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Routing an exact centre

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Forum topic by KnickKnack posted 09-30-2016 11:38 AM 279 views 0 times favorited 4 replies Add to Favorites Watch
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KnickKnack

1062 posts in 3034 days


09-30-2016 11:38 AM

So there I was 20 minutes ago, staring at my little piece of wood, wondering how i was going to manage to route a slot exactly in the centre of it.
Often I have a scrap piece of exactly the same width, so I experiment on that until I’m dead centre – but in this case I didn’t.
Sometimes I have “spare” at the end of the piece which I’m going to cut off later so, again, I can experiment until I get it right – but in this case I didn’t.

Then I had one of those “why didn’t I think of this 10 years ago” moments and came up with this monstrously obvious, blindingly obvious, method. But it’s not something I’ve ever seen mentioned anywhere (although, of course, I may have missed it).

If you want, for example, to route a 10mm slot – simply experiment with a smaller bit!

I picked a 5mm…

Which turned out to be 0.85mm wrong (I hadn’t tried too hard to centre it in the first place)...

Adjust fence – you can either raise the bit a little, or go further into the wood. It took me another 2 cuts to get to a difference of 0.1mm – I figured that was close enough…

Obviously without moving the fence, swap in the correct (for me 10mm) bit, and, well, there you go…

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."


4 replies so far

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Cooler

277 posts in 310 days


#1 posted 09-30-2016 12:39 PM

I take two passes with my dado blade to get a slot centered. I got that from Norm Abrams on his show.

I set up my mortising chisel by taking a cut from the right, then the left until the two only make one cut.

It is worthwhile repeating.

Also, when I am making dados for a 12” shelf, to ensure that the lefts and rights are exactly the same I start with a 25” wide piece and cut the dados across the sheet and then rip it to two 12” sides.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

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KnickKnack

1062 posts in 3034 days


#2 posted 09-30-2016 12:42 PM

I take two passes with my dado blade to get a slot centered. I got that from Norm Abrams on his show.
- Cooler

And flip the board in between?
That will be centred, yes, but of an indeterminate width – if you need the slot to be the exact width of the dado blade?

I set up my mortising chisel by taking a cut from the right, then the left until the two only make one cut.
- Cooler

Unless I’ve misunderstood this, you’ve done this on a scrap piece of wood before doing it on the “real” piece? That isn’t the situation I described in which you have only a single piece, the “real” piece, available.

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

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Cooler

277 posts in 310 days


#3 posted 09-30-2016 01:05 PM



I take two passes with my dado blade to get a slot centered. I got that from Norm Abrams on his show.
- Cooler

And flip the board in between?
That will be centred, yes, but of an indeterminate width – if you need the slot to be the exact width of the dado blade?

I set up my mortising chisel by taking a cut from the right, then the left until the two only make one cut.
- Cooler

Unless I ve misunderstood this, you ve done this on a scrap piece of wood before doing it on the “real” piece? That isn t the situation I described in which you have only a single piece, the “real” piece, available.

- KnickKnack

You are correct on both points. But for multiple grooves or dados setting up the dado head to the right width will be much quicker. For a single groove or dado your method can make sense.

I’ve seen jigs that make exact sized gooves or dados in two passes.

-- This post is a hand-crafted natural product. Slight variations in spelling and grammar should not be viewed as flaws or defects, but rather as an integral characteristic of the creative process.

View Joe Lyddon's profile

Joe Lyddon

9451 posts in 3519 days


#4 posted 09-30-2016 04:23 PM

For such a small dado, I would NOT use a dado blade, unless it was just ONE 1/8” blade.

I would find the middle by measuring, the old fashioned way…
... adjust fence to get wood Center in the center of the blade.
... THEN, make a Left cut, flip around, & Right cut…
... The cut WILL be in the Center of the wood… no question about it…
... Then, adjust the fence, ever so slightly, make L & R cuts again, to get the final Dado width to fit your needs.

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: http://www.ncwoodworker.net/pp/showgallery.php?ppuser=1389&cat=500"

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