I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it stood
relentlessly at 4". The ends were clamped securely and the micrometer took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?

Toller wrote:

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

Shouldn't this work, or at least do something?

Yes, and in fact FWW had an article on a tensiometer based on similar
technique (except they used feeler gauges).

Are you sure you were tensioning the blade properly?

Chris

"Chris Friesen" wrote in message
...
Toller wrote:

I opened a digital micrometer to 4" and clamped the two ends to a band
saw blade. I then tensioned the blade. I figured the micrometer jaws
would be pulled apart a few thousanths and I could determine the tension.

Shouldn't this work, or at least do something?

Yes, and in fact FWW had an article on a tensiometer based on similar
technique (except they used feeler gauges).

Are you sure you were tensioning the blade properly?

I hope so. I have the indicator set to 3/4". With the lever in one
position the blade is floppy; in the other it is taut. That's right isn't
it? Hey, I just bought the saw last week; I don't discount the possibility
that I don't know what I am doing.

I've seen this method written up before. In principle, it should work,
but you're looking for only a few thousandths of an inch of stretch.
Might be close to the limit of resolution of your measuring device.

On Mon, 03 Apr 2006 17:12:25 GMT, "Toller" wrote:

I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it stood
relentlessly at 4". The ends were clamped securely and the micrometer took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?



I can assure you it will work, at least with a dial indicator and
probe.

and the winner is?

Toller wrote:
I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it stood
relentlessly at 4". The ends were clamped securely and the micrometer took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?

If you clamp a micrometer spindle it won't turn. Why would you expect
the reading to change?

John Martin

"John Martin" wrote in message
oups.com...

Toller wrote:
I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band
saw
blade. I then tensioned the blade. I figured the micrometer jaws would
be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it
stood
relentlessly at 4". The ends were clamped securely and the micrometer
took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?

If you clamp a micrometer spindle it won't turn. Why would you expect
the reading to change?

John Martin

I assumed Toller meant to say he was using calipers, rather than a
micrometer.

todd

"Toller" wrote in message
...
I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would
be pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it
stood relentlessly at 4". The ends were clamped securely and the
micrometer took very little force to move, so I don't think they were just
slipping.

Shouldn't this work, or at least do something?

I'd be very dubious of any results you would get if you could even get this
to work. The amount of error in your measurement is bound to be a large
percentage of the measurement, which means your calculated readings would be
all over the map if you factored in measurement error.

The really cool way to do this would be with a strain gage. Glue it on,
load it up to a predetermined change in resistance, and voila.

todd

"todd" wrote in message
...
"John Martin" wrote in message
oups.com...

Toller wrote:
I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band
saw
blade. I then tensioned the blade. I figured the micrometer jaws would
be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it
stood
relentlessly at 4". The ends were clamped securely and the micrometer
took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?

If you clamp a micrometer spindle it won't turn. Why would you expect
the reading to change?

John Martin

I assumed Toller meant to say he was using calipers, rather than a
micrometer.

todd
That is correct, a caliper rather than a screw micrometer.

The article indicates that over a 5" length (open the calipers to 5") the blade
should stretch .001" per 6000 psi tension. Therefore a properly tensioned blade
should read about .003".
--
JeffB
remove no.spam. to email

"JeffB" wrote in message
...
The article indicates that over a 5" length (open the calipers to 5") the
blade should stretch .001" per 6000 psi tension. Therefore a properly
tensioned blade should read about .003".
--
My caliper gives repeatable measurements to .001", so it should be accurate
enough to do the job. Maybe it has more resistance than I think.

No.

"Toller" wrote in message
...
Shouldn't this work, or at least do something?

Toller wrote:
"JeffB" wrote in message
...

The article indicates that over a 5" length (open the calipers to 5") the
blade should stretch .001" per 6000 psi tension. Therefore a properly
tensioned blade should read about .003".
--

My caliper gives repeatable measurements to .001", so it should be accurate
enough to do the job. Maybe it has more resistance than I think.

Not to hijack this thread or anything, but I'd like very much to try
this with a dial indicator. You don't have a reference for the stretch
properties of the various metals for bandsaw blades, do you?

I'm using timberwolf silicon steel blades, but I didn't read anything on
this in the Suffolk brochure...

er
--
email not valid

On 4 Apr 2006 02:23:06 GMT, Bruce Barnett
wrote:

"Toller" writes:

I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

So you are measuring stretch?
What if you apply a deflection?

ok.. I guess it's better to ask a dumb question that make a dumb mistake...

Before measuring stretch and deflection, should the blade be at some preset
tightness or something?
Opps.. sorry, tightness wasn't listed, maybe preset tension?

Maybe I'm just not seeing something here, but if I take my cheap chi-wan-ese saw
and loosen the tensioning knob 5 turns would I get the same results from this
test as if I'd tightened it 5 turns instead?


Mac

https://home.comcast.net/~mac.davis
https://home.comcast.net/~mac.davis/wood_stuff.htm

On Mon, 03 Apr 2006 17:12:25 GMT, "Toller" wrote:

I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

Nothing happened. I flipped the tension lever back and fourth, but it stood
relentlessly at 4". The ends were clamped securely and the micrometer took
very little force to move, so I don't think they were just slipping.

Shouldn't this work, or at least do something?

yes and no, but not right away...

Sorry.. loan business flashback.. *g*

I find that I just don't CARE how correct my blade tension is... sinful by rec
standards, I admit, but the truth..

I set it to the gauge and "pluck" it like a guitar string... I've never found
out if it's the right pitch, but it comforts me, somehow..

If it cuts straight and sounds ok.. doesn't slide on the tire or bog the motor
down, I figure it's right enough..

I loosen it a couple of turns at night and try to tighten it about the same in
the morning..

I just can't get myself to care enough about a $12 blade to spend a lot of time
getting it ready, and then checking it again the next day..

This sort of leads (ok rambles) to another question... on the machines with
levers, does it leave the tension EXACTLY where it was when you loosen it, wait
over night and retighten?



Mac

https://home.comcast.net/~mac.davis
https://home.comcast.net/~mac.davis/wood_stuff.htm

Bruce Barnett wrote:
"Toller" writes:

I thought this was a brilliant idea, but it failed completely. Why?

I opened a digital micrometer to 4" and clamped the two ends to a band saw
blade. I then tensioned the blade. I figured the micrometer jaws would be
pulled apart a few thousanths and I could determine the tension.

So you are measuring stretch?
What if you apply a deflection?



problem with measuring deflection is variation from blade with and
tooth pattern. if you measure stretch the only variation you need to
account for is steel type, and that difference is tiny.

On Mon, 3 Apr 2006 11:29:16 -0600, Toller wrote
(in article ):


"Chris Friesen" wrote in message
...
Toller wrote:

I opened a digital micrometer to 4" and clamped the two ends to a band
saw blade. I then tensioned the blade. I figured the micrometer jaws
would be pulled apart a few thousanths and I could determine the tension.

Shouldn't this work, or at least do something?

Yes, and in fact FWW had an article on a tensiometer based on similar
technique (except they used feeler gauges).

Are you sure you were tensioning the blade properly?

I hope so. I have the indicator set to 3/4". With the lever in one
position the blade is floppy; in the other it is taut. That's right isn't
it? Hey, I just bought the saw last week; I don't discount the possibility
that I don't know what I am doing.



For my MM 16" saw I used a dial indicator with mounts about 12" apart. The
calculations are straight forward (I posted the process w/pictures on the
yahoo MM group several years ago). I don't remember exactly, but it was
somewhere about 0.003" to tension a 1" blade and my indicator was graduated
such that a full revolution is 0.004".
You really need a sensitive instrument to tension a blade especially if your
mount points are only 6" apart.

-Bruce

Recently 'inherited' an Iturra "Blade Gage" which works on the same
principle.

Made me immediately upgrade the tension spring in my US Delta 14" bandsaw.


--
www.e-woodshop.net
Last update: 12/13/05

On Wed, 12 Apr 2006 10:38:40 -0500, "Swingman" wrote:

Recently 'inherited' an Iturra "Blade Gage" which works on the same
principle.

Made me immediately upgrade the tension spring in my US Delta 14" bandsaw.

I would have thought that an old musician like you would have used the
"tuning fork method".

You can look it up.

When it first came out it didn't make a lot of sense for guys who
couldn't hear different notes, but in an age where a tuning checker
can be had for twenty bucks it might make sense to tune a bandsaw
blade according to the note it makes when plucked.


Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

"Tom Watson" wrote in message
"Swingman" wrote:

Recently 'inherited' an Iturra "Blade Gage" which works on the same
principle.

Made me immediately upgrade the tension spring in my US Delta 14"
bandsaw.

I would have thought that an old musician like you would have used the
"tuning fork method".

You can look it up.

When it first came out it didn't make a lot of sense for guys who
couldn't hear different notes, but in an age where a tuning checker
can be had for twenty bucks it might make sense to tune a bandsaw
blade according to the note it makes when plucked.

I've "plucked" on it for years, hell even executed a mean harp gliss on the
damn thing a time or two, but the old tension spring was shot to hell, so
even under full compression it was about 1/5th of the needed compression for
the size blade ... basically it would pluck the same old tune, but more than
a few octaves too low.

What a difference with the new tension spring ... now it really sings.

--
www.e-woodshop.net
Last update: 12/13/05

On Wed, 12 Apr 2006 21:19:19 -0400, Tom Watson wrote:

On Wed, 12 Apr 2006 10:38:40 -0500, "Swingman" wrote:

Recently 'inherited' an Iturra "Blade Gage" which works on the same
principle.

Made me immediately upgrade the tension spring in my US Delta 14" bandsaw.

I would have thought that an old musician like you would have used the
"tuning fork method".

You can look it up.

When it first came out it didn't make a lot of sense for guys who
couldn't hear different notes, but in an age where a tuning checker
can be had for twenty bucks it might make sense to tune a bandsaw
blade according to the note it makes when plucked.


Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

I think I got plucked when I bought my saw.. *g*


Mac

https://home.comcast.net/~mac.davis
https://home.comcast.net/~mac.davis/wood_stuff.htm