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Just a simple one.
I once asked how deep scratches from abrasives were for different grits, to estimate how much thickness I has to remove to eliminate those from previous grits.
No simple definitive information was forthcoming, so to give me an indication, I now rub chalk (smudging it in with my finger) into the sanding scratches/grooves made by the abrasive on the drum sander so I can see when the current abrasive has removed all the scratches from the previous coarser grit of abrasive.
I can then progress up though the grits efficiently.
Otherwise I feel I can either sand excessively on each grit, thus loading up my finer grits and wasting abrasive, or can risk ending up with scratches from the coarser grits which will show up when finishing.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Great idea, Colin! Out of curiosity, how fine do you go on your drum sander?

I like that idea but the only ever have 60 or 80 (depending on what rolls are available when I buy them) on my sander. I only use it to thickness then scrape and or sand to final finish later. But this would still be helpful for those steps. Do you ever have problems with chalk showing up in open pores?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

P120 Don.
No problem with pores so far Brian. Abrasive particle show up as long scratches.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Cool; that fits with the plan I have worked out in my head (haven’t had a chance to fully implement yet on guitar woods) for getting rid of drum sanding scratches, which do seem to be stubbornly deep. I was going to go most of the way with 80 grit on the drum, then switch to 120 on the drum for hitting the thickness I want. Then, after construction of the guitar, start the finish sanding process at 80 grit on a random orbital sander, just enough to completely get rid of any 120 sanding scratches. Then progress up the grits either with the ROS or by hand. I’ve had an issue with 80 grit drum sanding scratches, and I need a good solution. I will definitely use the chalk idea. Thanks!

The thumb rule that I have always told customers ( esp. in coarser grits ) dont jump more than 2 grit sizes IE 80-120 good 60-120 prob not etc:

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