Out of square miter gauges

I have both a Delta and a Rockwell miter gauge, neither of which has a vertical face square to the saw table, Before I do something dumb in modifying them is there a reason why the angle to the saw table should be around 88 degrees or so?
Joe
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Joseph wrote:

I think it would be interesting to bring in a new (different) miter gauge to compare, and learn where the problem really is. I would take several measurements (along the top), using each one. I suspect the results will be different, and then you will have isolated your problem. If the results are not different, then you still will have isolated your problem. I would put a face on the miter gauge and adjust the face.
Bill
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Bill wrote:

Hmm.. I see I really didn't answer your question. Sorry, I don't have the answer.
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Joseph wrote:

Interesting. I have never measured the vertical angle on my gauges. I can't think right off of any use I have made of a miter gauge where 2 degrees off vertical would make a difference.
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On 7/18/2012 8:52 PM, G. Ross wrote: ...

Well, a angle cut for a multi-sided box won't be square if the fence isn't vertical...by the time you add that up for eight faces of an octagon, it'll be pretty apparent...
The Delta from the old 1/2" spindle shaper ca. '75 and the Powermatic supplied w/ the Model 66 (ca. 82(?)) are both close enough I've never noticed an issue and have used them enough would surely have found it by now though I've never actually measured.
The one that bugs me is the sides of the fence on the Model 66 aren't vertical (nor adjustable)...
--



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On 7/18/2012 6:34 PM, Joseph wrote:

Not very good castings.
They need to be 90.. Put a face on it that brings it to 90. Just attach a wood face with a 2 degree bevel.
Just get it to 90.
it should be square to the table for proper cutting of pieces put on edge for tenon cutting and such.
Anything not fully cut through that is clamped to the miter gauge would be off by 2 degrees.
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On 7/18/2012 10:15 PM, tiredofspam wrote:

BTW if it is of any consolation, my incra wasn't 90. I have shims behind the fence to keep it at 90. Rather than remove the angle iron and lose my 90 and have to regain it. I found the miter was 90 but not the fence. so simple plastic shims fixed that. Mine was leaning back away from the blade.
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On Thu, 19 Jul 2012 11:24:19 -0400, tiredofspam <nospam.nospam.com> wrote:

My Incra is the same. The sheet metal flexes too much to keep that angle perfect. The JessEm is much better.
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On Jul 18, 9:15pm, tiredofspam <nospam.nospam.com> wrote:

Thanks. That settles it. I will epoxy bond a thin aluminum plate to miter gauge face and have it milled to 90 degrees. Luckily, I have a retired tool and die maker friend who has a nifty Bridgeport in has man cave, so it should be highly accurate when done. Problem was likely old, old die casting molds which escaped quality control inspection for years. Anticipating some decent miter joints fro now on.
Joe
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On 7/18/2012 9:15 PM, tiredofspam wrote: ...

I'm having hard time visualizing what you're thinking/trying to say here, TOS. The vertical angle makes a difference when making an angled cut and for that reason alone the face should be perpendicular to the table.
But I can't figure what the other effect would be for a tenon and the "not cut through" is referring to. It's the compound angle made w/ the blade when not a 90 that is the misalignment effect--if it's at 90 I can't think of a cut where the angle at which the board enters will have an effect--the top of the blade circle will control the depth and that will be consistent; the angle presented to the blade is vertical at the end of the piece w/o there being a corresponding miter angle as well...unless I'm missing something which is always possible... :)
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Your thinking through cut.
Think lap or tenon, where you secure the piece to the fence of the miter gauge. Now the piece is leaning 2 degrees off. so the back of the blade will not cut to the same depth. Also someone mentioned a miter ; not a picture miter, but a shallow box side miter. you will tilt the miter gauge to lets say 45, but you still have a tilt of 2 degrees.
It matters, a lot.
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On 7/19/2012 1:58 PM, tiredofspam wrote:

...
Ok, if you do hold the work against the face rather than the table and only use the gauge for guidance. It is probably that way if the work is on edge; I was thinking of the flat where it would be some effort to hold the material off the table...fortunately, for something like common 3/4" stock the small angle would translate to a pretty small difference--well, let's see. Hmmmm...that's actually almost a 32nd--that is enough to see/feel.
OK, I'm satisfied even there it can be significant...I guess I'm more certain despite measuring the ones here are far better than that. :)
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Joseph wrote:

If the face is tipped forward by 2 degrees, I can see a reason; namely, a board against it will still be correct even if there is a bit of sawdust along the the bottom of the gauge face which might otherwise screw stuff up.
The board you are going to cut will be at 90 degrees to the face of the gauge - as long as the face is flat - even though it isn't completely touching it.
--

dadiOH
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On Wed, 18 Jul 2012 15:34:16 -0700, Joseph wrote:

I do know that at least some miter gauges are, or were, cast in a mold. Could a slight angle be built in for mold release?
--
Intelligence is an experiment that failed - G. B. Shaw

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