Does anyone know of a way to determine the line weight of a blank?

Fly line weight, yes. Otherwise, not really. The suggested line "weights' for casting and spinning rods aren't really cast in stone. They're just recommendations mostly. Occasionally they've been set so that the line strength is below that of the blank's deadlift capability, but not always.

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Fasten the first 9" of the blank securely to a horizontal surface with the rest if the blank suspended in space. Measure the distance between the tip of the blank and the floor in inches. Then, from the tip of the blank suspend a weight of between 24 and 30 grams [1ounce = 28.4 grams]. Measure the distance between the tip of the weighted blank and the floor. (The blank must not be deflected more than 10% of its total length. If it is use a lighter weight.) Divide the number of inches the blank's tip was deflected into the amount of weight in grains you suspended from the rod tip. Determine the total deflection in inches. EXAMPLE: Tip to floor distance no weight: 20" Using one ounce weight (28.4 grams) tip to floor distance: 10" Total deflection: 10"
Finally, divide the total deflection in inches into the size of the weight used in grams. Refer that number to the following chart:
STIFFNESS RANGE AFTMA line weight
(grams/inch)
1.4 - 1.6 - - - - - - - 3 In the example where a 1 ounce (28.4) gram weight produces a 10" deflection 28.4 divided by 10 is 2.85 - a 7 wt.
1.6 - 1.9 - - - - - - - 4
2.0 - 2.2 - - - - - - - 5
2.2 - 2.6 - - - - - - - 6
2.6 - 3.0 - - - - - - - 7
3.0 - 3.5 - - - - - - - 8
3.5 - 4.15 - - - - - - - 9
4.15 - 5.0 - - - - - - - 10
5.0 - 5.9 - - - - - - - 11

For rods other than fly rods the recommended line test is the least valuable of the rod specs. If you use the rod right you can use any pound test you want and not damage the rod. It's about how you handle it, where you point it, and how you have your drag set. I would not let that spec be an important criteria in selecting a rod/blank.

if you have No Idea of what it is Give how long it is butt and tip size maybe you can get more help

Bill - willierods.com

Thanks Tom...So how about fly line weight?
Thanks

Wow thanks Phil impressive formula

Thanks Michael it's not real important for me personally but I have potential customers who do think it is. I recently purchased a lot of blanks that had no weight with them.

Thanks Bill I purchased a lot of blanks so there are several like this. It sounds like a good approach.

You could measure it on the CCS system and know for sure ??

Bill - willierods.com

Matthew,
I will ask the question.
Why do you care about the line rating of the blank?

Just wondering.

Be safe

I'm taking the advice of Bill and listing the blanks.
#1 - 4'9" with 4.0 tip and Butt OD is .300 and ID is .235
#2 - 4'9" with 4.5 tip and Butt OD is .355 and ID is .275
#3 - 4'5" with 5.0 tip and Butt OD is .325 and ID is .250
#4 - 4'6" with 5.5 tip and Butt OD is .250 and ID is .150
#5 - 4'10" with 5.0 tip and Butt OD is .365 and ID is .300
#6 - 4'8" with 5.0 tip and Butt OD is .365 and ID is .280
#7 - 5'0" with 5.5 tip and Butt OD is .330 and ID is .225 (the ID of this one may not be accurate there was some gloss finish buildup inside.)

Roger I personally don't care but I have potential customers who do care and it's all about making them happy.

OK

Where did you get the blank
How come you do not have the specks of it ??

Bill - willierods.com

Bill I bought a group or lot of 7 blanks....I don't have the specs because the person I bought them from didn't have specs on them.

Any company always has a DECAL on the rod telling what it is and line /lure weight
No company name

And you are going to seel these to a Customer ????
They could be Bootleg

Bill - willierods.com

Those are not fly rod blanks! Way too short.

The Common Cents System will give you the best results as it takes action/flex into account. Click the link to the CCS system in the top of the sponsor column.

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Phil your right they aren't fly blanks

Tom thanks for the info I didn't know what you meant by the CCS system...Now I do I'm new to the site so still learning what's on it. Thanks