Sanding Advise

[cwearing]

Is there an acceptable method to avoid the highs and lows when sanding elm and oak?😕

 

[MichaelMouse]

Rigid or semi-rigid sandpaper backing and don't press.

Best, of course, is to do reasonable gouge work. Both woods you mention don't benefit much by being sanded past (CAMI) 220 with the grain, so it's fairly easy to do a two and out on grits. More grits and more time you spend, worse the problem can get.

Look into these http://www.packardwoodworks.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=snding-adiscs-power as a good way to bridge the sander over soft spots. I use 'em, and one step further, because I use the handle of my flex shaft as if it were the shank of a tool. http://s35.photobucket.com/albums/d160/GoodOnesGone/?action=view&current=150Sand-1.flv

 

[Dave Roller]

What MM advises. I learned it after I discoverd that while sanding spalted walnut with a soft backing behind my sandpaper I had found a particularly soft spot about the size of a half dollar and had created a depression in an otherwise perfect bowl.

 

[Charlie Knighton]

sanding problem

thanks for bringing it up and for the information, i had never really thought about the problem but my highs and lows did seem to get worse the more i sanded oak

if i keep reading this board maybe with osmosis i will learn something 😀

 

[john lucas]

I find the trick is to get a better finish off the tools. Use a freshly sharpened gouge, speed up the lathe and move the tool slower to get a better cut. I'm not using a 40 degree grind on one bowl gouge that I use for finishing cuts or I use a pull cut on a bowl gouge with a long side grind for the outside. Then use a freshly sharpened shear scraper. If this is done properly you can start sanding with light pressure at 180 or 220 and you don't get lumps.

 

[MichaelMouse]

I find the trick is to get a better finish off the tools. Use a freshly sharpened gouge, speed up the lathe and move the tool slower to get a better cut. I'm not using a 40 degree grind on one bowl gouge that I use for finishing cuts or I use a pull cut on a bowl gouge with a long side grind for the outside. Then use a freshly sharpened shear scraper. If this is done properly you can start sanding with light pressure at 180 or 220 and you don't get lumps.

I think the entire answer is in the shear. It bridges the early/latewood just as the rigid sandpaper backing does, making a fair surface which can be extended into a fair curve. Since I use my shear with benefit of bevel, and push rather than pull so I can stay out of the way of a mishap while getting good visual as well as tactile feedback to start the cut, I cut out a step.

I vary the feed rate rather than speed the lathe. That way I don't get into a high-energy catch situation near the periphery. Square of the velocity, as you recall.

The shaving is wide, which indicates quite a shear, but the cut surface benefits. The shavings will get more narrow and tightly twisted toward the bottom where the curvature is changing rapidly.