QTR 52 Starrett Saw Blade Tension Tool
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- เผยแพร่เมื่อ 27 พ.ย. 2019
- Please Note: I am a beginning machinist and I do not pretend to know everything. Please always operate machinery in a safe manner and if you don't know, find a reliable source. DO NOT COPY ME. I make a lot of mistakes. I provide these videos for entertainment only.
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I had one and had no idea how to use it. thanks for the video.
Luck you. It is a really useful tool if you don't have someone with experience around who can diagnose tension problems for you.
Blade tension can also be calculated using a digital vernier caliper.
Open the caliper to an arbitrary length, say 5''.
With the blade loose clamp each jaw of the caliper to the blade with some clamp such as a toolmakers clamp or a small kant twist (square to it so that the main beam of the caliper runs parallel to the blade).
Zero the caliper.
Tension the blade so that the caliper reads a certain stretch.
Divide the stretch by the initial length and multiply by the steel modulus of elasticity which varies from 27.5-30.5 Million PSI.
If your stretch preload was correct you should have arrived at your required PSI that the blade manufacturer suggested.
Of course you can solve the equation for the proper stretch in the first place.
The equation is σ=Ε*ε,
where σ is the tension value in psi that you strive for,
E is the steel blade modulus of elasticity which varies from 27.5-30.5 Million PSI ,
ε is the relative stretch (aka the strain), aka ε=δL/Lo, where δL is the measured stretch of the digital caliper, and Lo is the initial opening of the caliper that you chose (5'' in my above assumption).
Example Lo=5'', i choose E=29 million psi, and required tension is σ=25 000 psi.
Solving the equation for δL we have:
ε=σ/Ε and substituting ε for δL/Lo we get δL/Lo=σ/E and finally δL=σ*Lo/E
So for the numeral example we get dL=25 000 * 5 / 29 000 000 = 0.0043 or 4.3 thousands of an inch
In practice it is much much easier to actually measure and calculate than to explain so don't be intimidated by the above explanation.
I bought one of these back when I did on sight machine repair because I had a string of bandsaws that I just needed one for.
Having it at hand settled a lot of argument in really short order, and got me a fair bit of business from blade sales people as to why thier blades were doing or failing to do the job. All but one time, the saw/ operator were the problem, not the blade.
I still have it, and don't plan on selling it.
Thanks for the formula. That is exactly the kind of missing info I was looking for. I really appreciate that.
Don't you just love it when you are the only one who bids on something you want! I always low-ball, and I win every now and then. Good luck on future eBay purchases. That was a nice score.
Thanks. I do the same. It kind of like playing the lottery with a hell of a lot better odds.
I get all of my starrett tools second hand. I got a starrett no. 644 depth indicator and a starrett surface gauge, don't know the number but it's about 4" along the side and maybe 3" wide for $20 for both off a dude that retired from where I work not too long ago. I'd never be caught dead paying full price for them. It's not like I need them, I'm not a machinist but I might get into it when I have the space for some machines.
Yea, I get the need for used if you are looking for one of the big boys. Compramise is necessary for most hobbyists.
In a manufacturing environment, this device is well worth the money. If you are cutting all day long the life of the band saw blade can have an impact on the cost of operation... a 3/4" or 1" bi-metal blade isn't cheap.
You mentioned improved saw cuts. Improvement there means the raw stock can safely be cut closer to size reducing machining costs. Sometimes when a saw is cutting square and to a repeated size, machining other than deburring or champhering can be eliminated all together.
I realize that it is much too expensive a tool, especially new, to purchase for most home shops. My bandsaw uses 3/4" blades and you are right, they aren't cheap. I have noticed a significant improvement in cuts since I have tensioned the blade more. I never would have realized that I wasn't tightening my blade no where near enough. It would be really handy if people could rent one to get a feel for the proper settings.
I can tell you from my woodworking days that vast majority of bandsaws are under-tensioned. Also, a lot of bandsaws are not designed /built to handle the proper tensions called out by the blade manufacturers
My bandsaw was definitely under tensioned. It felt a bit much to hit the proper amount of tension. I never would have gotten there without the gauge.
Interesting didn't even know that existed but makes sense it does. Been thinking I'm tightening to much causing the blade joint to break over just flexing from use. Horizontal band saws flex the blade a lot. Wonder if I can make one...
Check out the post below for info on a simple formula and a method for using a caliper.
Neat tool . I used to use a Petzing & Hartmann bandsaw that had hydraulic blade tension & a pressure gauge for the tension . I think the handle would snap off my small chinese one if i tightened the blade to propper specs ! Cheers .
A built in tension gauge...that is really neat. I was surprised at how hard I had to tighten the tensioner on my band saw to get to the prescribed value range. I never would have pushed things that far on my own.
@@DudleyToolwright It's a good test for the butt joint on the blade !
Looks like you could make one fairly easily. Should be able to calibrate the dial with a screw clamped to a section of saw blade in a frame with a scale or load cell.
I think you are spot on. Check the recommendation below for an exact formula. (dimtt2)
Nice tool find.👍
Thanks.
Interesting. It's a tool i never heard of.
Thanks. I'm glad the video was useful on some level.
Oh wow cool tool. I didn't know about this thing. Off to E-bay to find a deal because I change blades a lot. Do you have a horizontal bandsaw to try the tool on? Curious to see how it compares to that little color coded scale that is on the saws.
I don't have a horizontal band saw, sorry - just the sliding vertical one. I have such limited space I needed to combine functions.
Those gauges are sort of a boondoggle. Ok, they are a complete boondoggle. You can make one that is every bit the equal of the Lenox or Starret. Hell, you can make it from wood. And it will have the same problems:
They don't account for metal mass.
Simply put a greater mass of steel will require more force to stretch than a lesser amount of metal. So a one-inch x .060 " blade will be more mass and harder to stretch than a .250" wide x .025" blade. And there is nothing about them to make that distinction. I find that baffling. I'd think they'd come with a chart or something.
Very astute observation. The tension gauge does come with a sheet for suggested tensions that should only be a suggestion, rather the blade manufacturer specifies the proper tension for a specific blade. The wider the blade the more tension it is supposed to have. I am sorry I did not make that clear.
👍
Thanks.
Stop wasting your money on this ridiculous stuff and start saving for your wire EDM machine already! And sorry Anelisa, but it's going in the house.
Yea...I would love one, but am out of room inside and out.
@@DudleyToolwright I outgrew my old house and got a new one, but it's still not big enough! Our sheet metal place closed down- patriarch owner died, 10k a month to rent the building, and then Russian ransomware put them over the edge. We have lots of laser cut or punched 16 gauge parts, steel and aluminum, that are then folded that we will need to source. Unfortunately, the cad files were lost. A piece of hardened tool steel cut with wire EDM and fitted to a die set can punch-out those parts at minimal cost. I tried to get them to invest in this, which would have paid for itself long ago, but, no...