Thread: Osbourne EB-3 Mitre Gauge - calibration of

Is it just the 45° angle that is out or are they all out? Can't see why you can't do the 5 cut method to calibrate the 90°.
I just watched a video of assembling them and it says at the end that the manufacturer will look after your EB3 for the time you own it so that might be an option if you don't have any success here.

Originally Posted by Treecycle

Is it just the 45° angle that is out or are they all out? Can't see why you can't do the 5 cut method to calibrate the 90°.
I just watched a video of assembling them and it says at the end that the manufacturer will look after your EB3 for the time you own it so that might be an option if you don't have any success here.

I figure if one is out then they're all out because there's only one means of adjustment. I actually got it pretty close by trial and error but there has to be a better way. The five cut method relies on the base and fence being all one unit when you make the adjustment using the feeler gauge but here the gauge can move in relation to the table saw top. I can't see how that would work...

I have previously (years ago) emailed them about a similar problem and got an immediate response from the owner (so am assuming it's a one man show). I can try that again but I have a lot of faith in the folks here so will wait to see if I get a response...

I ended up writing to Osbourne last night about this and I got a reply from David Osbourne, This is the method he sent me:

EB-3 Setup.jpg

Funnily enough that's exactly the method I'd worked out for myself yesterday. In theory it should work fine but in practice it doesn't provide the accuracy needed to make a four sided frame with mitred corners, without gaps in those mitres. Sure you can hold a square up to a 90° cut and it looks spot on but it's the four mitred corners that will really tell you how accurate it is. You only need to be out by a very small amount for it to show.

I can use the method William Ng shows in his 5 cut method to measure the accuracy/inaccuracy of the gauge but converting that measurement into a way to correct it is what I'm struggling with. In the 5 cut method William Ng uses a formula to convert that number into a value, and it is this value that's used (with a feeler gauge) to move the fence either forward or backward, RELATIVE TO ITS CURRENT POSITION. This is done by clamping a stop block against the fence at it's current position. Unlike a sled I can't imagine a way to attach a stop block to mark that current position with the Osbourne.

Couldn't you clamp the sliding bar in the mitre slot so the gauge won't move in the slot and then clamp a piece of timber up against the moving end of the fence. Do your calculation and use the timber stop with the feeler gauge to make your adjustment. Depending on which way it is out you can clamp your stop in front or behind the fence.
Can't complain about the service from Osborne.

Thanks, that's certainly worth a try. I'll do that today.

I just tried what you suggested and got a good result. I had thought that clamping the bar to the table might have been difficult but it wasn't at all. So after doing the five cuts these are the measurements of the final fifth cut, top and bottom (they should ideally be identical):

Top.jpgBottom.jpg

Many thanks for your suggestion.

Now for the real test - making a four sided frame.

Fail!

Frame 1.jpg

Top and bottom rails are of equal length

Frame 5.jpg

My square says the cut is 45°

Frame3.jpg

And that the corner is 90°

Frame2.jpg

How can it not be perfect? Am I missing something really basic?

I finally managed to make a frame with mitre joints tight enough for my satisfaction. But I did this by adjusting the mitre gauge angle to get the 45° right rather than the 90° (because they seem to be mutually exclusive) and I did it by trial and error because I couldn't think of a way to do it more scientifically.

Winner.jpg

I then returned the gauge to the 90° position and did the five cut test again (without altering the angle of the gauge). This time there was a significant difference in the top and bottom measurement. I can only surmise from this that the detent for 45° is in the wrong place. It doesn't have to be very far out to make a significant difference when making a mitred frame as you can see from my example here. Of course that also calls into question the accuracy of all the other pre-set angles. A short term solution of course would be not to use the detents, at the expense of repeatability...

Changing the mitre gauge angle when I want to go from 90° to 45° is obviously not a sustainable solution in the long term and I'll be writing to David Osbourne again to see if he can suggest a way forward...

One other observation I made while doing all this is that to rely on a square to measure accuracy at this level is a fool's errand. My eyes just couldn't pick the difference between the accurate and inaccurate cuts. They both looked good according to the square.

Never used the Osbourne EB-3, but it seems that discussion about its accuracy and adjustment has been around for at least 17 years. This might be useful, especially Post #5. [Sawmill Creek Forum discussion]
Osborne Miter Gauge?

Originally Posted by GraemeCook

Never used the Osbourne EB-3, but it seems that discussion about its accuracy and adjustment has been around for at least 17 years. This might be useful, especially Post #5. [Sawmill Creek Forum discussion]
Osborne Miter Gauge?

Thanks. I read through all those posts and there seems to be an even distribution of likes and dislikes; a lot of the dislikes are related to the output from the interim company that manufactured them for a year till going broke. I've had mine for many many years and it could be that I have one of those because it seems obvious to me that my issue (the placement of the detent for 45°) didn't just happen, it's always been like that which suggests poor quality control. But until you really put it to the test (as in making a four sided mitred frame) it could go unnoticed, as mine obviously did.

The test will be what Osbourne do about it. I would think replacement of the bar would be an expedient solution...

Sadly I have to report that there was no response from Osbourne to my email of yesterday describing my findings and asking for assistance. Make of that what you will...