aligning orbital sander holes

[Marc Rochkind]

Just got a new orbital sander (Bosch GET75-6N) with pad holes as shown in photo A. The sanding disc that came with it is shown in photo B. I didn't bother putting that disc on, but actually lining up the small holes seems way too much to ask. Probably some of them would line up by happenstance. Is this the way it's supposed to be? I'm used to my 5 incher, with exactly 5 big holes that line up with the 5 holes on a disc.

I'm going to use mesh discs, so I got a Mirka protection pad, shown in photo C. Photo D shows it on the sander, and the large holes do indeed line up. But whether any small holes line is, again, a matter of luck. Does this seem right?

I'm not worried about the mesh sanding discs themselves, because they're mesh.

I find the awkward combination of the sander itself (sans protection pad) and the sanding disc that came with it very curious. What am I supposed to do if I decide to use conventional sanding discs instead of mesh?

[Jim Becker]

Appears to be an 8 hole format for "basic" abrasive discs, but is flexible in design so that you can use a variety of media, including mesh with an interface pad, and still maintain good dust collection. Your shot D looks just as it should and the mesh media will take advantage of all that available airflow.

The current generation Festool sander bases are similarly designed for the same reasons.

[Marc Rochkind]

Thanks, Jim. But does it seem to you that the sanding disc that came with the sander would have adequate air flow?

[Bruce Page]

Do you know someone with a cnc? My sander only has 8 holes and I found lining up the holes to be a pain in the rear. I made an alignment tool that took care of the problem.
I would have nightmares trying to line up the Bosch. I bet it works great once you have it lined up!

[Marc Rochkind]

Great idea, Bruce, for my 5-hole 5 in. ROS. I could make one on my 3D printer, I think. But not needed on my new sander, since I'll be using mesh discs. My questions were more about how disks like the one shipped with the sander are supposed to work.

[Jim Becker]

Thanks, Jim. But does it seem to you that the sanding disc that came with the sander would have adequate air flow?

Probably adequate, but not optimal. Air flow is obviously going to be better through larger openings on the media than small ones. And once you use up the samples...it's not going to be an issue.

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Bruce, that's a brilliant idea for lining up the media!

[Richard Coers]

Probably adequate, but not optimal. Air flow is obviously going to be better through larger openings on the media than small ones. And once you use up the samples...it's not going to be an issue.

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Bruce, that's a brilliant idea for lining up the media!

Wouldn't the area of the holes make the difference compared to size for air flow? Festool woke us up to the idea of variable speed vacs to get better dust collection with less drag from vacuum on the surface.

[Jim Becker]

It would, Richard, and that's a good point...but only if all those little holes lined up with holes in the pad. I think that would be the big challenge with what's in the OP's photos. The "average woodbutcher" is likely going to be more challenged loading up the "only little hole" version vs media like more recent Festool abrasives where you have the big holes for a decent change at registration which in turn gets the smaller holes over perforations where they can help with the effort. I think that the variable speed vac is a separate thing but it's most certainly going to work better with everything lined up. (And, of course, we have to remember to "dial the vacuum up or down"...I all too often forget)

[mike calabrese]

get some of these and forget about it
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
calabrese55

[Jim Becker]

get some of these and forget about it
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
calabrese55

The OP stated he is going to be using mesh abrasives. He's just curious about the hole pattern on the sample discs that came with the tool.

[mike calabrese]

just trying to help
calabrese55

[Marc Rochkind]

get some of these and forget about it
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
calabrese55

Yes, that is exactly what I am using. My main question is about how well discs like the one that came with the sander would work.

[Bill Dufour]

I bet the factory orders sample packs by the thousands. Rather then keep special inventory they get generic fits all hole spacing for every sander they ever made. Also when you buy the right fit ones from the factory, with their brand name on the package, you will be impressed by how much better the dust collection is. Makes you want to never try other brand products.
Do you think. new cars come with tires matched for best handling and performance or lowest cost, with volume discounts, that are good enough for most drivers. Also helps if all the vechles made at that factory use identical size tires to keep inventory down.
Bill D

[Bob Jones 5443]

My old Porter Cable random orbital sander gave up the ghost a couple of years ago. I was sorry it see it go: it had five holes and I have boxes of various-grit Mirka pads I had bought for it. The sander gave out as I was helping my daughter with a project, so we dashed out to Home Depot and bought a Makita ROS with eight holes. Since then I’ve been dogged by pads that don’t fit the sander’s holes (5 and 8 don’t play nicely). I’ve chosen to use powerful dust collection to try to brute-force the dust through the greatly reduced air clearance. I decided not to overthink it, but I’m probably overlooking something. I’m not sure I care.

When I use up the giant box of Mirka I’ll look for 8-hole pads.

Or if I was better with machines I’d replace the failed part in the P-C sander. As if.