1/4" Aluminum for an adapter plate?

The lightest option would be to conventionally mount the 7TMs -- offsetting aft a bit to avoid interferance with the inserts. 

Heh -- you've clearly not read my prior threads about tearing 7TMs out of these skis when they're mounted directly to the ski -- I need to use the inserts/bombproof adapter to keep my boots on the skis...  The 7TM mounts match up with the 4 hole pattern in width, but not in length.  My plan is to use the two front inserts, with long machine screws, to mount the binding directly to the ski, then thread the adapter plate for the two rear holes (since the 7TM mount is about 1.5 cm back from the 4-hole pattern).

Thanks for the additional info Ron.  I ordered 2 plates of 6061 Al from the site that trumpet recommended -- is that considered a soft aluminum?  For the inserts you recommend, you're talking about a 1/4" thick helicoil in the Al plate?

There's a set of Dynafit TLTs in my size in the Yardsale right now...

*** Edit -- looks like I ordered 6061 T6, so that's good, I guess.  I'm not sure how the inserts would work on something so thin (which is probably why a machine shop would be useful, eh?)

*** Edit again -- something like this?

You're a quick study, Marcus.
Yeah, I'd say you got the right material.
those inserts look like they should work as long as they can be locked in so as to not move.
All that said, I still say you'll become an expert on the current raft of possibilities by talking to some machinists/metal fabricators.

*** Edit -- looks like I ordered 6061 T6, so that's good, I guess. 

That's what you want. The 2000 series alloys are quite soft. 6000 and 7000 (and occasionally 5000) are what  appear in most industrial and outdoors products. The T-6 refers to the temper. Unless I had access to some 7075-T6 sitting around (slightly stronger, a little more brittle, nicer surface finish), I'd use 6061-T6 for any binding-related stuff.

<grain of salt - I've not made binding plates before, nor attempted anything quite like it>

As for threading the aluminum, I'd go with the largest diameter screw I could fit through the binding and whatever the national coarse thread pitch is for the size. A little web sleuthing suggests that you'll be able to get a 10-24 screw through the binding plate (I might work in metric all day, but I still think in standard). I'd be impressed if you could pull that out. Same's true for a 1/4-20, if you can make it fit. I'd expect the screw head to fail (especially with a fillister head) before you ripped 5-6 threads straight out of the aluminum. Locktite might be a good idea too, just to keep things snug.

As a first try, I'd definitely just thread the aluminum.

Oops - looks like the inserts are metric-threaded M5 - that should be reasonable in the binding plate too. Looks like Voile ships them with a Locktite coating (in several sizes)
www.voile-usa.com/Merchant2/merchant.mvc...&Product_Code=608-94

</grain of salt>

mcmaster.com is an excellent one-stop shop for screws/taps, urinals, bicycles, etc. , but there are plenty of others that may be less expensive (or brick and mortar in town).

Also, following ron j's suggestion of machinists, there's a few places like emachineshop.com that can quickly CNC you a part (including tapping) for prices that are sometimes quite inexpensive.

Good luck! !

Thanks y'all -- great info. I went down to Ballard Sheet Metal and talked to one of their machinists (of course, AFTER I ordered the plates from OnlineMetals) and he ended up just cutting two pieces of 1/4" for me and giving them to me for nothing (or the promise of a six-pack down the road).

So I think I'll try Trumpet's threading recommendations and see how well that works for me. And naturally, I'll drill a hole bunch of extra holes in the plate to reduce weight and so they look cooler .

I'll take a look at the M5 vs. the 10-24 and 1/4-20 that I have in the house -- are the threads similarly coarse?

Hmmm... I think I may be able to work this into the purchase of an inexpensive drill press

I love this stuff. Thanks for all the advice!

So I think I'll try Trumpet's threading recommendations and see how well that works for me.  And naturally, I'll drill a hole bunch of extra holes in the plate to reduce weight and so they look cooler .

I'll take a look at the M5 vs. the 10-24 and 1/4-20 that I have in the house -- are the threads similarly coarse?

Hmmm... I think I may be able to work this into the purchase of an inexpensive drill press

I'd be a little thoughtful about how to drill/lighten up the plate in order to prevent icing. Aluminum's 2.7 times more dense than water, so if a little ice packs in there, it's still a net win, but you don't want anything balling up. The B&D guys apparently mill out some region under the plate for weight savings, but it's not clear from their photo how they've chosen to do it (or how they've provided for good drainage when the snow melts).

Most metric screws conform to a standard (I suspect the inserts are the coarse variety):
www.kasthurimmc.com/tap-drill-chart.html

As for the drill press - a nice center drill, tap handle, and a couple nice files (with a little patience, a hacksaw and filing job (mill bastard file) can sometimes match the quality of work done on a mill, when it comes to cleaning up, shaping, and deburring your plate)  might make as big a difference to the final quality as perfectly drilled holes. It'd be pretty sweet (and anti-icing) to fair the profile of the plate smoothly down to the ski.... (Of course, drill presses are fun...  .  )