ski binding mounting question - Drill bit size?

[CaliBrit]

Actually I think the norm is 3.6 and 4.1, I have never heard 3.8 ever. So be careful with the snarkcasm.

3.5 is often used instead of 3.6 as it seems a 9/9.5mm stepped bit is available (I got mine from Jon at bindingfreedom) an 0.1mm is pretty much irrelevant.

Tongar sells the 3.6 and 4.1.

[Shorty_J]

Definitely 3.6 and not 3.8.

[glademaster]

Marker includes a 3.8mm bit with their Griffon demo bindings and recommends to use ONLY that bit when mounting said bindings, regardless of ski construction.

[AlpiNord]

By CE regulation, all current skis have the recommended drill size printed on the ski, either in the mounting area, on the adjacent sidewall or on the tail with the ski dimensions. If there are no drill sizes provided on the ski ( i.e. custom skis), contacting the manufacturer for their recommendations is your best course of action. If unsure, drill with 3.5mm diameter tip. If metal is present, then use a 4.1mm bit.

The general rule on alpine ski drill bit sizes is 3.5mm for non-metal skis and 4.1 for metal. There are exceptions, such as a metal binding plate in a non-metal ski, carbon fiber top sheets, etc.

The outside diameter of an alpine screw thread is just over 5mm. The inside diameter of the screw thread (shank) is just over 4mm which matches the tip of a 4.1 diameter bit. Softer materials such as wood or plastic will compress when driving a screw into a 3.5mm hole. Non-compressible materials like metal and carbon should be drilled with the larger diameter, 4.1mm hole so the shank does not compress and damage the material while being driven into the ski.

Binding Freedom & Quiver Killer stainless steel inserts & heli-coils require a 1/4" tipped bit.

The minimum depth for a screw for a binding mount is 6mm/1/4". Measure the screw less the binding thickness will provide you minimum drill tip length.

It is better to err towards a longer tip than one shorter than the embedded screw section length so the bindings can lay tight to the ski.

Make sure this will not exceed the thickness of the ski.

The excess depth of a hole deeper than the length of screw will be filled with the glue.

Tapping skis with metal and carbon top sheets using a 12AB tap is recommended. Tapping all holes regardless of top-sheet type or drill tip diameter is recommended. The same tap works for 3.5mm & 4.1mm diameter holes.

^^^^
Wonder where that came from???

If you can measure within 10th's of a millimeter while drilling with a wobbly hand drill, awesome. Why the 2 main different diameters is in red.

[PlayItLeo]

Ha.

[HHTELE]

Just re-reading this thread, and noticed Terry mentions carbon in with metal for 4.1. I mounted Backups recently, installed inserts. Could definitely feel the difference working with a layer of metal. Mounted up Carbon Converts yesterday, drilled with a 3.6. The screws threaded in like a wood core ski. Too late now, but looks like I should have used the bigger bit.

BTW- I know of a shop that mounts a lot of skis, that never taps metal. They have a tap. I saw one of the techs use it on specific request, and it took him under a minute per ski. But, they generally don't tap, and say they have never had a problem.

Same shop mounts BD tele binding with wood glue rather than manufacturer recommended epoxy.

Very nice guys, but this stuff is one reason I MMYOFB.

[Knut]

Actually I think the norm is 3.6 and 4.1, I have never heard 3.8 ever.

I didn't say it's the norm, I said it's the most common. General rule of thumb. In my experience.

Most shops here in Europe will use a 3.8x9mm stepped drill bit and it's the bit you can find most often sold by suppliers, too.
But of course the good ones have a 3.6, 3.8, 4.0, 4.1 and whatever available to meet any manufacturer's recommendations precisesly. And if it's just to be able to say "we did it correctly".
If you're interested in a variety of drill bits, have e.g. a look here: http://www.fk-sks.com/kunzmann/bindungsbohrer/
I guess they aren't a frequent find in North America, though....

But honestly, I don't think that 0.3mm will ever make the difference. The hardness of the ski's core is much more important and much more variable.

BUT: drilling a hole only 6mm deep is a sure recipe for desaster. That was my main point

[CaliBrit]

Marker includes a 3.8mm bit with their Griffon demo bindings and recommends to use ONLY that bit when mounting said bindings, regardless of ski construction.

Interesting, first I have heard of that size, as I said to Knut (norm and most common are essentially equal in my book) 3.6 and 4.1 are the accepted standards for ski mounting.

[1000-oaks]

I definitely tap metal skis, binding screws may start with a small thread at the tip but they don't have a cutting edge (like sheet metal screws) and are not technically "self tapping". Sure, they can be driven through an untapped aluminum sheet, but the fine edge of the threads is going to be abused. Better to tap and let the screw threads be as sharp as possible and not worn down.

[SchralphMacchio]

Another bump of a really old thread ...

seems like the 3.5/4.1 x 9.5mm double-step drill will be a handy one for metal and/or carbon topsheets, no?
http://www.slidewright.com/alpine--n...drill-bits.php

[buttahflake]

Drill everything with a 4.1 and call it good. Why is this so hard?

[DropCliffsNotBombs]

Drill everything with a 4.1 and call it good. Why is this so hard?

DON'T do this ^^^. You'll get spinners in your lightweight skis.

[tenB]

DON'T do this ^^^. You'll get spinners in your lightweight skis.

Fully agree. There is a big difference between 3.6 and 4.1, and why would anybody give up that much purchase when bits are cheap and readily available?