Help needed if you use an Incra fence on your router table
timhorchler
| Posted in General Discussion on
Help me out here.
I think I have a clear understanding off the thru and half dovetail using my Incra set-up. But the results say I am missing something, perhaps just a misunderstanding about the instruction. I am sure it has something to do with the height of bit when I do the “fit” step. I am learning from the Incra Master Reference guide and today I was trying to make a box about 12 x 12 and 9 inches high.
Here is what I did:
• selected DOVS, which has these settings: thickness 3/4″, 5/8″ 7º bit, depth of cut 3/4″, center at 8A (but I used 7A), and spacing depth of cut of 1 1/16″
• my soft maple was a bit over 3/4″ as I expected to have to plane it down to match the bit height.
• set my bit height at start at 3/4″. I did a fit cut and needed to raise my bit to about .9″ (which seemed to me the wrong direction to go but I had a tight fit, so it goes. I expected to have plane down my wood to something less than 3/4″ but what to do? Go ahead and see what happens; maybe the instructions are smarter than me.)
• I centered on my width per instructions
• did my tail cuts
• did my pin cuts vertical, then flat and clean up the cuts with a chisel
I have to say the fit was reasonable, meaning I could join a pin end to tail end; but tails and pins were about an 1/8th” + too long. In making the pin cuts with the pin boards flat on the table my bit was too high that it left maybe 1/32″ of wood at the table side uncut, so the bit was higher than what it is designed to cut.
What am I missing here? I think it has to do with bit height but I also think I follow the instructions correctly.
Thanks.
Tim in Georgia
Replies
Dovetail
After you made the adjustment up, did you run another test cut. The test cut should be perfect, if it is not, then you need to perfect it. When done, the routing of the dovetails will be perfect. It has been awhile since I cut dovetails on it, but clearly remember that it all relies on that test setup being correct. I learned that in a class years ago. Just looked at the master reference book, go to page three showing the results of the test cut. Hope that helps.
Dovetail
Yes, I confirmed the fit after adjustment with another test. Nice and firm. But with my stock at .75" and the bit now raised much higher, trouble is on the way. I would have expected a good fit at something less then .75" so I could plane down to to equal or less than adjusted bit height as the book says.
I have the book here and can confirm that I am following steps. Just think that my adjustment should have me going lower, not higher, given the .75" suggested height. But, "tighten/highten" and "lower/loosen".
Tim
Bit Height
I agree, the bit cannot be alot higher than the thickness of the wood. On through dovetails, it should be only slightly higher than the thickness so you have something to clean up. I'm going to go over what you said again and see if I can further help.
Fit
I just noticed that you originally stated that the fit was tight, and you raised the bit. But like you said, lower to loosen. Did you state that wrong or maybe that's where the problem is. Clearly the bit is too high from what you said.
Fit
The fit was loose, so "highten to tighten." Which I did by raising the bit for a a new test cut which fit perfectly, but now the bit is higher than the wood I have.
Tim
Solution, almost
I called the Incra people today and presented my observations and problems. It is what it is. While the suggested heigth of cut starts at .75" for this template and is so noted on the template, the "fit" process requires that it be raised up considerably, in this case to nearly .95". So my wood would need to be about this thickness, which I do not want.
So my use of wood that is about .75" thick will not work here. If I understand, I would have to use some other template whose bit height, after adjustment, results in about .75". So it would be trial and error to find a template that results in an adjusted fit height of about .75". But once determined, could be noted for future work.
I will have to noodle this a bit more (this is the weak link in all of this). If one tried all the templates to determine the final bit height and recorded all the results then you could select the template that is closest to actual wood thickness and start there.
Please kick me in the right direction if I am still off track.
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