Why is it?

Re: Why is it?

Carole in VA

>Or, if you're like me, better eyes! LOL I have found that my finger tips can see better than my eyeballs!

Re: Why is it?

Wally Page

>I am fighting the same issue. Everytime I use a heavy grade of Sandpaper, I wind up with grooves. So, the last couple of projects, I do as good as I can with the tool, go to 120 grit and start the progression. Unfortunately, I still have some marks. I will watch with interest if anyone gives you a serious reply. Good luck.

Re: Why is it?

Anthony

>Power sanding!!!

Re: Why is it?

Keith Tompkins

>Hi Gary, Ever hit a board with a hammer, then try to stain it? Even after sanding, the mark remains, taking more stain than the surrounding surface. The wood fibers have been crushed.

A torn surface on a bowl will have a similar effect....even after sanding, the damage will be apparent after the finish is applied.

Sometimes, the scratches from the 80 grit paper are still visible for the same reason..... One solution is to wet the piece slightly between sanding grits and let it dry, then move on to the next finer grit. This will raise the grain, allowing the damaged fibers to be sanded away.

Another solution is to use a sharp scraper to smooth the surface before sanding....hope this helps..

Re: Why is it?

Duane C.Leach

>Well Gary I think you may need to make a few changes. First, better light and lots of it.

If your eyes are failing as mine are use a magnifying glass.

Use compressed air frequently to blow the dust out so you can see the wood surface.

Locate the areas of bad tear out and hand sand or power sand those areas with lathe stoped.But not to much or you will creat a flat spot.

Try wetting the surface with denatured alcohol, this will help the visibility of torn grain fibber.

Try reversing the lathe rotaion every other grit.

And lastly practice, practice, practice, BUT only if you are practicing good technic. If you have been turning for say a year or more and are still getting the same problems then seek some professional help.

I hope this helps Gary.

Duane

Re: Why is it?

Walter Ahlgrim

>Try power sanding every other grit with trying to make the new scratch marks at 90� to the hand held paper marks. Be sure to remove all, the bits of old the grit before starting next grit. If the sharp edge of a fine piece of sandpaper makes contact with the wood it can make a deep scratch that looks like it came from courser sandpaper

More on Compressed Air -- Good Idea !

Brad Vietje

>One thought to bounce off Duane's:

The compressed air will not only help you see the wood better, it may very well improve your results. When sanding, a lot of the grit can come off the paper or cloth, and most of it flies off with the dust. Some abrasive particles also cleave and shatter, resulting in small, sharp-edged chunks of abrasive coming loose. These can get embedded in the pores of some woods, like Oak, Ash, Walnut, Padauk, Mohogany, and other more porous woods, or can become lodged in bark inclusions and small cracks in the wood surface. Eventually, these little buggers can come flying out again, especially as you sand down to where they are lodged in the wood.

One or two grains of 80 grit can make a real mess of a surface sanded to 600; even a few bits of 320 grit can produce annoying little scratches that magically appear after you've got a beautiful smooth surface.

Blowing all the dust off and out of a piece between each grit can help a lot. Before I had a compressor, I found a vacuum very helpful, too. For any piece I really care about, I blast it with compressed air between every grit.

Safe Spinning,

Brad Vietje

Thetford, VT

Re: Why is it?

John K Jordan

>I agree with Duane - applying some type of liquid (alcohol, naptha, etc) will help to see things that normally don't show up until later. I also use a bright flashlight to add light at a different angle to examine the surfaces. I read of someone who uses a mirror to look at the object from different perspectives while on the lathe.

Another thing that you probably already do - instead of just sanding through the grits on the lathe with a power sander (not by hand with the lathe spinning as it just adds concentric scratches), I turn the lathe off and sand by hand with the grain/figure until I can no longer see scratches going across the the grain. I don't always do this with every grit in the sequence, maybe every other grit.

However, I notice you said "tool marks", not sanding scratches. What kind of tool marks - broad ripples, deep subsurface damage,... ???

JKJ in East TN

Re: Why is it?

Mike Schwing from Md.

>Gary, in addition to all of the other good information given, an 80 grit scratch that goes a bit deeper or isn't in the same random pattern as the rest of your 80 grit scratches will not be visible until you start sanding the rest of the area to a higher grit - exactly as you have witnessed. That scratch was there starting with the roughest grit you used, and it went a little deeper than the others and never got removed with the others.

Often it is a bruise/compression. One of your first tricks should be to wet it with some very hot water (better yet, steam it), it will sometimes bring the depression back up to the surface. When dry start sanding again at the lowest grit.

If that doesn't work, you still have options - go down to 60 grit and work back up. If you're like me, take off your glasses or remove your contact lenses so your close up vision improves and examine the surface in bright light. Wetting the surface with a solvent will show those errant scratches.

You also might want to consider your sandpaper source. Good sandpaper has a particle size distribution that is carefully controlled - cheap stuff might have errant particles that are larger than most others, leaving particularly deep scratches. I don't think there is a better product on the market than the new 3X paper for even particle distribution.

It is very important to clean off the surface before moving to the next grit as sandpaper particles fracture and break off as the paper gets used, those heavier particles are on the work surface, and get mashed in with the next grit unless you clean off.

Good luck!

Re: Why is it?

Gary Evans, Tallassee, TN

>Thanks all,

I'm sure you are correct Keith. The area that I was having trouble with was just at the rim. I used a scraper, but I couldn't get by without a little chatter, I guess.

I had my tongue slightly in cheek, but it always seems that I don't see these ghost marks until after I've gone through several grits. On this platter, I power sanded with 80, 100, 120, 150, 180, 220, including hand sanding with the grain before changing grits and didn't see these marks until I got to hand sanding with the 320. Nothing to do but back up and punt.

I intend to rig a better light at the lathe, and I like the idea of blowing the dust off with compressed air. I'll try that next time.

Gary

Re: Why is it?

Gary Evans, Tallassee, TN

>Hi John,

I call them ghost marks, because they are not deep enough to feel them with your fingernail, but they sure show up when you start to get the surrounding surface slicked up.

I think on this one that more judicious use of the scraper would have been helpful.

Gary

Re: Why is it?

Gary Evans, Tallassee, TN

>Hi Mike,

I haven't tried wetting the surface, but that might well have resolved this problem. The grain wasn't exactly torn, so I think that bruising or burnishing is what I was dealing with.

I did wipe this down with mineral spirits at some point during the sanding, but it didn't reveal these particular marks. I think a better light will help in this regard.

I already wipe off all the sanding dust between grits, but I think I am going to try blowing it off with compressed air as was suggested. Makes sense to get the grit out of the pores.

I appreciate everyone's comments. We'll see how things go on the next project.

Gary

Why is it?

Dennis J. Gooding

>Gary, you have gotten a lot of good advice already on your sanding problem, but let me add one more bit. When I have the problem you mentioned, it is almost always because I did not use fresh sanding disks for the project. The worst problem occurs on the second grit of the series. It seems to be a fundamental law of physics that worn-out 120 grit paper will not take out the scratches made by worn-out 80 grit, and so on down the line. Dennis

Re: Why is it?

Gary Evans, Tallassee, TN

>You could be right, Dennis,

I tend to re-use my sanding discs until the paper starts to show. I guess I need to order some new discs.

Thanks,

Gary