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The nitty-gritty of power sanding

I think you are on to something there Clifton. I was just dealing with this today and had some trouble on a contoured surface using the green disks. I ended up going to some Abranet disks I had on hand and they worked better.
 
Steve Worcester said:
Actually, if you are working on warped or natural edge (or square), I highly recommend using a softer interface pad with all grits. You need to keep the pressure down and the speed lower to eliminate heat build up
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Keep the pressure down is the answer. Surface velocity is not a player. I'm sure you've noticed that pressing when sanding in close to the center produces just as much heat as pressing out on the edge of a large turning. Laws of Physics. Plus a couple extra thoughts. Soft backs allow for more flex, meaning more opportunity to increase heat thereby - same laws - and they encourage breaks in the adhesive binding the grit to the paper, shortening its life. Another point in favor of supported sanding. You use the rest, not the piece, to determine how light the touch!
 
MichaelMouse said:
.... Soft backs allow for more flex, meaning more opportunity to increase heat thereby - same laws - and they encourage breaks in the adhesive binding the grit to the paper, shortening its life. Another point in favor of supported sanding. You use the rest, not the piece, to determine how light the touch!
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If you are referring to rigid as a twist lock or some type of very stiff backing, I think in a convex shape like the inside of a bowl, you are asking for trouble. You won't get as much of the surface of the disc to conform to the interior and are going to be prone to the edge digging in.

Your reference to soft discs breaking down the adhesive and shortening the live, I would say that is absolutely true with a low quality disk, and with high heat. But the idea is to not to generate a lot of heat.
 
Supported sanding, like Odie's arm rests does help, in part because you can hand spin the bowl while sanding, think that was in another thread. From my experiments, 120 on a firm pad cuts better than 80 on a soft pad, which as near as I can tell has to do with the pressure you can apply. While coarser grits do tend to be stiffer, I haven't noticed that that contributes to wear on the disc, except for how Vince's discs wrap around the 1/4 round edges, and they kind of krinkle so you end up with some thing more like the wave discs. They still cut fine. There seems to be as much difference in quality of the various discs as there is in too steel or just about anything else. You really don't save money by buying the cheap stuff. While soft discs can fit into some curves better than firm ones, the edges on the curve press more than the center in the hollow, and you get better cutting by skewing the disc rather than heading in square to the curve. Slower speeds do cut faster.

robo hippy
 
(i have a big compressor, but didn't like the Grex. It is too easy to stall. Push too hard and it stopped)

The Grex sander has a power adjustment on the handle. If it stalls to easy or runs to fast it can be adjusted. If it adjusted properly it works good. When I first got mine I had to tinker with the power screw to get to work.
 
Steve Worcester said:
If you are referring to rigid as a twist lock or some type of very stiff backing, I think in a convex shape like the inside of a bowl, you are asking for trouble. You won't get as much of the surface of the disc to conform to the interior and are going to be prone to the edge digging in.

Your reference to soft discs breaking down the adhesive and shortening the live, I would say that is absolutely true with a low quality disk, and with high heat. But the idea is to not to generate a lot of heat.
Click to expand...

You mean conCAVE when referring to the inside surface of a bowl, I'm sure. The objective is to touch the surface so lightly that you can't dig. You are able to use the disk as if it were a gouge when you support and sand. Only the smallest of arcs on the disk actually makes contact with the surface, that being normally around the 9:00 o'clock or 12:00 o'clock position. Ten-twelve minutes of arc isn't much contact, and the disk really deflects next to nothing.

They do make flex-edge disks in power-loc style, but they have the same problems all flexible disks suffer from, loss of grit when the edge is flexed and the resin over resin cracks, and greater heat build up. I have some, but use them only for static sanding, because they will do only one or two pieces when sanding with the lathe on.
 
Fred Belknap said:
(i have a big compressor, but didn't like the Grex. It is too easy to stall. Push too hard and it stopped)

The Grex sander has a power adjustment on the handle. If it stalls to easy or runs to fast it can be adjusted. If it adjusted properly it works good. When I first got mine I had to tinker with the power screw to get to work.
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I will have to try that when I get back to turning
 
Jamie Straw said:
This recent bowl got me to pull out the virtually unused power sander, along with my starter kit from Vince. The only instruction I've had on using one is to use the edge to sand, and keep it moving. Things went pretty OK with the Madrona bowl, but not perfect, and there were areas of the bowl where it seemed touch-and-go keeping a steady, smooth contact. Any details on what direction to move the sander (using the clock-face references, for instance), especially if changing the spin on the sander from forward to reverse, what to do in a curve, that kind of thing. I used 2" for most of it, but on the coarser grits, I used 1" in the curve below the rim.

One thing I noticed is that Vince's kit skips from 80 to 120 (no 100), and from 120 to 180 (no 150). That didn't work so well, I filled in with Abranet H&L.
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Hi Jamie,
Vince here... The Sanding Suggestion form is usually sent out with every Starter Kit and it is also available on my website. http://vinceswoodnwonders.com/education I do not believe one needs to alternate sanding directions from one grit to the next when sanding domestic woods if that is what you are asking. However if you feel that gives you better results then by all means. Also use as much of the disk on the surface as possible. I say that in response to reading "use the edge to sand". I suggest starting with 80 grit and working your way through the grits. The reason there is not 100 and 150 is because the starter kits are designed to allow people to try the product at a cost effective price point. In short, I am trying to keep the cost of the starter kits as low as possible while including pads and discs. Also someone mention scalloped discs in this thread. Scallop discs have an interrupted edge which cause the disc to slap the surface when as the disc rotates. The reason my discs are oversized is to provide a constant edge allowing the disc to roll over the radius innerface pads when sanding a bowl or platter. Know you can always call me with your questions toll free 877.284.8969 and I will always be glad to help you. Thanks, Vince
 
Sir, would you like room for cream and sugar in your coffee? No, just knife and fork! Sir! I ain't no sir...

robo hippy
 
Vince Welch said:
The reason there is not 100 and 150 is because the starter kits are designed to allow people to try the product at a cost effective price point.
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And as much as any of us abrasive vendors would like it, it isn't needed. Mike Mahoneys theory is as long as you don't more than double the grit number when you jump, you are ok. While that works going 80 to 120 to 180, I would suggest something in the 200s then 300s then 400s. But I don't think you need to go 80,100,120,150. The idea is to eliminate the bigger scratch marks with smaller ones.
Only time I would see the need is when you want to lower where 120 wouldn't work and 80 would be too aggressive. It as you get better in cutting techniques, you use a lot less lower grits.
Do what needs to be done without overdoing it.
It gets really rediculous when using abrasives as the finish, or really no finish, or with plastics and resins.
 
Vince Welch said:
Hi Jamie,
Vince here... The Sanding Suggestion form is usually sent out with every Starter Kit and it is also available on my website. http://vinceswoodnwonders.com/education I do not believe one needs to alternate sanding directions from one grit to the next when sanding domestic woods if that is what you are asking. However if you feel that gives you better results then by all means. Also use as much of the disk on the surface as possible. I say that in response to reading "use the edge to sand". I suggest starting with 80 grit and working your way through the grits. The reason there is not 100 and 150 is because the starter kits are designed to allow people to try the product at a cost effective price point. In short, I am trying to keep the cost of the starter kits as low as possible while including pads and discs. Also someone mention scalloped discs in this thread. Scallop discs have an interrupted edge which cause the disc to slap the surface when as the disc rotates. The reason my discs are oversized is to provide a constant edge allowing the disc to roll over the radius innerface pads when sanding a bowl or platter. Know you can always call me with your questions toll free 877.284.8969 and I will always be glad to help you. Thanks, Vince
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Thanks so much, Vince, for stopping by an pitching in here.🙂 I wonder if I mis-described what my bowl mentor showed me -- perhaps "edge" gives the wrong idea. Though when I've been watching, he has used the outer part of the pad. With the particular bowl he was helping me with, it was but a 7.5"D bowl, and fairly shallow, not a lot of room for the pad. Anyways, I'll keep experimenting. I appreciate your keeping the starter kits affordable, it did make it easier to get started with the power sanding. Aforementioned bowl mentor has been out of the state for a couple of months now, so I'm seeking additional help. There's another member of our club who gets absolutely rave reviews on his finishing -- the "negative rake scraper guy" who's well known for his boxes but does very cool bowls also. Going to schedule some time with him soon, I hope.
 
Vince never stops experimenting, and has sent me a number of different discs to try out. I go back to the blue. They cut faster and last longer, and for the price, I haven't seen any thing better.

I have been finding, going through a sanding binge, that it seems to go faster if I start at 120, to hit 150, then 180. It just seems to be less work to pull the 120 out with the 150 than with the 180. Some jump from 120 to 220, which is way to big of a jump. Yes, you can get the scratches out with 220, but spend much longer if you use at least one grit in between. When I did start at 80 grit, I found it easier to go to 100 and then 120. Just took too much work to get out the 80 grit scratches with the 120. I spent a lot of time going back down a grit when I realized that at 180, the scratches I was still trying to get out were 80 grit scratches, not 120. Sanding still takes a lot longer than turning...

robo hippy
 
Jamie, I feel that the green disks are a little stiffer then the blue disks, probably no big deal, but to me there was a difference. Maybe they seemed more harsh, or maybe I had better feedback from the blue disks, I know it sounds kind of kooky. I agree with Robo about the faster cutting, long life and price. When I first started turning the only reason I started sanding with 80 grit was because I didn't know they made 36 grit...Now, for bowls, I usually start with 220 on a "bad" section of the bowl, if it sands quickly, I move on, if not I drop back to 180. Now, if I have to drop back to 100 grit, I reevaluate tool presentation, sharpening technique, sun in my eyes or, if all else fails...blame the wood...
cc
 
I have a set from 80-600 in the blue and green and gold because I wasn't sure what the differences were. I don't think i'm anywhere near experienced enough to comment on the differences except that the gold seems to last the least amount of time in my experience. But don't forget the old rule, never sand with the moon in the first half of the second phase of any month starting with a-j if you have eaten bread in the previous month! Just follow that rule and I imagine you'll be all set.
 
chrisdaniels said:
I have a set from 80-600 in the blue and green and gold because I wasn't sure what the differences were. I don't think i'm anywhere near experienced enough to comment on the differences except that the gold seems to last the least amount of time in my experience. But don't forget the old rule, never sand with the moon in the first half of the second phase of any month starting with a-j if you have eaten bread in the previous month! Just follow that rule and I imagine you'll be all set.
Click to expand...

Oh, you know that rule too?

🙂
 
robo hippy said:
Vince never stops experimenting, and has sent me a number of different discs to try out. I go back to the blue. They cut faster and last longer, and for the price, I haven't seen any thing better.

I have been finding, going through a sanding binge, that it seems to go faster if I start at 120, to hit 150, then 180. It just seems to be less work to pull the 120 out with the 150 than with the 180. Some jump from 120 to 220, which is way to big of a jump. Yes, you can get the scratches out with 220, but spend much longer if you use at least one grit in between. When I did start at 80 grit, I found it easier to go to 100 and then 120. Just took too much work to get out the 80 grit scratches with the 120. I spent a lot of time going back down a grit when I realized that at 180, the scratches I was still trying to get out were 80 grit scratches, not 120. Sanding still takes a lot longer than turning...

robo hippy
Click to expand...

I prefer the blue discs too. And I go through every grit also. There's really no shortcut. Still a newbie turner but 40+ years of hobbyist flat work and finally learned that lesson.
 
Mark Hepburn said:
And I go through every grit also. There's really no shortcut. Still a newbie turner but 40+ years of hobbyist flat work and finally learned that lesson.
Click to expand...
I totally agree. After making two bowls that were very challenging vis a vis sanding, I went to "every grit" and though it's still not perfect, there's no question that, in the long run, it's faster and less aggravating.
 
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