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Forum topic by irishmike336 posted 06-18-2015 04:57 AM 981 views 0 times favorited 8 replies Add to Favorites Watch
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irishmike336

4 posts in 562 days


06-18-2015 04:57 AM

I recently picked up a older delta clone 14 inch BS. Picked it up for $ 40.00 on Cl. Motor was fine but I replaced the drive belt and put new Urethane tires and guide bearings. It didn’t have a tension guide. Whats the easiest way to determine the correct tension ?? Thanks for any input you may have.. Thanks Mike


8 replies so far

View MrUnix's profile

MrUnix

4244 posts in 1666 days


#1 posted 06-18-2015 07:40 AM

Obligatory bandsaw tune up video:
Alex Snodgrass Band Saw Clinic

Cheers,
Brad

PS: As for tension.. I just strum it like a guitar and when it hits the right note, I’m done :)

-- Brad in FL - To be old and wise, you must first be young and stupid

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JeffP

573 posts in 858 days


#2 posted 06-18-2015 11:08 AM

The first thing most people learn about their new bandsaw is that the tension gauge is a joke.

You should be happy yours doesn’t have one…saves you the time of discovering the above.

After realizing the above, the method I came up with is pretty simple…tighten it up until you are sure the blade is about to snap and then give it another quarter turn. ;)

For those many here who are much more experienced than myself I have a followup question: Other than the blade snapping…is there any other symptom or downside to the blade being “too tight”?

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View Fred Hargis's profile

Fred Hargis

3949 posts in 1960 days


#3 posted 06-18-2015 11:45 AM

I’ve always used the ””flutter technique””:http://www.suffolkmachinery.com/six-rules-of-sawing.html. There are videos of it, but the easiest might be to read what Suffolk wrote.

-- Our village hasn't lost it's idiot, he was elected to congress.

View albachippie's profile

albachippie

758 posts in 2502 days


#4 posted 06-18-2015 12:03 PM

I watch with interest. I have a tension guide on the saws I use at home, and in work. In” “The Bandsaw Book by Lonnie Bird he recommends over tension by one band width on your scale. Since you don’t have a scale, he goes further, and says, raise the top guide approx 6” above the table, and tension the blade until it deflects no more than 1/4”, using “moderate” sideways pressure with your finger. He warns (somewhat tongue in cheek) to do this while the saw is switched off!

I highly recommend this book. It is the bandsaw users “bible”. I have gone to it time and again for setting up various bandsaws, and I know lots of people on LJs also use it.

Hope this helps,

Garry

-- Garry fae Bonnie Scotland - https://www.facebook.com/pages/Garry-Macdonald-Woodwork/425518554215355?ref=hl

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irishmike336

4 posts in 562 days


#5 posted 06-18-2015 02:13 PM

Thanks for the reply :)

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Woodbum

732 posts in 2532 days


#6 posted 06-18-2015 04:57 PM

Don’t need a tension gauge. Not very accurate. Use Alex Snodgrass’ method, or the one that Woodlicer sometimes puts in the Highland catalog. When you get it right you will know it; and then just do it the same way from then on. It’s not really complicated.

-- "Now I'm just another old guy wearing funny clothes"

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Blackie_

4535 posts in 1979 days


#7 posted 06-18-2015 05:12 PM

I’m a 100% believer and a +1 for Alex Snodgrass method.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at http://www.facebook.com/randy.blackstock.custom.wood.designs

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AHuxley

493 posts in 2788 days


#8 posted 06-18-2015 10:27 PM

Bandsaws are essentially unique in woodworking in that they use (highly) flexible tooling. The key is to get the tooling to effectively function as rigid tooling in as far as needed for the particular cut, this is the basis for the need for tension. In a very general sense you want the highest tension that does not negatively effect the life of the blade or have a negative impact on the saw itself. Be aware this is more true for ripping and resawing as lower tension can actually be used for contour (curve) cutting to allow tighter radii with a given blade but generally not necessary.

The US built 14” Delta saws are often talked about in hushed whispers with an air of reverence for their unmatched prowess in the hobby shop, but in the end they truly are very light weight machines with significant limitations. To illustrate the point compare the tensioning mechanism of a Powermatic 140/141/143 and a US made Delta 14” saw the former is built like a tank, the latter designed just well enough to get by. Then when you add the cost savings engineering approach of the off-shore clones one ends up with a under-engineered machine that highlights the Delta designs Achilles heel: the upper wheel hinge. While they tend to bend under too much pressure on a US built Delta (usually still allowing the machine to be used with certain limitations) they often break on off-shore built machines. I say this only to point out just continuing to crank on the tension on a Delta 14” or clone saw requires a solid level of mechanical sympathy and awareness of the amount of compression on the spring in order to prevent damage. In the end 14” cast saws (except the mentioned PM saws) are unlikely to be able to put optimum tension on all but the most narrow and thin carbon blades BUT they will be able to get acceptable tension on most carbon blades up to about 1/2” (5/8” in the case of very thin gauge blades like the Kerfmaster et al).

Most authors seem to simplify the area of tension in their books and articles most saying or alluding to the fact that the built in gauge is accurate enough. Again this goes to the idea of acceptable vs optimal. The idea that a gauge based on spring compression is accurate for the wide range of blades an average woodworker uses is simply false. Two blades of the same width may have very different backer gauges with one requiring an incerase of 50% or more spring compression to reach the same tension on the blade. If the thicker gauge blade is bi-metal or carbide tipped and the thinner gauge blade is carbon steel it is possible the first blade might require nearly 3 times the amount of spring pressure to reach optimum tension compared to the second blade. My point being the scale on the tension meter of a saw can only be calibrated to one gauge and type of blade so in the grand scheme is likely to be wrong more often than it is right. My suggestion would be to use the calibrations on a tension meter as nothing more than a reference to return to when one has determined the optimum amount of spring compression for a given blade.

How does one determine the optimum amount of pressure needed for the optimum tension for a given blade? The simplest, and in my opinion the most accurate and repeatable way is through the use of a strain gauge. Several manufacturers make them BUT the ~$300 price tag is usually too high for hobbyists. A fully effective one can be built with calipers and a couple of C-clamps (google: bandsaw tension gauge calipers) while it requires a little math and isn’t as quick nor direct reading as are the commercial products they do work well. Done once it gives you a reference regarding the amount of compression the spring requires to tension that particular blade, write it down and place a mark beside the blade and every time you use that blade or another identical blade getting the correct tension is simple.

Be aware Delta and the clones will not get most blades wider than 1/4-3/8” to optimum tension so don’t be surprised that 3/8” and wider blades will be asking for all the tension the saw can muster. Keep in mind the Delta was engineered over 75 years ago with 1/4” and narrower blades in mind, it was never designed for the expectations of a modern woodworker using it to resaw, however the low horsepower and resulting slow feed rates mask much of this limitation. An important note is keep in mind the weakness of the wheel hinge and NEVER bottom the spring out once all the coils are touching a small twist of the tension knob will skyrocket the pressure and you will certainly damage the saw.

Most of the Delta and clone 14” saws I have seen in use have under-tensioned blades, this is particularly true for ones tensioned by the flutter method. That said even this difficult to repeat method and its usual low tension can often give acceptable results with slow feed rates, so if one is a “good enough” type of person it isn’t a big deal but for me it is simple and quick to get the optimal tension (within the limits of the saw) so I see no need for any other approach. Remember, a bandsaw uses flexible tooling that we want to act like rigid tooling within the window of the cut, the OP can use his saw’s lack of scale to encourage himself to determine the correct tension for each type of blade he uses and allow better results than he would have had if the saw had a neat little scale to use as a crutch and any scale on any bandsaw is only going to be right for a certain gauge and type of blade, thus wrong more than it is right.

I have avoided talking about either finger deflection or pitch based (strumming) techniques. They can both be reasonable repeatable methods but both require not only a “calibrated” finger or ear they both require experience to employ and the experience must be gained on a band that is properly tensioned to establish the deflection or pitch to begin with, it is useless to repeat an incorrect tension. So my advise to the OP is use a commercial or more likely a DIY strain gauge to determine the correct tension of each type of blade they use and make a registration mark beside the spring and make note of it so each time you use that type of blade he can get an easily repeatable tension on the blade. I will say it is often useful to experiment with slightly higher and lower tensions (from textbook optimal) depending on the cut, type of wood and current condition of the blade but I suggest one needs to know the optimal tension and way to repeat it before going down that rabbit hole.

PS optimal tension for a carbon blade will be right around 15,000 PSI a bi-metal blade will be around 25,000 psi and a carbide tipped blade will prefer right at 30,000 psi.

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