Dado blade for table saw.

[conny]

I have an Ozito table mounted circular saw, (from B&Q and I know not exactly a top brand but serves most of my purposes), and I have been looking at finger joints.
On the YT video they talk about using dado blades, which appear to be several stackable blades.
Can you use these on most table saws or would I need a 'better quality' table saw to enable me to use them?
Can you buy a single blade which is, say, 1/4" kerf as opposed to the standard size kerf blade?

 

[Munroast]

Think they are pretty much frowned upon by health ans safety here in the UK (believe they have a reputation for removing peoples fingers ?) . Very popular in the USA, hence if you search ebay you can only import them

Totally by chance our table saw is the only type sold in the UK where the dado blades are available (an axminster) and will fit onto the saw. But I couldn't justify the £250+ cost of the dado stack.

I would still quite like to have one despite there reputation, don't really see why they are that dangerous myself. Have been cutting rabbet and lap joints for years on the table saw. Surely a dao stack would make it quicker and with less passes safer?

 

[Deleted member 174758]

The danger comes from the difficulty in adequately guarding them adequately. They tend to be used by amateur woodworkers in the USA (not so much by pros) - the same sort of people who think that crosscut sled on a table saw is safer and better than using s mitre saw (which says it all - try cutting a 16ft long piece of skirting that way and see where it gets you). Ignorance is bliss!

The argument that "I've done it this way for years, so it must be safe" really doesn't hold water in the face of the laws of physics

You can get 6 and 8mm solid groovers for use on table saws, they are derived from the limiter blocks designed for spindle moulders and are much safer than stacked saw blades because if you do contact them with, say, a hand, they tend to throw you outwards, not drag you in like a rotating saw blade will. Scheppach, Hamer and Felder all sell this type of tooling for their saws

An alternative approach to using a saw is to use a finger joint jig on a router table where it is relatively easy to find 6mm, 8mm, etc cutters

 

[Munroast]

What is the mechanics of how the injury occurs in using a tale saw to cut rabbets etc.

I get the mechanics around normal cutting along the fence, the wood gets trapped or nips the blade, kickback is lighting fast and fingers could get thrown into blade, or the bit of timber may fly back and knock your teeth out. But running a bit of wood over the blade to form a grove whilst pushing it through with the mitre fence with my fingers well away from the blade - where does it all go wrong ? I do genuinely want to know where the danger would come from, I don't want injured, but equally I don't want to stop doing something I have done for many years, just because says its dangerous.

 

[Deleted member 174758]

The danger comes quite simply because of the lack of guarding in most of the (American) examples I've seen.

Without getting into the mechanics of kickback, if a kickback does occur the material is often thrown bodily upwards and ejected rearwards towards the operator at in the region of 80 to 100mph. Or too fast tobe snle to predict and react. When using a table saw there is a tendency for some novices (and untrained users, like our apprentices) to put their hands too near to the saw blade or even run a hand past the blade, both the result of not understanding the need to keep the hands away and maintsin a stable stance (which you won't have if you are leaning over the saw tabke, or pushing very hard). Keeping hand at least 16in/400mm away from thr blade is simple enough if properly designed push sticks are made up (from scrap softwood skirting, plywood, etc). The next thing novices often do wrong is to stand directly behind the blade - you should never stand in the "line of fire", but rather slightly to one side. Anyway, if a kickback occurs it is easy for the user to become unbalanced, and if pushing the material the tendency is to fall forwards in tne direction they are pushing. In those circumstances most people will attempt to put a hand or hsnds out to arrest the fall - and if the blade is unguarded, guess where the hand or hand can go. So a crown guard mitigates the risk by giving both a visual indication of where the blade is and providing some additonal protection.

I have seen people write that they have never had a kickback. Well good for them. I've been in the trade approaching 5 decades (with no injuries from any table saw operation) and I've probably had a hundred or more kickbacks, often caused by things like hidden defects such as thunder shakes, live knots, resin pockets, glue pockets (in plywood), calcite inclusions, case hardening (badly kilned timber), etc. So it happens. The thing is to set the saw up properly with adequate guarding and position yourself correctly. I think that is called risk mitigation

Edit: Two asides. I am not just repeating a mantra about danger. In addition to being a trained joiner I am a trained wood machinist, so I do have a clue, and a long time ago I did work somewhere we used dado heads for a few jobs (not many, because there were often better and safer ways of achieving the same end)

Secondly, many people using dado heads aren't using them to produce housings (i.e dado rail grooves) across the middle of material, but rather to work edge rebates, in which case a guard could be simply made up by attaching a relatively small piece of timber, horizontally, to the fence above the blade. A moronically simple solution, wouldn't you say?

 

[big-all]

An alternative approach to using a saw is to use a finger joint jig on a router table where it is relatively easy to find 6mm, 8mm, etc cutters

sorry jxk this comment made me laugh
comments about loosing fingers earlier in the post and now turning surgeon by making make a "finger joint"
yes i know childish and immature but we have to find humour in times off adversity where ever we can

 

[Munroast]

The danger comes quite simply because of the lack of guarding in most of the (American) examples I've seen.

Without getting into the mechanics of kickback, if a kickback does occur the material is often thrown bodily upwards and ejected rearwards towards the operator at in the region of 80 to 100mph. Or too fast tobe snle to predict and react. When using a table saw there is a tendency for some novices (and untrained users, like our apprentices) to put their hands too near to the saw blade or even run a hand past the blade, both the result of not understanding the need to keep the hands away and maintsin a stable stance (which you won't have if you are leaning over the saw tabke, or pushing very hard). Keeping hand at least 16in/400mm away from thr blade is simple enough if properly designed push sticks are made up (from scrap softwood skirting, plywood, etc). The next thing novices often do wrong is to stand directly behind the blade - you should never stand in the "line of fire", but rather slightly to one side. Anyway, if a kickback occurs it is easy for the user to become unbalanced, and if pushing the material the tendency is to fall forwards in tne direction they are pushing. In those circumstances most people will attempt to put a hand or hsnds out to arrest the fall - and if the blade is unguarded, guess where the hand or hand can go. So a crown guard mitigates the risk by giving both a visual indication of where the blade is and providing some additonal protection.

I have seen people write that they have never had a kickback. Well good for them. I've been in the trade approaching 5 decades (with no injuries from any table saw operation) and I've probably had a hundred or more kickbacks, often caused by things like hidden defects such as thunder shakes, live knots, resin pockets, glue pockets (in plywood), calcite inclusions, case hardening (badly kilned timber), etc. So it happens. The thing is to set the saw up properly with adequate guarding and position yourself correctly. I think that is called risk mitigation

Edit: Two asides. I am not just repeating a mantra about danger. In addition to being a trained joiner I am a trained wood machinist, so I do have a clue, and a long time ago I did work somewhere we used dado heads for a few jobs (not many, because there were often better and safer ways of achieving the same end)

Secondly, many people using dado heads aren't using them to produce housings (i.e dado rail grooves) across the middle of material, but rather to work edge rebates, in which case a guard could be simply made up by attaching a relatively small piece of timber, horizontally, to the fence above the blade. A moronically simple solution, wouldn't you say?

none of that seems to address using mitre fences, and with your 16" rule I take it you would rule out such basic operations. Do you also rule out sleds?

 

[Diver Fred]

There is one item that most people have not considered - the power of the saw. A 'Dado' blade needs more grunt to be effective. If look the more powerful saws have thicker as well as larger diameter blades.I very much doubt the Ozito saw you have could have the power to drive a wide blade.
My family workshop has a 6HP table saw - when my father used the 'dado' cutter for cutting wide groves even that saw would struggle in hardwood. 'Cause of that we stopped using the blade and used a router instead (making several passes).

To be honest you will better off cutting finger joints on a Dovetail guide with a straight 1/2 cutter.

 

[Chunkytfg]

Think they are pretty much frowned upon by health ans safety here in the UK (believe they have a reputation for removing peoples fingers ?) . Very popular in the USA, hence if you search ebay you can only import them

Totally by chance our table saw is the only type sold in the UK where the dado blades are available (an axminster) and will fit onto the saw. But I couldn't justify the £250+ cost of the dado stack.

I would still quite like to have one despite there reputation, don't really see why they are that dangerous myself. Have been cutting rabbet and lap joints for years on the table saw. Surely a dao stack would make it quicker and with less passes safer?

Thats not actually true. My Laguna Fusion 3 table saw will take a Dado stack.

the issue with table saws accepting dado stacks is that the smaller saws use a bolt to hold the blade in place over an Arbor with nut, or the Arbor itself is too short to accomodate the width of the Dado stack.


To the OP. The easiest way of doing it is to get a blade with a flat top grind and then just cut either ends of the groove/dado youre after and then just systematically remove the material between those cuts.

 

[Chunkytfg]

There is one item that most people have not considered - the power of the saw. A 'Dado' blade needs more grunt to be effective. If look the more powerful saws have thicker as well as larger diameter blades.I very much doubt the Ozito saw you have could have the power to drive a wide blade.
My family workshop has a 6HP table saw - when my father used the 'dado' cutter for cutting wide groves even that saw would struggle in hardwood. 'Cause of that we stopped using the blade and used a router instead (making several passes).

To be honest you will better off cutting finger joints on a Dovetail guide with a straight 1/2 cutter.

I use an 8'' dado stack on my 10'' saw to help with the power issue.

 

[conny]

Thanks for all the replies guys. Safety is always my priority, especially with machinery, so I think I will be going down the router route.
I want to MAKE finger joints, not REMOVE them!

 

[Deleted member 174758]

none of that seems to address using mitre fences, and with your 16" rule I take it you would rule out such basic operations. Do you also rule out sleds?

Yes. Mitre fences on table saws are often woefully inadequate, even on most medium to heavy duty stuff like Wadkins or Startrites - a radial arm saw (many of which which can take a dado set) or a sliding compound mitre saw (many of which permit trench cutting) are both more accurate, safer and easier to use than a table saw with either a mitre fence or a sled (consider trying to cut a bevel or mitre on the end of an 12ft length of skirting as an illustration of this point) - and take a lot less space as well. In terms of sheet materials like plywood even a DIY plunge saw will run rings around most table saws in speed of use safety and again take less space. The only table saw which will be more accurate is the larger sliding carraige type saw used for sizing sheet materials but even hslf size saws like the Wadkin SP130 (see below) have a large footprint

IMHO for most purposes, therefore, there are better alternatives to the sled or mitre fence on a table saw. I feel this (almost) obsession with table saws as a primary need comes from the USA where it is driven by amateur woodworkers and salesmen. In reality a joiner would probably buy machines in something like the following order when setting up a shop:

1. Portable circular (rip) saw
2. Cross cut (mitre) saw
3. Planer/thicknesser
4. Plunge saw and rails
5. Band saw
6. Table saw

A table saw therefore isn't a must have unless you are doing a lot of ripping down of heavy solid stock

BTW, not my 16in rule - it is the recommended safety factor from the City & Guilds training, in literature from the Institute of Wood Machining (IWM) and the HSE.

 

[Deleted member 174758]

Thats not actually true. My Laguna Fusion 3 table saw will take a Dado stack.

Did you know that if your table saw is capable of taking a stack of greater thickness than 16mm it is breaching the regulations?

The issue with table saws accepting dado stacks is that the smaller saws use a bolt to hold the blade in place over an Arbor with nut, or the Arbor itself is too short to accomodate the width of the Dado stack.

Isn't the legal requirement of all new saws coming to a stop within 10 seconds if hitting the stop button as big an issue? I wonder if your saw complies? In order to secure a dado set adequately to withstand that level of braking you normally need to have a keyed arbor (and use something like a Woodruf key in it to secure the cutter set) or use a secondary locking nut on the arbor. On radial arm saws the requirements are different - in the case of those the blade needs to be closely guarded, return automatically to a home position behind the back fence if the handle is released and have a guarded home position. All really easy to achieve, although that said a RAS is really only suitable for cutting trenches such as shelf housings

One thing nobody ever seems to mention about using dado stacks is how long it takes and how much messing about it can be to set (or reset) the trench width accurately. If you constantly swapping from 6mm to 12mm to 18mm and back a stacked dado head can be a time-consuming PIA to use

 

[Chunkytfg]

Did you know that if your table saw is capable of taking a stack of greater thickness than 16mm it is breaching the regulations?

Nope I didnt know that. I have no idea if mine will exceed that as it is not mentioned in the literature for the Saw I have although google says it'll take up to 3/4'' however it goes on to talk about the need to remove the crown guard to accept the Dado stack and is therefore not acceptable in the workplace. I would assume the disclaimer is their way of saying, it'll technically take one but we know youre not allowed too.

Isn't the legal requirement of all new saws coming to a stop within 10 seconds if hitting the stop button as big an issue? I wonder if your saw complies? In order to secure a dado set adequately to withstand that level of braking you normally need to have a keyed arbor (and use something like a Woodruf key in it to secure the cutter set) or use a secondary locking nut on the arbor. On radial arm saws the requirements are different - in the case of those the blade needs to be closely guarded, return automatically to a home position behind the back fence if the handle is released and have a guarded home position. All really easy to achieve, although that said a RAS is really only suitable for cutting trenches such as shelf housings

The arbor isnt keyed with a woodruff style key but it does have flats on it which accept a matching outer plate the nut bolts down onto increasing the grip on the blade.

It does have a braked stop though so although I've never timed it, it does stop fairly sharpishly.

My Dad used to have a RAS and too be honest it scared the crap out of me! Way too much exposed spinning blade imo! Even with a 3/4'' wide dado in a table saw you're really not seeing a lot of the blade as it'll barely be poking out the table top. With a RAS its just always all there to see regardless of how wide it is

One thing nobody ever seems to mention about using dado stacks is how long it takes and how much messing about it can be to set (or reset) the trench width accurately. If you constantly swapping from 6mm to 12mm to 18mm and back a stacked dado head can be a time-consuming PIA to use

Oh I completely agree which is why I very rarely use it. Today in fact I have to cut 2 dados for a set of built in wardrobes I'm building and Its far simpler to just reach for my cordless trim router and a straight edge than to set up the Dado for 2 cuts and then again have to swap it all back again.

 

[Deleted member 174758]

I would assume the disclaimer is their way of saying, it'll technically take one but we know youre not allowed too.

It isn't a matter of "technical", it's a matter of legality - and in the event of an accident, insurance, etc. But what the heck. I am well aware that the law as it applies to professional woodworkers as regards usage, safety, etc does not apply to home woodworkers, but if you consider it for a moment, those standards we have to work to are really only good practice. And good practice reduces accidents

My Dad used to have a RAS and too be honest it scared the crap out of me! Way too much exposed spinning blade imo!

In that case the guard on the saw was old/non-compliant. DW radial arm saws as long ago as the late 1970s came with guards which covered the blade sufficiently - so did Wadkin machines. The current guarding regs came into force for us in 1992(?) which makes me wonder how old your dad's machine is. Even so, there are some significant differences between a dado head on a RAS and on a table saw - for starters on a RAS the work is automatically pulled towards the rear fence by the direction of cut of the saw (same as on a sliding compound mitre saw), secondly most users would have their right hand firm on the saw's handle, well away from the blade, thirdly the left hand should be positioned well to the left of the blade (and if the blade guide is set up correctly with a modern guard it is physically impossible to have contact between hand and blade) and finally when using a RAS to make a crosscut it is all but impossible to become unbalanced when making a cut, unlike on a table saw. This is what a modern, compliant RAS looks like, as delivered (note the size of the guard):

Even with a 3/4'' wide dado in a table saw you're really not seeing a lot of the blade as it'll barely be poking out the table top. With a RAS its just always all there to see regardless of how wide it is,

Your estimation of correct use of a radial arm saw obviously comes from seeing your dad using one incorrectly and with illegal/incomplete guards (based on your previous comments). And as I said, propery set up the blades should not be visible on a table saw if the saw is properly configured, This is what the guard set up should look like for even a basic RAS:



Note the nose piece. The side guards are sprung and slide along the top of the material, the nose piece at the front is adjusted to within about 2 or 3mm of the surface of the material so you aren't going to get your fingers beneath that. Even my old dewalt DW125 from 40 years ago had a similar arrangement. And just to show that even old saws can be adapted to the current standards, here is an old Wadkin BRA14 with guards which meet the current standards:

Today in fact I have to cut 2 dados for a set of built in wardrobes I'm building and Its far simpler to just reach for my cordless trim router and a straight edge than to set up the Dado for 2 cuts and then again have to swap it all back again.

Just to clarify, did you cut rebates or housings? The heads we were discussing might be called dado heads (which originates, allegedly, from the cross grain grooves cut in dado screen panels to hold dado rails), but the terminology here is somewhat more concise than American amateur woodworkers use. I'd hazard a guess that you cut two housings (cross grain grooves)