WW Forum Users BUG Me, sometimes!

[Dave Anderson]

A few days ago, a fellow woodworker make a shoot-from-the-hip comment about 12" disc sanders. What he said was very "authoritative" but struck me wrong so I posted a reply questioning his assertion and asking him to "educate" me.

No response from the "authority!"

This really bugs me to no end! Someone makes a statement and is asked a question about that statement = no response! Why? We are all here because we think we can learn something from fellow woodworkers. So, I'm trying to be better educated about 12" disc sanders. I've always thought I "needed" one! :D

This poster made the comment that if you are going to get a disc sander - <i>"you needed at least a 12" disc because only two inches of the disc is 'usable'."</i> <b>Say what?!!!</b>

I can buy into only 6" as being usable - the half of the disc rotating down toward the table BUT where does this guy come up with a 2" usable number?

Any thoughts or help out there? I'm still lookin' to learn... Hello?!!! hello...

[Dave Anderson NH]

I didn't make the comment, but I would say the person who did is partially correct. The first couple of inches out from the center are of limited use and run the risk of burning your work if you are not exceptionally careful(DAMHIKT). Essentially it is moving at too high a surface speed to cool adequarely. Having said that I often use this area for rough stock removal to get the maximum wear out of my discs. Personally I think the 10" which I use (a Delta) is more than adequate for most folks and is a lot easier on the wallet when you buy the open stand version for about $300. The big bucks 12" version does give you a wider usable area, but the big difference is in the sturdiness of the front tilt table. To my mind, the most important purchase with one of these things is the gum rubber "eraser" which greatly extends the belt life when you use it to remove the loading in both the belts and the discs. Remember that because of speed, any grit you use will behave and give results as if it was the next finer grit. By the way, I agree about folks not answering questions, but sometimes there are excuses like vacations, etc, etc.

[Dave Arbuckle]

East Coast Dave (dang, this gonna get confusing quick):

The first couple of inches out from the center are of limited use and run the risk of burning your work ...(due to speed)

I'm confused, Dave. Further out on the disc is moving faster in SFPM than the middle. I think if the inner portion burns, it's probably because the area you are using is so small, there isn't enough heat dissipation?

Dave A... ;)
Not a discsander user.

[Dave Anderson NH]

That's one of the hazards of writing something up too quickly. Closer to the center there are fewer liner inches of circumference which means less tiime for the abrasive to cool before contacting the workpiece again. Now I suppose we should solicit an answer from someone who isn't named Dave.

[Dave Hammelef]

That's one of the hazards of writing something up too quickly. Closer to the center there are fewer liner inches of circumference which means less tiime for the abrasive to cool before contacting the workpiece again. Now I suppose we should solicit an answer from someone who isn't named Dave.


Hmm, so the inside has less time to cool than the outside? Nope both make 1 rev. in the same time. But it is traveling slower so may not have as much air passing over it to help cool it. But Im just another dave

[Steve Jenkins]

I have a 20" disc sander and why it burns near the center is for me a moot point.I think the more important fact is that if you are careful with your pressure it sands much less agressively the closer you get to the center. If you apply the same pressure near the center and near the edge it will sand much faster near the edge.For sanding off half a line I try to stay near the center. Steve

[David Ripley]

Did I hear my name called?
David, don't call me Dave in Sacramento, CA.

[Sam Chambers]

Hmm, so the inside has less time to cool than the outside? Nope both make 1 rev. in the same time. But it is traveling slower so may not have as much air passing over it to help cool it.

While both the inside and outside move at the same RPM, the outside travels farther each revolution. Therefore, it is out of contact with the workpiece for a longer period of time, allowing it to cool better. The inside is out of contact with the same piece of wood for less time, increasing to chance of overheating.

Not to mention that if you're sanding near the center and move accidentally to the other side of center, you have a big surprise on your hands. Or on your head, if that's where the wood lands.

[David Rose]

I have an old KC 3/4 HP motor, about the size of a modern 5 HP physically, with a 12" disk that I use for smoothing trimmed stocks for buttplates. For non shooters, this is a piece of walnut (usually) about 1" x 5". I cut just end grain with this job. It is pretty sensitive to burning anywhere on the wheel. Closer to the center burns really fast, but to do the 5" cut I have to get close to it. I can only do a few jobs before the paper is kapoot. No burning is allowed as the stocks are normally finished and the very edge will will show. And normally the cut has to be uniform amounts all the way across. I end up applying more pressure at the center to get it to cut as fast as the edge cuts. But it works fine. I just have to use light pressure at the outside and slightly heavier inside. If the pressure is increased just a bit much it instantly burns. But it is all usable within these limits of pressure and good abrasive.

David

[Keith Starosta]

One thing's for sure......we've learned that a lot of guys named "Dave" use disk sanders...... :D

[Dave Anderson NH]

use disc sanders, but there are a total of 45 registered Daves on this website. I've always been a master of useless information.

Of course there is always the question of how many unregistered Daves are here too.

[David Rose]

Hmmm... ;)

David

[Dave Hammelef]

While both the inside and outside move at the same RPM, the outside travels farther each revolution. Therefore, it is out of contact with the workpiece for a longer period of time, allowing it to cool better. The inside is out of contact with the same piece of wood for less time, increasing to chance of overheating.

Not to mention that if you're sanding near the center and move accidentally to the other side of center, you have a big surprise on your hands. Or on your head, if that's where the wood lands.

Ok this is splitting hare but the distance traveled does not explain why it is out of contact for a longer time. If the item being sanded were a point the amount of time out of contact would be identical.( It would be the amount of time it takes the disk to make 1 revolution).

But most things being sanded are not points they have a thickness. toward the center of the wheel this thickness covers a larger portion of the circumference and therefore the item may be in contact with the same peice of sandpaper for 1/4 rev. at 1" away from the center and only 1/20 rev at 5".

Just adding more confusion I think

Dave