What scratches tell you.

[Tiger]

I'm reviewing some of my pens and I thought I'd ask the question as to whether scratch patterns can reveal anything about technique. On my pens under a fair amount of light I can see either faint radial scratches or more often faint axial scratches. From this can you deduce that perhaps not enough time was spent sanding at a particular grit or that sandpaper had become dull or anything else? Can it also reveal that not enough time was spent sanding in an axial manner if you can still see radial scratches?

 

[wyone]

Or starting with too course of grit to start with. I used to always start with 120 grit and seemed like I sanded forever to get rid of sanding marks. Now I go up a step or two from there and it seems like I get a better finish and it is actually less work.

I have to say that since I switched to Abranet my sanding skills have really improved as well. I still use standard sandpaper for some things, but the Abranet does such a great job normally

 

[plantman]

I'm reviewing some of my pens and I thought I'd ask the question as to whether scratch patterns can reveal anything about technique. On my pens under a fair amount of light I can see either faint radial scratches or more often faint axial scratches. From this can you deduce that perhaps not enough time was spent sanding at a particular grit or that sandpaper had become dull or anything else? Can it also reveal that not enough time was spent sanding in an axial manner if you can still see radial scratches?

Your problem may be that you are not sanding enough in the lengthwise directions. Radial marks are left when you sand with the lathe running. There are several ways to remove or avoid these lines altogether. 1- Use a Scotch Brite pad or something like it to do your sanding with the lathe running to aviod any lines to begin with. 2- Use a fine metal file to remove the radial lines, should they turn up, with the lathe running. 3-Sand with the grain while the lathe is stopped. 240-400-900 should be fine than add your CA finish. 4- Sand your CA finish with 400-900-1200 until all shiny spots are removed. You can now use MM to 12000 if you want, or use a one or two step Plastic Polish to bring to a glass shine. Be sure to wipe your blank down after each grade change !! As Mitch said above, use top grade papers or pads. Jim S

 

[Tiger]

Thanks guys, I should have mentioned that I start sanding at 320 or 400 grit. I use the skew chisel and it leaves a pretty good finish. Not seeing so much the radial marks as the axial marks, I have on occasions used the buffing wheels and they may have contributed but I didn't keep any records as to what I used so going from memory a bit here.

 

[ed4copies]

I am 100% in favor of analysis!!!

And, I suspect you are isolating factors in YOUR analysis. However, an answer on the forum will be relatively useless, since so many variables are in play.

Are all the pens made from the same material? Even different colors of acrylic can react somewhat differently, and most certainly the scratches will be easier to SEE on black than white, even if they have the same scratch patterns.

"Scientific" analysis means reducing the variables to as few as possible (ONE is ideal).
So, isolate all the pens that are made of exactly the same material and see if they exhibit exactly the same pattern. Then, remember exactly what regimen you used for them----

OR accept what you have observed and look at your blanks more carefully BEFORE you assemble the pen. You know you have an affinity for axial marks, CHECK your new pens BEFORE assembling. In this way, you CAN benefit from what you know. AND, you may learn a lot more as you spend more time examining your work!!

At least that is what happened for me.

Good turning and good improving!!
Ed

 

[wouldentu2?]

If you are going to experiment to discover what is causing the problem use only dark blanks as the marks are more noticeable in dark materials.

 

[hebertjo]

Do you wipe down the blank between sanding grits? If not you might have some grit from a more course paper rolling around with the finer paper causing scratches you were trying to remove. Make sure your sand paper is new and clean as well.

I agree with Ed that there are many variables and you need to experiment with your technique to find what works, but folks here will give helpful hints as to what to try and what to look out for.

Good luck!

 

[Tiger]

Thanks for the feedback, Ed you make some good points so I'll try and address these. Firstly I've concluded that the current lighting system over the lathe is ok but could be better. When I look at a blank under the current lighting I see no scratches of any type. Take them inside where there's more powerful lighting and I see scratches. Definitely more apparent on the acrylics. I do wipe down after every grit so we can remove that as a factor. Worn micromesh is a possibility, i reckon I've made about 30 pens with the current batch, I clean it up every couple of pens and it seems to still be cutting ok.

 

[1080Wayne]

For sure , you can learn from the scratch patterns , but before you do too much of that it helps to learn the slightly different things that different lighting conditions show you . Daylight or incandescent , direct overhead or low angle of incidence , barrel held lengthwise or crosswise - wood or plastic , low gloss or high gloss . You will find that a defect which is totally invisible when you make a barrel becomes glaringly obvious on the assembled pen a week later under different lighting conditions .

In my opinion , the most important grit used is the first one . It has the job of removing radial tool marks , which many interpret as sanding scratch marks . On soft wood they can be fairly deep , particularly if the tool was on the dull side . I would recommend doing lengthwise sanding off the lathe , inspection both lengthwise and crosswise under low incident light , with 3 diopter magnification , unless you have perfect vision .

 

[Tom T]

I wet sand with micro mess all plastics. That seems to help. I cover the bed of the lathe with plastic and paper towels. And cover part of the floor

 

[PJVitkus]

Scratch patterns

Good advice all the way down the pike!

Most folks I know start with radial finishing then switch to axial. Try starting with axial (length-wise) then do radial, stopping periodically or even frequently to check the barrel surface.

It helps, with this, to make sure you are consciously applying the same pressure in both directions at all grits. Make sense?

Also consider going axial-radial-axial.

I presume when you all mention wiping off between grits you are using denatured alcohol, yes?

Phil