sanding problem

[avbill]

After using the prochuck on a PR blank, I started sanding with 600wet/dry. 600,800,1000,2000, then mm to 4000 to 12,000 I saw scratches and re did the sanding again. I still see scratches. Could the stratches be below the 600 mark?

 

[Padre]

After using the prochuck on a PR blank, I started sanding with 600wet/dry. 600,800,1000,2000, then mm to 4000 to 12,000 I saw scratches and re did the sanding again. I still see scratches. Could the stratches be below the 600 mark?

I always start my PR sanding with 220. Then 320, 400, 600 and then MM. It could be that your 600 is not getting out some of the tool marks.

 

[aggromere]

If they are circular scratches you could try stopping the lathe and sanding back and forth between grits. I have never used a prochuck so I don't know if that would leave scratches or not. Sometimes, if I finish with a skew, I can start at 320 and be fine. I actually think someone really good with a skew could go right to micromesh.

I too would lower my starting grit. That and sanding end to end should eliminate the scratches.

 

[turbowagon]

Buffing is the only way I've found to completely remove scratches. They are especially noticeable on darker acrylics/resins.

It's just too difficult to consistently remove all of the scratches from the previous grit without oversanding, which will lead to problems with the next grit. It is a snowballing effect that gets worse with each successive grit.

I've solved this by sanding through 12,000 grit micromesh and then buffing with white diamond. Give it a try and see what you think.

 

[Muggsy1776]

I may start as low as 150 grit to shape the blank if I'm not 100% happy with it after turning. For PR and my skew I can start at 320 or even 400 grit. I had the same problems as you have- to fix it I started sanding back and forth (lightly) on the blank after sanding with the lathe on (cross sanding), then I moved up grits to 400 each time doing the same technique. I use the sanding pads (micro mesh) to around 10,000 (i've stopped going to 12K as I found it really didn't do much). What really fixed the scratches was getting a buffing wheel. I now use the 2 wheel set that PSI advertises as the Barry Gross set- I run both my PR and ca finishes on it at the end and it makes the surface like glass and takes out the scratches.