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Sanding disk comparison or probably confusion

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Forum topic by unclearthur posted 03-22-2017 06:42 AM 523 views 0 times favorited 8 replies Add to Favorites Watch
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unclearthur

123 posts in 1627 days


03-22-2017 06:42 AM

Topic tags/keywords: shop smith mirka sanding discs

So I am making an end grain cutting board, and after the final glueup I had to level it a bit with a belt sander (no drum sander available). That left a lot of scratches across the end grain.

So out came my Random Orbital sander with 60 grit disks (brand = “Mirka – Gold” which is not I think a cheapo brand). I sand and I sand and I sand, probably for 40 minutes, replacing the sanding disk a couple of times, and basically nothing happens to the scratches. The surface of the board actually got strangely smooth – almost marbled feeling – but the scratches from the belt sander were not being diminished at all. Zero progress.

Next day, having pretty much given up on ever sanding any end grain again, I picked up a couple of 40 grit “Abrasive Film Discs” by Shop Smith and gave them a try. In half the time the scratches were all gone, and the surface was back to having the sort of roughness you’d expect from sanding at that large of a grit.

One small note – my ROS has 8 holes as does the Shop Smith disks, but the Mirka Gold disks are 5 hole (old inventory).

Anyone have any thoughts as to what is going on here? Is the difference just due to the change in grit? Or the type or quality of the sandpaper?


8 replies so far

View Fred Hargis's profile

Fred Hargis

4762 posts in 2332 days


#1 posted 03-22-2017 11:01 AM

The mismatched holes may have been part of the problem, you were (maybe) just burnishing the surface with dust trapped between the grit of the Mirka disks. Only a guess…

-- Our village hasn't lost it's idiot, he was elected to congress.

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Rick_M

10640 posts in 2219 days


#2 posted 03-22-2017 05:26 PM

In other words it may be a combination of things

-- http://thewoodknack.blogspot.com/

View Kelly's profile

Kelly

1821 posts in 2783 days


#3 posted 03-22-2017 07:33 PM

I’m going to back Fred here. The disks I use on my Festool (the special sale one for a hundred bucks – so I don’t get full snob status yet) work about the same as the ones on my PC version of the same. However, the better dust collection does seem to make a big difference.

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Craftsman on the lake

2708 posts in 3276 days


#4 posted 03-22-2017 07:39 PM

Try this… no kidding it works for me. Try sanding with the sanding surface vertical. Seems that the dust falls instead of filling the grain and causing slow sanding. Your mileage may vary but worth a shot.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View Ub1chris's profile

Ub1chris

114 posts in 1219 days


#5 posted 03-22-2017 08:05 PM

You could try a finer grit on the belt sander before switching to the ROS. And as mentioned by others the proper holes were probably a factor.

View JBrow's profile

JBrow

1274 posts in 759 days


#6 posted 03-22-2017 08:45 PM

Unclearthur,

My guess as to what happened is a combination of factors. The first, as others have stated, the 60 grit Mirka Gold was doing a lot of floating on sanding dust. I also suspect that the 40 grit helped a lot in removing the scratches especially with improved dust extraction with the 8 hole alignment.

I recently gave two products a try in my Porter Cable 382 5” random orbital sanders with an 8 hole hook and loop pad. Both products seem to work very well and strike me as superior to Mirka Gold. I attribute the seemingly improved performance and added longevity of the sanding discs to longer lasting abrasive and improved dust extraction from the sanded surface. Both products removed material quickly and even with only on-board dust extraction on the random orbital sander, seem to leave only a very slight film of fine sanding dust.

The Mirka Abranet mesh style disk mount to a multi-hole sanding pad. The multi-hole sanding pad mounts to the random orbital sander’s sanding pad. However, the mesh disks seem to tear easily along the edges.

I also tried Norton’s ProSand multi-air disk. It is a paper backed hook and loop disk which I stuck to the Mirka Abranet sanding pad. My preference is the Norton product since the disks seem to hold up better than the Abranet mesh.

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unclearthur

123 posts in 1627 days


#7 posted 03-22-2017 10:12 PM


Try this… no kidding it works for me. Try sanding with the sanding surface vertical. Seems that the dust falls instead of filling the grain and causing slow sanding. Your mileage may vary but worth a shot.

- Craftsman on the lake

Interesting idea but you must have a lot stronger forearms than me …....

I never really thought the 5vs8 hole / dust extraction would be much of an issue as the dust extraction never seems that great in any case but it does seem like I was doing more burnishing than sanding with the 5 hole papers.

Have any of you tried these abrasive cleaning sticks or similar? Did they help? My problem is I still have a big inventory of 5 hole paper and an 8 hole sander.

View Kelly's profile

Kelly

1821 posts in 2783 days


#8 posted 03-23-2017 02:15 AM

I keep an abrasive stick on both the edge and the drum-disk sanders. They are a good investment. As to hand sanders, I have one inch thick horse mats covering my floors and I ran the sander on it and it helped for what I was working at the time. That said, it’s more of a stop gap approach than a practice I’d want to apply.

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