Author Topic: I've been sanding incorrectly all these years.  (Read 1532 times)

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Offline Packard

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I've been sanding incorrectly all these years.
« on: May 11, 2022, 12:29 PM »
I watched a video (I think it was Rockler) where they said that you should only advance the random orbital sander about 1" per second across a board. 

I always moved the sander quickly over and over on the sanding surface. 

They did not say why this is preferred.  Does anyone know?

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Online squall_line

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Re: I've been sanding incorrectly all these years.
« Reply #1 on: May 11, 2022, 01:53 PM »
They want you to buy more plywood from them when you burn through it, or buy more sanding media?

Honestly, the "how to sand" videos from Sedge and other major Youtubers shows that a feed rate of 1 inch per second is on the low side.

The correct answer isn't 1 FOOT per second, either, but there's a happy medium.

As with all things, "it depends".  And what it depends on is:
  • grit
  • wood/surface type
  • grain/figure
  • stage of process (rough, finish, topcoat prep
  • pad size
  • extraction
  • phase of moon (note: this may or may not have as much of an effect)

It may be a "starting point" for suggestions on the feed speed, but it seems a bit slow, even as a starting point.

IMHO.

YMMV. Caveat emptor. This advice is not valid in Alaska, Hawai'i, Puerto Rico, or where prohibited by law.
« Last Edit: May 11, 2022, 01:56 PM by squall_line »

Offline Cheese

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Re: I've been sanding incorrectly all these years.
« Reply #2 on: May 11, 2022, 02:12 PM »
There’s a Festool sanding video with Larry Smith that’s become a hallmark for a lot of folks.

Offline Michael Kellough

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Re: I've been sanding incorrectly all these years.
« Reply #3 on: May 11, 2022, 02:54 PM »
That feed rate might make some kind of sense but ONLY if you’ve “broken-in” the abrasive first. Put a fresh abrasive on a sander and go that slow right of the bat and you’ll regret it.

I suppose you could sand a piece of scrap wood for half minute or so before sanding the real workpiece but I just go right to the real thing and move the sander especially fast all over, gradually slowing down to a pace that I can maintain without getting too bored. 3M Worktunes help when I fell the need to go slower.

I scribble all over the workpiece with a very soft pencil (4B or 6B) and sand all traces away before changing to a finer grit.

Offline Packard

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Re: I've been sanding incorrectly all these years.
« Reply #4 on: May 11, 2022, 03:28 PM »
What grit would you start with on sanded plywood?  I always started with 100 or 120 grit.

Offline GoingMyWay

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Re: I've been sanding incorrectly all these years.
« Reply #5 on: May 11, 2022, 03:53 PM »
Stumpy Nubs just posted a video about sanding speed.  He also references an average speed of 1" per second:
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Offline Packard

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Re: I've been sanding incorrectly all these years.
« Reply #6 on: May 11, 2022, 04:03 PM »
I never even knew that there was a wrong way to sand.   

Offline mino

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Re: I've been sanding incorrectly all these years.
« Reply #7 on: May 11, 2022, 04:17 PM »
As usual IT DEPENDS.

Not a pro here, but that means I got to sand some properly crappy setups like trying to make something out of softwood, lots of particle board stuff as well as hardwood HDF and lots of sticky paint.

With those tasks, I came to appreciate fast  the utility of having both hard and soft pads, taking advantage of speed selection as well as adjusting the speed I move the sander around.

Using a hard pad, sanding a softwood board to flatness. You REALLY REALLY do not want to go that slow.

Using a soft pad, sanding hardwood to a given grit, you do not really /need/ to go any faster than 1"/s AND you do not need to make too many passes as a result of that.

An then there is a whole world in between.

Sanding-off a paint or varnish, even with Granat you will heat the pad enough so the paint will stick to it like crazy. No way you can go that slow either.

The message for me is, IF I am sanding-to-grit and not sanding-to-shape-or-removing-paint THEN I CAN /and mostly should/ make fewer passes at lower speed, allowing the sander to do its work. I love my RS200 for that.

Anything beyond that and I learned the hard way that you better adjust your speed to not mess up /softwood case/, not clog the disc /paint/ etc. etc.
When The Machine has no brains, use yours.

Offline FestitaMakool

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Re: I've been sanding incorrectly all these years.
« Reply #8 on: May 11, 2022, 04:49 PM »
- Not a pro by any means either.
But I do use the speed dial - depending on how hard or soft the wood is.
Also when doing edges and sanding chamfers I go slow on the speed. I also do slow rpm if I need to work a small area, and go slower with the movement of the sander too as a result. The speed of movement I do in relation to if I were hand sanding - I think I do that automatically.
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Offline fraz

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Re: I've been sanding incorrectly all these years.
« Reply #9 on: May 11, 2022, 04:58 PM »
Another fun topic.  I have checked out some of Sedge's stuff but not all.  Anybody have a good pointer on how to prevent "pigtails" or "curly-q" showing up when using random orbit sanders?  I have a 150/3 and that may be part of the problem when I use heavier grits and work down to finer.  I read somewhere (here) that turning down vac pressure helps but I got some anyways even when the pressure was down.  Also tried slower speeds and don't quite have a complete correlation as to the cause.

It doesn't happen all the time, but it has happened a few times and enough for me to ask how to prevent it.

Offline GoingMyWay

  • Posts: 1898
Re: I've been sanding incorrectly all these years.
« Reply #10 on: May 11, 2022, 05:07 PM »
Another fun topic.  I have checked out some of Sedge's stuff but not all.  Anybody have a good pointer on how to prevent "pigtails" or "curly-q" showing up when using random orbit sanders?  I have a 150/3 and that may be part of the problem when I use heavier grits and work down to finer.  I read somewhere (here) that turning down vac pressure helps but I got some anyways even when the pressure was down.  Also tried slower speeds and don't quite have a complete correlation as to the cause.

It doesn't happen all the time, but it has happened a few times and enough for me to ask how to prevent it.

Stumpy Nubs talks about pigtails around the 5:59 mark of the video I shared in my post above.  He says they could be caused by a bit of grit stuck beneath the sanding disc, inadequate dust collection, or improper sanding speeds.
Inquiring Minds Want to Know

TS55, CT26, RO150, CXS, ETS 150/3, ETS EC 150/5, MFT/3, TS75, DF500, DTS400, OF1400, CT SYS

Offline FestitaMakool

  • Posts: 1336
Re: I've been sanding incorrectly all these years.
« Reply #11 on: May 11, 2022, 05:33 PM »
I was thinking another thing: Many, including me, are moving a RO sander in a circular motion, I noticed swirl marks on my work too a while ago; I figured I went towards the rotational direction of the sander, not WITH the direction, this may have made the swirl marks. This can cause the movement (rotation) to almost stop, just like a carousel on the fairgrounds.. where it seems like you momentarily stop moving..
“The Stig” Yes, it is true, at least some part of it..
“If you have an old Land Rover and a fit wife, you’re most likely always busy”

Offline RobS888

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Re: I've been sanding incorrectly all these years.
« Reply #12 on: May 11, 2022, 05:49 PM »
Another fun topic.  I have checked out some of Sedge's stuff but not all.  Anybody have a good pointer on how to prevent "pigtails" or "curly-q" showing up when using random orbit sanders?  I have a 150/3 and that may be part of the problem when I use heavier grits and work down to finer.  I read somewhere (here) that turning down vac pressure helps but I got some anyways even when the pressure was down.  Also tried slower speeds and don't quite have a complete correlation as to the cause.

It doesn't happen all the time, but it has happened a few times and enough for me to ask how to prevent it.

Do you start the sander on the wood? I do and I think I have only seen pigs tails once. if I'm doing several boards I slide from one to the other.  From reading the above posts I go pretty slow full length wise and then across at least twice both ways. sliding my hand ahead of the sander.

Offline Michael Kellough

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Re: I've been sanding incorrectly all these years.
« Reply #13 on: May 11, 2022, 08:51 PM »
Didn't watch the video so and I'm not familiar with the "pigtail" term but if refers to the swirls that are a normal result of the random orbit motion then you should know that they are created with every grit you use. In the normal progression from coarse to fine the swirls get so small that you can't see them.

If you do see them then you didn't sand to a fine enough grit, or you aren't vacuuming the surface between grits and a coarse grit that was left behind was captured and ground into the surface.

You're more likely to see swirls if you use a stain or pigmented finish. The finish should be the deciding factor in choosing the final grit.

On the other hand, if you are staining and you want to significantly change the color of the wood you might want to hand sand with the grain using a slightly coarser grit than what you'd normally end with.
« Last Edit: May 11, 2022, 08:59 PM by Michael Kellough »

Offline jimbo51

  • Posts: 541
Re: I've been sanding incorrectly all these years.
« Reply #14 on: May 11, 2022, 09:27 PM »
"I never even knew that there was a wrong way to sand."

Rough side up does not work very well.

Offline Peter Halle

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Re: I've been sanding incorrectly all these years.
« Reply #15 on: May 11, 2022, 09:45 PM »
I believe that this might be the video that @Cheese was referencing:



Peter

Offline Cheese

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Re: I've been sanding incorrectly all these years.
« Reply #16 on: May 12, 2022, 10:02 AM »
I believe that this might be the video that @Cheese was referencing:

Thanks @Peter Halle that is the video, I learn something every time I watch it.  [smile]

Offline rvieceli

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Re: I've been sanding incorrectly all these years.
« Reply #17 on: May 12, 2022, 11:20 AM »
@Cheese One of my biggest take aways from that video is how purposeful he is while sanding. If you notice his stance changes, his elbows come in close to his body to give him more control over the sander. Required with the Rotex models but also helpful with others as well.

He is very focused on the task at hand and has a set pattern that he follows when sanding.

I usually set up a strong low angle cross light on the work piece and find that it makes seeing imperfections so much easier.

Ron

Offline jeffinsgf

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Re: I've been sanding incorrectly all these years.
« Reply #18 on: May 12, 2022, 02:56 PM »
I've had the privilege of seeing Larry do that demonstration live. I wish I could get in the zen place he seems to find.

Offline fraz

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Re: I've been sanding incorrectly all these years.
« Reply #19 on: May 12, 2022, 04:21 PM »
Great suggestions, thanks guys.

On the coarse to fine progression taking out pigtails, swirls it kinda depends what grit created the swirls.  One butcher top I did I had to rough it with 40 grit and some of those were a royal B to get out.  It also got me thinking if it mattered that my tiny 3mm orbit was somewhat to blame as well.

I have top say my ETSC150/3 is one of the most awesome tools ever.  Gosh it sure was a fortune but it made sanding a more palatable task now.

Hey, we wouldn't be good woodworkers if we didn't second/third/fourth-guess everything we did.  [big grin]

I'm off to do some more research, thanks again.

Offline Chris Wong

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Re: I've been sanding incorrectly all these years.
« Reply #20 on: May 12, 2022, 05:58 PM »
I believe random orbit sanders are best moved slowly over the surface, but orbital sanders are better moved quickly over the surface. This is to make the scratch pattern harder to see.
Chris Wong, http://FlairWoodworks.com and https://www.ultimatetools.ca/
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