Tips for working with aluminum

[Crazyraceguy]

I'm down to my last couple of disks and the one on the machine is ready to be replaced. They use a particularly nasty PSA that necessitates scraping off the disk surface and scrubbing it with lacquer thinner, it's enough of a PITA that I'll run a disk well beyond the point it should be replaced.

RMW

There's a little body shop trick that I learned back in the early 90's to mitigate that problem.
Of course, you have to go through the PITA to get the platen clean first, but hopefully it will be the last time.
You simply stick the new abrasive disc to your shirt, pull it off, and re-stick it (in a different place) then apply it to your machine's platen. The fibers and dust from your shirt will interfere with the "over-bonding" that most PSA discs experience. It won't make it so bad that it won't stick properly, but it will come off much easier the next time. If your shirt is sweaty, stick the disc to a cotton rag, stretched out on the bench top. Sweat is too much.
I do this with the 8" geared orbital sanders that I use for leveling solid surface seems. Ingersol-Rand 328b. The bigger problem with them is that the platen is not metal, therefore harder to clean. It's an aluminum backer with a dense foam padding and some kind of plastic skin? PVC maybe? so cleaning it with solvent takes a lot of care, which is why I avoid it like the plague. The shirt fibers do the trick.

[member=44099]Cheese[/member] do you have a part number for that 3M disc that fits the RAS?

 

[Cheese]

Here's the disc that I mentioned that was cupped, it adheres initially but after 4-5 minutes it starts to release from the platen. You can see that it's not really been used a lot.

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So I finally purchased a couple of Cubitron discs in 60 & 80 grit. I may also purchase one in 120 grit...we'll see how these work.

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This next part is for you [member=8712]Richard/RMW[/member] ...for 12" discs 3M strangely produces a limited assortment. For general woodworking they produce the 348D series which uses aluminum oxide grit. The other series is 777F which uses an aluminum oxide & ceramic matrix, and is known as Cubitron. Cubitron II is also aluminum oxide & ceramic however it is a Precision Shaped Grain (PSG) product and oddly not available in large 12" diameter discs.

Cubitron & Cubitron II can both be used on stainless and produce a reduced level of heat when used on SST. Cubitron produces less heat through a coating while Cubitron II produces less heat because of the PSG grains. Here's an example of Cubitron vs Cubitron II products.

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And finally here are the 3M 12" disc numbers for both 348D & 777F. Also here's the vendor I purchased them through because they are offered in single quantities.
https://www.rshughes.com/p/3M-348D-88903-PSA-Disc-12-In-60-Medium-Aluminum-Oxide/051144_88903/
https://www.rshughes.com/p/3M-Cubitron-777F-88871-PSA-Disc-12-In-60-Medium-Ceramic/051144_88871/

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[Cheese]

[member=44099]Cheese[/member] do you have a part number for that 3M disc that fits the RAS?

Just so that you're aware [member=58857]Crazyraceguy[/member] there is a considerable difference between the hook & loop profile of the RAS pad versus the 3M pad. Which means that the Scotch-Brite disc can be attached to the RAS but it's not a solid connection. You have to be careful because the Scotch-Brite disc can jettison itself at maximum RAS speed. Here's a comparison between the RAS pad & the 3M pad and the part numbers of the Scotch-Brite discs I purchased.

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[rvieceli]

A sometimes good source for 3M abrasives locally is an auto parts store that caters to body shops. They don’t usually have everything and usually not 12 inch disks. But my local one will sell one sheet or one roloc if you want try something or open a box you thought was half full to find it empty.  [eek]

Ron

 

[Crazyraceguy]

Thanks [member=44099]Cheese[/member] that's what I was looking for. Seems like the 88656 backing pad is the one I need.
Festool's hook and loop is quite different from the rest of the brands, so compatibility issues might be solved by this. The main thing is that it can get me into 5" paper, in which I have far more variety of grits, plus the Scotch-Brite.

 

[Cheese]

No [member=58857]Crazyraceguy[/member] you don’t want that pad, it’s a hard backer pad for Cubitron grinding discs. Let me get back to you later tonight after I’m done preparing dinner. Chicken tacos with tomatillo/poblano sauce.  [cool]

 

[rmwarren]

[member=44099]Cheese[/member] thanks for the info and links. I couldn't find those disks when I search thru the 3M PDF catalog.

RMW

 

[Cheese]

No [member=58857]Crazyraceguy[/member] you don’t want that pad, it’s a hard backer pad for Cubitron grinding discs. Let me get back to you later tonight after I’m done preparing dinner. Chicken tacos with tomatillo/poblano sauce.  [cool]

If I remember correctly, the RAS has a M14 thread, so that's fact number one.

Secondly the RAS is 115 mm while the 3M discs are 125 mm so that's fact number two.

The 3M pad needed for the Scotch-Brite Precision Surface Conditioniong Discs is 3M p/n 89871 which is 125 mm in diameter and comes with nuts that will fit M10, M14 & 5/8-11 threads. It looks like this.

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The 88656 pad you referred to looks like this. It's a back-up pad used on Cubitron fiber discs.

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I guess you have some options but you need to decide which options are amenable to you.

Unfortunately the 3M pad will not fit within the RAS without removing the RAS guard/vacuum housing surround or modifying the pad and the 3M discs.
I'd start with ordering a couple of 3M Scotch-Brite discs, attaching them to the current RAS pad and see if that meets your needs. And then go from. there.

 

[Cheese]

[member=44099]Cheese[/member] thanks for the info and links. I couldn't find those disks when I search thru the 3M PDF catalog.

RMW

So you're good to go?  Mother mining can be very confusing at times.  [big grin]

 

[Cheese]

[member=58857]Crazyraceguy[/member] here's some supporting evidence, the 125 mm 3M pad placed on the RAS 115. The pad overhangs the guard and yet it is still not centered as can be seen when looking at the alignment of the center of the pad and the RAS attachment spindle.

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[rmwarren]

[member=44099]Cheese[/member] thanks for the info and links. I couldn't find those disks when I search thru the 3M PDF catalog.

RMW

So you're good to go?  Mother mining can be very confusing at times.  [big grin]

Yep, appreciate your guidance. I'll add the Cubitron to a future order and see if it's 3X as good as the zirconia disks. It'll be interesting to see if the heat reduction applies to AL and mild steel. 

RMW

 

[Crazyraceguy]

[member=58857]Crazyraceguy[/member] here's some supporting evidence, the 125 mm 3M pad placed on the RAS 115. The pad overhangs the guard and yet it is still not centered as can be seen when looking at the alignment of the center of the pad and the RAS attachment spindle.

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Thanks so much [member=44099]Cheese[/member] I had it wrong. What I was looking for was a backing pad with regular (Velcro style) hooks that fits 5" discs.

From the pics, It looks like that pad is too "flat", not enough off-set to work with the RAS? Maybe I could make a spindle adapter of sorts? An M14 internal thread and use the more common 5/8-11 outside. I'll have to measure the depth of the RAS pad to figure out the overall length.

What would be ideal is an arbor thing that would allow flap discs.

 

[Cheese]

From the pics, It looks like that pad is too "flat", not enough off-set to work with the RAS? Maybe I could make a spindle adapter of sorts? An M14 internal thread and use the more common 5/8-11 outside. I'll have to measure the depth of the RAS pad to figure out the overall length.

What would be ideal is an arbor thing that would allow flap discs.

The M14 internal x 5/8-11 external is a pretty common adapter, used on wet tools so there's usually a small coolant hole through the center.

I'll take a couple of side view photos showing the 3M pad placed on the RAS. I'm assuming you want to retain the stock RAS dust collection guard & brushes?

 

[Cheese]

Hey [member=58857]Crazyraceguy[/member] here are some interesting photos for the RAS.

I don't know if you're aware of it but Festool does offer a pad that you can attach 4-1/2 sanding/grinding discs to, 485298.

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Here's a side view of the RAS pad on the left & the 3M pad on the right. There is an 18 mm height difference between them so an adapter may work, it just needs to be the correct length.

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[Crazyraceguy]

[member=44099]Cheese[/member] that's great information. Thank you so much.

 

[Cheese]

Thanks so much [member=44099]Cheese[/member] I had it wrong. What I was looking for was a backing pad with regular (Velcro style) hooks that fits 5" discs.

From the pics, It looks like that pad is too "flat", not enough off-set to work with the RAS? Maybe I could make a spindle adapter of sorts? An M14 internal thread and use the more common 5/8-11 outside. I'll have to measure the depth of the RAS pad to figure out the overall length.

What would be ideal is an arbor thing that would allow flap discs.

If you remove the RAS housing, the 3M pad will easily fit on the RAS and for surface conditioning as compared to surface cleaning, that's not a bad option as the material removal will be insignificant.

Take the 3M pad & remove the 5/8-11 nut and install the M14 (black) nut. Attach the 3M pad and you're done.

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[rmwarren]

[member=44099]Cheese[/member] is it an optical illusion or do the threads extend above the pad?

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RMW

 

[rvieceli]

On the subject of disk sanders, Ameribrade seems to be coming out with a very nice looking albeit expensive piece of kit. Seems well thought out and fitted out for different operations

Here’s a link to the presale page:
https://www.ameribrade.com/hyper-disc-bench-grinder

Ron

 

[Cheese]

[member=44099]Cheese[/member] is it an optical illusion or do the threads extend above the pad?

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RMW

Ya [member=8712]Richard/RMW[/member] the threads do extend above the pad but placing a thick washer between the pad & the arbor would take care of that issue.

 

[Cheese]

I recently received the 3M belts I ordered, an aluminum oxide 36 grit, and a 60 grit & 120 grit Cubitron II. The 36 grit will be for wood use only (probably) while the other 2 will be used on both wood & metals. Here are a few photos of the belts for quick identification purposes.

Aluminum oxide on the top, Cubitron II on the bottom.

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Here are the important belt identifiers:
Red = grit
White = grit material
Blue = grit bond strength

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