The Evolution of the Tillering Gizmo, Lets Make One

[Eric Krewson]

My peg is a piece of 1/2" poplar dowel.

[NYArrow]

awesome tool Eric! Where did you dream this up? I could have used this earlier in my tillering but I'm still 6" away from target perhaps it will set me straight! (or bent)

[hova]

i had the same issue. i use a piece of bamboo now , or a screwdriver. i had a dowel split , that wont  happen again...


-hov

[inksoup]

after i read the second time, now i understand how it works. i mean the logic behind it.
it is really brilliant idea. so simple yet so useful. like fire!

[oneraindog]

hoping to revive this for an answer:

i assume this thing will not work so god on limbs with reflex/recurve?

[SEMO_HUNTER]

It doesn't work on R/D hybrid type profile bows raindog, that's the only draw back. I sure wish it did, cause the R/D bows are a bugger to tiller!

[DVSHUNTER]

I think the tool is very useful as a learning tool. it teaches perfect tiller. IT doesnt work as well imo for d/r bows, but i hear it does work. I tiller by eye now, after learning with a tool similar, but without a pencil. I always though abouto having one here in the shop to help/show others what i see, but have never made one yet.  Kudos to Mr. Krewson for sharing his idea free for all to use. Not to mention all the free ones he's sent out.  Lota guys building real nice bows because of him.

[SEMO_HUNTER]

I got one of those free ones myself, Eric is a fine fella.  

[Blackie76]

This is amazing. Needs a better name though.  I hereby propose we refer to it as a Krewson Hinge Stopper. Before long, 3 Rivers will be carrying them in stock!  

Simply ingenious tool. Great work!

[Eric Krewson]

I thought about marketing them but I am retired and don't want a job, I guess I will keep giving them away.

Gave two away at an ASTB tournament this weekend and am completely out of them at the present. When I get caught up on other projects I will spend the day making them to restock my supply.

I have changed the way I hand them out. Used to be, I would give them to anybody who expressed an interest. Now I only give them to someone who is actually making a wood bow. I have given away dozens to people who were thinking about making a bow but I  found out thinking about making a bow seldom translated into actually making one.

Lots of the gizmos I handed out were never were put to use and probably ended up in the trash.

[eflanders]

With all due respect to Mr. Krewson, I modified his version to make it even more useful.  What I did was add a 1" long wooden dowel on each end of the tillering gizmo.  I also countersunk and glued in the nut so it is secured in halfway through the thickness of the wood.  

Now the jig can do two functions:  1) Mark/find the center of the stave.  2) Tillering jig.

To use as a centering jig, have the pencil mounted on the opposite side of the dowels.  Twist the jig so that the dowels constantly touch the side of the stave and run the jig down the entire stave.  A pencil mark will be left right down the middle of the stave no matter how snakey the stave is.

Eric has already described very well how to use the tillering gizmo.  All you have to do with my version is to mount the pencil so that it is on the same side as the the dowels.

Two useful jigs in one simple to make package!

[vanillabear?]

[**DONOTDELETE**]

Originally posted by Eric Krewson:
I took it for granted that everyone would use the gizmo like I do but found I should have explained it's use more in depth.

One guy said when he used the gizmo it caused stiff spots to move from one place in the limb to another. Another said he works one stiff spot then uses the gizmo to find another to work on.

For the gizmo to to work at it's maximum potential, every time you put it on a limb to check for stiff spots, run it the entire length of the limb, not in one small spot.

When you start scraping off the pencil marks and removing wood, work on all the stiff spots at the same time, not just one spot at a time.

This way the whole limb will be corrected when the pencil no longer marks the limb with a gizmo swipe from fade to tip.

This is a great gizmo Eric.  This is one aspect of fine tuning limbs that a lot of glass bow builders overlook completely. they just assume that the limbs bend evenly because of the glass backing.

i know there are a lot of self bow procedures that just don't apply to composite building. But this isn't one of them.  i don't use a pencil in mine like you have, but use a block and a ruler or tape to check the consistency of my working limbs, and it makes a HUGE difference in performance and hand shock issues.

this is a perfect example how a limb can measure perfectly on tiller measurements and still be out of whack.

of course on a hybrid long bow the whole limb is not going to bend the same... But!  the location of the working portion can easily shift, or be shifted to time the limbs properly on both a wood bow and glass bows alike.

 

[Dennis La Varenne]

Eric,

Very impressed with your simple device. Did you know that a very similar tool was in use waaaaay back in the pre-WWII days? It is described at length in Robert Elmer's book "Target Archery" and there are pictures of it being used by Russ Wilcox on one of his duoflex bows, the precursor of the modern recurved bow.

Yours has the advantage of the pencil to mark as it goes, whereas those in Elmer's book use a dial micrometer gauge to actually measure the amount of curvature in the limb surface.

Your design has the advantage of actually marking high spots when the pencil is set to contact any wood above a certain level. You can even keep screwing the pencil down until it contacts and use that level as the datum level until the limb bends evenly.

However, I do not see that it will work on other than circularly bending limbs. Elliptical limbs where there is either increasing (whip-ended) or decreasing bending (stiff-ended) toward the tips will be difficult to cater for.

Have you worked out any way around this at all? I would be particularly interested.

[Eric Krewson]

For stiff tips I ignore the pencil marks within about 4" of the tips, don't make any whip ended bows so I don't have any experience with such.

[30coupe]

No offense, Mr. Krewson, but unless your nuts are bigger than mine, you will need a 3/8" forstner bit for the larger hole. A 5/16" nut will drop right into a 1/2" hole.

Here's another tip on installing the nut into the block. Instead of using a dowel, screw a 5/16" bolt into the nut, and then use the bolt to drive the nut into the block. The threads will be undamaged and you can use the bolt to make sure the nut is squared to the hole. I use a long enough bolt to to through the block. Then I screw the bolt all the way through the block. This will align the nut with the hole in the block.

The gizmo does work pretty slick and is really simple to make. Thanks for the tip!

[Eric Krewson]

Always a smarty pants in the crowd. You are wrong Russ you must not have taught shop class.

I have just about used up my second box of 100 5/16" brass nuts so I have made almost 200 gizmos. A 5/16th brass nut has an inside hole diameter of 5/16".

My 1/2" forstner cuts a hole this diameter.

   

A 5/16" nut has an maximum outside measurement of this;

   

A 5/16" nut taps right in a 1/2" hole in soft wood by expanding the wood slightly for a tight fit. The best way to tap the nut in is with a slightly smaller bolt, 1/4" in this case(thats bolt diameter Russ not head diameter).

   

[KellyG]

All I know is if you are trying to make a self bow you need to make one of these.

[30coupe]

Originally posted by Eric Krewson:
Always a smarty pants in the crowd. You are wrong Russ you must not have taught shop class.
 

Yup, you got me!    

My bits are a mix of old and new in a plastic box. The shaft for the 1/2" and 3/8" bits are the same size, but the slot for the original 1/2" is too big for the one I have now, so I shifted them over one and forgot that I had done that. I also find that I have two 5/8" bits in that box; one of which I used instead of the correct 1/2" bit.

Nope, I didn't teach shop class, but I should have used my brain anyway!

Anyway, this is how I put the nut into the (1/2") hole.

I thread the nut onto a 5/16" bolt like this:

 

Then I tap it into the hole like this:

   

I thread the bolt on far enough so that the bolt gets into the 5/16" hole. That keeps everything lined up and the nut won't tip as you drive it in. Once it bottoms out in the 1/2" hole, it should be pretty straight anyway.

See, I'm not totally stupid, even though I did appear to be in my other post.    :rolleyes:

My apologies, sir!    

[wood carver 2]

More than one way to skin a cat eh?    
Dave.