More info for posterity:
So, after I realized that I can source all manner of third-party produced 115mm (4-1/2") abrasives and related wire wheels and pads and other accessories (featuring M14 x 2 threading) for the RAS 115 that's set to be delivered to my doorstep sometime this week, I was completely flummoxed why I couldn't find anything in the world comparable to the FiberFix backing pad (485298):
Well, it finally dawned on me why.
So, for anyone out there hoping (like I was) to use a readily available "standard" 115mm (M14 x 2) backing pad like this:
[Source:
https://www.weldingoutfitter.com/products/walter-15d042-4-5-x-m14-x-2-0-backing-pad-assembly?variant=19323707782]
...along with the machine's integral dust shroud, listen up:
It appears that the (so it turns out) unique-in-the-world FiberFix pad is unique because, without its thick profile (and absent a jury rigged threaded spacer/standoff to make up the difference - maybe one removed from a cheap standard backing pad since M14x2 threaded spacers are hard to come by), a fiber sanding disc would sit well shy of the hard plastic rim/lip of the dust shroud.
As you can see from the following snip, the shroud is quite deep:
Here's a clearer image:
[Thanks Cheese!
]
Moreover, even with a thick pad installed (this shows one of the hook and loop pads but same diff), the paper sits just shy of the brushes:
[Thanks Paul!
]
Now just imagine how far shy of the brushes the paper would sit if a low profile backing pad is used! I'll know once I have the machine in hand, but it may be that there's not even enough clearance to mount a low profile backing pad when the dust shroud is attached - it sure looks like it.
Getting back to the FiberFix pad...since no other manufacturer or user has any need for such a "thick" backing pad (given that no other machine in the marketplace features a dust shroud like the RAS 115's), it appears that Festool (or ProTool or whoever) had to design a special "extra-thick" fiber backing pad around their innovative dust shroud (as opposed to the other way 'round); an accessory which, from what I can tell, is 100% proprietary (so stock up!).
As a curious aside, even though Festool sells - in Europe and Oz - a standard backing pad (#439580) - basically a Festool-branded version of the one shown above:
[Source:
https://www.festool.com/accessory/439580---st-d1150-el]
...there is no associated warning included in the UK-version of the RAS 115's manual (I don't speak German so can't easily compare to the German-language version). Similarly, there's also no heads-up provided in the guidance that comes with the accessory itself (which is because there
isn't any):
[Source:
https://industrie-restposten-kurz.de/produkt/festool-elastic-schleifteller-st-d115-0-el-stuetzteller-439580/In other words, minus common sense (in short supply with me apparently) - and before now - there wasn't anything that would otherwise alert a user to the incompatibility issue that arises when one attempts to use a standard "low-profile" backing pad in conjunction with the dust shroud. I'm willing to bet that more than one customer over the years has unexpectedly run headlong into this issue and shaken a fist in Wendlingen's general direction.
Anyways, consider yourself forewarned.
Yup, it turns out that even thinking outside the box has its limitations!
[Edit - IOW while you should feel free to use a standard fiber backing pad with 115mm (4-1/2") fiber discs, just don't expect to be able to use the dust shroud at the same time. This combination just won't work (unless, I suppose, you're comfortable employing the use of a separate threaded spacer on a shaft spinning at upwards of 4000RPM in order to build the backing pad out the required distance).] 
Topic: What is m14 thread type on RAS 115? (Read 8240 times)