High speed sanding

Re: High speed sanding

keith tompkins

>Bill mentioned his high-speed sanding technique via emai....It sounds like a good thing!! I'd like to hear more.

Re: High speed sanding

George Van

>Keith, maybe Bill will jump in here but he sands at 6000-8000rpm and the lathe at 800 to 1000 rpm in the opposite direction with the 3M Roloc disks which are very similar to the Powerlock. He also uses Astro Dot sanding disks from John at Woodchuckers Supply.

Re: High speed sanding

eliot d

>I tend to sand at fairly high speed, too. ( And I use AstorDot disks from Woodchukers.) But everybody tells me that it's a bad idea to sand fast because of heat buildup, which supposedly wears out the disks and backing -- and ,even worse, causes heat checking in the wood. So who's right?

Re: High speed sanding

Dave Belser

>You answered your own question - what really matters is the heat build up and generally it's way easier to overheat at high speeds. The advantage I find to higher speeds is that the pad has less time to bounce and hence you can get a more even surface. For best results I really like wet sanding with walnut oil. The sanding stays cool and the disks don't clog. But it can be awfully messy. I'd enjoy hearing more about Bill's technique.

- Dave

Re: High speed sanding

George Van

>Eliot, Bill stresses light pressure while sanding so the heat does not develop. Just let the paper kiss the wood and let the grit do it's job. I use a different disk for each grit and following his advise with a light touch, heat has not been a problem.

Re: High speed sanding

Bill Neddow

>Well, here goes for a second time. I just lost about an hour of typing when I went to check the address for Turning 2007, being presented by the Ohio Valley Woodturners Guild. I will be giving a presentation there on high speed sanding (and sanding in general) October 12-14. (http://www.ovwg.org/) Now, i don't have to go searching again!

People who have tried high speed sanding have abandoned it for several reasons:

1. They are afraid of heat buildup and cracking.

2. The sandpaper disintegrates

3. The stiff sanding pad and paper cut the bowl

4. It creates a lot of dust.

First, to tackle heat buildup. This is caused by two factors. One is the pressure you are putting on the pad. This is the main culprit. Most people lean far to heavily on the sanding pad, compressing it significantly. This does speed up the sanding a bit (with that particular grit), but it does several other things. First, it pushes the sanding grit way down into the wood, creating Grand Canyons that are difficult to get out with the next finer grit of sandpaper. All this extra stress dulls the "sand" crystals -- and this causes heat buildup, and cracking. And all the extra sanding to get out the previous scratches simply adds to the time you are sanding.

The other factor is speed. Most people have tried this with a 4 1/2 inch auto body grinder or a die grinder. These are meant for sanding steel, auto body filler, and paint. They turn at 11,000 rpm. And this really is too fast for wood. It will cause scorching if you try to sand with fine grits (240) with a stationary lathe.

This is why I do two things. I turn up the speed of the lathe a bit -- around 800 rpm or slightly higher on a small bowl. And I turn down the speed of the grinder. You can achieve this with a variable speed grinder, but they are expensive (about $250). You can get the same results with a cheap non-variable speed grinder by adding a rheostat into the system. Simply put a double electrical outlet box on the end of an extension cord. In the box, wire in a house light dimmer switch (rheostat) and wire that to a plug, which will take up the other half of the box. Then, plug this device into your house power, plug the cheap grinder into the plug in the box and dial your speed. About half way up (or down) is about right. This should be about 6,000 to 8,000 rpm -- which is the speed I find most efficient. Total cost of my set-up was $40 for the grinder and $10 for the rheostat ( I had a spare extension cord I used).

Now use this just kissing the wood -- very little pressure. There should be no heat buildup. I use the hard rubber backing pads produced for the Roloc disks by 3M, or a similar pad from Craft Supplies USA. These systems are not compatible so you have to stick with one or the other. Craft Supplies USA has been carrying these pads and disks in their catalog for years, so somebody must be using them besides me. Both companies carry the full range of grits we want in both 3 inch and 2 inch formats. Get the 3M from auto body suppliers. Neither of these systems appear to be cheap, at first glance. But the disks last five or more times longer than regular sandpaper -- so they are very inexpensive in the long run. This is extremely important to me as a a production turner.

The reason for using the high speed (6,000 to 8,000 rpm) is the nature of these sanding disks. The so-called "sand" on our papers has evolved into a very sophisticated product.

The sand on our papers is meant to fracture and produce sharp edges, thus keeping the paper sharp longer. The regular paper we use is manufactured to do this best at 800 rpm to 1,600 rpm. However, the 3M (and Craft Supplies )stuff is meant to grind metal at 11,000 rpm. The grit will not fracture at low speed, so it just goes dull. At the higher speed, it stays sharp about five times as long as regular sandpaper. Tougher stuff, designed for a tougher job.

I have one grinder fixed up with a Tim Skilton velcro disk attached. I have been using this regularly for over a year and the velcro still looks like new -- because I am using light pressure. By comparison, the velcro and pad on my 1,600 rpm drill looks like the dog chewed it. Guess I am not very patient with it.

I would recommending sticking with the 3M or Craft Supplies system, but if you must use a velcro system, then there are three papers I can recommend that will stand up to the abuse of high speed sanding. First is Astra Dot, sold by WoodChuckers Supply in Toronto, Ontario. You can get it in rolls 6 inchs wide and 39 inches long and punch out disks yourself using a hole saw (teeth ground off) in a drill press. That way, the disks cost the same or less than regular sandpapers. You can get this by calling the company at 1-800-551-0192. (Ask for John.) There is also a new paper on the market (all ceramic) called Norton A975 (Dry Ice). It is available to the industry now in 6 inch disks, which will make 2-three inch sanding disks for you as well as 2 two-inch disks. It should be available from anyone stocking Norton 3X -- if you can convince them to order it. The other, of course, is #3M 900 DZ, which you can get pre-cut to 2 or 3 inch disks from The SandingGlove (www.thesandingglove.com) But it costs about 54 cents a disk and is sticky backed. That means you have to have another sanding pad, or a conversion pad for the velcro disk -- and I keep losing the conversion pads in the garbage. The conversion pads stand up well for low speed sanding, but I turned one into a blob of jelly trying it at 6,000 rpm.

I think this answers the second issue. These sandpapers do not disintegrate at high speed. It is not that there are bad sandpapers out there -- they are made for a different purpose.

People also complain that the stiff backing pad made by 3M cuts the bowl. They also complain that the velcro-backed pads cut the bowl. There is even a solution to the problem -- the wavy-edged oversized papers. But the problem is not the disk, It is they way people hold them. Most people sand with the disk tipped way up on edge. Of course the edge of the sandpaper will cut. You are pounding the edge straight down into the grain. Sand with the pad almost flat. If you get too flat, you will get what appears to be a catch as the center of the disk touches and the pad swings around in a quick jerk. When that happens, note the angle you are holding it at. Add five degrees of angle. And you will have the perfect angle -- no cuts. Besides, you will be using almost the whole of the pad to sand. If you can cut a 2 inch disk out of your used 3 inch pads, you are definitely sanding way too far up on edge. I learned about holding the sanding pad flat from an old fellow who used to sand out boats for a living years ago. He used a Black and Decker 7 inch auto body grinder with a fiber backing pad It was literally hard as a board. Everybody said it would not work. But he made a good living sanding out old wood hull boats. He would start with 60 grit to knock of barnacles, and end with 220 grit. He could do the whole hull of a 45 foot trawler in six hours. Not a gouge. Not a ripple. And he used to sing the whole time! His secret -- holding the pad as flat as possible.

Creating dust is a problem no matter how you sand a bowl. You have to decide if you want to stand for a long time in a medium cloud of dust, or a short time in a thick cloud. You have to accomplish X amount of sanding on a bowl, no matter what system you use. And you really need personal protection from the dust as well as a dust extractor for the shop. These are really important to your health.

If you do not create X amount of dust, what you are doing is burnishing the wood (usually with sandpaper that is no longer sharp). It may look good. But when you put the finish on (or worse, when the new owner goes to wash the bowl), the fibers will stand back up again and the bowl will look like porcupine roadkill.

Next, note on how to get the 2" or 3" pads onto the grinder. Get a grinder that has a 5/8" x 11 tpi arbor. this is an industry standard, but there are metric one out there and the conversion of these becomes difficult. Of course, the pad will not fit on this. It has a hole to take a 1\4" x 20 tpi bolt. So you need an adaptor.

Most places, you can get an adaptor with a 5/8 inch female end and a 5/16 inch male thread on the other end. These are meant for converting a grinder to the 5 inch sanding backing pads. Simply put the adaptor in the wood lathe. File almost all the thread off the 5/16 inch end. There should be just a hint of thread left. This is one-quarter inch. Get a 1/4" x 20 tpi threading die (should cost less than $5) and put a thread on this filed stub. Then, you can screw the pad on (either 3M type or Tim Skilton) and put the whole thing on your grinder. Total elapsed time for doing this conversion -- five minutes.

If you cannot get an adaptor with a female 5/8" end, get one with a male end. Also buy a long 5/8" x 11 nut. Thread it onto your grinder. Figure out how much thread it will take for the adaptor to thread in to the hilt. Cut the nut the right length. Thread it together, and away you go.

What are the advantage for going to all this work?

1. It dramatically speeds up sanding. I can now sand out an 18 inch bowl in 20-30 minutes instead of 2 hours in wood like Ash, which has both hard and soft growth rings. The soft backing pads gouge out the soft fibers -- so you end up doing a mixture of hand and power sanding to get a good result. On Maple, and other such hard woods, I can sand out an 18 inch bowl in less than half an hour on a sustained production run with the 3M system, as opposed to close to an hour for the velcro backed system.

Because the sanding disk is perfectly centered, you can sand right up to a bead without obliterating it like you do with a velcro system. You can never get velcro sandpaper perfectly centered, so it obliterates all your carefully created detail. Especially if you use the wavy over-sized stuff.

Because you are not putting a lot of pressure on the sandpaper, you get a finer finish. 320 grit finish shines like a 400 grit.

I am not against soft sanding pads. Just do not use them for the coarser grits of sandpaper. When I finish sanding out the bowl with the 3M pads ( to 320) I will switch over to a softer velcro pad and give it a quick swipe with 400 and then 600 grit. If you put several layers of finish on a bowl and sand between layers, use a very soft pad. You do not want to cut through your finish.

There is lots I have missed, here, so I hope it will spark an exchange as questions and answers will fill in the gaps. If I get a chance this fall, I intend to try to write this up and post it somewhere on the web. But, at least, this is a start.

Re: High speed sanding

Doug Thompson near Cleveland

>Thank you for taking the time to write this all down. In the future this will be worth a try.

Good Job!

Thanks Bill!

Gary in Zirconia,NC

>

Re: High speed sanding

Barry Turner

>Better sand lightly of you will have heat checks........

Re: High speed sanding

eliot d

>Thanks Bill; I'm going to print this one out and study it carefully.

Re: High speed sanding

Bill Neddow

>Sanding lightly is the key, but most people lean far to hard on the sander even for a velcro-based pad turning at 800 rpm. That is why they melt the velcro.

I finish turn and sand about 250 bowls a year, and have not had a heat check yet.

Re: High speed sanding

Gary in Zirconia,NC

>Bill,

Do you have a recomendation for a variable speed grinder?

Thanks,

Gary

Re: High speed sanding

Clay Foster

>Bill,

Thanks for sharing your experience with us. Astradot is my preferred brand for sanding green wood because it doesn't clog as much. I think wood embedded in the sandpaper is a big culprit in producing bad swirl marks.

Look forward to seeing you and your beautiful work at OVWG. With Graeme Priddle, Molly, Jennifer, John Jordan, and Andi there, fun will be unavoidable.

Re: High speed sanding

Bill Neddow

>Gary, if you do a lot of sanding, I think a variable speed is mandatory. The cheaper ones will wear out and you will probably spend more over the long run repairing or replacing them. I have a couple of Walters variable speed that I use all the time. They are professional tools, meant to be used in a welding shop 7 hours a day year in and year out. Not cheap.

But, if you are only doing a few bowls a month, I do not think the expense is justifiable. A less expensive grinder, with the house dimmer switch attached will probably last you several years -- or longer. Also, if you are not sure you have a use for the more expensive tool if you do not like my method -- go the cheap route.

Re: High speed sanding

Bill Neddow

>Gary, I misread your very clearly worded question. There are several good variable speeds out there. Besides the Walters (Metabo), which is probably the high-end, there is also the Makita 9564CV (about $139 off the Internet). There is also the Flex from Porter Cable. This is a 5 inch angle grinder with a speed range of 2,200 to 6,800. The motor is small enough to get a good hand grip on, even though it is 5 inch grinder. I am sure there are others, but these are the ones I have discovered.

Re: High speed sanding

john lucas

>Bill Thanks very much for sharing that info. I find it interesting but due to the expense probably won't change my method any time soon. I have one question. I can sand my bowls in about 30 minutes or less for most bowls even big ones. I occasionally need to hand sand some spots on certain woods and this takes longer. You mentioned that it takes 2 hours to sand a big bowl. Is this correct? It could be I'm not sanding to the same level of quality as you. Wish I could attend your demo so we could talk, I'd love to see it in action.

Re: High speed sanding

Gary in Zirconia,NC

>OK Bill, That clears up a lot for me. I thought you were talking about a smaller grinder. Too bad the Proxxon wouldn't hold up the constant use, it would be a good size. Thanks again for all the information. Gary

Re: High speed sanding

Bill Neddow

>Gary, the Proxxon is a really well built tool and I think it would stand up to sanding with 2 inch disks. Another alternative that I had not thought about. However, I think it might be pushing the limits to put a three inch disk on it. Maybe someone who regularly uses this tool could come in here and enlighten both of us.

Re: High speed sanding

robo hippy

>Well, this gives me something else to ponder. I am a fan of slow speed sanding. Sioux/Milwaukee angle drills with a 1/4 inch piece of cork under the trigger so that it doesn't go over about 600 rpm. I have found out that slow speed sands out just as fast, or even a bit faster than the high end speeds on this sanding style. My bowls are warped, so slow speed on the lathe also, in the 20 to 50 rpm. Sanding time for me on an 18 inch bowl is about a half hour. I sanded out 14 bowls yesterday in about 4 hours. Range in sizes from 6 to 14 inches. Sanding time seems to take just a bit less time than turning them.

robo hippy

Re: High speed sanding

Bill Neddow

>When I was referring to two hours I was thinking of a large (18" or over) Ash bowl, which I mentioned. If you are going to avoid the "starved horse" effect, you are going to have to do a lot of hand sanding along with the velcro-backed sanding using traditional techniques. Even the good Tim Skilton pads are too soft for sanding this type of wood and gouge out the soft layers. So you have to do a lot of hand work with the paper wrapped around something like a piece of wood.

In that post, I also mentioned working with Maple and other woods. My experience there, is that it cuts the time sanding in half.

It is difficult to compare "large" to "large". When I was referring to 18 inches, I was thinking 18 inches plus. A lot of my bowls go up to 24 inches and beyond. A good friend of mine has a lathe that will turn a 12 inch bowl, which is pretty common. To him, a 10 inch bowl is large.

I think he simple answer is that I have found it cuts sanding time in half. And that leaves me some leeway, because I can often do better than that.

Re: High speed sanding

eliot d

>I am clearly missing something. After reading all these posts about Bill Neddow's high speed sanding methods, it's clear that he advocates some kind of high speed -- more or less professional -- grinder, which is different , of course, from the close quarter Milwalkee sort of drill that many of us use. I did a search for posts by him but only found recent ones that apparently didn't go back far enough for the first message. Can someone direct me to the original message?

Re: High speed sanding

Bill Neddow

>Eliot, it is a 4 1/2inch auto body grinder, or angle grinder. Most of them turn at about 11,000 rpm, so they have to be slowed down. One way, (the expensive one) is to get a variable speed grinder. The more logical way to try it is to get a $20 - $40 Chinese import. In this series of posts I mention how to make a box including a house light dimmer switch and an electrical plug. Run the power through the dimmer switch to the plug. Then plug your tool into this plug and you can dial up the speed you want. About half way along the speed range is right.

Re: High speed sanding

eliot d

>Isn't it too large for most bowl interiors?

Re: High speed sanding

Bill Neddow

>In my first post in this series I mention an adaptor which will allow you to use 2 inch or 3 inch velcro or 3M Roloc style disk pads. Otherwise, it would be too big for most bowls