sanding

Re: sanding

Reed Gray

Abrasives are cutting tools. For efficient cutting you have to have proper 'traction'. So if you are going too slow, it cuts slower. If you are going too fast, you are like a dragster spinning its wheels. You get lots of smoke and heat, but are going no where. At proper speeds, the abrasive particles get a chance to dig in and cut. Too fast and you generate heat and some dust, but they don't cut nearly as well. I never sand (3 inch discs always) at more than about 600 rpm, or with the trigger pulled down about half way. With coarser grits you can go about 600, but with the finer grits, I slow down to 200 or so. It really does make a difference. First time I heard about slow speed sanding was From Vince Welch of VincesWoodNWonders. I have since heard it from a number of other big name turners. Oh, your angle drills last a lot longer at slow speeds as well. As for pressure, same thing, if you push too hard, you wear out your drill a lot faster, and generate more heat, but it doesn't really cut any better.

robo hippy

Re: sanding

George Balock

Art,

Are you asking lathe speed or sander speed? If it is lathe speed, the one thing that comes to mind is heat. You are going to generate a lot more heat at the higher speed. Also the diameter of the work makes a difference. If a 4” piece is running at 2000 rpm, compared to a 1” piece at the same speed, the linear feet per minute sowing past the sandpaper is going to be a lot different.

Some woods like cedar hates heat and will crack in a heartbeat. Other woods like rose woods in particular are oily and the oils seem to clog the paper more at higher speeds.

So to answer your question, it depends.

Re: sanding

john lucas

lathe speed should be slow. I find that the sandpaper skips over some areas particularly torn grain areas. If you slow the lathe down it will be more likely to sand these areas. what I usually do is slow down the lathe and then sand with whatever grit I think it needs. Then I stop the lathe and check.Usually most of it will look great with just one or two spots needing more. I will sand these areas with the lathe off. Once it matches the surrounding areas I hit it again with the lathe running and then switch to the next grit. I will repeat the stopping if necessary but usually if I spend enough time on the first grit i can sand through all the other grits without stopping. that's hand sanding.

When power sanding I do basically the same thing but I try to make sure the sandpaper is traveling faster than the wood.I try not to apply too much pressure. Pressure + speed equals friction and heat. You don't want that. Light presssure with the proper grit and you can keep the heat to a minimum. I don't sand with the drill at high speed. Usually about half or less, and then the wood is traveling slow as well.

Re: sanding

John K Jordan

Art, You don't provide very much detail. The following assumes the lathe is spinning and the paper is held by hand. If you meant something different maybe you could ask the question in a different way.

I do much of my sanding by hand with the lathe off. With the lathe running I sand at low lathe speeds. One thing - with the lathe spinning it is best to always keep the sandpaper moving to avoid grinding relatively deep groves in certain places. With the lathe off or the speed very slow, moving the sandpaper from side to side with a given motion will result in more "crosshatched" sanding scratches. Moving the sandpaper with the same motion at a high lathe speed will create more circular or nearly circular scratches. This is the same as moving a gouge at very slow speeds for the best finishing cuts.

The sandpaper will load up with dust much quicker with higher speeds requiring more cleaning. (Or wasting more paper.)

The heat is another thing - some woods like ERC may check badly with heat.

The dust is another. I like to sand with the lathe in reverse so the dust from the top of a piece will be aimed more at the dust collector pickup. Sanding a higher speed throws dust further and more gets in the air.

Even when holding the sandpaper by hand with the work spinning I still stop between grits and sand by hand, preferably across the previous scratches. If a scratch won't come out easily with the 320 paper in my hand 400 grit will have a problem.

BTW, I personally do not use rotating sandpaper to sand pieces on or off the lathe. I use hand scrapers when possible to remove tool marks then if power sanding is still useful, I use a gentle pneumatic random orbital sander.

JKJ

Re: sanding

Mark Paulley

Art,

Vince has a tutorial on u-tube regarding sanding. I found it useful.

Yes Vince and I are friends but do not hold that against me please

Re: sanding

Mark Paulley

Art,

I forgot on the articles drop down on the left Russ gives great tip on sanding too!

Re: sanding

art demers

Again your help is spot on thanks