Is this a safe table saw operation?

[Zach England]

I was talking to someone I work with who also does woodworking about how I can flatten a large end-grain top and he suggested, instead of the mess of the belt sander or the hard work of the hand planing, that I attach a jointed board to each side and run it top-down over the dade set, moving the fence the width of the dado with each pass. Does that make sense? Sort of like the method people have used with the router to flatten bench tops, but upside down (and on a table saw).

I do not see any reason it would be inherently unsafe if done properly, but something about it makes me hesitant.

Thanks.

[Ben Hatcher]

This seems fine to me. You may want to check to see that your dado set makes a flat bottom. My freud set puts tiny scores on the outside edges that are just slightly deeper than the rest of the dado.

[Caleb Larru]

I was talking to someone I work with who also does woodworking about how I can flatten a large end-grain top and he suggested, instead of the mess of the belt sander or the hard work of the hand planing, that I attach a jointed board to each side and run it top-down over the dade set, moving the fence the width of the dado with each pass. Does that make sense? Sort of like the method people have used with the router to flatten bench tops, but upside down (and on a table saw).

I do not see any reason it would be inherently unsafe if done properly, but something about it makes me hesitant.

Thanks.

Depends on how much you need to remove but it sounds like more work to me than hand planning.

[Richard Dragin]

If there is any flex in the board it will end up cupped. Why not the router and rails method?

[Myk Rian]

+1 on the router with rails.

[Zach England]

Just to clarify, it is little pieces glued up to make something like an end-grain cutting board. It is about two inches thick and VERY heavy. I need to remove maybe a 1/16 of an inch off of some of the individual blocks. There's no flex--it's extremely stiff. Total size is 24x28 inches. I was going to just joint two 30 inch sections of 2x4 and attach the work piece so that I can set the dado stack at about 1/4 inch above the saw top and have it barely skim the lowest point of the workpiece. With a dado stack slightly wider than 3/4 that should take 30-40 passes.

I started doing it with a bevel-up smoothing plane, and was surprised at how well it worked, but I can still take only very light cuts and it takes the edge off the veritas a2 steel very quickly.

I was hoping to avoid doing the router method because I don't want to bother building the sled thingy.

[Rob Woodman]

The problem I see with the first system is how do you machine both ends of the project stock? The bearers will either get in the way or the fixing method will leave holes in the sides of the project.

Trying to short cut methodology can often create greater time consuming issues. As I found out doing this one, went back to using the 1/2" router bit over the 1" one using the router sled method.
http://lh6.ggpht.com/_4Prh-kD7KMY/SvBJvFH9HzI/AAAAAAAAAC8/OLHH6Lr62Wc/Euc_Top2.JPG

Eucalyptus Burr 3' x 3' 7"

Rob.

[Peter Aeschliman]

To address your safety question (and not addressing whether this is the best way to solve your problem) if you do this, just make sure you are careful about the exposed blade at the end of each pass. don't wear any lose clothing that could get caught up as you lean forward to push the workpiece across the blade. I guess this concept is no different than any other dado or rabbet cut.

Dado blades won't cut your fingers off- they'll mince them to shreds.

[Rob Woodman]

Dado blades won't cut your fingers off- they'll mince them to shreds.

This is like saying..."Worse things happen at sea" to a boat builder undertaking the maiden voyage! But, oh! so true!
Also Dado blades are not allowed on UK table saws but can be used on radial arm saws..... now that may be an alternative for Zach!

[Richard Dragin]

......
Also Dado blades are not allowed on UK table saws but can be used on radial arm saws....

Never knew that, could you elaborate?

[James Carmichael]

+1 on the router/rails. Or use it as an excuse to treat yourself to a nice bevel-up jack plane.

I agree it's not significantly more dangerous than dadoing a panel on a TS, but your workpiece is big enough to present some feed challenges. The sleds you attach to the workpiece would have to ride on an outfeed table a during each cut, and, if you have a contractor saw, on the table extentsions as well. Very unlikely that all of those surfaces plus the TS top will be pefectly co-planar to each other.

If only there was a GSS that could swing a dado. Hmmm???

[Lee Schierer]

While the process you are suggesting may work, it seems to be marginal at best safety wise. Those alarm bells you heard that made you ask the question really do mean something.

Let's say you put rails on the sides of your piece and get the blade height right so you don't get kick back. How does the saw blade know when to stop cutting as you move from side to side so you don't cut into the side rails. Sure you can clamp guides to the table, but there is more work for you to do. Also cutting blind with the proposed set up will surely result in skipped areas that have to be redone and a fairly rough surface too.

I'd look for another way, like the router and sled method, where you can see what you are doing.

[Cody Colston]

There is nothing unsafe about the operation you are suggesting. If you use a full 13/16" dado stack and move the fence 3/4" at a time, you should be able to walk across the piece pretty quickly. I hope you have good dust collection.

Have you ever seen the modern method used to shape the sides of a Bombe' chest? It's basically done the way you are suggesting, except that there are no rails and a lot more than 1/16" is removed.

There might be more cleanup left using the dado blade vs a router on rails. It depends on the quality of the dado stack. Removing only 1/16" isn't a power issue with either method.

[Zach England]

Never knew that, could you elaborate?


I believe it is an EU regulation.

[Jeff Bratt]

Also Dado blades are not allowed on UK table saws ...


Never knew that, could you elaborate?

My understanding about this - when powering down, EU table saws are required to have a brake that stops the blade rotation in 5 or 10 seconds. If a dado stack is mounted, this braking action will loosen the arbor nut and allow the dado blades to come loose (and spin on the arbor). Also, blades larger than 10" diameter have little pins in the arbor - and corresponding holes in the saw blades - to prevent the same sort of thing from happening with large blades. In addition, EU regulators take the view that a dado operation in a table saw does not allow the blade to be visible to the operator - and that this is also less safe.

[Peter Quinn]

Safety? I suppose it depends on how much blade is in play and how well guided your stock is by those rails. I suppose you could glue them on and rip them off later. But my intuition is that is a fairly poor idea unless the board is very warped and it is your only viable option at this point. I suspect you will spend more time cleaning up witness lines and marks left by the dado stack than the process could possibly save you. Yup, back to the smooth planes and belt sander.

I like the router rails method, or a drum/wide belt sander if you have access, though I guess you wouldn't be considering the dado if you did?

Have you considered grinding a knife to match the curve of the board? Like a giant single blade mezzeluna?

[Rob Woodman]

To clarify my earlier post.
The ban on using dado heads/blades in table saws came about when the woodworking machines regulations stated that table saws had to be guarded and fitted with a riving knife.
As far as I know they are not banned by the EU, I had a Kity table saw and could have gotten a dado head for it from France just a few years ago. The WW Regs changed back in the 1970's. On my next trip I will have a look in Leroy Merlin's a french Home Depot type place.

Of course as with many UK regs this all only applies to commercial woodworking companies that are not one man owner and operator outfits.
All regs are enforced by The Health & Safety Executive, who employ people who have not a clue on how to make anything other than paperwork and act like over zealous parking wardens, well all those I've met anyway. :D
Rob.

[Dan West02]

Trying to short cut methodology can often create greater time consuming issues. As I found out doing this one, went back to using the 1/2" router bit over the 1" one using the router sled method.

Rob.

Could you expand on your reason for the "went back to the using the 1/2" router bit over the 1" one using the router sled method" statement?

I agree with the router sled method, but don't understand wanting to make more passes rather than fewer. I have done both and get about the same surface type either way and then start sanding. What am I missing?

[tim rowledge]

Leaving aside safety issues for a moment (personally I think it would well outside my comfort zone but they're your fingers), what about the quality of cut you're likely to get from a dado set? All the dado blades I've seen have outer blades that cut a bit deeper than the mid-blades, sometimes quite a bit deeper. Unless your dado set does a virtually perfectly flat cut I'd find another solution. By and large I'd go for the router on rails approach or even look around for a local commercial shop with a big belt/drum sander.

[Glen Butler]

If there is any flex in the board it will end up cupped. Why not the router and rails method?


Explain this. I have a glue-lam beam that was leftover from a job site. Made glue up for a workbench a sinch but as the beam continued drying it twisted slightly and I want to make it flat again. The beam is 22" deep. I tried the belt sander and straight edges but realized it was bad enough and big enough the belt sander was a no go.

[Harold Burrell]

Why not the router and rails method?

Forgive me, but what are you talking about???

[John Coloccia]

I have to say that this seems perfectly safe to me. It's no different than cutting a rabbet. I would just do it with handplanes, though.

[John Coloccia]

Forgive me, but what are you talking about???

You just make some rails with some scrap wood. The router slides straight along the rails (presumably flat to some table). The piece slides underneath and the router goes back and forth, thereby flattening the top.

[Zach England]

For the curious:

I weighed everyone's thoughtful input and decided to go ahead and try this. It was quick and easy and gave a surprisingly good finish. However, if my piece had been any larger it would have posed some serious feed challenges (as someone mentioned) because the space between the blade and the left-hand edge of the saw would be smaller than half the width of the workpiece. I actually had not considered this when I started, so fortunately it just fit. Obviously I had to do the operation over half of the piece, then rotate it 180 degrees and begin moving the fence the other way.


Thanks all.

[Zach England]

I should add that I felt like it was as safe as working with a dade stack can be. I will also add that if your table saw dust collection like mine and not very good that this gets a bit messy since the cut is entirely above the top of the saw. It is still a lot less messy than a belt sander.