Thread: Norton Dry Ice ceramic power sanding discs.. first impression is

My std power drill tops out at 3k rpm.

On reflection, I guess the real issue is rate of travel in relation to the bowl, so if you spin the pad in the reverse direction to the travel of the wood, which is what I normally do ....

The only abrasive I haven't tried is the 3M ceramic purple discs which are only available in PSA (pressure sensitive adhseive). Just can't understand why they won't use hook and loop. They are what Mike Mahoney prefers. My favorite are the blue discs from Vince. I tried his ceramic discs, and didn't consider them to be any better than his blue discs. For me, the blue discs last about twice as long as any other disc I have used. I consider the Astra dot to be among the lowest performing discs. The dots may work for less clogging, but the draw back is there is a lot less abrasive on the discs.

I did an experiment with the Norton Dry Ice discs when I first heard about them. I had 2 Oregon Myrtle wood cored bowl sets, 4 bowls each, the large ones being about 14 inch diameter. I sanded them out. Each set of bowls took one set of discs to sand out. By the time I got to the smallest cored bowls (6 inch diameter) it was probably time to get fresh discs, but since they were small, it didn't really make a lot of difference. I did use one extra 80 grit disc with Vinces blue discs as the inside was a bit rough. Since the Dry Ice discs are more than twice the cost of Vinces discs, I won't use them again.

A few notes here:

One, I use a LDD (liquid dishwashing detergent) soak. Use cheap brown hand dishwashing soap, mixed half and half with water, soak for 24 hours, rinse off lightly, then dry. I do turn green to final thickness. The only effect this has it to make sanding a LOT easier. The LDD soak was first done by Ron Kent to help with sanding out Norfolk Island Pine.

I sand at slow speeds, slow speed on the lathe, and slow speed on the drill. This was done after listening to Vince talk about sanding. All my bowls are warped, so I can't have the lathe running above about 10 to 20 rpm. The phase converters can be programmed to run this slow. Manufactures are worried that this can cause the motor to overheat, but the motor runs cool because there is no real load applied to the motor (hand temps on the motor are cooler than when under turning loads). I talked to a tech with Powermatic, and they told me that this was not true. I informed them that I had sanded thousands of bowls out this way and the motor ran true, and they told me that was not possible.

With the drill running at slower speeds (I have a piece of 1/4 inch cork under the trigger) the abrasives cut better. You do it the same as with normal sanding, light pressure, which to me means use the weight of the tool and no more. This prevents heat build up. I also noticed that my drills would go longer before the bearings went out, some thing like 300 plus bowls to 400 plus bowls. You get less bounce from the sanding pads. A firm pad works better than a soft pad, at least till you get to the high (220 and above) grits. A 120 grit disc, on a firm pad cuts better than an 80 grit disc on a soft pad. The firm disc from Vince also has a 1/4 round profile, which is much better than the standard square edge on most other firm discs.

Sanding time is about the same as when sanding at higher speeds. Really! Another small benefit is that slower speeds on the drill don't throw the dust out as far.

robo hippy

Thanks for sharing your experience RH.

It does leave me wondering about the effect of green wood and LDD on various abrasive types. Bill Neddow advises fast and light with the Dry Ice; the assumption there is that the wood is dry.

In that article, BN states that "the speed of the lathe is less important" and prefers 6000 rpm on the sander and 500 on the lathe. The diametre of the pad and of the object being sanded is not even mentioned in this context. I do not understand the basis for this statement. The length of time a point of the pad surface remains in contact with a point of the object's surface is a function of all four variables. Can anybody shed some light on this?

There seems to be two schools of thought on power sanding. One is high speed and light as air pressure (some rpm speeds up to 6,000 to 10,000 rpm), and the other is slow speed and low pressure. I do have a drill that has max speed of 3200 rpm. I tried that a few months ago, and went back to the slower speeds. One reason is that my warped bowls are almost impossible to sand at those high speeds. An open flatter form, with almost no transition is easier. I went back to the slower speeds because it does seem to cut better/more efficiently. I could find no time advantage either way.

As to sanding green wood, it can be done, but you spend a lot more time cleaning your discs off, so I let them dry first. As near as I can tell, the soap seems to act as a lubricant. Maybe it is the glycerine, I don't really know. It does keep woods like cherry and maple from burning and glazing. I also think that having the lubricant in the wood rather than the anti clogging stuff on the abrasive works better. Very little clogging.

robo hippy

Thanks RH.

I've done a few bowls green, without any soaking, and with std alox discs, high pressure, low speed, got adequate results. Some species are resinous and almost a waste of time but most seem to dry as you go, so not a waste of time.

As posted above, the Dry Ice discs in the finer grits on dry timber worked but only when with high speed and low pressure.

Frank, yes, there's some uncertainty about BN's advice.

Let's assume it's a foam-backed pad, so it won't be a point but an arc in contact.

We don't know what quadrant of that pad he's engaged, so it might be with the spin or against it or some point in between.

Yes, Ern, a comprehensive analysis would require the consideration of a greater number of factors. I was only wondering what was the reasoning behind the statement that one speed is more important than the other.

The Dry Ice discs worked fine for me at slow speeds and low pressure. Little loading, and cut fine. Maybe it is the wood.

As to speed considerations, I think, like all things woodturning and life related, it is what works best for you. You do want to avoid heat. The heat comes from 2 things, speed and pressure. Too much of either, and heat builds.

robo hippy

Originally Posted by NeilS

Just ordered the sample ceramic pack from Vince, along with some Blue Flex to see how they compare with the Dry Ice samples that Ern has kindly offered to send. Guess I might have to also get some Astra Dot to complete the comparisons.
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I've also added some Cera~Max to my order. It's a ceramic-alox hybrid that I understand increases the alox component as the grit sizes get finer. According to Bill Neddow, the ceramic disks lose their advantage over alox in the higher grits, so the Cera~Max should provide the optimum mix of the two abrasive types at any grit size.

I'll share my findings when I've given the various abrasive types a test run. It won't be a laboratory style comparison, with controlled variables, just a workshop comparison on whatever is on the go.

Will also send some Ern's way so there is a second opinion.
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Look forward to it, thanks Neil.

I have an order for some salad bowls so there's be plenty of opportunity to try various discs.

(Only wrinkle is finding enough biggish dry blanks in the 'bank'. May have to hit the remaining lumps of green elm. Will also be a good opportunity to learn more about the use of the Thompson 5/8 U gouge.)

Can't find Neil's thread that covered a thorough test of various discs so am adding my last word on the Dry Ice here.

Not impressed in short. Same with Neil from memory.

Latest trial was with one Box Elder and one Red Oak bowl.

The coarse grits leave deep scratches.

And despite doing my best with light and fast I trashed a pad due to excessive heat.

K, may be user error.

Whatever. I'm looking for other options and next to try out will be Vince's discs that Neil kindly sent me.

It seems that whenever I use 80 grit, there are residual scratches left in the wood. Some times I do have to use it, but if possible, I start at 120. This has been a constant with every type of abrasive I have used.

robo hippy

Yeah, but you're green turning and sanding. Diff. ball game with dry wood.

I've used a range of other abrasives on dry wood from #60 up and not had the same poor result as Dry Ice.

I turn green, let them dry and warp, and then sand them. Takes way too much time to sand while the wood is green.

robo hippy