Tutorial for putting metal inserts into skis

[Patches]

I just finished putting metal inserts into two pairs of skis so I could swap from Dukes to Dynafits, and it worked well, so I'm posting the info here. I'll add some pictures next time I do a round. Definitely more work than Jondrums' plates ([ame="http://www.tetongravity.com/forums/showthread.php?t=169419"]link here[/ame]), which look awesome, but I wanted a lower binding height.

[Edit added 12/17/09]
This tutorial is a bit out of date because of puderluder's inserts, which have sealed bottoms but require tapping and look great. The following will work and is cheaper ($0.30 per insert vs $0.75) but I would opt to spend the extra monies.

Also, I describe using handtools guided by locator holes drilled with a shop jig. This worked fine on the two sets of duke hols and two sets of dynafit holes I've done, but there is some wandering. If you have access to a drill press it would be better to use that.
[/Edit]

Here is a couple of the finished inserts:


I used Yardley TRISERT inserts:
http://yardleyproducts.thomasnet.com...203?&forward=1

Get the short brass series in M5, part number 5008JS19-19BR
Price is $0.93/ea but drops to about $0.30/ea if you buy 500. I bought 500 and plan on doing skis for a bunch of friends as well.

I also purchased from McMaster Carr:
2931A26 17/64" drill bit ($2.29)
8865A185 17/64" stop collar ($3.90)
75045A78 3M 2216 epoxy ($31.55)
8569K16 teflon film, 2 feet ($3.74)
92010A320 stainless m5x10mm flat head screws ($11.05 for 100)
92015A117 stainless M5 socket head set screws ($11.50 for 100)

And (bought at local hardware store)
M5x10 pan head screws for Duke center screws
M5x10 pan head screws (zinc, whatever is cheap) for installing inserts


You'll also need cardboard, toothpicks for mixing glue, tape, allen wrenches (for stop collar), #2 phillips screwdriver, razor blades, a pin or needle, vise grips, and a few fender washers that fit the screws. Fender washers are just big washers.


This picture shows a piece of the teflon taped to cardboard to stiffen it (will be explained later). In the back from left to right are:
1) An insert
2) A cheap M5x10 pan head screw for installing the inserts
3) Expensive M5x10 pan head screw for center screw on Dukes
4) Stainless M5x10 flat head screws for the rest of the screws attaching the binders
In the front is a fender washer, and a 17/64" bit with stop collar.


So... the problem with metal inserts is the open bottom isn't sealed. So the first step is to seal the bottoms of the inserts with epoxy. Do this 12 hours before using the inserts if you use the 3M glue above, which I recommend. It is a very very slow setting epoxy, and you are getting a lot for your $30.

To seal the inserts, tape a square piece of the teflon onto a larger piece of cardboard so it stays flat. Mix up some epoxy and use the toothpick to make small round dabs on the teflon- little circles of epoxy the same size as the inserts. Place an insert on top of each dab of epoxy. Let them cure for 12 hours at room temperature, then pull them off the teflon. Check each one, they should have a nice seal on the bottom. If any have holes, set them aside to patch the next time you mix more glue. The process of sealing the inserts takes about 10 minutes for 100 inserts, so its pretty fast.

The beauty of the 3M epoxy is the epoxy is firm but still pliable at this point, its not hard and brittle when you go to put the inserts into the skis.

Here are pictures of a finished insert. THIS ONE IS NOT USABLE. I dropped it into a pile of fiberglass and aluminum chips. Its disgusting at 100x magnification like this picture. But its the only one I have left right now to take a picture of. You can see that one end is covered with a thin film of epoxy, maybe 0.5 mm thick.





Assuming your skis are already drilled for regular ski screws in the right places, drill the holes out to 17/64" and clean the edges of the holes up with the razor blade. Since the stop collar is so close to the end of the bit, chips and glass fibers jam up in the drill, so after each hole use a pin or needle to clean the drill bit out.

Once the inserts are ready, mix up some more epoxy to seal the inserts to the skis. To make an installation tool, use a fender washer and an M5 screw. Coat each insert with epoxy and run 'em in. Piece of cake! The epoxy seal done earlier keeps the installation epoxy from getting into the threads from the bottom.

To seal hem even more, put some extra epoxy in the hole before putting in the insert, and when you are done, lay the skis bases up to cure. That way to glue will flow down and collect on the underside of the insert.

Here are the parts for installing the inserts. Note- I would use THREE washers not two:


And all put together, ready to coat with glue and screw into ski:


I've done this to two sets of skis. The first were Lotus 120s which have no metal, and it was very easy. The second pair was Big Troubles, which have a metal layer. This were harder. The metal meant that the inserts were harder to put in, which means that sometimes when I went to unscrew the installation tool, the whole insert backed out since it was torqued onto the M5 screw. When that happened I unscrewed the whole rig from the ski and used the visegrips to pull the insert off the screw and threw it away and did a mulligan.

It takes 18 inserts to mount a pair of Dukes. On the 120s, I used 18 inserts. On the Big Troubles I had to throw 6 away, so make some extras.

[Added 12/10/09]
If you are having problems with insert backing out instead of just the tool...
a) Run inserts in most of the way with a big electric drill
b) Do last 20% of install by hand so you don't strip em out
c) To remove installation "tool" go back to the drill, push down hard and get on the trigger
Once I started doing it that way (hard pushdown with the drill + fast start) the problem ended.
[/end 12/10/09 addition]



I'll try to take some pictures later. But based on the force it took to install them they feel really solid.

I'm planning on sealing unused holes with the set screws and blue locktite. I just ordered those, so I haven't actually used them, but the size looks right - double check though its the only part of this process I can't vouch for. You probably actually don't need to use set screws since the inserts should have two layers of epoxy on the bottom when they are installed but it couldn't hurt.

One thing to consider is the cure time on this epoxy is 30 days. Yes, 30 days. That's at 70 degrees though. At 150 degrees the cure is only 4 hours. So if you plan on using the skis right away it would be a good idea to pay for a night in the waxing hotbox.

Ways process could be better:
1) Find a glue with a long working life with a shorter cure at room temp. McMaster sells a faster setting version of the 2216. The specs for both are in the link at the top of this post in the materials list. I actually really like the glue I used, super long pot life, seemed to wash off hands easily with soap and water, and should be very resilient. But if I get a chance to ski within the next two weeks I'll have to hotbox the skis.
2) Inserts would be better if they were solid metal on the bottom instead of hollow. This would probably mean a lot more $$$ though.
3) Inserts would arguably be better if the self-cutting threads were taller and had more bite. Yardley makes "Fiberserts" which have taller cutters, but they are a lot longer so they would need to be cut down, which is a lot of $$$. Also those would have a tough time making it through any metal layers.

[skideeppow]

Pixs woudl be really helpful?

[jondrums]

sounds real good!

Here's some more information for the M5 inserts I made and succesfully use with dukes and 188 bros:
[ame="http://www.tetongravity.com/forums/showthread.php?t=113720"]repeatedly changing ski bindings on a ski - Teton Gravity Research Forums[/ame]

on page two, I have a drawing you could take to a machine shop and have them make you some inserts.

check here too:
http://www.tetongravity.com/forums/a...?t-100847.html

also good info here:
http://backcountryworld.com/showthre...hreaded+insert

[DHogg]

I've often thought about this, the idea of having snowboard like inserts on skis would be key! I never tried but now i know it works i'll have to give it a go.

[hitmanbob]

this is a pretty good idea! Instead of putting these in the ski and having exposed holes, has anyone tried having a mounting plate system that allows for different tracks on top of a rail like mountplate so the binding can flex and for each set of bindings you drill them onto another plate that can just slide on. Sort of akin to snowboard binding systems

or is that making a simple problem have a complex solution?

[b dubya]

Great work! maybe a pic of the final result? I'd be very interested in how they go once you get them on snow! Thanks for taking the time to put this up, good idea with the epoxy sealing on teflon, wouldn't have thought of that...

[moose pit]

Sounds like a lotta work but well worth it. Can't wait to find out how it works in the longer run.

I'd be all over this for my tele set ups.

[Patches]

Pictures added.

[b dubya]

Pictures added.

Great! thanks once more for the effort... I can see my ski fleet now sharing the axl's that are soon coming my way!
peace.

[DHogg]

What do you think the strength would be like compared to straight mounting? I guess its essentially the same as having a screw in the ski, but i guess time will tell. Nice pics by the way, looks spot on. Would be awesome for traveling. You could easily fit 2 pairs of skis in a one pair ski bag.

The only bad thing i can see is that you would have to carry a tool around like a boarder to tighten screws which come a bit loose.

[El Chupacabra]

I'm planning on sealing unused holes with the set screws and blue locktite.

What about nylon screws? Wouldn't need loctite; they should deform a bit when threading into the inserts, so they should seal pretty well on their own. And they're lighter.

Nice job -- that's a lot of work and commitment to the project.

[Patches]

Just tested pullout strength - not very scientific, I just put a bolt on an unepoxied insert and yanked on it with a crowbar. They were surprisingly easy to pull out, so I tried the same test with a ski screw in a normal-sized hole, and that came out even easier.

I'm guessing that without epoxy the inserts are stronger than ski screws, and with epoxy they would be better still. If anyone has ideas for how to do proper testing let me know.

[Patches]

... or even better if someone has a way to test I can mail you some inserts and a 17/64" bit.

[hitmanbob]

I'd be willing to give these a try. I'm looking for a way to switch between AT and tele bindings. do you think these would do the job as far as pull out concerns with a tele mount? I'd be down for 30 or so if they are (naxo mount(14) and tbd tele mount). I'll send you a pm and we can work out some details. ive got the other supplies

[lobstahmeatwad]

I went through this all last year. I tried to do this with a pair of karhus with metal. I could not get the inserts to stop from stripping the threads off the brass inserts even with tapping because the pitch of the tap is no where near the pitch of the insert. If you can find a tap with a wood type pitch I am all ears.

I would be pretty skeptical of the metal topped skis with inserts. I think you would find that all the threads are flat in there and the only thing holding them in is the epoxy with a slip fit.

I did get some in but I was unsure so I backed them out and they were flat and smooth.
The AL/titinal in your skis is a hell off allot harder than that crappy brass they make those inserts from.

The wood ONLY skis I did worked awesome.

[jamesp]

you can get stainless insets which might work on skis with metal. The catch is the stainless insets cost 2.5 times more than brass...

[hitmanbob]

I went through this all last year. I tried to do this with a pair of karhus with metal. I could not get the inserts to stop from stripping the threads off the brass inserts even with tapping because the pitch of the tap is no where near the pitch of the insert. If you can find a tap with a wood type pitch I am all ears.

I would be pretty skeptical of the metal topped skis with inserts. I think you would find that all the threads are flat in there and the only thing holding them in is the epoxy with a slip fit.

I did get some in but I was unsure so I backed them out and they were flat and smooth.
The AL/titinal in your skis is a hell off allot harder than that crappy brass they make those inserts from.

The wood ONLY skis I did worked awesome.

good to know. PMgear only makes woodcore skis, right? except the doortech* in the toe area

[Patches]

I'd be willing to give these a try. I'm looking for a way to switch between AT and tele bindings. do you think these would do the job as far as pull out concerns with a tele mount? I'd be down for 30 or so if they are (naxo mount(14) and tbd tele mount). I'll send you a pm and we can work out some details. ive got the other supplies

I don't know about tele- don't you guys rip screws out all the time? It would be nice to have real numerical pullout figures.

[Patches]

I would be pretty skeptical of the metal topped skis with inserts. I think you would find that all the threads are flat in there and the only thing holding them in is the epoxy with a slip fit.

The wood ONLY skis I did worked awesome.

The insert shown in the pics above are ones that had been into and out of the Big Troubles. You can see the threads are smashed up, but not too bad? Big Troubles have a ton of fiberglass on top of the metal (the metal is in towards the core)- also they are soft skis so maybe the metal is softer than your Karhus.

Again I have no numerical pullout data- if anyone does this proceed at your own risk.

[lobstahmeatwad]

hmm yeah a little smashed. Mine were totally smooth.
I found it very difficult to get the brass ones in there cleanly.
The poplar in my homebuilts was very difficult to thread into, has a bit of metal in there also but very little. Maybe a bit of a technique issue but for each ski I farked maybe 2.
I would like to find this type of aggressive wood pitch in a stainless one but they don't exist hence the reason I though some were to be made. I signed up. I guess I could have them made but I'm not really in a place with a mass abundance of machinists.
My bros went in very easy in comparison. The plastic topsheet seemed to help.
Those karhus though, that metal was thick.

[10% Groomed]

So... the problem with metal inserts is the open bottom isn't sealed. So the first step is to seal the bottoms of the inserts with epoxy.

Is it necessary to seal the bottoms prior to installation? Could you put a dab of epoxy on the end of the insert or in the bed of the hole during installation?

Is it really necessary to seal the bottoms at all? If the insert is epoxied to the ski, and you are talking about using loctite when you mount the binding, will moisture still find a way in?

Just curious for thoughts.

[10% Groomed]

Great write up by the way.

[lobstahmeatwad]

I relize these q's is not addressed to me.
I did not seal the bottom, I just didn't used allot of epoxy and made sure the threads were clear.
I used silicon when holes were not in use and its easy to remove when you need to.

[10% Groomed]

Ahhh. So the cap on the bottom doesn't have anything to do with moisture. It's to keep the epoxy from bubbling up in the threads during installation. That makes more sense.

Thanks.

[altis]

Good write-up Patches. I like the idea for sealing the inserts.

Zeno over on Telemark Tips has done lots of pull out tests but, unfortunately, he's never used inserts.

http://www.telemarktalk.com/phpBB/viewtopic.php?t=34239
http://www.telemarktalk.com/phpBB/viewtopic.php?t=39781

And I'd recommend Avdel Nutserts or similar for metal topsheet skis:
[ame=http://backcountryworld.com/showthread.php?t=233][/ame]