Tolerances for ISO 6004:1991 Alpine Ski Binding Screws?

**Jonathan S.** · 06-16-2012, 08:30 AM

Anyone know?
I suppose we could pony up the $ to buy the pdf, but speculating is more fun, right?
Based on measuring a couple dozen alpine screws of all sorts of sizes and vintages, I'm finding a very consistent ~5.4mm major diameter ... except for Dynafit Speed heel screws at ~5.7mm. Any other exceptions like that?
Pitch is very consistent at ~1.8mm (measured at 9mm across six crests).
Minor diameter I can't measure accurately.
Thread form, hard to say -- some seem "sharper" than others, but could just be the color, etc.?
Nordic screws are definitely different, but they have their own ISO 7794:2011, so that makes sense.

**gregL** · 06-16-2012, 11:49 AM

That seems right. In my box of 28 different alpine binding screws, including screws for Salomon, Marker, Look, Tyrolia and Geze, the major diameter ranges from 5.34 to 5.49 depending on the individual screw and the precise cross section you are measuring. Average is around 5.4 even though they are all nominally 5.5.

**coldfeet** · 06-17-2012, 01:46 AM

I bet if you buy some #12 sheet metal screws (NOT wood screws) at the hardware store, they will measure very similar and have a thread depth that looks similar. The Nordic screws I looked at seemed to have a deeper thread but same pitch.

#12 sheet metal screws are easy to get, but harder in stainless, and pretty impossible with a Pozidriv head. Lengths may or may not be ideal. Occasionally useful for spares/projects.

**Spyderjon** · 06-17-2012, 08:36 AM

A ski binding screw thread is a ST5.5x1.8 were:

The ST prefix = self-tapping.
The 5.5 = 5.5mm outside thread diameter
The 1.8 = 1.8mm pitch

The nearest imperial thread size is a 12AB which in metric is a M5.3x1.81. Because it's so close to the binding screw spec & is more readily available it's the 12AB taps that are used to tap the metal top sheets for skis.

Don't have any info re the thread size tolerances.

**GeezerSteve** · 10-31-2013, 01:06 PM

Bumping this thread because I'm doing some Dyna toe shimming and not finding sufficiently long 5.5mm alpine binding screws (ABS).

Analysis and observation is a work in progress, but here are some preliminary observations:

I've recently seen #12 sheet metal screws used on mounts where local bootfitters installed shims. I won't name names, but some of you can guess. I've personally mounted with #12 sheet metal screws with no pullouts. Also note LouD's post indicating that he uses #12 screws for shimmed Dyna toes.

ETA: Those bootfitters and I grind the point of a #12 screw to make it blunt, like ABS.

As JS notes, most ABS major diameters are around 5.4mm with some exceptions, and ABS thread pitch is c. 14 TPI.

#12 non-tapered wood screw/sheet metal screw major diameter is c. 5.3-5.4mm and pitch of 11TPI.

(Sorry for mixing metric and imperial; my thread gauge is the latter.)

Minor diameters seem to be similar but my calipers are yielding varying results. I'll check that again via chucking samples in my lathe and turning off the threads then measuring.

My ABS tap seems to be close to ABS c. 14 TPI. So for #12 screws I'll be tapping for #12 with a modded #12 screw + DIY guide.

Thread profiles seem to vary among manufacturers, both with ABS and #12 sheet metal screws, but appear similar. This observation is based on looking a numerous samples via a magnifying glass. I'm not tooled up to measure. Given the ostensibly small variances, not sure it makes any material difference in ski core application.

Surprisingly, per my preliminary measurements, the ski helicoils sold by Slidewright, Tognar, etc. seem to be closer to 11 TPI than 14 TPI, but both the 5.5ABS and #12 screws seem to get good purchase in them when installed.

That's it for now. Will supplement, will revise if I reconsider any of the foregoing.