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Sanding bowls (high speed or low)

Abrasives cut better at lower speeds, generally speaking. I know there are some who use an angle grinder with sanding discs, where the grinder turns about 10,000 rpm, but I would think one has to be very light in their touch or burning would occur.
 
The challenge/problem with turning at high speed, is that you will over heat the sandpaper and the wood. With the wood over heating, there is a tendency for the heat to cause cracks in the wood surface. You want to thus turn at a slow speed and try and keep from over heating the sandpaper.
 
I run the lathe fairly slow 300 rpm
I use 3” and most 3” Velcro pads on an angle drill at high speed.
Not sure what the rpm of the drill is but it can’t be all that much


I watch for a stream of sanding dust coming off the bowl.
If it is not there time to switch sanding discs. Or slow the lathe down
 
hockenbery said:
I run the lathe fairly slow 300 rpm
I use 3” and most 3” Velcro pads on an angle drill at high speed.
Not sure what the rpm of the drill is but it can’t be all that much


I watch for a stream of sanding dust coming off the bowl.
If it is not there time to switch sanding discs. Or slow the lathe down
Click to expand...
Thanks guys
Roger Chandler said:
Abrasives cut better at lower speeds, generally speaking. I know there are some who use an angle grinder with sanding discs, where the grinder turns about 10,000 rpm, but I would think one has to be very light in their touch or burning would occur.
Click to expand...
Thank you much!
 
I also, keep the lathe at a slow speed, and also mostly run my angle drill at about half, to 3/4 speed, and do very brief sanding at 240 grit on up to 320 or 400 grit. I also watch for a stream of sanding dust with all grits, and if I don't see it coming off, I will stop and put on a new disk. Sandpaper is cheap, and I do my best to never over use it. When using too much speed, and or pressure on over used sandpaper, you will end up overheating and burnishing the wood, and make it very difficult to sand. When that happens, the only way to correct it is to go back down about two grits with new sandpaper, and start over with the sanding. While some seem to like it, I do not feel speed is your friend when sanding.
 
Robert Johns said:
I enjoy turning on the lathe. I do not enjoy sanding. Is it better to run the lathe at high speed for sanding or low speed. Which do you fellas prefer. Thanks.
Click to expand...
The higher the speed, the more heat you generate while sanding. When I started out turning, I created more than a few surface cracks in pieces by having the speed too high, and the sandpaper too old.
In general, I sand at the same, or lower, speed that I turned the piece.
 
Well, Vince Welch of VincesWoodNWonders started me on slow speed sanding. I never have the drill going over half speed. With a cutting edge, where the cutting teeth are on a blade, higher speeds seems to work great, and cut clean as long as you let the wood cut rather than trying to hog lots off as you do a finish cut. With abrasives, the cutting teeth are on a plane/flat surface. Getting them to cut is all about traction. Too fast, and like the dragsters heating up their tires, you get lots of smoke, but go no where. Too fast with the abrasives, and they don't get to dig in well and cut, they do more of a skipping over the surface. Coarser abrasives, 80 to 120 you can go maybe over half speed with the slow speed angle drills. As you get up into the finer grits, you slow down even more. Pressure is another factor. You don't want any more then the weight of the drill. If you are having to push to get the abrasives to cut, they are most likely dull, and pushing dull abrasives into wood will generate heat and can cause heat checking. Firm pads up to 180 or so, medium pads up to 320 or 400, and soft pads from 400 up. 120 on a firm pad cuts better than 80 on a soft pad....

Some where in this forum, I did a post about an articulated arm that goes in my banjo so that it holds the drill and all that hand has to do is squeeze the trigger. I can spin the bowl with the other hand. All of my bowls are warped, so the lathe is spinning at about 15rpm. Can't remember if I did a video or not....

Aha! I was actually able to use the search thing and find the video..... This really takes a lot of the work out of sanding.... Now, to figure out how to hook up a good sized flex shaft to a variable speed mini lathe and find a good mandrill to mount on the arm, well new and improve the arm as well....

View: https://www.youtube.com/watch?v=dnhdZh2Ens8


robo hippy
 
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As a new woodturner, I quickly discovered surface checking from sanding too fast (or too enthusiastically). :D What I do find helpful in sanding bowls is a DIY spinning bowl sander (a skate board roller worked fine) with hook & loop disks to change paper often. I have two diameters. You can make up a large supply of small disks from larger ones. I also take care to wipe off the piece between papers.

DJR_7851.jpg DJR_7856.jpg
 
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Slow speed. Picture it like trying to get traction in the snow. If you just floor it the treads (abrasive in this case) just skip over the surface and don't dig in, but if you slow down the speed it gives it a chance to dig in and get traction.
 
It is a cruel woodturner's fact that the finest cut and innovative design on a piece of wood means nothing to us if, in our eyes, we have what we view as an inadequate sanding job. As such, I hate to sand so badly that I have tried every technique (wet and dry) and gadget (air and electric) that I even remotely think might cut down on the nasty task. It is my lowly finding that just like using every tool in my lathe kit...there is no substitute for time in the saddle. On some woods and projects you just can't beat hand-sanding...on some the electric drill is indispensable...on some a ROS works just fine. They make these nifty sandblast containers now...and I can't help but confess that my mind wanders down that path from time to time. By the way, one of the gadgets I have not tried is a sand-o-flex. I'd appreciate it if anyone has any review details to relay.
'
 
Easy rule--- If the sandpaper is too hot to hold while sanding, it's too fast.
(almost sounds like a Foxworthyism)
 
David Hill said:
Easy rule--- If the sandpaper is too hot to hold while sanding, it's too fast.
(almost sounds like a Foxworthyism)
Click to expand...
Another rule is if you are melting the velcro on the sanding pads, you are going too fast! I would not recommend an angle grinder for sanding.
 
I generally run the lathe fairly slow (like 50-100 rpm - depending on diameter) and power sand.
Angle grinders are way too fast.

My favourite tool is: a Dewalt Polisher, because it will run all day at 300 rpm. But they arn't cheap, or light!

On the reasonable end of the scale are various car polishers, like Harbour Freight etc.
But I've gone through several in 3 years. You get what you pay for.
 
In addition to all the good advice already here...the faster you have the lathe and/or power sander turning, the faster the sandpaper needs changed. Not just because you're sanding faster, but because heat apparently causes the abrasive to wear out faster.

At least that's my theory based on my experience. ;)
 
Depends on the wood and the abrasive. Some woods speed makes little difference, some it makes a huge difference. Heat may bring out and burnish oils to the finish, like Teak Also coarse abrasives seem to generate higher heat at fast speeds. Maple burns/scorches easily, poplar doesn't..
 
I always figured sanding worked better faster, at least that's my theory. As others have mentioned you have to replace the abrasives frequently. There is an issue with sanding bowls, you can have an horrendously too high speed at the rim and too slow at the center.

When I was in the architectural mill work business I learned a lot about abrasives for my wide belt sander. The machine dealer recommended a source of 3M belts (custom size since the machine was Italian, the belts are expensive due to size). I must have wasted thousand$ on generic 3M belts until I came across an abrasives supplier in LA. They were able to recommend specific abrasives based on what we were sanding. I'm big on having the correct abrasive for the wood. But, when buying off-the-shelf you don't always have much choice. .
 
A very key point Doug. Having the proper abrasive for what you are sanding really helps. One thing I want to do when I get 'A Round 2 It' is to change the size of the pulleys on my old Performax drum sander to see if slower speeds help the woods to cut better and faster. The red abrasive belts seem to always have problems from loading up and burning. Having ample air flow for removing dust is not the problem, and trying to take off too much on one pass isn't the problem either. Changing the feed belt speed doesn't seem to make any difference, and talking to Performax about it, shall we say they don't think like I do.... I am seeing if I can get Vince Welch to make me some belts out of his blue abrasive. The polymer backing on it seem very strong, but I would think heat could be a problem. I did get some discs made for my Festool sanders, with the custom holes, and they work far better than the red or white abrasive discs. "If it ain't broke, take it apart and fix it anyway!"

robo hippy
 
Robo, I've wondered about those drum sanders, the abrasive looks very much like the 3M stuff I had so much trouble with. The 3M belts sometimes clogged almost immediately. The first thing my supplier did was switch me to a paper back belt, no stretching like cloth backed. Then a different kind of abrasive and resin bond. It made all the difference in the world, the belts would last a reasonable time. They could also be cleaned in a lacquer thinner bath if there was a stripe of pitch build up or burn.

I suggest is you call the place I used in LA. Back then it had two names, Jet Abrasives and Western Abrasives (I don't know why two names). They didn't sell direct, but will have suggestions of better abrasives and a local industrial supplier to order through.

I bet they're aware of the drum sanders.
 
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