5x6 Bandsaw Blades

[BadDog]

Unless you are a power grip competitor or something, "about as tight as you can get it without it getting painful" seems to work very well on mine. I was told or read somewhere that using the knob to tighten the blade on these little import jobs it's almost impossible to overtighten. I have no proof study or engineering degree to support that, but it's been working for me for the nearly 20 years I've owned and thrashed my HF 4x6...

[NP317]

Well, being a musician, I find my 1/2" x 64-1/2" long band saw blades likes to be tightened to a tone in the middle octave on a piano when "twanged."
That is done on the return side of the blade, opposite of the support rollers.
That description may "sound" strange, but that's what I do.
RussN

[John Hasler]

> Any more effective suggestions other than buying a tension gauge?

Two small C clamps and calipers works for me. You want 20,000 psi. Young's modulus for steel is 30,000,000 so you need .00067 elongation for 20,0000 psi. Set the calipers to 5", clamp them to the relaxed blade (but not slack) , and tighten it until you see 5.0033". High accuracy is not needed: anything between 5.003 and 5.004 is close enough. This works the same way for any system of units, of course. The elongation is unitless. This depends only on the material and the required tension (in units of pressure, not force). It does not depend on the dimensions of the blade.

Then remember what that felt like so you can do it without instruments next time. It would not be hard to make a simple gauge for this.

[jmpharrington]

Thanks. I was able to follow the math...
I will give this a try in the morning.

Tightening the knob by hand as tight as I could results in far greater than 0.004” deflection with pressure, but it does “pluck” a tone, though rather flat...

Jimmy

[jmpharrington]

Next question - breaking-in a new blade. (More of an observation)
The manufacturer(s) recommend breaking-in a new blade. The suggested approach and amount of material to be cut breaking one in is more cutting than I will likely do in a year...
So I made half a dozen slices through a 2” diameter aluminum bar and called it good. The blade speeds suggested by JET are much slower than the blade manufacturer suggests anyway.
Jimmy

[Harold_V]

Hmmm! Breaking in a blade. Been in the shop since 1957 and I've never been advised to do so.
Unless the teeth of a blade have a burr, there's no reason to break it in by any particular action. The best possible performance you're going to get from a blade is most likely the first cut it makes, assuming the teeth are properly ground and set, you observe recommended speeds and feeds, and you're adhering to the concept of no fewer than two teeth in the cut at all times. Three is even better. Any cuts taken, even in aluminum, come off the number of cuts a blade is capable of making. Even when a blade may still be sharp (from cutting only aluminum, for example), it may fail from fatigue, and is more likely to do so on small saws, where the wheels are of limited diameter, so the blade flexes more severely.

I'm not critical of your break in. It's just foreign to me. I'll gladly read anything you're willing to offer so I better understand the reason why a blade needs to "break in".

Edit: I can honestly say that when I put on a new blade, it performs very differently from a used blade. One of the things I've noticed is that a new blade will often chatter while cutting, while a used one does not. I wonder if, maybe, that's one of the reasons a break-in is suggested.

H

[BadDog]

I don't claim to understand the full import, but Echol's Saw, where I get my blades made, also recommends a break in cut, though not as extensive as it appears some recommend. I questioned the need way back when, and for what I recall, it came down to being "too sharp" for what is normally expected to be an acceptable pitch to thickness match when blade feed is not well controlled (i.e. typical small/cheap saws). To paraphrase from my understanding/memory, if you consider the "3 teeth in the cut" rule of thumb, when the blades are new and "too sharp", those 3 teeth are going to bite much harder at the same feed rate/pressure, and can result in shedding teeth, particularly at the weld joint. So he recommended (again, from memory) one cut (in steel, don't recall aluminum?) of a sufficiently thick cross section to keep 10(?) or more teeth in the cut for a period of a minute or two. Just enough to wear/remove that tiny razor sharp point and prevent digging when you do go close to the limits with only a few teeth in the cut.

Those may not be the exact amounts/words (my memory for such details is terrible), but I've adopted the spirit of the advise ever since. It also provides an opportunity to evaluate the cut, though he makes almost all my blades from Lenox Diemaster bimetal stock, and they last a LONG time, as long as I don't do something stupid...

[Harold_V]

Your comments tend to ring true when I consider the chatter I mentioned. There's no question that a new blade has a keen edge, yet the blade will perform well enough after that edge has been slightly dulled. I can see the value of a "break in" cut, which every blade gets, whether by intention, or not.

I have always used a saw with controlled feed, although it is adjustable and can be too fast for any given condition. Without that capability, a new blade could certainly be fed too quickly on thin or small diameter material.

H

[John Hasler]

Harold writes:
> I have always used a saw with controlled feed,

Controlled rate of advance or controlled force?

[jmpharrington]

I'm not critical of your break in. It's just foreign to me. I'll gladly read anything you're willing to offer so I better understand the reason why a blade needs to "break in".

https://www.starrett.com/docs/saw-resou ... f?sfvrsn=2

I guess it is like shaving with a brand new razor...
First shave is usually a bit harsh.

-Jimmy

[Harold_V]

Harold writes:
> I have always used a saw with controlled feed,

Controlled rate of advance or controlled force?

Controlled rate of advance, at least initially. It is the typical hydraulic cylinder, and works well so long as the cut progresses as quickly as the feed allows. However, with that type of a system, once the area in contact with the blade increases, the feed rate slows, so the applied force, then, is the weight of the blade assembly (no longer controlled). That works adequately unless one is using an extremely coarse blade, which has the potential to offer a little trouble when the blade breaks through the cut. If has not proven to be much of an issue, however, as I rarely use a coarse blade on my cutoff saw.

H

[Harold_V]

Thanks, Jimmy. Without knowing it, I've pretty much followed those guidelines, although I never considered that I was breaking in a blade. The chatter I spoke of was the reason I'd slow feed rates. Seemed to make a difference.

H