Lathe sanding speed

[William C Rogers]

What lathe speed do you use for sanding. I usually start with a coarse piece of paper sandpaper and then use a HF angle drill with the 2" pads for bowls. For spindles just the sheet sandpaper. I've been sanding at about 500 rpm for both. Should you use different speeds depending on the method or the grit?

[Justin Stephen]

Between 50-100 rpm, or about as slow as my lathe will go, and then I go over the piece even slower (slowly spinning the piece by hand) at least once with each grit as well. I think most people do go faster though.

[John K Jordan]

What lathe speed do you use for sanding. I usually start with a coarse piece of paper sandpaper and then use a HF angle drill with the 2" pads for bowls. For spindles just the sheet sandpaper. I've been sanding at about 500 rpm for both. Should you use different speeds depending on the method or the grit?

I go by "turn fast, sand slow". If sanding while the lathe is turning the speed is as slow as it will go.

I refuse to use a rotary tool for power sanding. I don't like the clouds of dust and I don't like what it does to the wood. When I used to power sand like that most of the time I did it with the lathe turned off and rotated the piece back and forth by hand. This allowed me to sand selectively where needed, for example on end grain..

I gave up power sanding for a technique using small hand scrapers and sanding also by hand. The scrapers remove any ripples or tool marks. This does not require coarse sandpaper, usually starting with 320 or so. I get a very nice finish this way with no danger of rounding over fine detail. Note that I've seen people use coarse sandpaper to remove tearout. If I see tearout I don't try to sand it but make additional finish cuts until the tearout is gone.

One thing I always do with hand sanding, especially useful for harder exotics: after sanding in one direction I sand 90 deg to that direction with the same paper before switching to a finer grit. My theory is that if there are scratches that I can't sand out with the current grit, no way will I get them out with a finer grit!

This year I began experimenting with a little pneumatic Grex random orbital sander with 2" sanding pads. This came recommended by turner Rudy Lopez. This thing is fantastic since it can be run slow and sand very gently. For this, I have also been sanding mostly with the lathe off but sometimes with the lathe moving slowly for only a short time then switch to sanding with the lathe off, turning it back and forth by hand for most of the sanding. I started with 180 grit paper on bowl I sanded last night.

BTW, this is with dry wood.

JKJ

[Alan Heffernan]

I sand by hand - slow speed and keep the paper moving so not to embed scratches and/or gouges. I also have a Grex ROS and like the results it produces.

So like others, I highly recommend running the lathe slow and you perform a lot of the sanding motion.

BTW, I have learned to always run a suction dust collector along with a room filtration system to keep the small stuff out of the air. I use a dust mask as well. I have learned to do this by multiple mistakes thinking I would do it without the dust precautions because I was in a hurry. I have learned multiple lessons the hard way and now make sure the dust is kept down and I protect my lungs.

[Reed Gray]

Cutting with tools is about how hard you push. Hard for heavy stock removal, soft for finish cuts. Sanding is about traction. Too fast and you are spinning your tires and getting little traction. Slower and you are getting plenty of traction. If you are hand sanding and your fingers are getting hot, reduce the speed and hand pressure. I use the angle drills, and keep my drill speed at half or less. The abrasives just cut better. I don't know that it is possible to make a chart for each grit to determine exactly how fast/slow you can go to get the best cutting action, but Vince Welch (who sells excellent abrasives) said that with the coarser grits you can go a bit faster, and with the finer grits you can go a bit slower.

I do try to get alternating scratch patterns when sanding. With the power sanding, that means cutting with the 12 o'clock and 6 o'clock parts of the pad, and with the 3 and 9 o'clock parts of the pad. You get different arc patterns so it is a bit easier to see if you are getting out ALL of the previous grit's scratches. This is a bit more difficult to do with hand sanding. I hand wipe off the pieces to check for remaining scratches. You actually push the finer dust into the coarser scratches and this does high light them a bit.

My converter was programmed to spin down to about 20 rpm for sanding. Since my bowls are all warped, I can not keep the abrasives on the wood at any higher rpm. I am finding it far more useful in the sanding process to spin with one hand and hold the drill with the other. You can see progress at the slow speeds that just blur with higher rpm's. I made an articulated arm to hold my drill hand. Odie, over at the AAW forum made a couple of padded arm rests that sit on his lathe. This takes all of the weight off your holding hand, which is a huge muscle saver. Now, to see if I can find that clip about my arm rest.

Found it, at about the 3 minute mark:

https://www.youtube.com/watch?v=o84c5e73YMM

I was over at the AAW site and when I bought it up there was a 'Hacked by .....' by some one and not the page. No idea what is going on...

robo hippy

[Justin Stephen]

I'll add that I do not use the Grex or any air sander because I don't have the CFM through my fairly small Makita compressor to run a sander for very long. That said, any electric angle drill (like the fairly ubiquitous Neiko and variants) that has a paddle trigger can be manually governored to keep the speed down. You just have to tape something underneath the trigger to keep it from compressing all the way.

[robert baccus]

Abrasives cut by speed, grit and pressure. Pressure causes scratches and heat. Grit should be chosen by the scratches/defects to be removed. Speed is fine(power) as it cools by moving air across the wood. Pressure should be reduced when using coarser grits or more speed. My dust is eliminated by an exhaust fan. Sanding effect can be judged by the amount of dust coming off the pad.

[William C Rogers]

Thanks for the helpful information. What I have is a PM 90 with a single phase 1hp motor. Earlier this year I raised it for a 18" swing. I did look at a new lathe with more features, but in the end (previous post recommendations) I kept the PM 90. No regrets. I have also looked at changing it to a 3 phase 2hp with a VFD, but budget right now is not available. I checked the lowest speed with a meter and that was around 300 rpm. This appears to be faster than any of you sand. So for bowls I'll sand with lathe off and just hand turning. For spindles I'll sand at the 300 rpm.
Alan, Justin, I have a 6 X 10" duct hooked up to a 6" DC inlet that does a good job getting the dust. Also wear a mask when sanding.
John, I am trying the card scrapers, but need to improve putting a burr on the curved ones.
Reed, thanks for the video link, your videos are always informative. That 20 rpm speed is nice.

[John K Jordan]

... Speed is fine(power) as it cools by moving air across the wood. Pressure should be reduced when using coarser grits or more speed.

Yes, overheating can certainly be reduced with reduced pressure. However I think the primary issue with a higher lathe speed is not the heat (which should always be avoided) but the circular scratches, especially with hand-held paper. A slower speed allows the paper to move more for each revolution. Sanding without the lathe turning gives even more control.

Sanding with coarse grit without moving the paper enough can create lines with sub-surface damage that can be hard to remove and might not show up until finish sanding. That's why I sand across the sanding lines before moving to the next finer grit. (Another thing that really helps to see problem sanding scratches at any grit, in addition to good lighting at a glancing angle, is wipe the surface with some liquid. I use naptha for this.)

I occasionally see small circular scratches from too much pressure on coarse grits with a rotating power sander. I suspect some of these are not noticed by the turner until the finer grits and by then maybe he not inclined to start over. I think the small random orbital sander is a real help here.

I once watched a guy demoing bowl turning. He hand-held sandpaper against the wood with a LOT of pressure and recommended using a piece of scotch bright pad as insulation between the wood and the paper to keep from burning the fingers. His bowls often showed horrible circular scratches. It is sad to see circular scratches in otherwise good work. The scratches evidently didn't bother him, perhaps because his eyesight was poor.

JKJ

[Reed Gray]

300 rpm is fine if you have twice turned bowls, or are turning from dry stock. With my warped bowls, it is impossible.

One source of scratches that remain when I am done, and it took me a long time to figure this one out, can be from the sanding pads. If the disc is the same size as the pad, the stiffer part of the hooks on the pad can leave scratches. We all know how hard it is to perfectly center a pad, and/or the disc. Even a tiny bit of that disc hanging out will leave marks. I trim all of mine down a tiny bit, except the radius edged ones. This pretty much eliminated that problem. If you are using a stiffer paper backing, it can do the same thing. This is more of a problem if you are up on the edge of the abrasive rather than using it more flat on the wood.

There is one school of thought when sanding that I don't do as well, and that is using an air hose to blow off the outside, and blow out the inside. Reasoning generally seems to be that there are/can be remaining particles of abrasive stuck in the wood or loose on the inside of a bowl, and this is an explanation of the 'mystery' scratches that we discover when done with sanding. I always wipe out by hand, and have never felt any remaining grit. Add to that, the way the hose will blow dust every where, it just isn't worth it. As near as I can tell, every time I have found the mystery scratches, they are from not finishing with the previous grit...

When hand sanding, if you are feeling heat, it means too much pressure, too much speed, and dull abrasives, or a combination of all three.

robo hippy

[Alan Heffernan]

Thanks for the helpful information. What I have is a PM 90 with a single phase 1hp motor. Earlier this year I raised it for a 18" swing. I did look at a new lathe with more features, but in the end (previous post recommendations) I kept the PM 90. No regrets. I have also looked at changing it to a 3 phase 2hp with a VFD, but budget right now is not available. I checked the lowest speed with a meter and that was around 300 rpm. This appears to be faster than any of you sand. So for bowls I'll sand with lathe off and just hand turning. For spindles I'll sand at the 300 rpm.
Alan, Justin, I have a 6 X 10" duct hooked up to a 6" DC inlet that does a good job getting the dust. Also wear a mask when sanding.
John, I am trying the card scrapers, but need to improve putting a burr on the curved ones.
Reed, thanks for the video link, your videos are always informative. That 20 rpm speed is nice.

I am building a knife maker's grinder right now and just bought a 2 HP 3 phase motor along with a VFD.

That would be a very pricey modification to say the least. You need a VFD rated motor (for heat transfer issues) and a decent VFD. By the time you get them in hand you have spent in the neighborhood of 600 to 700 bucks for new equipment. These items are not easy to find used. So at that price point, I think it begins to make sense to consider a finding a used machine with them installed already.

[William C Rogers]

I am building a knife maker's grinder right now and just bought a 2 HP 3 phase motor along with a VFD.

That would be a very pricey modification to say the least. You need a VFD rated motor (for heat transfer issues) and a decent VFD. By the time you get them in hand you have spent in the neighborhood of 600 to 700 bucks for new equipment. These items are not easy to find used. So at that price point, I think it begins to make sense to consider a finding a used machine with them installed already.

I agree it would be costly. When I was increasing the swing on my lathe, I looked for a long time for a used 2hp 3 phase motor. $300 was the cheapest I found as there just not a lot in my area. Then a VFD and misc items would be needed. I decided to see how the 1hp motor would work. So far I have not needed more power, with the biggest bowl blank about 16". It would be nice to have lower rpm and reverse, but not a necessity for the cost for me. Not exactly sure what you mean by finding a used machine with them already installed. If you mean buying a used machine ane putting them in my lathe I don't think I would be any better than buying a motor and VFD. If you mean buying a used machine with them installed and getting rid of my lathe, I would not do that. My lathe is old and not many features, but also not many failures. I actually bought some OEM replacement parts from Powermatic. The still have many of the original replacement parts in stock. What other 50+ year old lathe can you still get OEM parts for?

[Alan Heffernan]

I did mean buy a different machine. You could keep the one you are attached to and get a new one too. Don't you need two lathes??

[William C Rogers]

I did mean buy a different machine. You could keep the one you are attached to and get a new one too. Don't you need two lathes??

Yes, I need two lathes, however if I bought another one I would have 5 (counting the Shopsmith). I have a Delta midi and a Jet midi. I thought long before I decided to keep the PM vs buying a new G0766 (what my budget would allow). Based on feedback here most everyone recommended keeping the PM 90. My biggest concern was the swing being 12". So I raised it and now have an 18" swing. I ended up buying 5 new Robust tool rest for the increased swing. To date I have less than $1000 in it including the tool rest, initial cost, updates, etc. I have two banjos, offset tool rest, and numerous faceplates and chucks. To get to this point with a new lathe I am guessing about $2500. I'm happy with the lathe, but would like more speed options.