center-line. Even trying to hold the piece flat to the table, it may still be moving off square.
Thanks for any insights.

 

[jttheclockman]

With rare exceptions, I see these designs patterned after the dedicated units in that the table is set at the center of the disk.
I use a small 6" one that I made years ago and it is set about 1" below center. Until I started planing a bigger unit, I had not given this much thought.
There are a lot of manufactured ones that even have a guard on the back half of the disk.
Is there a reason they are set up this way?
My though is that on the front half the disk is pushing down toward the table and at the back it is pushing up. So that in fact may contribute to an uneven sanded surface on my small one when I run the piece back and forth across the center-line. Even trying to hold the piece flat to the table, it may still be moving off square.
Thanks for any insights.

Dale I am getting older by the days and my comprehensive skills are diminishing for sure. :biggrin:I tried my best to follow what you are asking but i failed. Could you post a photo of what you are attempting somehow. Maybe show us what you made already. When you say lathe disc sander it is a round faceplate and is mounted always dead center. The forces and speed change the further away from center you get no matter weather you are on the right or left side of center.

When using a disc sander you want your work to be sanded on the downward side of the disc usually the left. To sand faster use the outer edges of the disc. For more control over small pieces use the center more. Always keep the piece moving to avoid burning. Not much more I can add to this. The table is center to maximize the use of the sandpaper. Good luck and if you post something other than what I mentioned than please disreguard because as i said I am getting old. :biggrin:

 

[Dale Allen]

I was just referring to the location of the table top in reference to the disk center. And thus the effect it has on the way the piece is sanded.

 

[Curly]

The two reasons I can think of that manufacturers put the table on the disc centre are for safety and dust collection. If too far below the disc is effectively sanding to the side so could snatch the wood from your hands if not paying attention and the dust is moving sideways and won't be collected as effectively since it isn't going to be picked up by the shroud. You can make your sander anyway you like.

 

[conandy]

Safety. You want the disc to be forcing your workpiece downward. With table below centerline, you have possibility of disc pushing it in a number of different directions, possibly grabbing it and throwing it across the room.

 

[Dale Allen]

OK, I see all the points noted.
I've had pieces fly around when using the disk without the table.
So, if I use an 8" diameter disc the max I can safely have is a 4" area, front and center.
Even so, it will be a different sanding speed depending on the distance from center.
Not a big deal on small pieces but trying to get a 45 angle cleaned up on a 3" wide board will still be a small problem. So I'll take it slow...right?

Thanks all for the input and enlightening me.