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Main Boards => The Bowyer's Bench => Topic started by: Austin P on January 06, 2014, 10:13:00 AM

Title: How do you measure grain?
Post by: Austin P on January 06, 2014, 10:13:00 AM

I'm pretty new to traditional archery. I've been getting into making my own arrows, but I'm unsure of how grain is measured. If I'm not mistaken, it is a measurement of weight, right? What does one grain equal? is it equal to the weight of one grain of rice? why not measure in ounces or grams? Also, I wasn't sure if there was a better place for this question. Please let me know if there is.

Title: Re: How do you measure grain?
Post by: macbow on January 06, 2014, 10:28:00 AM

The best way to measure is with a,grain scale.
It is a measure of weight. Used with firearms when measuring powder for bullets and in all weights pertaining to arrows.

There are grain scales sold at stores,dealing with firearms. You can buy a small electronic one for about $20 that is very nice, these can measure in several types like oz. and grams.

Title: Re: How do you measure grain?
Post by: Roy from Pa on January 06, 2014, 10:29:00 AM

http://www.3riversarchery.com/3Rivers+Digital+Pocket+Grain+Scale_i5962_baseitem.html

Title: Re: How do you measure grain?
Post by: LittleBen on January 06, 2014, 10:30:00 AM

1 pound = 7000 grains

1 gram = ~15grains

So sometimes grams is used in countries which use the metric system.

The reason ounce is not used in the US system for arrow is because arrows are typically too light to make it a useful measure.

Many digital scales will measure in grains as well as grams, ounces, and carats

Title: Re: How do you measure grain?
Post by: Austin P on January 06, 2014, 10:31:00 AM

Hey, thanks everyone.

Title: Re: How do you measure grain?
Post by: Pat B on January 06, 2014, 10:50:00 AM

437.5 grains in an ounce
You can get a digital grain scale from 3Rivers for less than $10. It measures grains, grams and ounces

Title: Re: How do you measure grain?
Post by: Austin P on January 06, 2014, 08:31:00 PM

Hey, While we're here, how about some info on spine? Is arrow spine just the measure of the diameter of the arrow? I understand that it is relative to the type of bow and weight of bow, but are there any other factors for determining spine? Any good links to spine charts? How is spine measured for different types of arrows i.e. wood, aluminum, carbon fiber etc.?

Title: Re: How do you measure grain?
Post by: Brock on January 06, 2014, 09:16:00 PM

spine is relative to the amount of deflection that can be put on a shaft between two centers by a standard weight....how much it bends all things being equal compared to other shafts.

Title: Re: How do you measure grain?
Post by: Austin P on January 06, 2014, 10:13:00 PM

Ok, that's some good info. Is there a standard distance between the two centers? What is the standard weight? Or does the individual arrow maker just pick a consistent distance and weight and spine all of his arrows that way?

Title: Re: How do you measure grain?
Post by: macbow on January 06, 2014, 10:20:00 PM

Us old guys with wood arrows use 26 inch centers and a 2 pound weight. The amount of travel on the shaft calculates into spine.

Title: Re: How do you measure grain?
Post by: Austin P on January 06, 2014, 10:38:00 PM

So, how does all of that correspond to bow type and weight? When i see shafts that are 5/16 or 11/32, that refers to the amount of travel on the shaft and not the diameter? I have a hickory longbow with a draw weight between 40 and 45#. What spine do you recommend for that bow?

Title: Re: How do you measure grain?
Post by: macbow on January 06, 2014, 11:43:00 PM

The 5/16 and 11/32 refers to the shaft diameter.
On your bow if it doesn't have a deep shelf cut in  I'd be looking at,40 to 45 pound spine or 45 to 50 depending on your draw length.