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Best way to measure for bandsaw blade length?

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Forum topic by hig789 posted 12-19-2016 12:43 AM 562 views 0 times favorited 8 replies Add to Favorites Watch
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hig789

39 posts in 679 days


12-19-2016 12:43 AM

Recently I bought a 1940’s Wards Power Kraft 12” bandsaw to restore and replace my 3 wheel Craftsman. I have it mostly cleaned up, new urethane tires and bearings. It came with a 78” blade but the new tires are thicker than the old ones and I really don’t want to trust the length on a broken blade either.

What’s the best way to measure for the proper size? Adjust the top wheel all the way down and use string as the blade?

This is the blade I was looking at ordering just for general cutting right now.
http://timberwolfblades.com/proddetail.php?prod=1404PC

Or would a 3/8” be better?

Thanks for any help you can offer.

Here’s a before picture and after picture.



Original crinkle finish on the body.


8 replies so far

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shampeon

1775 posts in 2021 days


#1 posted 12-19-2016 01:06 AM

Looks like it’s 78”. Duro made it for Montgomery Wards.
http://www.vintagemachinery.org/pubs/270/10559.pdf

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

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hig789

39 posts in 679 days


#2 posted 12-19-2016 01:08 AM



Looks like it s 78”. Duro made it for Montgomery Wards.
http://www.vintagemachinery.org/pubs/270/10559.pdf

- shampeon

Yeah I’ve found that. Just wanted to measure it right to be sure. I got the thick urethane tires for it so I’m sure it added length to the blade

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hig789

39 posts in 679 days


#3 posted 12-19-2016 01:10 AM

I thought it was a Duro when I was going to get it but yeah its just a rebadged one for Wards.

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shampeon

1775 posts in 2021 days


#4 posted 12-19-2016 01:13 AM

I wouldn’t go longer than spec’d, even with new tires. The tensioning system will only have so much travel. The specified length accounts for that. Going up a 1/2” or something might mean bottoming out the tensioner before it hits the correct blade tension.

Put another way, the difference between the original rubber tires and your new tires is probably on the order of a 1/64”. Not worth it.

-- ian | "You can't stop what's coming. It ain't all waiting on you. That's vanity."

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MrUnix

6006 posts in 2037 days


#5 posted 12-19-2016 01:58 AM

What Ian sez… the minimal difference in tire thickness is not going to alter your blade length. Just use what is specified for the saw (78”) and don’t overthink it.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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hig789

39 posts in 679 days


#6 posted 12-19-2016 02:10 AM



What Ian sez… the minimal difference in tire thickness is not going to alter your blade length. Just use what is specified for the saw (78”) and don t overthink it.

Cheers,
Brad

- MrUnix

Alright. Thanks guys. I just wanted to be sure since I have to order a custom blade for it.

View joek30296's profile

joek30296

53 posts in 2705 days


#7 posted 12-21-2016 07:40 PM

If both wheels are the same diameter, IIRC you can use the old formula we learned in school:

pi times the diameter of the wheel plus 2 times the distance between centers.

If both wheels aren’t the same size, figure the circumference of each using pi times the diameter divided by 2 and then add 2 times the distance between centers.
Should work.

-- "There are two theories to arguing with a woman....neither of them work"

View JBrow's profile

JBrow

1274 posts in 758 days


#8 posted 12-23-2016 04:39 PM

hig789,

Comparing the results from the math method suggested by joek30296 to that of the string method you are considering would be my approach. Both methods should yield the same result, but will likely will be off by a little due to measuring errors inherent in each method. The average of the two methods would be one way to reconcile the slightly different values. But if one method is way off it will be immediately apparent.

I would also make two measurements using both methods. The two measurements would be at the extremes offered by the saw’s tension mechanism. This would result in a range of values; minimum and maximum band length. Buying a blade a little larger that the average of the two extreme measurements would give a bandsaw welder a little extra blade length to play with should you ever have a new blade that breaks and you elect to repair the new blade. I would think all measurements should be close to the 78” specified by the saw maker.

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