Question about interface pads for power sanding

[Jack Gaskins]

I use vinces sanding mandrels and blue disks. I still have scratches in my bowls after 400 grit. The scratches look like about 180 maybe 220 and mixed with some finer scratches. Anyway. I was wondering if I am using the wrong interface pads for the grit. What pads do you use for a particular grit? I have been using the intermediate interface pad on the thin padded mandrel. Im also using a regular craftsman drill since my HF close quarters drill broke. I have been paying close attention to my pressure that I apply to the sanding pad.
Thanks, Jack.

[Steve Schlumpf]

Jack - I have been using the harder pads as I tend to force the sanding a bit. Only thing I can suggest is to get some light on the turning and wipe it down occasionally with mineral spirits to show the scratch pattern. I believe that the sanding dust fills the small scratches and you never see a problem until you apply finish! DAMHIKT!!

[David DeCristoforo]

Sanding problems like this are not restricted to turned pieces! As Steve suggested, it is most important that you have sufficient light and that the light source is positioned in such a manner that the light bounces off the piece. In other words, the work is between you and the light source. Bright sunlight is best but if you don't have that luxury in your shop, dismount the piece and take it outside. This will reveal sanding scratches that you might otherwise miss. I often just unscrew the chuck and take the whole thing outside to inspect it. That way, you don't have to worry about getting it back in the chuck just right.

Also, do not "skip grits". 150 grit paper will probably not remove 80 grit scratches. You need the "intermediate" 100 grit. Needless to say, it is pointless to expect a finer grit to remove scratches that a courser one left! If you are sanding out 80 grit scratches with 100 grit, you gotta stay with 100 grit until all of the 80 grit scratches are gone.

Also, again as Steve suggested, any finish is going to reveal scratches that you did not see on the raw wood. So use that to your advantage and apply a "sacrificial" finish coat. Thin shellac or sanding sealer will work fine for this and is easily removed by finish sanding, leaving your wood ready for whatever actual finish you choose. My process has always involved a finial sanding "by hand". This means setting aside the power sander and turning the lathe off for sanding with any grit finer than 180. Sometimes I will sand with the piece turning but I always stop it and go over the piece one more time. To me, sanding is the least enjoyable part of woodworking! but it is a necessary part so I try to relax and not rush it.

[John Keeton]

For me, bowls are so much more difficult than forms! But, to your question, I use the harder pads (intermediate??) from Vince up to 220, but for 320 and up, I use the softer pads. That said, on forms, I rarely power sand and I use sheet sandpaper nearly all of the time. I also try to wet sand from 320 on up, and sometimes even at 220.

David and Steve gave you some good advice on lighting and applying a little "pre-finish" to show up the scratch patterns. I hate sanding as much as anyone, but I have found that if I spend most of my time at the lower grits, once you get to 220, it should go pretty quickly.

If you can get your tool control to the point where you don't have to start at 80 grit, the job gets A LOT easier!

[Paul Heely]

To add to the excellent advice you have already gotten. If you do find a few scratches, try sanding them out without the lathe running, same way you would spot sand a small patch of torn end grain. I use denatured alcohol to wet the piece and look for scratches, sort of like Jimmy Clewes, but without the wood flambe :)

[Jamie Donaldson]

Paul beat me to the suggestion of selectively sanding scratches out with the lathe off, then blending those areas back to the adjacent areas with the lathe turning at a relatively slow speed. I suspect that you may also be sanding at a speed that is too high, causing the sanding material to jump over some areas of the wood from high spot to high spot, and I use only the harder(yellow?) intermediate pads

[Bernie Weishapl]

I also use the hard pads to 180 or 220 and the soft pads from there up to 400. Ditto on the mineral spirits or DNA to see the scratches clearly.

[Mark Levitski]

Wow, a lot of replies in a short period. Here's one more:

IMO, the mandrel or interface pads are somewhat irrelelvant in this case. As others have said, spend more time on finding and removing marks in the lower grits by whatever method, then it's smoother sailing on the finer ones. I also agree that stopping the lathe and concentrating on specific trouble spots without creating obvious sanding depressions is the way to go. We have all been disappointed at finding those coarser grit marks after we think that we are finished through 600 and above.


My wife and I recently noticed pretty obvious drum sander marks left in a finished, live-edge table top created by a well-established woodworker/artist and displayed for sale at a high-end gallery. My wife makes pieces similar to this and takes pains to produce a perfect finish and leave no trace of this kind of thing. None of us are immune to missing them, and some of us seem not to care.

[Harry Robinette]

Jack
Try looking up Bill Neddow woodturner from Canada. Bill has studied sanding for something like 12 years and does high speed sanding that does not cause heat and you can sand a bowl in no time at all. He also explains allot about sand paper.

[Reed Gray]

Well, I use the firm pads at least to 220, and some times to 400. I also sand at slow lathe and drill speeds. I get less jumping/skipping of the disc. Seems that I can never get the disc or the interface pad on perfectly centered.

Having good lighting is just as important as anything else. Have you ever taken a bowl out into direct sun light before you put on the finish? Amazing what you will see. The lights in our shops do not come close to the natural sun light that our eyes have evolved to see best in. I do use Blue Max lights (They used to advertise on the back of Woodturning Design mag), and Ott lights are another brand name. If you know of any one who does fine hand sewing like quilting, or needle point, they know all about this type of lamp. One word of caution, do not take the lamp out to the shop. This is a much more serious offence than using the house hold microwave to dry stinky wood in.

Having good perscription glasses is another necessity. The reading glasses from the stores just don't do it.

I do not want mineral spirits on my bowls, ever. I wipe them down by hand, and the finer dust will fill in larger scratches and high light them, especially with the higher grits, 320 or so. I so spin the bowl by hand a lot, to make sure I am not missing some thing.

robo hippy

[Scott Hackler]

I have all the interface pads but honestly only use the thin yellow one. I also have discovered a preference to the smaller discs and bought a bunch more of the Ceramax (pink) discs while in Waco. Most woods don't give me issues but I sand in forward and reverse, at about 400rpm (I think? Its the second to the slowest belt speed on my lathe) and blow the wood off after every grit. I will wipe down the stubborn darker woods with mineral spirits or Dna, after I get to 320 grit or so, just to see what a finish will look like at the current sanding quality. Usually, with the darker woods, this means MORE sanding and mostly by hand.

[Wally Dickerman]

On the subject of lighting, use an incandescent task light at your lathe, shine it at an angle so that the sanding scratches can be seen. Flourescent lights leave no shadow so scratches are easily missed.

[Jack Gaskins]

For lighting I have one of those lights that uses a standard house ligth and it also has a magnification lense. One of those you can pick up at the office store or Micheals. I purposly do not take the bowls out of the garage in the sun because I dont want to see the thousands of scratch marks......My lathe speed is 250 and the drill speed is high at around 2500. I usually dont use anything to wet the bowl because it clogs up the sandpaper to fast but I did use some danish oil tonight sanding a bowl and it seemed to help.

[Michael Mills]

I do similar to Wally and shine a light almost parallel with the item (I also dampen the item with mineral spirits). The shadows down in the valleys show up well.

I use Vinces blue disc also. I only have one pad :( and that is what I have always used. Do I need to buy some more pads? :D :D