Sandpaper, how long can you go?

[Mark J]

Are there any quick and easy tricks to determine when a piece of sandpaper is worn out?  

I love the pencil trick where you scribble on the board you are going to sand, then sand until the pencil marks are gone.  This has really helped me.  Is there something equally simple and clever that I could use to decide that the sandpaper has done its duty and should be "retired". 

In the past I think that I was tossing paper out with a lot left to give.  Now that I am using paper longer I see that what looked worn to me in the past is still removing the pencil marks.  But when to toss it?  

[treeslayer]

i usually change it out when it stops" working" as its supposed to, i.e not removing material as fast, i think its pretty easy to push it past its useful life without any benefit, sandpaper is relatively cheap compared to all the other stuff we use, changing it out speeds up the process of sanding and i see no benefit to using it past its useful life.

[RichardA]

When it stops removing wood, get a new sheet!  And use the old piece as birdcage liner.

[Tpt life]

This is totally dependant on your usage.  I change 40 most often because I use 40 for hogging material. When working through the grits, my dad's rule of thumb (which I still follow) was 3 passes of an ROS. So from 80 to 120, the 80 scratches should be gone in 3 passes of 120. Hand sanding then is kind of a guess based on that flow. The pencil is deceptive in some ways because it hits the high points. It only shows you where you have hit and missed, not where you have completed your process. 

[Chet]

I think Dave's got it.  I think it gets real obvious when the paper has lost its usefulness.  Yes, you can stretch it's life but you need to put a value on you time too and paper that is done and you keep using it just wastes your time.

[..Kev]

I change out paper fairly frequently but, I hang on to the old ones and use them for breaking edges on corners, hand sanding round overs, and especially for use at the lathe.  Where they're a bit dead for the ROS, they still have other uses in the shop!  They make great coasters on the shop furniture too

 

[Tpt life]

Hardly takes any "usefulness" to knock down raised grain. 220 that is shot for woodwork will still polish rust off of cast iron. It really does depend on the job you are doing. 

[wtnhighlander]

Just don't over-use the hook and loop sheets for your ROS..They can overheat, and melt the hook part in the pad. DAMHIK.

[JosephThomas]

 I do as stated above and at some point just decide based on appearance to move the paper from primary use over to "extra" for hand sanding, scuffing a metal surface to remove grime, etc. I'm far too lazy to have a more scientific approach about this.

[AceHoleInOne]

Buy good papers, they last longer and do a better job. The more woodworking you do, you'll learn how to tell when paper is no longer effective.

I'm not a fan of the pencil over the wood. You need to add color over the entire piece. After all, you're sanding the entire piece, aren't you?

I like using colored chalk and turning it on it's side and rub over the surface. The chalk with collect on the high, as well as, get in the low spots. Typically, this is done while using the coarse grits, you need to see that deep scratch so it can be sanded it out. On larger surfaces like table tops. Use a weak dye solution.

-Ace- 

[Eric.]

I find that you start getting pigtails long before a sheet is "worn out."  Especially in the lower grits.  I don't know, maybe it's me, or my equipment, or I look more closely at the surface than most people...I have no idea...but it seems like I can only get ten or twenty minutes out of any given sheet before pigtails start happening.  Swapping out for a new sheet fixes it.  That seems ridiculous given the cost of Festool paper, but that's my experience nonetheless.

[AceHoleInOne]

16 minutes ago, Eric. said:

I find that you start getting pigtails long before a sheet is "worn out."  Especially in the lower grits.  I don't know, maybe it's me, or my equipment, or I look more closely at the surface than most people...I have no idea...but it seems like I can only get ten or twenty minutes out of any given sheet before pigtails start happening.  Swapping out for a new sheet fixes it.  That seems ridiculous given the cost of Festool paper, but that's my experience nonetheless.

It happens...but sanding through the grits is important to help remove them. I never go straight from machine sanding to a finish, (even with higher grits). Always hand sand with the grain, then go to your finish. This step will help with the fish hooks.

 

-Ace-  

[Eric.]

I never skip grits.

And it shouldn't happen as quickly as it does when you pay like a buck per sheet or whatever ridiculous price it is.  Pigtails is perhaps the most infuriating thing I experience in my shop.  Makes me wanna throw stuff.

[Tom Cancelleri]

There's too many variables. What are you sanding? Are you pressing on your sander or letting the machine do the job? How much are you sanding? I find if I sand something, it's 2 passes at 1 inch per second with over lapping strokes both vertically then horizontally then it's on to the next grit. That piece is good until it stops doing what it's supposed to. Easy enough..

[AceHoleInOne]

2 hours ago, Eric. said:

I never skip grits.

And it shouldn't happen as quickly as it does when you pay like a buck per sheet or whatever ridiculous price it is.  Pigtails is perhaps the most infuriating thing I experience in my shop.  Makes me wanna throw stuff.

Sounds to me your struggling with more than an occasional fish hook?

Possibly it's the Indian not the arrow? Stop sanding from time to time and slap the paper like you would the old lady's butt after she gets out of the shower . 2 or maybe 3 quick one's and keep sanding. Keep that pad clean and free of dust. Even though you have dust collection, it's a good Idea. Dust off the board from time to time. The work surface must be clean.

You may want to try tipping the sander up some so the leading edge is more in contact with the wood. Don't focus so much on keeping it flat to the work piece. This will also aid in evacuate sanding dust and sand paper grit that has fallen off the paper..

-Ace- 

[Eric.]

I have tried everything, Ace.  And I do mean everything.  I even sold my 150/3 because I thought it was defective.  My 150/5 does the same thing with slightly less frequency.  The only thing that fixes the problem is switching to a brand new disc.

[Chestnut]

I had an ETS sander and it went back to the store. I couldn't get it to sand with out pigtails on brand new paper. I probably spent 12 hours strait one day sanding trying out every technique and setting. I'm glad I'm not the only one that had pigtail trouble with festool sanders. Hate me for the dewlat that i have eric but i don't get pigtails with it period, ever.

[treeslayer]

i don't feel so bad about my dewalt now, thanks guys, although a friend has a mirka deros and really likes it, i just can't pull the trigger on a $600 sander just yet.

[drzaius]

I have like a 1000 year old Dewalt ROS (5" no less) that I never get pigtails with. I'ts a great sander, except for the vibration thing..

[Mark J]

3 hours ago, Eric. said:

I never skip grits.

 

I never skip grits either.  Love them with butter. 

[Eric.]

25 minutes ago, Chestnut said:

I had an ETS sander and it went back to the store. I couldn't get it to sand with out pigtails on brand new paper. I probably spent 12 hours strait one day sanding trying out every technique and setting. I'm glad I'm not the only one that had pigtail trouble with festool sanders. Hate me for the dewlat that i have eric but i don't get pigtails with it period, ever.

It's not the sander, it's the paper.  The Festool is superior in a million other ways, most importantly comfort and dust collection...but I do find the paper to be less than perfect.

[Llama]

Wait, you're supposed to change them? 

[Coop]

I either have a darn good sander or darn bad eye sight. What's a pig tail?

[Ronn W]

8 hours ago, drzaius said:

I have like a 1000 year old Dewalt ROS (5" no less) that I never get pigtails with. I'ts a great sander, except for the vibration thing..

My only sander is a ROS, 1/4 sheet.  Much less money spent on paper.  I use it for 80 grit and sometimes 120. After that I hand sand.  Maybe I am a knuckle-dragger but I am a knuckle-dragger without pigtails.

[TerryMcK]

7 hours ago, K Cooper said:

I either have a darn good sander or darn bad eye sight. What's a pig tail?

It looks like a series of tiny curly lines looking like pig tails on the surface when you look in raking light. It's caused by some schmutz adhering to the pad describing the orbit of the sander - if the vacuum is too high you see it even more as the pad is pulled down harder. You see it a lot with clogged pads. My vacuum hose has an air bleed on it to reduce the vacuum. I use Bosch paper nowadays and don't see it as much.