Slow Speed Sanding

Well, after the Symposium in North Carolina (I think it was North) some years back, a bunch of people were ranting and raving about this new guy with really good abrasives, Vinces-WoodNWonders. I had to experiment, and really liked them. I did chat with him, and he started me on slow speed sanding. Before, I had the trigger on my drills pushed all the way down. He said slow speed sanding worked better, so, being the curious sort, I had to try it out, and found out that it did seem to work better than full speed, and I have both high and slow speed drills. I also found out my drills lasted longer before the bearings went, from 300 plus bowls to 400 plus bowls (note here, I am rough on my tools). What drove me crazy was trying to figure out why the slow speed sanding worked more efficiently. I may have it now, thanks to a comment from Jimmy Clewes. He said that he doesn't think abrasives are cutting tools, they really just scratch the wood. I pondered that, and thought, well the difference between the steel and the abrasives isn't the serrated profile of what is cutting, it is on a steel tool, they are on a line/knife edge, and on abrasives they are on a plane or flat surface. So, both are cutting, but slightly differently. With a knife edge you can dig in as far as your lathe, tool size, rpm, torque, handle, and personal strength will let you. You can't do that with abrasives because they are on a bigger surface. With slow speed sanding, if you are at high speeds, the abrasives never really have a chance to dig in and get real traction to cut effectively. The abrasives will skip a lot more. I find myself now with the trigger mostly at 1/4 to 1/2 speed max, and most of the time it is in the 1/4 speed range. My lathe rpm is at 15 to 20 rpm, but that is because my bowls are warped, and if I go any faster than that, I can't keep the abrasives on the wood. It really does seem to work much better.

robo hippy

I also have had many discussions with Vince and since then I generally place the lathe on the 600ish RPM pulley grove and sand at about half trigger on the drill. Sometimes though.... I don't want to take the time to change the speeds and although I can get it done... it's by far more efficient to slow it down. That being said, I still hand sand my finials at 2000rpm (same speed as they are turned) and that works well for me.

I sand bowls at 175 rpm and about half speed on the close angle drill. Seems to work for me. Using a back up pad really helps keep the abrasive a bit cooler

Reed, I think your right on the money with your assessment.

I think you have a good analysis. Slow speed sanding is definitely better in my opinion. I like 50 to 70 RPMS and 1/4 to 1/2 speed on the drill. Burl is easier to sand than regular wood because it doesnt have the cross grain issues - the density is more consistent- grain direction is more consistent. I always have issues with the cross grain on bowls and it appears to be tear out. This is probably more technique than the wood or the tool. I probably need to take finer finish cuts.

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Originally Posted by Reed Gray

Well, after the Symposium in North Carolina (I think it was North) some years back, a bunch of people were ranting and raving about this new guy with really good abrasives, Vinces-WoodNWonders. I had to experiment, and really liked them. I did chat with him, and he started me on slow speed sanding. Before, I had the trigger on my drills pushed all the way down. He said slow speed sanding worked better, so, being the curious sort, I had to try it out, and found out that it did seem to work better than full speed, and I have both high and slow speed drills. I also found out my drills lasted longer before the bearings went, from 300 plus bowls to 400 plus bowls (note here, I am rough on my tools). What drove me crazy was trying to figure out why the slow speed sanding worked more efficiently. I may have it now, thanks to a comment from Jimmy Clewes. He said that he doesn't think abrasives are cutting tools, they really just scratch the wood. I pondered that, and thought, well the difference between the steel and the abrasives isn't the serrated profile of what is cutting, it is on a steel tool, they are on a line/knife edge, and on abrasives they are on a plane or flat surface. So, both are cutting, but slightly differently. With a knife edge you can dig in as far as your lathe, tool size, rpm, torque, handle, and personal strength will let you. You can't do that with abrasives because they are on a bigger surface. With slow speed sanding, if you are at high speeds, the abrasives never really have a chance to dig in and get real traction to cut effectively. The abrasives will skip a lot more. I find myself now with the trigger mostly at 1/4 to 1/2 speed max, and most of the time it is in the 1/4 speed range. My lathe rpm is at 15 to 20 rpm, but that is because my bowls are warped, and if I go any faster than that, I can't keep the abrasives on the wood. It really does seem to work much better.

robo hippy

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It is correct to say the sanding paper is able to dig deeper at slow speeds... There are a number of other factors at play also. Heat buildup is much less because the rpms slows the heat buildup so its more easily dissapated which will significantly affect the wood dust trapped in the paper grit. I.e. burnt, scorched or glazed surface marks on the work and paper that plugs real fast. Also the paper is able to clear properly as you sand which will reduce the heat, speed the process and allow the paper to cut properly...

I discovered the virtues of slowing things way down about 25 years ago. Grinding your tools at very slow speeds is cutting edge also - so to speak.

Slow speed sanding with orbital sanders benefits from slowing things down also. I once had a job where there were two of us sanding down a mountain of maple raised panel doors. I used the typical high rpm random orbital where as the other guy used one of those old school porter cable all cast aluminum 1/2 sheet sanders that run at less than half the rpms of a typical random orbit sander (buzz box). We sanded for days and over the corse of the project he was able to sand just as many doors to an equal if not better finish in the same amount of time and used about 1/3 less paper.

I can only add my own preference. Can't really insist that it's "right" but here it is: Slow speed, light pressure. I primarily see the benefits mentioned above: more even surface, less heat, less clogging of the paper, etc... So there's my vote/opinion.