Several weeks back, there was a discussion on spine testers that stimulated me to make one. It took about 5 weeks to receive the dial indicator that I ordered, so it took awhile to get to the project. Once the indicator came in, it took about 2 hours to construct the tester. So far, I've only played with it, putting in arrows that were already cut. It seems to work very well. I plan on making up a new dozen within the next few days to put the tester through it's paces.
I used
Jim Hill's Spine Tester as a guide, with a few adjustments.
Please excuse the mess.
I decided to use wood end supports, so I could make a finer adjustment when trying to get the arrow to just slightly depress the dial indicator, before the weight is applied. I did this by mounting cabinet door rollers (which have an easily adjustable height), on to the side supports. I could then set the supports next to the base, without actually attaching them, just to test the height. I made the supports a bit long and them shaved off small amounts with a table saw to end up with exactly the correct height.
The cabinet rollers:
I found an order to construction that worked particularly well. First cut the base to the length of tester, plus width of rollers. I used 28" as the space between the rollers. It seems Easton used this when testing modern arrows. The weight is 1.94 lbs.
I then cut a dado in the exact center, to accept the 6" angle bracket. I mounted the angle bracket and then attached the extention with the eye bolts to accept the weight. I then figured an approximate center from the edge of the base to the center of the eye bolts. I used this measurement to mount the rollers the correct distance from the edge of the end supports.
The dial indicator was attaced to it's bracket, and then was put into approximately the correct position. It was attached to the base with only one screw at this point.
This is where the fine adjustments come in. I used a bar clamp to keep the supports in position while I fiddled with getting the height of the supports correct, and the exact position of the dial indicator right. With an arrow in place, I moved the dial indicator until it's point was in the exact center of the arrow. I then attached the second screw to it's bracket to fix the dial indicator in it's final, correct position.
Once the indicator was permantely mounted, I started shaving off the bottoms of the supports, until the exact correct height was obtained. Once this is correct (and the clamp still on), glue and screw.
I made a spine chart based on the 28" length and put a clear expoxy over the whole base to keep the chart permanently in view, and protected.
I have the advantage of owning an electronic scale, so I was able to get the weight close to exact (not that it's very important). When buying washers I got extras, because they were variable thicknesses and I could use different combinations to get different weights. I found a combination that came to 1.94 lbs. I set the bolt on a table, as in the photo, and then added a bit of epoxy between the bolt and the washers. It turned out as a nice solid piece.
I highly recommend making your own spine tester. It was a very easy project. I had about $35 into it of which half was the dial indicator. You can save a bit of money by eliminating the main bracket and using a wood support. I didn't think of the wood support until after I was done, but I think it would have not only been cheaper but would have made mounting and adjusting the eye bolts much easier. The 3/4" x 8" bolt and washers, and brackets are more expensive than one would think. I would imagine that you could come up with something that would work just as well and much cheaper.
I hope this helps anyone wanting to make one.
My Homemade spine tester w/photos
