# Slab Flattening Fixture: build thread



## BlueRider (Jun 16, 2016)

Lately I've been using more live edged slabs in my work rather than cutting them up. So I figured its about time I built a flattening set up. I'm not talking about throwing a couple 2x4's on the floor and cobbling together some scraps of plywood into a sled, although that would get the job done. Nothing wrong with that approach, but I have a welder and I know how to use it... hold my beer and watch this.

My good friend 820wards and I have been sharing Instagram photos and chatting on the phone about different designs. Some of my design is dictated by having a very small shop and no outside work area. My shop is so small that I don't have enough floor space to set up something without a major moving of heavy iron, Ouch! My solution was to design something that could be set up over the top of my cabinet saw and extend into the open floor space. Of course it would also have to knock down easily and store in various rat holes around the shop and in the rafters. 820 wards was a great sounding board for my ideas. I really liked the idea of building a gantry style sled that used rollers or wheels on the guide rails, I even have a set of Thompson linear bearings and 50" of guide rail for the router. We discussed various options for wheels and ways to control racking, how to build in ways of adjusting and truing things up. In the end I opted not to use any wheels or linear bearings and to go with simplicity, but with a couple of features that I hope will make my set up hold up well and easy to use.

Most of the parts are cut and welding starts today. I'll post some pics tonight but since I know everyone licks photos I post a little teaser. The concrete in my shop is very uneven and since the whole point of this is to level the slab I have to have a way or leveling the bed and guide rails. I buy 1/4" 20 furniture glides that I use on my furniture so I will be using them in exactly the same way I do on the steel furniture legs. I cut some 2" long pieces of 1/2" steel round rod and chuck them up in my lathe using a four jaw chuck so I can drill and tap them. The lathe is not under power for the taping part but used as a way of holding the steel rod and guiding the tap, that's what the dimple in the end of the tap wrench is for. I'll be drilling holes near the end of the legs and welding these in so the glides have something to thread into.


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## Quietfly (Jun 16, 2016)

Watching for ideas... great start!!!


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## Raganr (Jun 16, 2016)

Look forward to seeing your build. Been wanting to make a jig similar to this for a bit (out of steel).


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## Quietfly (Jun 16, 2016)

Watching for ideas... great start!!!


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## ChoppyChoppy (Jun 16, 2016)

Can't just resaw if it's twisted?


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## BlueRider (Jun 17, 2016)

Had a couple of distractions today but still managed to make a bit of progress. The first picture is of those little pieces of round rod that I drilled and threaded on my lathe that are the anchors for the adjustable furniture glides, and how they get used in the build. using a unibit I drilled a 1/2" diameter hole 3/4" from the end of each leg. After inserting the anchors I thread in a furniture glide and make sure it is close to being centered, no need to get all precision here because the glides have a ball joint and will self level if they are a tiny bit off. I tack weld the anchor to the tubing and then remove the glide so I don't melt the plastic and weld it completely from each side. When I do this in a piece of furniture I reach up and add a couple of tack welds on the inside because I grind the welds flush on the outside but since this is a shop fixture I won't be doing that.








The next photo shows the legs, top, and a middle support and how they are arranged. I always tack weld everything from both sides before going back and completing the welds. Next up will be adding the hardware to allow me to attach the guide rails to the legs and some lower stretchers for added rigidity.


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## BlueRider (Jun 17, 2016)

ValleyFirewood said:


> Can't just resaw if it's twisted?



I'm building a fixture to allow me to use a router to not only get the slab flat but also remove the marks left by the chainsaw when milling. Also, the only thing more abusive to a chainsaw then milling is resawing a dry slab.


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## ChoppyChoppy (Jun 17, 2016)

I didn't think of a chainsaw cut. We use a Woodmizer LT40 so the slabs just need a few minutes with a belt sander.


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## Cease232 (Jun 20, 2016)

I chainsaw mill slabs that are too big for my band saw mill. I use a flattening jig identical to the one in the video above. Surprisingly the router leaves a very nice finish with no tear out. I follow up with light hand planing and scraping. I hope you have dust collection, especially for a small shop because it makes a huge mess. Good luck with your build.


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## IyaMan (Jun 20, 2016)

BlueRider said:


> I'm building a fixture to allow me to use a router to not only get the slab flat but also remove the marks left by the chainsaw when milling.



I've never done this but once I get some big slabs I may set up something simple like in the video (though I'm really looking forward to seeing your all metal build).

But is there a reason to use a router instead of an electric hand planer? Do you have an extra wide bit for the router, or is there a better result with the router's finish? I imagine with a planer you'd need to go with the grain instead of side-to-side as with the router.

Again, I haven't done this yet but was considering using my 4" wide hand planer. Just wanted to know if there was an advantage to the router.

Happy building!


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## Cease232 (Jun 20, 2016)

The bit I use is 1-3/4. I've never tried an electric planer but I know it still takes some skill to get it flat, level and without twist. You'll have to use a long straight edge and winding sticks. With a router jig as long as the rails are parrallel it's a no brainier. And it leaves a very nice finish. 

https://www.amazon.com/gp/aw/d/B000...c_redir=T1&redirect=true&tag=thewoodwhispe-20


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## BlueRider (Jun 22, 2016)

The plan is to use my shop vac as a dust collector but add a barrel inline for all the chips to fall into. Not exactly sure of the details and will sort that out once its up and running. I also have a large dust collector motor and blower I could use if the shop vac isn't strong enough.

I ordered a 1.5" diameter spoilboard router bit that should be arriving in the mail today. Most spoilboard bits are $400+ but Amana has several of their 2+2 line that are only $175. I know that sounds crazy expensive for a router bit but these use indexed carbide inserts so sharpening is as simple as unscrewing and rotating the carbide insert. Amana insets are available for $16/ set but inserts are a commonly available item and often can be found for $1 -$2 ea. I like the way Amana positions two cutters to shear cut the bottom as well as two to sheer cut the edges. it comes highly recommended by a couple of furniture makers that specialize in slab tables.


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## BlueRider (Jun 22, 2016)

The legs are all finished but I will have to wait until I finish with the sled before I set up the legs. I do have a few pics and some initial thoughts to share though. A couple of the details are working out beautifully. First off I opted to drill and tap plates that are welded to the legs that will act as clamps for both the rails and lower stretchers and I like how that is working. I considered drilling oversized holes and welding nuts instead of drilling and taping but I like the cleaner look. Also, because I put the clamping nuts for the top rail on the outside I wanted as low a profile as possible so I don't snag myself as I am working the jig. I put the clamping bolts on the outside for increased clearance of the router bit and I wanted as clean a space as possible for the slab with nothing to snag or bend. Another detail I added that I like how it turned out is the clamping pads, which are 2" x 1.5" x 1/8" and spaced 1/8" from the clamping plates and tack welded only at the bottom. The idea here is that because I am using thin wall tubing I didn't want the bolts to make dents in the tubing. The following photo is the clamping fixture for the lower stretchers and you can clearly see the clamping plates.











One of the details that I will be able to make work but might do differently is the inside stop for the rails. Because I have a 42" bar on my chainsaw and the maximum width of my slabs is 36" that is what this is designed for. To save room I opted to use two pieces of round rod as stops for the inside of the rail at each clamping location. I'll have a bit of tweaking an truing up to do due to warping during welding and because of this I wish I had used 1.5" angle iron which would have required that I make the top 3" wider than I did. (45" vs. 42") I initially rejected this method because I didn't want that 1.5" of angle extending out onto the top rail where a slap might end up sitting on it and either damaging the already planed surface or accidentally tilting a slab . I'm still up in the air a bit wheter this is something I would so differently and will have to wait until I use it to know for sure. here is a photo of the rail clamping fixture











I'm about half way on the sled, lots of little bits. I am screwing UHMW polyethylene on the bottom of the sled and also making a router sub plate out of UHMW. If that isn't something you're familiar with its that white plastic that looks like a cutting board and is often used as wear strips on jigs and fixtures. It is very similar to the HDPE poly used for cutting boards but has a lower coefficient of friction. Either would work but since I had to mail order it I figured I'd get the good stuff. I ordered from American Plastics Corp in Camarillo CA, very helpful and friendly people, plus they were $104 vs. McMaster -Carr's $181. I am also using the same plastic for a retaining strip for the router base. This may not be necessary but because of how narrow the sled is I have to drill and tap these holes before the metal tubing is welded so adding them afterwards would not be an option. Just a quick fabrication note- I am drilling all the holes in the plastic and then only drilling and tapping one hole. the plastic closes up a tiny bit after drilling so if the hole is drilled at 1/4" a 1/4" transfer punch is excessively tight. instead I drilled the plastic at 17/64 and put a point on the end of a 1/4 20 tap to use as a transfer punch. I then drill the holes in the steel and reattach the plastic with the one tapped hole and use it as a guide when tapping. This is actually working very well. For the counter sinks in the plastic I am fortunate enough to own a piloted single flute counter sink with the correct angle for machine screws. Here is a mock up with some of the parts screwed together.










Thought I'd add a little gratuitous tool ****. This is my late 50's Delta UniDrill. There is a column at the back of the table that an arm pivots on and the arm has a small column on the end that the head pivots on, the end result is a radial drill that can hit any point on its 24" x 24" table. Because the head and arm can be pivoted all the way off the table it makes a great work table. Oh yeah, the table and legs combined weigh 240lbs so nice and solid too.


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## IyaMan (Jun 22, 2016)

Looks like its gonna be an awesome build! I didn't even know router bits could cost that much!

One question though: I noticed a bit of a sketch pad in one photo but hardly a blueprint. So about how much of this have you actually planned on paper with specific calculations before beginning, and how much are you doing in your head and/or making up as it goes?

Oh, and thats a sweet drill


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## blades (Jun 22, 2016)

What little i do, I set it up on one of the Bridgeport mills or my old horizontal unit - both have auto feed on the long axis. As I am not doing 8ft long stuff ( mostly under 40") this works for me. Because the ram can be moved in and out ( bridgeport) besides the x& y axis I can get pretty wide within that 40" x travel ( mutiple passes of course) some stacked helical shell cutters on the horizontal unit can take care of slightly longer stuff with a wider cut in one pass. 
You could call these giant over arm routers if you like.


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## BlueRider (Jun 22, 2016)

IyaMan said:


> Looks like its gonna be an awesome build! I didn't even know router bits could cost that much!
> 
> One question though: I noticed a bit of a sketch pad in one photo but hardly a blueprint. So about how much of this have you actually planned on paper with specific calculations before beginning, and how much are you doing in your head and/or making up as it goes?
> 
> Oh, and thats a sweet drill



The pad of paper is just a cut list for the steel and some sizes and notes from ordering the plastic. I did do a couple of sketches mostly just so I could add up the different distances so I got the width of the sled right. I wanted the end of the sled to act as the stop for the router base and have it travel the maximum width and not have the router bit hit the steel rails or the 3/8" rods that hold the rails. No working drawings or blueprints, but that's also the way I build furniture.

There are even more expensive bits that the one I bought. At one shop I worked at we had a bit custom made and it cost $250, and that was 25 years ago.


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## BlueRider (Jun 23, 2016)

The spoilboard flattening bit I ordered came in the mail yesterday. Most fly cutter type bits, and even some straight two cutter carbide wood bits are not actually flat on the bottom and will leave a trail of circular marks as you feed across the material. The two cutters that sheer the bottom and are actually co-planar, meaning the bit is flat on the bottom. I can't wait it get this thing dirty.


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## blades (Jun 23, 2016)

Devil in the tooling, in comparison the base machine is cheap. That is similar to what I use - 4" shell mill with carbide inserts set up on a R8 shank to fit the bridgeport spindle. 1-2 deg off vertical no trailing edge swirls same set up for steel or alum when I need to thin a piece down a bit or just remove heavy mill scale- common bar stock isn't all that perfect as far as flat sides go.


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## BlueRider (Jul 1, 2016)

So the Binford Slabmaster 6100 is finally up and running. It took a bit if fiddling to get it set up the first time but wasn't too difficult to get dead flat. The 2x3" tubing that I used for my top rail is actually pretty straight, maybe not certified granite surface plate flat, but certainly dead flat by eye, and close enough for the work I will be doing. I started by clamping one lower stretcher and setting one top rail in p[lace and it was surprisingly stable at that point. I leveled the three legs using the one rail sitting in its place as a guide. Using the other top rail I set it on one diagonal and then the other to get a feel for the middle leg on the other side. I had to drop one end a bit and then re do the middle but it was pretty straight forward and easy to do using the top rail as a guide. After clamping all the rails and stretchers it was rock solid with no wiggle or wobble, or movement of any kind. I marked the floor and will number the legs so next time I set it up should go even faster. Only one last detail to go.


I had calculated the width of the sled based on the width of the cut of my chainsaw(maximum width of slabs I would need to flatten), the width of the top rails of my flattening jig, the router sub base, and the router bit I would be using. The design of the sled included a built in stop for the router but I wanted to wait until I could set everything up and double check everything before attaching the stops on the bottom of the sled that would prevent the sled from sliding too far and allowing the router to come in contact with the steel rails. I made some stops out of 1" square tubing with a strip of UHMW plastic screwed to one side and clamped these to the sled. I added 1/32" space and was pleased to discover that my rails were dead nut parallel and that with that small of a gap the sled travels the full length with no racking. I drilled and treaded the holes to attach the sled stops and it was ready for action.










The initial set up took the most time, just as with milling a log. I had thought about different ideas for leveling the slab and in the end opted for some wedges to get the warp evenly split and to stabilize the slab at the correct height to maximize the depth travel of the router bit. I then cut some blocks of wood and attached them to the underside of the slab using hot melt glue and positioned those blocks so I could clamp them to the frame. Once I maxed out the depth of cut I was able to draw a reference line on the blocks of wood and then unclamp and raise one end at a time. I think this is a very effective way to level and clamp the slab for the first cut and will make no changes going forward. here is a close up and a distance shot showing the blocks of wood and clamps.















Once I had flat areas where the cross bars of the frame were I decided to flip the slab over and work from the other side in case I didn't get things perfect and needed to take another pass at the first side. In the future I will completely flatten the first side before flipping it over as this was an un necessary step. to get the other side at a suitable height I ran some scrap boards through my planer and clamped them to the cross bars at one end. The weight of the slab and friction keep it from moving length wise and to keep it from moving width wise I hot glued some small blocks to the scrap board. to adjust the cutting height once I maxed out the depth of cut planed another scrap board and put it between the first board and the frame. 


All in all I am very happy with the results. I'm open to suggestions for ways of leveling and clamping slabs and then raising them up but I think the way I did it will likely be the fastest and most accurate. One change I have thought about is to switch from the 1/2" UHMW for a router sub base to a piece of 1/4" G10 with some UHMW tape applied for runners. that would get me another 1/4" depth of cut and I could do the same with the sled runners too for a total increase of 1/2", that might eliminate the need for raising the slab. I could also extend the router bit out a bit further but as big as it is I don't feel comfortable with less than 3/4" in the collet. Here is one more shot and the end of the day yesterday. I still need to take another 1/16" and then flip it over and finish up the show side.


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## rarefish383 (Jul 1, 2016)

NICE, Joe.


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## Jesse snowden (Jul 7, 2016)

So I do have a question for you my friend. Why did you go the extra mile as you did? I don't mean it sarcastically at all. 

I flatten slabs with scrap wood and they come out perfectly flat. Joint a couple 2x4's, clamp them to my flattened work top, and shims to balance out the twist. Once one side is done there is no need to shim the other side, just a jack plane to take off the fuzzies. no doubt your work station gets it all done and is smooth to use, but did you see a great need to make such a piece? Or just wanted a dedicated spot to do it instead of taking up another bench top? Great work with the welding either way, looks fantastic


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## kimosawboy (Jul 7, 2016)

I'am curious as to your answer to the above question as well.
Besides taking up a chunk of floor space, you are limited to your slab width??
I use the same approach of 2 sticks of wood and shims and I never have had a problem, my sled is good up to 48" but I can easily stretch it to whatever and when done I just hang the sled on the wall..


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## BlueRider (Jul 7, 2016)

I should probably start by saying that I had an immediate need to flatten a 33" x 10' slab of claro walnut. Other than that there were several reasons I built what I did and the way I did:

First off I have a very small shop and have no outdoor paved area to work on. My shop space is so small that there isn't room to set up for a 33" wide 10' long slab, other than in the same space as my table saw and extend from there into the open area of my shop. The saw wasn't wide enough to use as a surface to support a couple of 2x4's, nor was it long enough. That lead me to the idea of making something that could be repeatedly put together and taken apart for storage. 

I suppose I could have made what I did out of wood, but over time it would likely warp and move a bit. I've never had any 2x4's, even kiln dried ones, stored for several years and have them stay straight and true. That led me to think about using 2 x 6 metal studs, but as I thought about the other details I eventually settled on square and rectangular tubing. I have nearly 150 slabs, almost 90 of which are walnut and similar in size to the test slab I flattened. There is no way a wood jig would hold up the the wear and tear of flattening even half that many slabs without being rebuilt. 

Perhaps the best reason for making it out of metal is because I can. I have a TIG welder and a metal cold cut saw so in some ways it is just as fast for me to build in metal. The time consuming part of my build was the need for it to be bolt together and I could have simplified that part but I did it the way I did so I could easily assemble it by myself and easily change the length of the rails as well as substitute different height rails for thicker slabs.

Before starting my build I think I looked at every Youtube video and every photo and video on Instagram of any kind of slab flattening set up. One thing I noticed was that a lot of guys that do this for a living or at least as a money making gig have some sort of wood /metal mixture to their builds or all metal. That told me that others had also done a cost benefit analysis and come the the same conclusion as me. My goal was to make something that was simple to use as well as sturdy and maintenance free. In some ways my Granberg mill inspired at least the spirit of my build. It is amazingly simple, reasonable sturdy and maintenance free. And just like with your question about why not use wood, there are ways of building a milling jig out of wood blocks and all thread, and I have no doubt they work and meet the needs of those that use them, just as I'm sure your wood sled and 2x4 flattening jig meets your needs.


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## wombler (Jul 7, 2016)

BlueRider said:


> because I can



Best reason to do anything.


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## Jesse snowden (Jul 7, 2016)

Because I can is the only reason anyone needs. Haha awesome! I must have missed the part where it bolts together, that makes a lot more sense. Have you thought of using your welding experience to put together a mill? Or have you already done that?


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## BlueRider (Jul 8, 2016)

Jesse snowden said:


> .... Have you thought of using your welding experience to put together a mill? Or have you already done that?



At one point I considered building a bandmill or something like a Procut but I started milling so I would have wood to use not to sell and with the stockpile I have I'm concentrating my time on using up the wood I have rather than milling more. I still mill wood with my chainsaw but it has to be something special.


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## Calisdad (Jul 22, 2016)

Christmas in July ! Sanitary is the word that comes to mind.

So what kind of dogs do you have?


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## BlueRider (Jul 25, 2016)

Thanks. I have Borzoi. I've hunted with them in the past but with the two I have now I do mostly racing


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## Czech_Made (Jul 26, 2016)

BlueRider said:


> Thanks. I have Borzoi. I've hunted with them in the past but with the two I have now I do mostly racing



Ha, my wife dreams of Borzois, how do you like the breed?


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## BlueRider (Jul 26, 2016)

I've had borzoi for over 20 years, always at least 2 and for a short time as many as 5. They are a fantastic breed, very laid back and easy going. Even when owning several they are strongly bonded to their owners and very affectionate. They really don't require much room as long as they get regular walks and an occasional run. However they are a hunting breed and will chase anything that moves and for that reason they need a fenced yard. At one time I had a cat and he was very wise, when the dogs would run in the house he would turn around and ignore them and they would jump over him without touching a hair. if a stray cat jumps into the yard it is nearly always a fatal mistake. They are very intelligent, just not in the same way as a Lab. I had a male that I used to hunt with and he used to lunge at seemingly random bushes while hunting. It took me a while to realize he was lunging at bushes that on previous trips to that field had yielded jack rabbits.

These are the two I currently have. They just turned 3 and are both females from the same litter.


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## Czech_Made (Jul 27, 2016)

Thank you, BlueRider, beautiful dogs.

We had airedales, Great Pyrenees - she was an amazing houdini  Four dogs total for a while. Now only black lab. We have close to 4 acres in Virginia and airedales would kill anything they found on the property, coons, foxes, cats, rabbits. 

But wife got this borzoi vision and only the scarcity of the breed kept her from getting one so far. I am sure she will eventually get what she wants.


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## ML12 (Sep 10, 2019)

We built a more permanent sled setup over the weekend. Based on various internet photos, it used 1 sheet of 3/4" prefinished birch cabinet plywood. That made the sled, the rails and some misc. other pieces. The slab is held to the cross pieces by "dogs" similar to what a machinist uses on a mill table. I am planning on making a set of "cams" next to aid in holding the slabs. The sled can be adjusted up/down to accommodate different slab thicknesses. The router is the big 3-1/4HP portercable unit spinning a 1" bit.

We still need to add some dust collection and make some adjustments to optimize it. The reason it is so wide is that our maximum cut width on the mill is 55" so this can accommodate slabs that size. Took about 4 hours to crank out, but it is very nice and solid and works great so far.










The slab being flattened is 3ft x 3ft cedar for a friend's table.


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## goncalo alves (Sep 11, 2019)

why are the pictures showing up blurry for me?


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## ML12 (Sep 11, 2019)

goncalo alves said:


> why are the pictures showing up blurry for me?


Not sure, they're large files (5mB or so) so that might cause it?


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