Making and using a tillering gizmo;
Easy to make, a "1X6" piece of softwood, drill a 5/16' hole in the center and a 1/2" hole about halfway through the wood on top of the 5/16" hole.
Tap a 5/16" nut in the 1/2" hole, I used to use a dowel then started using a 1/4 bolt to tap the nut in because it did a better job. I did find the bolt head would slightly deform the brass nut I use and it would thread on a pencil well. Now when I make a gizmo I run a 5/16 18 tap through the nut to make sure the threads are sharp for screwing in the pencil.
I cut the excess wood off the block to this shape so the tool will go further up the limb with out string interference.
Screw a golf pencil in the nut and you are good to go.
A blunt pencil work best.
Here are the instructions I send out with the tool;
After floor tillering your bow, bend the bow slightly on your tillering tree or tillering stick, I start at about 3” of bend using the long string. Retract the pencil in the Gizmo and run the wood block up the bow’s belly and find the widest gap. Screw the pencil in the block to a point it is almost touching the bow’s belly at the point where you found the widest gap. I change the sharp angle the pencil has been sharpened to a blunt angle for the best results in marking the limb. This lets you work very slight bends.
Run the Gizmo up the belly making sure it is centered on the limb. The
pencil will mark non bending areas that need wood removed. Start on the long string, continue at brace and up to about 20” of draw. You do need to have a way to hold your bow string while you mark the limbs with the Gizmo.
I have holes in my tillering tree and insert a 3” piece of dowel in one of the holes to hold the string with the limbs slightly bent while I mark the limbs with the gizmo.
Go slow, no more than ten scrapes on the marked areas of the limb, flex the limb 30 times and recheck. My bow limbs tend to be slightly round belly so the Gizmo only marks the top of the crown on the limbs belly. I scrape the marked area as well as the rest of the limb side to side to keep things even. You can get the limb bending perfectly this way. You will still have to eyeball bending in the fades but the rest of the limb will be perfectly tillered, hinges will be a thing of the past.
I adjust the gizmo one time on the long string and set it to the deepest bend on the weakest limb. I use this setting for both limbs. If you continually adjust the gizmo you will chase weak spots up and down your limb. One adjustment and hold this adjustment until you have removed enough wood to the point that can run the gizmo up both limbs without making a mark. As you increase draw length readjust the gizmo.
Make a few passes with the gizmo on your limb and the areas that need attention will be perfectly obvious. You can fine tune the tillering by closing the gap between the pencil and limb to almost nothing. At this point I like to use a cheap orbital sander to remove both wood and any tool marks that are left. With course sandpaper, the sander will leave tiny swirls in the wood so I like 220 grit for my final tillering work and follow with a light hand sanding.
The gizmo doesn’t work in the fade out area of the riser so you will have to eyeball the bend in this area or put a flat board across the back of the bow in your tillering tree and watch the gap between the back of the bow and the board to see where the limb is bending.
Tillering that once took me hours to get close takes me about 45 minutes with the Gizmo and the end result is close to perfect.
Remember the key thing to proper tillering is using a scraper or sand paper. If you ever get the urge to grab a course rasp or use a belt sander to speed things up even more, take a coffee break and come back when these thoughts have passed.
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