Sanding advise please...

[oldgriz]

I am working on a nice little cherry bowl and am about to use my power sander for the first time on this...
The question is...
What speed do I want my Jet 1236 at and how fast should I be running the sander.. it is a Sioux Slow Speed Variable... I am using 2" disks..
Thanks..

 

[Dr_dewey]

sanding speeds

i spin the lathe around 500 rpm and use the drill at full speed. For the nasty endgrain tearouts, will hand sand with 60X if its bad, and then give it a squirt or two of DW40 to wet sand the problem areas. Use the sanding disc in the 2:30 to 5:00 O'clock portion of the bowl and keep moving the head to avoid depressions -you'll find the soft spot. If the bowl is not quite dry you can get a lot of heat build-up and the bowl will warp. You'll see that because the sander starts to buck. Stop and let things cool, even for a day if need be - let the new wood surface climatize to the new humidity.

 

[Steve Worcester]

(I really need to write that article on power sanding!)

All variables aside, I would say sand at about 500 rpm and try not to top out the sander in RPMs. A lower RPM at the lathe means the sanding pad will not bounce as much as the wood turns. Stay at lower RPMs also because as pitch and such builds up on the disk, it will increase the heat and the heat can check (or contribute to warpaging) the bowl and melt the velcro "fingers" on the surface of the pad. In addition to that, play with the sander going with the spin of the wood and against it. Against it will take off more material, but may leave a more course finish. With many of the softer or more open woods, as you sand, you will remove more of the early wood (closer to the inside of the growth rings) and less late wood (more dense area on the outer edges of the growth ring). Assuming you are sanding a side grain bowl, if you sand too much you will feel slight variations in the rings that slant toward the late wood.
It is also a good idea to keep a crepe pad near when you are sanding to clean off the sandpaper. Remember wornout sandpaper does not become a finer grit, it is just worn out sandpaper.
An example of the crepe block
http://www.rockler.com/ecom7/product_details.cfm?&offerings_id=10623&objectgroup_id=218&catid=3&filter=cleaner

The old saying (attibuted to many) goes....
use the sandpaper like it free. Start at the grit low enough to remove tool marks and tearout, don't use the sandpaper to reshape when a cutting tool would work better. Don't skip grits, you will be wasting more time than the sandpaper you think you are saving.

 

[Dr_dewey]

sanding paper makes a big difference

I use Astra dot disks - a japanese product - the grit is segregated in little islands which do not clog up as much as the homogenous type. seems to help a lot.

 

[Whit]

I pretty much agree with Steve, but (there's always a "but" ain't there?) I have a couple additional thoughts regarding sanding Cherry (or most any fruitwood, for that matter).

Most every fruitwood I've encountered (Cherry, Apple, Peach. Pear, etc.) seems to have a lot of sugar in the wood. If that sugar gets overheated at all it, at best, blotches. Ugly! To avoid overheating I:

1. turn at the slowest speed my lathe will turn (250 RPM)
2. run the sander about as slow as I can (I'm guessing about 300 RPM)
3. change discs often. As Steve suggests, spend sandpaper as if someone
else is paying for it.
4. keep in mind the direction I'm cutting. With a gouge, on the outside of
a bowl I cut from the base to the rim, on the inside from the rim to the
base. It's no different with sandpaper which is, after all, just another
cutting tool. And yes, when it's worn out it's just another dull tool.

Whit

 

[DennisM]

Tear out trick

One trick that I have folund works for tearout is to apply a coat if sanding sealer or shellac, let it dry, then take one last pass with the bowl gouge. The sealer/shellac helps to stabilize the grain so that you can cut it with less tear out. Bottom line is the best way to sand, is to not need to.

Hope that helps

 

[dkulze]

One trick I read about on a post and tried, with great sucess is using past wax on the rough spots. Pile on a big gob of wax on the spots of tearout, rub it in a little, then sand immediately (while the wax is still wet). Best explanation I can come up with is that it lubricates the wood so that the paper can cut but not catch and pull. Whatever the explanation, it works really well.

Dietrich

 

[PapaDoc]

Steve,
Write the article!