Safe way to use a dado stack

[jimwillsher]

Hi all

First off...I know about the official HSE statements regarding dados in the UK. But I have one, and I need to use it.

I have a requirement to make a "comb" in the end of a piece of sarking. So about 8 or 9 long cuts, stretching about 20 CM up the length of sarking, with each cut being around 1CM wide. Think of a fork!

So, two questions around the dado:

1) Are there any safety implications with feeding the wood into the saw, then retracting it once I have reached the right length of cut? e.g. not feeding it right through
2) To avoid an angled top to the cut, am I okay to raise the blade as high as it will go, so that the cut will be as close to 90 degrees as it can be. Aside from the obvious spinning blades with no crown guard.

I'm approaching these questions from a kickback perspective. I'm aware that having 3 or 4 blades spinning at full lick with no guard brings a few risks.

Many thanks


Jim

 

[Noel]

Hi Jim.
Dado stacks not too popular around these parts, many use a router instead which makes sense in many cases.
I assume you haven't used a dado stack too often? Would suggest not going in at full height*, way too much work for the blades, especially if you are using a 2 wing set. A little bit at a time is better and if your arbour/blades aren't perpendicular to begin with then they will never be, I don't see why they shouldn't be if all is adjusted correctly and work piece is square..
As for retracting the work piece, best not do that, stop the saw first, then remove the wood. Depends on the the overall length of wood but if it's not pulled back cleanly and exactly the way it was fed in it indeed gets a little sketchy.

* You don't mention final depth/thickness of wood..

 

[jimwillsher]

Hi Noel

Many thanks for taking the time to reply, it's much appreciated.

You would be right When I say that I have one, it's been despatched but hasn't arrived yet So I have zero experience

Comments/advice noted, thank you. For the perpendicular bit, I may have explained poorly. I'm trying to make it so that the top of the cut (the point where I would retract the wood) has a "flat top". If I have the blades just beyond the top of the wood thickness then I'll end up with a very angled top to the cut. If that makes sense.


Jim

 

[Noel]

Hi Noel

Many thanks for taking the time to reply, it's much appreciated.

You would be right When I say that I have one, it's been despatched but hasn't arrived yet So I have zero experience

Comments/advice noted, thank you. For the perpendicular bit, I may have explained poorly. I'm trying to make it so that the top of the cut (the point where I would retract the wood) has a "flat top". If I have the blades just beyond the top of the wood thickness then I'll end up with a very angled top to the cut. If that makes sense.


Jim

Ah, ok. You want a vertical end to the 10mm wide cut, where you stop the cut? How thick is the timber?

 

[jimwillsher]

That's it

It's about 18mm thick.

 

[Joshjosh]

Hi Jim, I regularly use a dado stack on my table saw and would feel comfortable backing the timber out of a cut while keeping pressure against the fence, but if I didn't either a router table or router with a fence could achieve the same operation. Is raising the blade to maximum necessary? As you'll need to square off the cuts with a chisel anyway.
Hope it goes well
Josh

 

[jimwillsher]

Thanks Josh. Squaring off isn't critical, it was just the icing on the cake. It's a fair point, thank you.

 

[Noel]

Firstly, be very, very careful, you know all the risks involved. Minimise those risks, respect the tool and keep your focus on the job.

I’ve used dado stacks for a long time. I’ve a 4 wing set, 3 hp saw so please adjust things to suit your set, saw and learning curve.
First thing is experiment/test with scrap, which I’m sure you planned to do. 18 mm is ok in one go in most cases. Raising blade to max height maybe not a great idea as a lot of exposed blade even with an 8” set. As said above, chisel out. You’ll have to anyway to get a square finish no matter what height.
Lastly, once first finger is cut try and not put any pressure towards the fence in the cut area.

 

[jimwillsher]

Thanks Noel, great advice. And that got me thinking. I would probably have started at the wrong end first!

I have fence to the right of the blade, and would have cut the rightmost cut first, then moved the fence. But it sounds like I should do the leftmost cut first, so that the cut part is to the left of the blade, rather than between blade and fence. Correct?


Jim

 

[Inspector]

I live in the land of dados and do not recommend you back out of a dado cut or any other cut while the saw is running. If the boards are long enough that you are far from the blade cutting at max depth will give you the steepest angle to the end of the cut but if the cut has you ending with any part of you over the table, DON'T. Square them up with a handsaw and chisel instead.

If you want a nice even line of cuts, clamp a block on the fence to limit the distance of the cut.

Just curious. What is the comb for? And how many do you need to do?

Pete

 

[Noel]

Thanks Noel, great advice. And that got me thinking. I would probably have started at the wrong end first!

I have fence to the right of the blade, and would have cut the rightmost cut first, then moved the fence. But it sounds like I should do the leftmost cut first, so that the cut part is to the left of the blade, rather than between blade and fence. Correct?


Jim

Exactly. There’ll be a lot less across the grain strength in the timber once it starts getting such a wide cut resulting in inconsistent fingers/gaps and possibly safety issues.

 

[jimwillsher]

Just curious. What is the comb for? And how many do you need to do?

Pete

It's for a local wildlife charity. They have traps for squirrels, and once trapped there is a need to pen the squirrel towards one end of the cage so that it has less space during handling. So the comb has to fit through the wire mesh. We need 100 or so.

 

[HamsterJam]

Can you achieve the same result by gluing long dowels into a backing strip?
Might cost a little more but will be a safer manufacturing process.

 

[jimwillsher]

Lateral thinking I'm not sure, let me check with the charity. Thanks

 

[Bob Chapman]

Sorry to reveal my ignorance, but what is a 'dado stack'?

 

[HamsterJam]

Sorry to reveal my ignorance, but what is a 'dado stack'?

In simple terms it is a stack of saw blades used on a table saw to cut a wide groove or slot. In practice, special Blades are used.
They are popular in the US but not the UK as saw makers struggle to meet HSE guidelines, especially regarding the fitment of appropriate guards and rundown time.

 

[Inspector]

It's for a local wildlife charity. They have traps for squirrels, and once trapped there is a need to pen the squirrel towards one end of the cage so that it has less space during handling. So the comb has to fit through the wire mesh. We need 100 or so.

Okay I understand. In that case, being that they are going to be relatively short, I suggest you work with longer boards, say 2 meters, and cut one end and then the other, repeating your way through 25 boards. Then move your fence and do the operation again, repeating until all the cuts at each end are made and the comb is complete. Then crosscut what you need from the ends of the boards. Now you repeat the process again with the remaining lengths and you have the 100 combs. That keeps you and your hands back from the blades. Now if and only if you are using longer boards you don't need to turn off the saw at the end of each cut. When the board reaches the fence stop you push down on the end (without drawing back) you are holding and the board will pivot up off the saw blade from the edge of the table by your side. Even if it somehow were to catch, your hands are no where near the blade and the board is to your right so it won't gut you. Pulling the wood back from the blade is more dangerous than pivoting it up and off. I have used the method for another type of dado cutting operation without a problem. Try doing a dry run with the saw off and the blade below the table to understand what will happen. If you get the heebie jeebies or don't feel right about it don't do it. Turn the saw off instead. The left over can be used for another project down the road.

So when you catch all the squirrels, what do you do with them? Take them somewhere to be released to become someone else problem or do they go to a zoo for some kind of predators lunch? We had a fox den and were concerned about our small dogs so we called the Conservation office and they said they would only come and kill them because if they took them somewhere else they would be a problem for the next guy. We left them to raise four kits and then they left on their own.

Pete

 

[Bob Chapman]

Thanks H-J, I understand now.

 

[Droogs]

Hopefull they go into squabbit pie. it is illeagal to trap reds in scotland so it must be the pesky disease ridden foreigners they are getting rid of.

 

[jimwillsher]

it is indeed. It's a project run by Scottish Wildlife Trust. Not only is it illegal to trap a red, but it's also illegal to release a grey. Even vets and animals rescues would be breaking the law if they released a grey. So yes, the ultimate objective is to catch the greys and then deal with them accordingly. The comb allows the trapper to "shrink" a long trap into a much shorter one by hemming the squibble at one end, therefor simplifying the next part of the process.

Some good tips above, thank you. I just need to wait for my throat plate to arrive, it's stuck in the Brexit customs saga.....