A Knock Down Spine Tester

[fish n chicks]

After gathering up some really nice cherry shafts at woodcraft, I realized I had no way of testing their capabilities. Captain J's "tester in a box" is gorgeous, and brilliant to boot. But I didn't have the time something that nice would take to make. My little nugget can only handle so many computations at once.

In an effort to help my other rookie friends in starting their journey into bowyerism, I have tried to put together a little build along of my interpretation of a spine tester. This particular build cost me about $15, cause I had scrap wood that I used to make this. If you don't have scrap wood, how are you a bowyer? JK! You can get it from lowes. A 2' x 2' piece of MDF (see my notes on wood choice on the cut sheet and material list)or plywood is around $10. $2 for brass rod, and dowels are around $1 a piece. There are hundreds of ways of doing this, but they must all employ the same factors:

26" span, 2# weight at mid-span.

So this is my variation. I used this table found on Jim Hill's spine tester's site to calculate the info once my tester is operational. Just wanted it on here before I forgot it. I printed and laminated it.

 http://www.jamesmhill.com/Image16.gif

I have also drawn up a dimensioned cut sheet for the parts, and a material list. Although I have not figured out how to attach PDF's, I can email it to those interested. Just PM me.


OK here we go. This is going to be tough with only 8 pics per post so bear with me as it may take a few posts.

First, you need the dial indicator. The brains of your operation. Being broke and a DIY'er, I went to Wholesale Tool for this one. I am fortunate to live about 5 minutes away from one, but you can order the indicator online for $11 from them. MAKE SURE YOU GET THE 1" CAPABLE INDICATOR!! This was a note on Hill's site, and a good one. It allows you to test some pretty light spines, which is awesome for youth arrows and the like under 40#'s.

I guess you can do this without the indicator, and wait for it to come and finish it, but it's good to have all your materials in case you need to modify anything.

First thing I did was make my base. I had some common cherry in the scrap bin, perfect for this task. I also sketched up some ideas prior to getting started. I can't emphasize how important it is to use paper and pencil as a tool as well. You can prevent many foreseeable issues that way.

   


The pics will seem a little out of order at times, but I'm not used to directing BAL's, so bear with me. This is what my base will look like once I drill my 1" and 1/2" diameter holes. You can go all the way through the base with your holes, but I recommend using forstner bits and drilling about 3/4" deep. Keep in mind i'm using 4/4 inch material (1" thick). If you are using 3/4" or 1/2" material, compensate your dimensions. The groove in the back of the base holds my laminated cheat sheet. There are also 1/2" holes drilled in the center of my base's sides, 1.25" from the front. These holes will hold my outriggers when in use.

   


   


Next, I can make my indicator's post. This is made from a 9 1/4" long piece of 1" diameter dowel. Oak in my case. I cut a 2" deep by 1/4" wide groove in one end, using a little home made one-time use jig, and my dado blade in my table saw. I would recommend using a fence mounted perpendicular to your miter gauge, and clamping your dowel to that while you make your cut. Things can get a little hairy once the blade cuts off the other half of your jig. The slot is 1/4" because the indicator's mounting bracket is a 1/4" wide.

   

 
   

Drill a 1/4" hole, and you can now use your 1/4" x 20 bolt and wing nut to assemble the indicator post. You see a nut here, but I ultimately replaced it with a much more user friendly wing nut.

   


At this time, you can also fabricate your outriggers. These are just blocks that are glued to 1/2" x 12" long dowels with a cut on top of the block to accept and hold your arrow. The location of the cut will ultimately depend on the way you finish your pendulum, and its dimensions, so wait to drill that until you are done with the pendulum. This is what your 2 outrigger blocks will look like:

   

And once you have glued your dowels to your holding blocks. I would cut these dowels about 2" longer at this point. Insert them into your base's sides making sure to bottom out the shaft in the hole, and measure from the center of your base to the inside edge of your blocks. Factor whatever amount you are over 13" and cut that off your shaft. Label it's side accordingly (R & L) and you should get your perfect 26" span.

   

In the background of the last pic, you can see the pendulum. This is the muscle of the build, and for that i'll need to add more pics. so I will continue this in another post. But at this time, you should have completed your base, your indicator post, and your outriggers. Hopefully, only having spent $12 or so (+ shipping for some of you) at this point. Ok, BRB.

[fish n chicks]

Ok, now for the make or break factor of this build. The pendulum. I totally stole this idea from Captain J. In fact, I had a picture of his tester next to me as a reference the whole time! Sorry to poach your idea brother, but the wheel, microwave, and 2 piece bikini's caught on pretty fast for a reason, they were brilliant! And yes, I always say that with a guinness commercial accent to it.

First, you'll want to grab that little piece of 3/16" hardboard. You're going to cut out of it (4) pieces at 4 1/2" long by 1/2" wide. Then you are going to drill 9/64" holes in em, at 1/4" from each end, and in the center. You wanna go 9/64 because you don't want your pendulum getting hung up on itself due to friction. Using 1/8" rods and 9/64" holes gives you just enough play. A drill press and a piece of scrap as a stop give you consistent results in a hurry.

   

   

Now that those are done, we will move on to the pendulum's post. This is nothing more than 1" dowel, cut to 5" long, and shaped a bit. I first took the piece to my table saw, and took off about 1/16" from the dowel's edge. This gives me a reference edge. I flip the piece, move my fence another 1/16", and repeat. I then take my now referencable piece and cut reliefs for my pendulum's arms. Again, I use a little jig, my miter gauge, and my dado blade. A regular blade works too, just have to double your passes. Now I have two parallel surfaces on a round object, thanks to my little flat edges.

   

   

At this point, i'm also going to make my heads, which are nothing more than 1/2" x 1/2" x 2" long pieces of scrap with (2) 9/64" holes drilled in each to accept the pins. 1/2" from the end opposite the business side, and 1" down from that. These dimensions are all on the cut sheet. I cut a curve in one and use it for my arrow end, and I attach a little piece of scrap to create a lip for the other head so it always contacts the indicator's needle. I then cut my brass pins to length of 1 1/8". I need (6) of them. We are going to be peining these, so cleaning up the heads with a file or sander after cutting will give you a far better result. I also took and sliced up a couple business cards, and drilled holes on one end, and then slit from the hole to the edge with my Xacto. These will be used as spacers in case you cut your dowels too short, or peined em too far. Assmeble the pendulum with the spacers between the arms and heads, and between the arms and post, and then you will simply pull the spacers out once you are satisfied with your hammer job. Now I have my pendulum parts. It is now time for the fun part!

   
 

   


The pins we are using are brass or aluminum for a reason. We can really work them like wood without fancy metal tools. So for our case, we are going to fabricate our own pins, using a ball pein hammer, and if you have one on your vice, the anvil, or a flat piece of metal on the garage floor. Now before you go all blacksmith on me, realize brass is pretty soft. Hard banging with the hammer is NOT what we're after. It will bend your pins, and you will get NO motion out of your pendulum. Trust me on this one. Guess how I learned! You need to take LOTS of love taps, and try to aim for the edge of the pins with your hammer's ball side. I had to redo my pendulum because I wanted my pins to look fancy, but they were too tight, and not even my 2# weight would move it. That's obviously NOT what we want.

About 15 - 20 hits on each side, and you should certainly have enough of a mushroom to hold your arms in place. Once you've STARTED EVERYTHING, you can finally finish everything too. Don't finish any one side before you start all your pins.

They should be looking something like this:

   


   
 


Your pendulum should look like this before you pull your spacers out. At this point, I would go ahead, and give my pins another round of peining, and then pull all my card spacers out, giving me a free-motioned pendulum. The weight of the screw hook alone should prove if your system is impedance free. It should drop on it's own when raised by your finger.

[fish n chicks]

Now we can pull out our spacers, and our pendulum is done. I sand the post's base a little so I can easily get it in and out of it's hole without damage, but not to a point to give it any play. At this point, we are one part away from finally testing.

   


   


For our 2# weight, I racked my brain for ideas. I even took my scale to Meijer, and weighed stuff out everywhere. Fitness weights, marbles, you name it. I finally came across a cheap easy fix. I have a ton of BB's, and a bottle koozie. I filled the koozie up with bb's while on the scale, and once it read 896 grams (28 grams to an ounce x 16 ounces a pound x 2#'s)  I sewed the opening and the zipper tight.

   

   

   


Guess what!? You're done! You can now test the spines of wooden arrows on your own tester with confidence. Be sure to adjust your indicator so as it makes contact with your head when the other head contacts the shaft. Some fiddling will be required but it's pretty straight forward.

   

   

   

[fish n chicks]

Using the tester can't be simpler. Insert your outriggers into the side of your base, lay your arrow on em, and zero your indicator by making contact with the shaft, and the indicator at the same time with the pendulum's heads.

   

   

   

   

Hang your 2 pound weight, tap your pendulum a few times, making sure you see if you are getting a consistent number each time once the shaft comes to rest. Grain orientation and actual arrow factors will vary. Keep in mind you'll want to test your arrow with the edge grains facing up, like it would be if it was arranged on your shelf, grain perpendicular to riser, or in this case, indicator. Take a reading from your indicator, inner number is your tenths, and the remaining reading is your ten thousandths. For example:

   

   

This shafts is reading 0.387 and some change, so I cross reference my chart (the one I posted earlier) and I get my weight, between 67 and 68 pounds.

   

At this point, I label my shaft, and continue on.

[fish n chicks]

The great thing about this is it packs up nicely and stores on a shelf, or you can pack it up into a case and take it on the road with you if needed.  


 


Here I have the indicator packed for storage to avoid damage. Within minutes I can be spining arrows, and a few more be completely packed up. There, of course, was one more thing I had to do, and that is give my boy an identity.

Hey, it's what I do.

   


Thanks for checking out my knock down spine tester. Hopefully I can figure out how to attach PDF's so I can make it easy to get the cut sheets to those who want them.

[Grey Taylor]

Wow, I'm impressed.
Great job and thanks for doing such a thorough build along.

Guy

[razorback]

Nice build-along. I did one of 2Jays spine testers as I was too cheap to even spend $11 on a dial indicator, but I like the design and look of yours. May have to knock one of them up.
hardest part I found was getting an accurate weight. I used an old peanut butter jar and filled it with nails. I used small washers and nuts to fine tune the weight. I attached a hook through the lid and voila, 2# weight.

It is fun to make these bits of bowyering stuff, thanks for the effort.

[KellyG]

Fish,
This is a great build along. I have on question, I keep looking at the dail indacator and dont see the .3 I see the .087 just fine and understand that. I just cant see the .3.  :(  I see he litte dial but i looks like it is on a four. I might have ansewered the question. Is it because the little hand is not quit on the 4. thanks,
Kelly

[fish n chicks]

Originally posted by KellyG:
Fish,
This is a great build along. I have on question, I keep looking at the dail indacator and dont see the .3 I see the .087 just fine and understand that. I just cant see the .3.   :(   I see he litte dial but i looks like it is on a four. I might have ansewered the question. Is it because the little hand is not quit on the 4. thanks,
Kelly

That's exactly it Kelly. Since it's so close to .400, it's hard to tell. Thanks for checking it out.

[fish n chicks]

Is there any way I can add PDF's to this thread so people can download them?

[KellyG]

No thank you Fish for posting it. I can't build one of these now for my current location is not really set up for such projects. BUT some day I may. I think my just look at the finish project the rest makes more since. Thanks again it is an awesome build,
Kelly

[razorback]

Fish,
I would shoot Rob DiSteffano an e-mail. He is the local tech guy who keeps this ship afloat.

[fish n chicks]

Originally posted by razorback:
Fish,
I would shoot Rob DiSteffano an e-mail. He is the local tech guy who keeps this ship afloat.

Thanks! I'll do that now.

[kentowl]

Great build-along, Fish:
I'm a bit puzzled by one design aspect, though - perhaps I've missed something. But it looks like the hook that holds the weight is farther from the pivot point than the block which presses on the arrow shaft. Based on mechanical leverage, I think you'd be applying more than 2# downforce on the shaft.
If I'm right the fix is easy, though - use your tester to press down on your scale, and remove weights until the scale reads exactly 8960 grains and you've corrected for leverage, friction,and everything!

[beetlebailey1977]

Looks good I have been thinking of doing the same thing....I am a Machinist so it will not be that hard to make.  Thanks for the inspiration.  

[fish n chicks]

Originally posted by kentowl:
Great build-along, Fish:
I'm a bit puzzled by one design aspect, though - perhaps I've missed something. But it looks like the hook that holds the weight is farther from the pivot point than the block which presses on the arrow shaft. Based on mechanical leverage, I think you'd be applying more than 2# downforce on the shaft.
If I'm right the fix is easy, though - use your tester to press down on your scale, and remove weights until the scale reads exactly 8960 grains and you've corrected for leverage, friction,and everything!

You're absolutely right! I'll check that out and see what it says. I can take out bb's from my weight to adjust.

[fish n chicks]

Originally posted by beetlebailey1977:
Looks good I have been thinking of doing the same thing....I am a Machinist so it will not be that hard to make.  Thanks for the inspiration.    

Hey man, you better not show me up with some sweet polished aluminum decepticon looking thing!

Actually i'd love to see a machinist's version. That would be wicked with your resources.

[CaptainJ]

Beautiful! Nice work fish n chicks!
That is just too cool!

 

Originally posted by fish n chicks:
Ok, now for the make or break factor of this build. The pendulum. I totally stole this idea from Captain J. Sorry to poach your idea brother

Wow, I'm flattered!

 

Then you are going to drill 9/64" holes in em, at 1/4" from each end, and in the center. You wanna go 9/64 because you don't want your pendulum getting hung up on itself due to friction. Using 1/8" rods and 9/64" holes gives you just enough play.

I like your use of the brass peening to hold the arms. I over drilled the posts and under drilled the arms to get the stability without the friction. I just used some brads I had lying around so your brass is much better.
I stack drilled the arms to be sure they were exact but your jig may be even better in case the drill press is not perfect.

OK guys! This is the build along I promised.
Just put this in a box and you're finished.
Thanks fish and chicks! A job very well done.

CJ

[Roy from Pa]

Nice fish..

[fish n chicks]

Originally posted by CaptainJ:
Beautiful! Nice work fish n chicks!
That is just too cool!

 

Originally posted by fish n chicks:
Ok, now for the make or break factor of this build. The pendulum. I totally stole this idea from Captain J. Sorry to poach your idea brother

Wow, I'm flattered!

 

Then you are going to drill 9/64" holes in em, at 1/4" from each end, and in the center. You wanna go 9/64 because you don't want your pendulum getting hung up on itself due to friction. Using 1/8" rods and 9/64" holes gives you just enough play.

I like your use of the brass peening to hold the arms. I over drilled the posts and under drilled the arms to get the stability without the friction. I just used some brads I had lying around so your brass is much better.
I stack drilled the arms to be sure they were exact but your jig may be even better in case the drill press is not perfect.
  OK guys! This is the build along I promised. Just put this in a box and you're finished.  
OK guys! This is the build along I promised.
Just put this in a box and you're finished.
Thanks fish and chicks! A job very well done.

CJ [/b]

That right there is funny as hell. Thanks for the cheers CJ. Your post certainly lead me in the right direction.