Another thing to consider, and something that's glommed over by many; simply grinding the cabide together (doesn't everyone?) isn't enough to ensure alignment, yes, this will make sure they're on-plane with each other when it's closed, but the alignment pins, their seats and mating holes are *critical* here. Otherwise, even though the guide may be "perfectly" flat and parallel closed, doesn't mean they will be once the sides are separated and clamped to a knife.
I haven't used the Behnke guides, but I mention this above, since looking at the link, implies that just grinding them together is all that's necessary. In a perfect world the holes for the pins, should be spotted and bored for press fit precision dowel pins, and just to clearance for the receiving side. Maybe these are, I'm just mentioning it.
I had two of the original Bruce Bump file guides, and maybe I'm mistaken, but I think these evolved from those? I got one of the extra-wide and one of the standard width ones from some of the early offerings, and while I did keep the wide one, I eventually passed the standard width one along to an ABS School student, because I wasn't happy with it. I wanted to love them, because I always have issues with tools rusting in my shop due to the climate. In the end, I replaced it with a Riverside one (kept the wide one for the rare case that I'd need it), which ultimately, was just much better built.
The ones I had (have), do not have precision dowel pins, although they are hard, but the alignment is bad enough that it wants to bind especially at certain points, and the accuracy isn't what I expect, across the faces, one was worse than the other. However, my main gripe, was that the narrower carbide, especially in relation to the file guide body itself, made it much easier when "riding the carbide" face, to rock or not intuitively be able to feel "flat".
The Behnke guides have slightly wider carbide at 5/16"(0.3125") according to the website, where as the older Bruce Bump ones were around 0.260", this is an upgrade, however, the Riverside ones use 1/2"(0.500") wide carbide which is seated in a relieved pocket, and also slightly thicker at a full 1/8". Mine, and the others I've seen at other maker's shops, are all very well aligned, with accurately bored and parallel to the carbide, very accurate, and smooth sliding pins. The overall width is 1.25", which with the half inch per side carbide faces, gives a very nice "sweet spot" to me, in terms of feedback and intuitiveness when using it with a grinder. You always know when you're riding the flats of the carbide, or once you've reached flat. I believe the bodies are hardened also, either way, while they're not as corrosion resistant as the 416 ones, they've not had any major rust issues. For me, and I've carried mine all over the world at this point.
They generally just clamp more evenly, and don't bind or have any issues releasing like the others did.
Which leads me to one of the reasons I wouldn't buy an aluminum one, and I want to be clear when I say that I wouldn't hesitate to buy an aluminum bodied belt grinder (and I refuse to use steel tooling arms, or platen plates, etc, where wear isn't a concern) or numerous other things, that generally people think *have* to be made from steel: flex. Forget the durability concerns, which, having dropped my file guide about a 100 times (carbide still completely intact and like new btw, and I've gotten it smoking hot grinding, and the carbide has never come loose), I can tell you, is a concern; but just the flexibility of aluminum that small, would be of great worry to me. You want to crank your file guide down TIGHT, especially on a less than perfectly (and I mean accurate to sub-thousandths of an inch) flat and parallel surface, because otherwise, the blade or fitting, can, and will, move inside the guide. Flex not only will reduce holding when really tight, but compound the mating, and alignment issues, and I also think, increase the likeliness of getting the screws stuck. Which is another major concern, galvanic corrosion: I often dunk my work piece, guide and all, in water to cool, mixed materials, such as aluminum and those hardened steel screws, will exacerbate galvanic corrosion of the aluminum inside those threaded holes, if this happens, when you've got it torqued down tight, and you set it down for a few days like that, don't be surprised if you have to destroy the file guide to get your blade loose.
I've got a tooling arm that is aluminum with oxide coated bolts like that inside blind threaded holes, holding a tool rest on, that I eventually had to cut off, because I broke the cores out of the bolt heads trying to remove them, with some extreme methods of trying to break them loose in the first place.
I can see how the softer aluminum does make the guide "grip" better in certain circumstances and torque loads on the screws, but for the way *I* use a file guide, I wouldn't want it. I've got no skin in this game, and nothing against anybody, like I said, I still keep my wide clearance stainless Bump guide for the rare situation where I need it, and I knew i couldn't make one for the same price at the time. I haven't used the newer ones, so my issues with the older ones may have been addressed, and in fairness, accuracy is always relative to the user, their expectations, and their level of insanity when it comes to the pursuit of "perfection".
The question of aluminum, just my opinion, based on my experiences. No matter who you go with, I'd pick steel for this sort of tool.
Edit to add: maybe I've got this Bump/Behnke connection all wrong, I just remember Bruce stopped making them and someone else started, but I know he was offering them in stainless also. Either way, I think the above things merit consideration regardless. My point being, that the Riverside guide is the standard which the rest must live up to.
javand
) shop last week and he showed me his Riverside carbide file guide (steel) and it is impressive how well it is machined and assembled. I also like the much larger carbide surface compared to my Bump guide. If I ever feel inclined to replace mine or just pick up another, the Riverside will be at the top of the list for sure!
