# Slab flattening router bit tear-out



## whitedogone (Jul 13, 2012)

My first time flattening a slab. I am getting some tearout as I go. I'm taking shallow cuts a little over an 1/8, feed rate seems to help some but not completely. Started slab with a new bit. On the final pass maybe get a fresh bit? Increase pressure? Slower feed rate? Change feed direction? . Be nice to not have to sand these out.


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## John Smith_inFL (Dec 15, 2017)

wood is a finicky creature.
so are the craftsmen that work with it.
wood characterics will be different with every log.
so you must try all that you mentioned above to see what works for you
in your project. also, it could cut differently from one end to the other.
it is just the nature of the beast.

for me personally, I like to bite on my right side in a clockwise motion.
pulling the router with the grain, whenever possible.

.

.


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## Lazyman (Aug 8, 2014)

You don't say what kind of wood it is. Some bits are better than others too.


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## whitedogone (Jul 13, 2012)

It's walnut and a cheap Amazon bit. The bit did get decend ratings.


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## wildwoodbybrianjohns (Aug 22, 2019)

I havent had this issue when flattening slabs. I use a 25mm CMT bit, and for the first 2 or 3 runs I cut heavy, maybe around an 1/8th, then as I get closer to final level, I make much shallower passes, like a 1/16th or less. I also alternate runs, so cross-grain, with grain, cross-grain, etc.

I think your culprit is the bit. Just my 2cents.


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## therealSteveN (Oct 29, 2016)

Usually it's about too deep, and too fast.

You say 1/8" So that is an 1/8" from the very highest point, so much of the time you are cutting air? Or is it 1/8" from the lowest spot, so some times you are trying to take off 1" plus? If it's an average, then maybe sometimes you are only trying to chunk off 1/2"?

Other thoughts…

Bit diameter? Router used? Are ya trying to zoom from side to side, or allowing the bit to cut?

If it isn't a 4" diameter plate cutter getting run on a palm router the wood is tough stuff, gnarly grain, maybe interlocked. Or your cheap Amazoo bit isn't up to the task. This is one time where a quality bit will pay dividends.


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## John Smith_inFL (Dec 15, 2017)

what Steve said: if you are using a palm or trim router, that may be some
of your problem. the wrong bit and your technique also comes into play.
are you using a router sled ?? or, just free-handing it.

some photos of your situation will put everyone on the same page for the most
accurate responses. without photos, it is a shot in the dark to help you.

.

.


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## whitedogone (Jul 13, 2012)

I wish I could post pics. I'm not sure how to load them here. I don't have them on a cloud type service. I guess I need that.


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## Lazyman (Aug 8, 2014)

Just click the img button right above the text box and it will allow you to upload them directly to the text box. No cloud service necessary. Pretty simple.


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## whitedogone (Jul 13, 2012)

> Just click the img button right above the text box and it will allow you to upload them directly to the text box. No cloud service necessary. Pretty simple.
> 
> - Lazyman


Thanks!


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## whitedogone (Jul 13, 2012)




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## bondogaposis (Dec 18, 2011)

Make your final pass a real light cut. 1/8" is pretty aggressive.


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## Lazyman (Aug 8, 2014)

How about a close up of your bit.

Are you sure that everything is nice and solid and doesn't rock in any way? It looks to me like either the slab or the router/sled is not staying level as you move it or at least between passes.


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## John Smith_inFL (Dec 15, 2017)

to me, the tear out looks like your router came off of plane.
it dipped into the wood the whole pass you took.
I would get a larger bit that is super sharp.
if you plan to do much of this work in the future, there are router bits
specifically designed for flattening slabs like you are doing. (well worth the investment).
you may want to check the part that the router slides in - it may not be stiff enough.


*how are those 2×4s attached to the table* ??

.

.


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## HokieKen (Apr 14, 2015)

+1 to what Bondo and SteveN. Make your last pass much lighter than what you're cutting now. 1/32-1/16" Also, like Nathan said, everything needs to be rigid and fixed against movement for your slab and your side rails. Finally, do like John suggested and try making your final pass with the grain instead of across it. Good luck!


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## Lazyman (Aug 8, 2014)

A large bowl and tray bit, which has edges that curve up, can help reduce tear out.

Hot glue and wedges are a great way to hold the slab in place to prevent rocking as you plane it.


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## OSU55 (Dec 14, 2012)

The router sled/cross slide method is great for rough planing large surfaces. Final prep for finishing is where hand planes really shine. Even without tearout, and with a rounded corner tray bit, the surface is not truly flat. Sanding wont get it truly flat A smoothing handplane will.


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## MadMark (Jun 3, 2014)

Cut with the grain not across it …

M


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## Lazyman (Aug 8, 2014)

> ... and with a rounded corner tray bit, the surface is not truly flat…
> 
> - OSU55


Looks flat on the bottom to me. Making flat bottoms is what they are designed for. Of course, you have to make sure that you overlap but that is true with the planing bit as well. With either type of bit, you will have to do some clean up-hand/power planing and sanding.


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## whitedogone (Jul 13, 2012)

> to me, the tear out looks like your router came off of plane.
> it dipped into the wood the whole pass you took.
> I would get a larger bit that is super sharp.
> if you plan to do much of this work in the future, there are router bits
> ...


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## John Smith_inFL (Dec 15, 2017)

just stay with what you have for now - change your technique around
so you can take about a 1/16" off going with the grain.
I think you will be satisfied with the results.
then, before you do another slab, put more research into it coupled with
the experience of doing this one and you will be just fine.
it's not rocket science (until you get to the finishing part).
there are many good bits that work well for processing a slab.
just search around and see what fits you, your projects and your budget.
(some are over a $100).

.

.


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## LeeRoyMan (Feb 23, 2019)

Looks like 100 grit on a ROS would take that right out. 
If it were mine I wouldn't worry about it, but then, we all have our own standards.


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## Lazyman (Aug 8, 2014)

So what does going with the grain when planing with a router bit really mean? Not trying to be a contrarian, it just never occurred to me before. If you move the router lengthwise down the slab (with the grain), you are really cutting across the grain with the leading edge of the bit. When moving across the slab, the leading edge is cutting mostly with the grain. Would you get less tearout for example, if you work outside ->in, moving in a counterclockwise direction?

Just sort of thinking out loud. Any thoughts?


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## whitedogone (Jul 13, 2012)

> Looks like 100 grit on a ROS would take that right out.
> If it were mine I wouldn t worry about it, but then, we all have our own standards.
> 
> - LeeRoyMan


Not without a heck of a lot of grinding. RO sanded pic


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## John Smith_inFL (Dec 15, 2017)

okay - I will try to illustrate "my technique" of going with the grain.
I don't mean up and down Helter Skelter like you are scrubbing a dog.
make directional cuts (bites) from top to bottom, cutting on the right side.
just as you would route an ogee edge on a table edge.
don't walk the router all over the board. make one solid pass from top to bottom.
bring the router back to the top and pull it down again, and again, and again, and again.
of course, everyone has "their way" of what works best for them. this just happens to be mine.
you may have to re-arrange your setup to accommodate this technique so it will be comfortable
and safe making the long continuous cuts.










and the way I address any "imperfections" in the process, I am very proficient with a belt sander.
a 4" belt sander is my first choice - then the RO - and finish it up with a half-sheet inline sander.
labor intensive, yes. but I cut the labor time down with power tools used correctly.

all the best to everyone !!

.

.

*Edit: * and off-topic a little; once you get the hang of this technique, of cutting in a clock-wise
fashion, you can easily draw letters and graphics on wood and use the same technique to
make some very nice routed wood signs without using templates - just follow the lines.


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## Kazooman (Jan 20, 2013)

One more thought on the Jig set up. It is hard to tell from the picture of your entire workpiece, but the close up picture almost looks like the assembly might be sagging in the middle of the cut and digging in deeper.

Reiterating what has been said and adding a bit to bring all the tips together in one place: Your guide rails have to be very straight, parallel to each other, and well anchored in place. A 2×4 straight from the big box store is probably not good enough. Joint the edges to get them flat. The workpiece needs to be well anchored in place. The router guide sled you have bridging the rails needs to be strong enough to not flex and sag midway through the pass. You need a good quality router bit and the passes need to overlap to avoid leaving ridges. The final passes should be shallow cuts. Going with the grain is a great idea, but not always practical.

With all that in mind, you may well decide to have your lumber supplier joint one face flat and plane the other parallel with their big-a$$ equipment. That, or have a go at hand planes and winding sticks!


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## therealSteveN (Oct 29, 2016)

I think your waves are from movement. Double down on Nathans suggestion, and make it flat, and secured. If it were to go all the way over, you could be looking at physical hurt on top of a rough cut. That is some wildly grained wood, so just try kissing the surface, and go slower, see if it cleans up, once you get the sled tightened up.


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## OSU55 (Dec 14, 2012)

> ... and with a rounded corner tray bit, the surface is not truly flat…
> 
> - OSU55
> 
> ...


The as planed surface not the bit. After planing with a router, take a 1/2 sheet flat hand sander, remove the rubber pad, and rub across the surface. Just how flat is it? Sanding wont take it all out. With a matte finish it wont show, but as gloss increases so does the visibility. A well tuned and operated hand plane will make it perceptibly flat with a gloss finish.


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## whitedogone (Jul 13, 2012)

Maybe I need to get this this in shape


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## Lazyman (Aug 8, 2014)

> The as planed surface not the bit. After planing with a router, take a 1/2 sheet flat hand sander, remove the rubber pad, and rub across the surface. Just how flat is it? Sanding wont take it all out. With a matte finish it wont show, but as gloss increases so does the visibility. A well tuned and operated hand plane will make it perceptibly flat with a gloss finish.
> 
> - OSU55


I guess I misunderstood what you were saying. I thought your point was that a tray bit would not leave a flat surface for some reason. If you are getting a non-flat surface, it is more a function of the jig's rigidity, setup accuracy and process than anything else. No doubt that someone who has mastered the setup, sharpening and use of a hand planes can get a nearly perfectly flat surface but for us mere mortals who are not there yet, this method can yield excellent results.


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## whitedogone (Jul 13, 2012)

Well, I did some adjustments…..much better. Almost close enough to start sanding. Or maybe I should use scraper and or planes? I used the same bit. I will be ordering a new bit for the last pass. Another 1/16 or so to go.


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## John Smith_inFL (Dec 15, 2017)

looking much better.
I still don't understand the horizontal lines.
my technique is to start off with the most aggressive means
necessary to remove as much material as possible.
then the RO and inline half-sheet sander.
and end up with the card scraper last before final sanding.
(not necessarily in that order on all projects).
is the RO sander all you have for sanding ?
certainly, the hand plane will work just fine, if you are comfortable with it.
if you are going to order a new bit and remove another 1/6" of material,
there is no need to do any sanding at this time.
IMO, sanding is done after all the router flattening is complete as can be.

.

.


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## whitedogone (Jul 13, 2012)

> looking much better.
> I still don t understand the horizontal lines.
> my technique is to start off with the most aggressive means
> necessary to remove as much material as possible.
> ...


Just practicing, I just used my block plane. Wonder if I should switch to a jack. The block is the only low angle plane I have. On smaller stuff with wild grains in places, it seems that after finishing things pop so much more if I don't touch it with a sander.


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## Andybb (Sep 30, 2016)

> I think you will be satisfied with the results.
> then, before you do another slab, put more research into it coupled with
> the experience of doing this one and you will be just fine.
> - John Smith


+1 After doing 3-4 slabs I decided that EVERYTHING makes a huge difference (bit, sled, rigid base) and it is a learned technique that I now try to avoid whenever possible.


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## Dark_Lightning (Nov 20, 2009)

I used a 1" CNC spoilboard surfacing router bit after having a project look like your early pictures- though my router bed is a piece of 3/4" particle board with aluminum angles screwed to it. I cut with the grain and took very light cuts on the past passes. I haven't sanded the parts yet, and I'm pretty sure that I can start with 180 grit. I can't tell for sure in the picture, but when I did this set of boards, I had the bit as far into the collet as far as it would go to reduce vibration.


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## OSU55 (Dec 14, 2012)

You dont want a low angle plane for face grain - min 45 deg cutting angle, most bench planes. For swirly grain get the chip breaker as close as possible to the edge, the next step is a steeper cut angle to prevent tear out. Yes your jack plane but with very little camber on the edge for smoothing.


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