Bandsaw Tracking – Revisited

[everettdavis]

Degrees / Minutes /Seconds is a less common expression today other than topographical references for most folks.

Degrees are more commonly understood as 360° = a full circle.

However the symbols are not (') feet or (") inches:

(') 60 Minutes in an hour also can be used to represent a full circle
(") 60 Seconds in a minute also can be used to represent a full circle

It helps to envision a Clock Face. 15 Minutes = 1/4 hour, 30 Minutes = 1/2 hour and so on.

Thus: 1° + 15'/60 would equal or 1 1/4 or in decimal representation 1.25°

Had there been Seconds expressed, there would have been additional decimal places expressed. Another way of expressing that would be:

1° + 15'/60 + 0"/3600 which equals 1.2500° or 1.25°

Does that help?

Everett

[beeg]

Iiuc, the upper wheel. Cant angle is 1 degree 15 minutes.

So WHAT is that in inches?

??? An angle is not a length.

It IS, when it's expressed in 16ths of an inch from the other wheel when a straight edge is used on the top wheel .

[everettdavis]

Equally machinists have to deal with the term say in cases where they are working with rotations and feed rate calculations in threading etc. Some are expressed in degrees / minutes there as well.

Everett

[dusty]

I deleted my comments but plan to post latter with better detail.

[JPG]

We can get totally buried in a discussion regarding fractional degrees.

It should suffice to understand that there are 60 minutes(') in a degree and 60 seconds(") in a minute. Yes it is confusing since those are also 'time' terms(minutes seconds) and length indicators(' ").

What Beeg is attempting(I think) is to relate all of this to our historic measuring cant angle by placing a straight edge against the wheels and determining the clearance of the straight edge to the other wheel.

We have since gained insight into the better indicator that is the positioning of the back(spine) of the blade relative to the back edge of the upper wheel(about 1/4 inch).


What the patent application has done is eliminate the conjecture and second guessing that occurred in a lengthy previous thread.

Interesting from an understanding view, but not much help since we cannot measure the extremely small angles involved. All we can do is observe the effect they have on other things. The blade to back edge of the upper wheel is IMHO the best secondary reference/observation.

[everettdavis]

Very true. And all of our measurements using that method depends on the wheel itself remaining true to the axis around its outer circumference and not being warped during extended periods of time with tension on the blade for months, even years in some cases.

I know we all have found some that weren't true anymore, which makes it really difficult to measure. I replace those. There are a variety of ways to measure that.

I usually just lay the bandsaw on its back on my work bench and place the heavy base for my magnetic mount of my dial indicator at a point on the back at a suitable spot and zero the indicator at some point on the wheel to measure it vertically.

As I rotate it through the full circle, I can tell if the wheel is warped regardless of angle offset etc. If it is flat, it will be nearly the same through the entire rotation if the bearings are good.

You can gently lift up on it to see if there is much run out from the upper bearing or the shaft assembly on the lower wheel suggesting they need to be replaced.

If there is deviation and it is warped it will show up since my reference point doesn't move from the fixed spot, thus the distance from it should be the same all the way around on the dial indicator.

You can do the same type of reference on the outer lip measuring horizontally to see if the wheel itself is a bit out of round.

If it is much out of round you may see it even on the first measurement as the contact point for the dial indicator will not hit the same reference point on the circumference as it is rotated, regardless of vertical deviation it may exhibit.

I like that method because I don't have to disassemble anything other than taking the blade off and front cover open. It's a pretty quick pass or fail test.

Everett

[dusty]

We can get totally buried in a discussion regarding fractional degrees.

It should suffice to understand that there are 60 minutes(') in a degree and 60 seconds(") in a minute. Yes it is confusing since those are also 'time' terms(minutes seconds) and length indicators(' ").

What Beeg is attempting(I think) is to relate all of this to our historic measuring cant angle by placing a straight edge against the wheels and determining the clearance of the straight edge to the other wheel.

Which I contend is on the order of 7/64".

We have since gained insight into the better indicator that is the positioning of the back(spine) of the blade relative to the back edge of the upper wheel(about 1/4 inch).

Which I do not accept at face value. and

Not to be confused with the dimension of 7/64".


What the patent application has done is eliminate the conjecture and second guessing that occurred in a lengthy previous thread.

Interesting from an understanding view, but not much help since we cannot measure the extremely small angles involved. All we can do is observe the effect they have on other things. The blade to back edge of the upper wheel is IMHO the best secondary reference/observation.

The 1/4" offset mentioned above is an empirical figure and is very likely to be different on different machines. The 1/4" is at best an approximation.

[JPG]

The 1/4" offset mentioned above is an empirical figure and is very likely to be different on different machines. The 1/4" is at best an approximation.

Agreed!

An indicator of what it should be for a particular bandsaw would be that which the lower wheel exhibits.

[everettdavis]

Very interesting and very informative read. Thank you, Everett for the time spent and the effort expended to provide this document.

I'll have to read it two or three more times before I begin to think I understand it all but that is good.

I decided to reorient this document in coming weeks to help graphics and text be in the areas where it's easier to conceptualize.

Some of the patent verbiage is different than we speak today, but I will leave in place and add some colors in the drawings and text.

No timeline, just a project I will engage to help understanding.

Everett

[JPG]

I found it 'interesting' that the wheel bevel angle is stated to be "ABOUT" 2 degrees and that it is implied by the remaining info to be "37.5 minutes" which is 0.625 degrees.

Very close to some of our earlier calculated/empirical measurements.

In other measurements we concluded the angle was near 2 degrees.

We still do not understand why "2 degrees" is relevant.

So the patent doc does not clear that detail much.

BUT THANKS Everett for this thread.

I have to conclude that if the bevel angle is indeed 2 degrees that the rubber tire absorbs some of the difference and that the excess angle is so the inner rim has a larger diameter thus causing the blade drift in that direction(towards the guide bearings).