Washer weights

[Significent]

Looks like these could work too:

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http://www.ebay.com/itm/Aluminum-Binding-Post-Screw-8-32-X-1-4-Extension-/370309716725?pt=LH_DefaultDomain_0&hash=item56382ddaf5

Only question is, how much do they weigh. If I calculate the volume and multiply by the density of aluminum, I come up with about 5.2gr (corrected, not 7.7gr). That's heavier than I need, but they could be filed down to any weight.

I think I like the idea of using the Slick Trick washers in tandem with the #8-32 set screws. The set screws would work for the heavier weight changes while the washers would likely weigh half as much and allow for finer adjustments.

[Normous]

They appear to be 1/4, 1/2 and 3/4". Your guess of 7-8 grains for the 3/4" one would be my guess as well.

[Significent]

Norm, I just checked my math. Must have fat-fingered something cause I got a different number. Here are my corrected weight estimates for each of the three binding post lengths:

.25" = 5.2gr
.5" = 10.5gr
.75" = 15.7gr

Maybe you used the diameter of the threaded portion of the binding post (0.164") in your estimate rather than the full diameter (0.197")?

Here's my calculation: Pi x radius squared x height x 0.098 lbs/cubic inch x 7000 grains/lb

Since even the shortest binding post is still pretty heavy, I think mixing & matching the 3gr +/- set screws I have on order with awshucks' 1gr +/- Slick Trick washers is probably a better solution cause I won't have to do any filing.

[Normous]

I used the eyeball method holding 1"- 8/32 threaded 10 grain aluminum set screw in my hand. Not too mathimatical that way.

[Significent]

Norm, I've added a tab to the end of the String Jump spreadsheet to make approximating weights of threaded rods and cylinders easier in the future:

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https://dl.dropboxusercontent.com/u/14080410/StringJumpCalc.xlsx

It can be used for Aluminum, Brass and Stainless Steel (304)

[awshucks]

I have a bunch of Slick Trick washers I'll send ya, for free, but yer spinning your wheels.

'Met' a fellow on another forum that had 6" variance at 30 yds and was convinced it was 125 gr mixed w/ 100 gr he normally shot.

I made up one of each, the shafts were touching at 30

That's certainly meaningful. What xbow were you shooting them from? Any idea about the speed difference between the two? What's the outside diameter of the Slick Trick washers?

Didn't measure them, but they are smaller than the O.D. of your inserts. I can't recall the xbow for sure, but think it was my Emax. The speed of the bow is immaterial. The 7 gn diff in your arrows, the same, lol.

You can't put more than 1 set screw in an insert or nock, no room for the 2nd set of threads.

I answered your email w/ much of the same, tried to call but your line was tied up. The washers weigh 3 gn.

Have fun!

[diesel]

I like to use set screws when building the arrows and or cut down the nock or insert on a lathe is best but have put them in a drill press and used a file. As far as washers go I do not know if I have any that lite cause I have a lot of copper gaskets that come in repair kits that are let over and I have used them seems like they are closer to 5 grains if I remember correctly.
May have some shims there for some of the real old stuff not in use will have to look.

[evaughan]

some 25 years ago I bought some of those kolpin 4 blade heads with the offset blades. Came with a huge pack of weighted washers which I kept. Last spring I killed a turkey with a 100 grain wasp Jak-hammer with 4 washers behind it to bring it up to 125. Have another one of these set up for this spring.

[nchunterkw]

I have a bunch of Slick Trick washers I'll send ya, for free, but yer spinning your wheels.

'Met' a fellow on another forum that had 6" variance at 30 yds and was convinced it was 125 gr mixed w/ 100 gr he normally shot.

I made up one of each, the shafts were touching at 30

I would think stacking up washers would put your BH out of square and cause it to not spin true....potentially. You are essentially adding up a bunch of manufacturing tolerances. I like the set screw idea deep in the insert better.

[Significent]

OK, so I received the 100 ea, 1/8th", 8-32 set screws I ordered. When I plopped them down on the scale, they all weighed 2.3gr, pretty consistently.

My first dozen bolts are a little more consistent in weight than my second dozen, so I've started with the the first. After a little figuring, I realized I could get all of the first dozen to plus or minus 1 grain by adding 0, 1 or 2 set screws.

To keep the blue loctite in the right place, I figured I had to screw in the set screws from the nock-end of the bolts and only in so far as the screws were flush with the back of the insert. So, I pieced together a long rod with a 5/64th" hex bit at the end that would fit inside the bolt. Then I tried a couple of dry runs without loctite and discovered that there were burrs at the back of some of the inserts that wouldn't allow the set screw to rotate in easily. So, I ran the set screws in from the front of the insert with a regular hex wrench, powering through the burrs. That worked well except for one arrow where either the burr was really big or the insert hadn't been tapped all the way through. I had to dig out my tap set to remedy that one.

Between my newly weighted nocks (10-32 set screws to match new Lumenoks) and the new weights in the inserts, I think they turned out well. This first batch weighs 421.9gr on average. Hopefully, I'll have a chance to make any necessary trajectory adjustments at the range this weekend. Depending how that goes, I'll probably start on the second batch.