sanding on the lathe

[Pete Staehling]

Okay, so I ordered a flexible shaft with a 1/4" chuck to sand small bowls an other items on my mini lathe. I am trying to decide what to drive it with. I have an old unused small 5 speed bench top drill press. I am thinking that the head from it might be a good way to drive the flex shaft. I am curious what the best speed to drive the shaft would be. I am guessing it might be within the range of speeds that the drill press supports without modification. In another thread someone mentioned they were driving one at 1750 rpm. That sounded a little fast to me. If 1750 is indeed a good speed for this application I'd just use the motor with a diy direct drive coupler, but I am guessing that stepping down the speed a bit is probably a good idea. That would be easy to accommodate with the existing stepped pulleys if they are in the right range (760 rpm is the lowest speed as currently configured). It would get more complicated but I could add different pulley or another shaft and step it down more. I guess that a speed control pedal may be another option.

Thoughts?

[Joe Kaufman]

How about a inexpensive corded electric drill mounted on a wood base with a screw adjustment for the trigger switch speed control. Add a 120V switch to operate the drill so you don't have to mess with the trigger switch to start & stop the drill.

[John K Jordan]

I am curious what the best speed to drive the shaft would be. I am guessing it might be within the range of speeds that the drill press supports without modification. In another thread someone mentioned they were driving one at 1750 rpm. That sounded a little fast to me. If 1750 is indeed a good speed for this application I'd just use the motor with a diy direct drive coupler, but I am guessing that stepping down the speed a bit is probably a good idea.

I can't answer with numbers, but back when I power sanded with rotating disks I got a better surface when sanding slower. Think of it this way: sanding with zero speed is the same as holding the sandpaper stationary which is not a particularly good idea for the best surface. Sanding at high speed is closer sanding while not rotating the bowl, harder to control the smoothness. To me, sanding at a slow speed with the bowl rotating slowly was more like the gentle hand sanding motion that gave me the best results.

I suggest connecting the shaft to a variable speed electric drill and experimenting with different speeds of the disk and of the lathe. Also, experiment with different grits.

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BTW, one reason I'm not up on power sanding is I quit power sanding with rotating disks a long time ago. Instead, I now remove major tool marks with negative rake and hand scrapers then sand by hand or with small random orbital sanders. (The scrapers will also easily remove tearout that would take forever by sanding.)

I have two small ROS, both pneumatic, and both are capable of sanding with slow and very gentle motion. The combination of the hand scraping and gentle ROS gives me a far better surface than what I used to get. It also lets me start with finer grits, seldom coarser than 320, often starting with 400. It also minimizes the clouds of dust and the accidental oversanding of softer areas of the wood, as well as that "oops" from temporarily losing control of a coarse disk.

I use a Grex ROS with 1" and 2" disks, and a palm sander from Woodturner's Wonders with 3" disks. I have extensions to reach deep into a turned box or deeper bowl. The Grex is incredibly light weight and small/maneuverable. Here's a student using the larger sander on the upper side of a small dished platter.

sanding_IMG_20171212_094330_319.jpg

JKJ

[Pete Staehling]

Thanks guys. Good suggestions on the variable speed drill.

[Marvin Hasenak]

I used a power drill connected to a router speed controller. A simple mount was made out of plywood that held the drill and the controller. The shaft was an off brand that I picked up at a junk shop decades ago. It had a good handle and a 1/4" drill chuck. I used it for everything from a grinder for sharpening lawnmower blades, to drilling holes that were not accessible by the bulk of the drill. My son even used it with a buffing head to polish the wax on his car. Over the years the controller and shaft set up wore out about 3 drills before the shaft unit finally snapped.