One of the great things about snowboarding is the infinite number of stancepositions available. However, not all board insert patterns accommodate allbindings and positions. And sometimes, inserts may become damaged and haveto be replaced. If you run into such a situation, you may need to t-nut yourboard.
A t-nut is a threaded insert installed through the bottom of the board toreplace a blown factory insert or to customize binding placement. Burtonwas one of the first to use t-nuts–brass ones crudely punched into the bottomof the board and left in plain sight–to replace the factory inserts thatwere pulling out of some of their Performers back in the mid 80’s. Todaythere are several types of easily installed t-nuts available, and they canbe covered up in much the same way you would repair major base damage.
The two basic shapes of t-nuts are: those with a flat flange (resemblingan upside-down “T”, hence the name) and those with a tapered flange. Eachcomes in different sizes, but those with tapered flanges are usually smaller.Size is something to consider depending on where the t-nut is needed.
Before you go drilling holes in your board check with the manufacturer. Ifthe board is still under warranty, you may void it if you do not follow themanufacturer’s suggestion for installing new inserts. However, if you haveto customize a stance, most manufacturers recommend a t-nut installed byan experienced shop tech. Please note: this is a procedure best performedby a trained technician. If you have never installed a t-nut, it is a procedureyou will want to practice on a junk board before drilling holes in your own.
The most common use for t-nuts is extending an insert pattern to accommodatea wider stance. For the t-nut installation you will need these items:
- Hammer and punch
- T-nuts. These can be purchased in kit form, including drill bits, from such tool distributors as Aunt Mables and Spirakut.
- Drill bits. You will need three: a small one (about 2 mm or 1/16) used to drill a pilot hole; one to match the shaft diameter on the t-nut; and a countersink bit specifically shaped for which ever t-nut you are using.
- Epoxy. Use only a long-set, ski-specific epoxy (such as Epon); these epoxies are designed to hold well at a variety of temperatures and not get brittle when cold.
- Stir sticks
- Mixing cup
- Rubber gloves (epoxy can be nasty stuff)
- Masking tape
- Grub screws (plastic plugs with a slotted screwdriver head and a 6mm thread pitch).
- All the tools and hardware you would use to mount your bindings, but specifically you will need: 6mm screws with washers and the appropriate driver (usually a number 3 Phillips but occasionally a number 3 pozi-drive; make sure you know the difference).
- A binding disk that matches the hole pattern on the board. The one from the binding to be used will work, but a metal one with holes and not slots is preferred.
- Something to cover the bottom of the t-nut: a plastic cap, hot extruded material, a urethane epoxy/powdered graphite mixture, or ideally a base patch.
Now that you have the necessary tools and parts, and have checked with themanufacturer for their recommendation of which insert to use, it’s time tobegin.
You will first want to decide where to place the binding and mark it on theboard either by outlining the binding with a grease pencil or wax crayonor by marking the actual holes. If you are extending the hole pattern it’sbest to mount only the binding disk to the board using whatever holes areavailable. Use a carpenter’s punch and a hammer to mark the spot on the topof the board, through the binding disk, where the t-nut is needed. The punchshould put a small dimple in the top-sheet so the drill bit doesn’t wander.
Your next step is to drill a pilot hole through the top of the board. Thekey phrase here is “through the board,” so make sure that’s where you wantthe t-nut ’cause there’s no going back once you drill. The pilot hole mustbe straight as this is the hole all other drillings will follow; your t-nutwill not go in properly if this hole is not straight. Be sure the pilot bitis not so big that its hole allows the next bit to wander.
Once you have the pilot hole drilled, turn the board over and drill all otherholes into the bottom of the board. Be sure the board is securely held inthe vice as the larger bits are designed to remove a lot of material andwill spin the board if it is not held down. The next bit used depends onwhich t-nut you are using. For our purpose let’s use a 3/4 inch, flat-flangedt-nut as the mounting process takes a little more care to get just right.
Take your Forschner bit and drill the countersink hole for the flange ofthe t-nut. Drill slowly and carefully–this bit has no shoulder to indicatethe correct depth or keep the bit from going through the board. You willwant to drill deep enough to countersink the flange of the t-nut into theboard but not so deep that the top of the t-nut protrudes through the top-sheet.It’s always a good idea to hold the t-nut up to the sidewall to be sure justhow far to drill and that it’s not too thick for that area of the board.Drill through the base material and into the core. By drilling a little ata time you can check for depth and a level drill by sighting the materialsyou have drilled through; i.e., If you can see fiberglass on one side ofthe hole and core material on the other, you know that you are not drillingstraight. Drop the t-nut into the hole to judge the proper depth of thecountersink.
Once you have drilled the countersink hole for this t-nut, it’s time to drillthe hole for the shaft. Hold the appropriate drill bit up to the shaft ofthe t-nut to be sure that it is slightly smaller than the shaft (if thereare teeth on the shaft of the t-nut they should have enough material to biteinto). Drill the hole and make sure it is in the center of the countersinkhole; if it is not, the t-nut won’t sit properly in the hole.
If you find yourself installing many t-nuts, there are special bits thatallow drilling of the shaft hole and countersink for the flange all in one;they are certainly worth purchasing if they accommodate the t-nut you prefer.A drill guide to keep your holes straight may also be a worthy investment.
When all holes are drilled to your satisfaction, there is some prep workto do before installing the t-nut. The epoxy you use and whatever you choseto cover the base of the t-nut with may not stick without some preparation.The t-nuts you get may still have some of the machine oil on them that aidedcutting in their production; you will want to clean them with denatured alcoholbefore applying epoxy. Also, once you clean the t-nut put it on a piece ofmasking tape so you don’t have to touch it (Remember, the oil from your skinmay keep epoxy from sticking–don’t touch!). You will also want to take thetime to score the bottom of the t-nut using a Dremel tool to ensure whateveryou use to patch the base with will stick. Screw a grub screw into the t-nutif it has no cap to cover the threads; this will keep epoxy and other debrisout of the threaded area. Finally, put a piece of masking tape over the topof the hole you have drilled to keep epoxy from oozing onto the bench.
Now it’s time to break out the caustic stuff and install the t-nut. Use onlya ski/snowboard specific epoxy with a long set time–at least 12 hours.Ski/snowboard specific epoxy is designed to stay flexible at very lowtemperatures. Apply a thin layer of epoxy to the inside of the hole and possiblysome to the t-nut itself. Remember: a thin layer will bond better than athick layer. Put the t-nut into the hole and tap it in with a hammer. Thereshould be some resistance as the teeth of the t-nut bite into the hole.
Now turn the board over, peel off the masking tape, and remove the grub screwfrom the t-nut. It will probably not be seated all the way in the board;use a short 6mm screw with a couple washers or the binding disk to pull thet-nut the rest of the way into the board. Or you may want to use a metalbinding disk to make sure all the holes line up–the old ones and the newones. Keep one hand under the board while tightening the screw to make surethe t-nut doesn’t spin in the hole. If it does, it will likely chew too muchmaterial and not allow the t-nut sufficient bite. Once the t-nut is seated,apply a thin layer of epoxy to the bottom of it to aid in whatever you useto cover the bottom. At this point, set the board aside and allow the epoxyto cure.
Whatever you use to cover the bottom of the t-nut, you will want to installit while the epoxy is still slightly tacky. With some t-nuts there are plasticcaps you can simply press onto the bottom over the still tacky epoxy. Youmay also use your hot extruder gun to fill the void with some extruded basematerial; be sure the epoxy is nearly set before you do this as the heatfrom the gun will probably pull off soft epoxy. The ultimate way to patcha t-nut is with a base patch of sintered base material. Using this methodwill allow something for wax to penetrate and give the best bond.
My preferred method of patching the base of the t-nut is to use some urethaneepoxy mixed with a little powdered graphite or glass micro-beads. When sandedeven with the bottom of the base, the graphite or glass beads will leavetiny pockets for a little wax to stick in. Whatever method used to coverthe base of the t-nut, be sure that you hand sand, or file, or Surform thematerial as close to the level of the surrounding base material as possible.If you do not and go immediately to your belt sander, you stand the chanceof inadvertently beveling one or both of the edges as the higher area liftsthe center of the board off the belt. Once the new material is level withthat of the surrounding base material, a few rough grinds on the contactwheel of the belt grinder should even everything out.
Since a rough grind of the whole board is necessary to finish the job, afull tune is in order to get the board riding again. You might want to takethe time to fill any other gouges; then do your finish grind, edge filingand polishing, and waxing just as you would normally. Since you have hadto wait for the epoxy to dry to finish the cap over the bottom of the t-nut,about 36 hours have passed and everything should be plenty set-up. (Note:you can cut this time dramatically without degrading the curing of the epoxyby using a hot box. A hot box can be as simple as an enclosed box with asmall rack and four or five 100 watt bulbs inside.) You can now take thescrew out of the t-nut, and the washers or binding disk off. All you shouldhave to do now is install the binding in the new position and you (or yourcustomer) are ready to ride.
Installing a t-nut is a bomber way to add a new or replace an old insert.Two things are key: patience and practice, so find an old board to practiceon a few times before you start drilling into your own board. And remember,always check with the manufacturer before drilling any holes; you may voidthe warranty on that board if you do not follow the manufacturer’srecommendations. When it’s all done–go ride!