# Minimizing the waves from a router sled



## MaxK (Oct 1, 2012)

So, after determining that the width of skis I need would require a larger diameter rod than 9mm, and that My router base was laid out in a way that prevents me from just drilling the holes larger, I set about building a plywood sled as seen in many a "how to flatting your end grain cutting board/workbench" youtube video. Bar a sloppy slot which I will be enlarging a hair and cleaning up when my template bit gets here, I'm pretty pleased with myself lol. 

Anyways, I am building an electric bass body, and am planing the blank flat (It's made from 3 pieces of hard white ash). I'm using a 1 1/4" mortising flat bottom bit from Freud to do the cutting. At the thickest point, I'll be taking out just shy of 1/8" of material. I've gotten about 1/4 of the way across the blank, and the waves where one cut leads to the next are a bit bigger than anticipated. Maybe 1/4 to 1/2 mm? Is that roughly what one would expect, or is that bigger than normal?

If it is bigger than normal, what would cause that? The only thing i could think of is if my routers base plate was not perpendicular to the cutting bit somehow. Am I missing something obvious here? I would post pics of the whole thing, but I'm a few posts away from there yet. Thanks in advance guys


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## Chris Curl (Feb 13, 2012)

sounds like the bit is not quite perdendicular to the wood.

the more perpendicular the bit is to the wood, the smaller the waves should be.


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## MaxK (Oct 1, 2012)

Forgive me if I misunderstand the whole process lol. Why would the surface of the wood pre -routing affect the plane of the wood post-routing? I've checked to the best of my ability that tops of my rails as well as the surface of my sled are all coplanar, and as far as i can tell theyre pretty darned close. 

In the meantime, I've found that by routing moving the sled along the rails, then moving the router in the sled a bit and starting over, I get much fewer lines than if i route along the sled, move the sled a bit on the rails, and repeat. Is there anything wrong with this approach?


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## harrysin (Jan 15, 2007)

MaxK said:


> Forgive me if I misunderstand the whole process lol. Why would the surface of the wood pre -routing affect the plane of the wood post-routing? I've checked to the best of my ability that tops of my rails as well as the surface of my sled are all coplanar, and as far as i can tell theyre pretty darned close.
> 
> In the meantime, I've found that by routing moving the sled along the rails, then moving the router in the sled a bit and starting over, I get much fewer lines than if i route along the sled, move the sled a bit on the rails, and repeat. Is there anything wrong with this approach?


 I'm sure that it's as Chris has said. This is a problem that I encountered and wrote about the first time that I used a 1 3/4" bottom cleaning bit. I hadn't ensured that the height of the ski rods was identical in all four corners, the result was that the cut was a fraction deeper on the left side prodicing a surface that if magnified would have resembled a saw-tooth. Once the skis were accurately set-up the results were perfect.


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## damnitboy (Mar 3, 2012)

Howdy Max,
Harry is absolutly right, you must have the router set up perpendicular to your work but if you have slop in your setup you could minimize it by tensioning your setup with a couple of springs set at 20 degrees off parallel out to keep your router from rocking in the cut. I.E. tension the slop out of your setup and you will improve your results.
Good Luck,
-Eloy


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## MaxK (Oct 1, 2012)

I think I originally misunderstood. Yeah if one or more for corners of the railing aren't coplanar that would cause the surface being routed to not come out flat. I don't know why that didn't click last night. 

I also do have plenty of slop. I may have over waxed the rails that the sled sits on. It might be a little TOO easy to slide the sled along the rails. 

In better news, this is my first piece of joined wood (simply edge joined) with a power jointer or otherwise, and where I've flattened it the glue line is only visible to due the grain changes. Its a super tight seam. At least something is going smoothly lol.


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## MaxK (Oct 1, 2012)

It just needed a hair more downward pressure to keep the router flat in the sled, and it is much better. 

Unfortunately, I slipped and knocked the sled off one edge, and it gouged the piece. I can salvage it for something else quite easily, but not for this. This is why you learn on inexpensive woods like ash and such, I suppose.


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## MaxK (Oct 1, 2012)

Well, upon busting out a precision straight edge and a set of calipers, the 4 corners of my rails are out of plane from the base by up to half a mm from the lowest to the highest point, and while i flattened the blank (the top and bottom sides both came out amazingly smooth, once i started adding a hair of pressure and scraped off some excess wax, to the point where theres very little light that makes it under a straight edge), it's not of a uniform thickness, by a difference of around 2.75 mm or so between the thinnest and thickest sections. Is the offset in the rails height enough to cause that much variance?
I may need to pick up another router and make some adjustable skis. I can take a good 7 or 8 mm off and still find a use for the blank, so I can keep adjusting and taking off miniscule amounts.

Here you can see the sled (I'll link it, since it's large)
http://www.8bytealchemy.com/wp-content/uploads/2012/10/IMG_20121009_185659-1024x768.jpg

and here is its construction (and use)
Building a Sled and Planing the Blank | 8 Byte Alchemy


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## Mike (Nov 22, 2004)

Max, the easiest way I have found to level both of the plywood ski jigs shown is to have the H frame level on your work surface and tighten the wing nuts/knobs. Once this is square then place a block measuring 1 x 2 x 3" under two diagonal corners of the H frame where it supports the router. (I use an inexpensive pair of steel 1,2,3 blocks for this) Tighten the wing nuts/knobs on the risers and you will get level cuts.


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## MaxK (Oct 1, 2012)

Yeah, I'm going to try to knock my rails flat with a hand plane, and if that doesn't work, I'll build an adjustable sled like those. In the mean time, one of my good friends it turns out has a 2 piece blank ready to go that just needs to be edge jointed. I think I'm going to step away from the project for a day or so, before I start getting frustrated lol.


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## giltic (Sep 27, 2010)

You could try my approach. I have 2 screws from each side so I can adjust the height.
The thickness of the working piece is in 0.1mm tolerance. Not that you need so close tolerances in woodworking, still....
Regards


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## harrysin (Jan 15, 2007)

MaxK said:


> I think I originally misunderstood. Yeah if one or more for corners of the railing aren't coplanar that would cause the surface being routed to not come out flat. I don't know why that didn't click last night.
> 
> I also do have plenty of slop. I may have over waxed the rails that the sled sits on. It might be a little TOO easy to slide the sled along the rails.
> 
> In better news, this is my first piece of joined wood (simply edge joined) with a power jointer or otherwise, and where I've flattened it the glue line is only visible to due the grain changes. Its a super tight seam. At least something is going smoothly lol.


Max, are you saying that you SLIDE the router along the rods when planing? Whilst there are no laws governing the way router skis are used, the way that I use and teach ski routing, the router is positioned on the rods to suit the particular job then LOCKED and the complete assembly moved by holding the end cheeks, NOT the router's handles.
This collection of shots from some of my many threads may give you a deeper insight into router skis. The second shot shows how the skis can't go any further to the right, so the router was then un-locked, moved to the right, re-locked allowing the rest of the board to be planed.


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## MaxK (Oct 1, 2012)

That was my thought. A bit of ptfe and it would work, I would think.

Anyways, I'd need some very wide skis to make it work by sliding the whole unit. The blank i have is ~ 19x22 inches. I'd have to have skis like, a meter wide or more, no?

Heres an image of the sled I built.









Anyways, the project is on temporary hold. Unfortunately I had a grease fire on saturday. It started heading south fast, but I caught it before it did too bad. I'll need to replace my microwave, and refinish/replace a single cabinet, and then do smoke damage all around. Nothing too bad fortunately, but I'm having to clean the cabinets with an abrasive pad, and then touch up the finish in some spots, then rebuff them. 

Fortunately, I have a friend with another blank I'll be using, which is already planed and ready to go. I'll be salvaging this one though for a different project. I'm hoping to resume work by next weekend.


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