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Dado's - This practice is UNSAFE.

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Anonymous

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Having purchased a Startrite table saw and proving that the blade is sharp by sticking the end of my finger in it, (don't ask,I still don't know why I did it neither) I was contemplating trying my dado set on it to see if the motor was powerful enough to drive it.My dado set is 30mm bore my startrite isn't.(It's 5/8ths) I have had some reduction rings made but as the blades and chippers are of different thicknesses they are not interchangable and combined with the narrow slot in the table the palaver was not worth the effort. I therefore needed a cheap dado set with the correct bore.Having noticed that you can use the two outer blades of the dado set together I wondered if you can use multiple blades instead of blades and chippers.Presumably they use chippers in order to keep the cost down.Having purchased 10 cheap new blades on e-bay I tried them out today.Seems to work o.k. Dado set for £12.50 anyone? The guy on e-bay has some more.

Mod note: Title edited for safety.
 
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Anonymous

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Use a router.

Whilst dado's are safe enough when used correctly, in a suitable saw and with due care, a stack of saw blades is DOWNRIGHT DANGEROUS
 

Jake

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Having purchased a Startrite table saw and proving that the blade is sharp by sticking the end of my finger in it...... followed by dado madness...

UK Workshop's first troll, surely?
 
A

Anonymous

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Why is a stack of blades any different to blades and chippers?If you can use the outside blades together then what is the difference?
As for the troll comment I will treat it with the contempt it deserves.
 

Jake

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Well, you couldn't have chosen a better topic if you were a troll, and you introduced a frankly pretty dumb idea with a light-hearted reference to an accident you'd already had on the same machine without adding the extra layer of danger. I think I gave you the benefit of the doubt, actually, by assuming that you weren't serious but were just seeking to provoke a reaction. The alternative interpretation is less flattering, to my mind.

The chippers are designed to clear the stock away, not to save money. Dados have their dangers, mostly to do with inadequate guarding, but that is with properly engineered dado blades, not just slinging a bunch of blades on because they fit and cost a quid each on ebay.
 
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Anonymous

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If chippers are there to clear waste why can you use two blades together? It does not seem to me to be any different using two,three, or more blades.
 

Newbie_Neil

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Harry

harry":1v9rkc0c said:
If chippers are there to clear waste why can you use two blades together? It does not seem to me to be any different using two,three, or more blades.
Why do you think that nobody else does what you are suggesting? The simple answer is that it is not safe. Please, for your own sake, stop.

Why don't you make a simple router jig and produce your dados safely? Have a look at this dado jig which can be made for a few pounds.
Just scroll down for Tony's dado jig.

Neil
 

jasonB

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harry":uglc2hvz said:
If chippers are there to clear waste why can you use two blades together? It does not seem to me to be any different using two,three, or more blades.
1. the saw blades will have a lot more inertia(sp) than two blades and chippers which will take a lot longer to stop and put a lot of load on the motor brake assuming its a new saw with brake.

2. trying to tighten ten large areas of metal together with the arbour nut may not be very easy, there will be a risk of it comming loose

3. Hope you have made a suitable guard to use with the dado as you won't be able to count your 10 blades if you carry-on at this rate.

Jason
 

Woodythepecker

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Jake, i suspect you meant well, but resulting to name calling isn't going to help. All it does is put the other person on the defensive, and when this happens they are not hearing the real message eg, "You are only trying to help"

Harry in all honesty, using the blades like you are is utter madness and asking for trouble.
Jake is right, the reason dado head cutters have got a bad name, is not because there are a number of blades bolted together, it is because you have to remove the blade guard to use them, and so you have no protection if anything goes wrong. Now put them on a radial arm saw and they become a little safer.

As others will tell you, i have just got over a stupid accident that could have so easily killed me, or if it had gone in further, taken one of my kidneys out. In the end i just received a load of stitches and was off work for a few weeks.

One thing it did do was to bring workshop safety to the forefront of my thinking, and now the way i look at things is, if i have two ways to complete a job, i will always take the safest option and not the quickest.

Harry we are not know all's. We just want fellow members to enjoy their hobby (or profession) safely. So come on and dump those blades, or use them one at a time.

Regards

Woody
 

Jake

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I was serious in thinking it might be a troll actually.

Apologies for any offence, if that isn't the case.
 

Aragorn

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A regular crosscut sawblade has teeth that alternate: pointing left and right of the blade slightly (some have a third pointing straight). If you stack two of these together there is the potential for the teeth to hit against each other if the blades were to rotate on the arbour.
Dado sets have teeth that point straight up only, so when the two outer blades are used (no chippers) there is no risk of the teeth colliding.

Harry - Check out the teeth on your stacked blades. If they were to rotate against each other on the arbour, would any of the teeth have contact? If no, then you are right - this is no different from a dado set. If yes, then ... well, they're your body parts!
 

Jake

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But it is not the same if you are stacking more than 2 and the amount of waste that has to be removed increases accordingly, that is when the chipper blades' function of removing waste quickly comes into play.
 
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Anonymous

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Well at least I've got you all thinking.Lets just clear a couple of points up.I have read all your replies and apart from the slightly abusive terms enjoyed your answers.The whole point of the question was to learn about a field of woodworking practised in the US but feared in the UK. I have not ventured into my experiment lightly and apologise if my light-hearted tone suggests otherwise. The obvious danger when using a single or multiple blades and chippers is the removal of the crown guard. An overhead guard could be constructed but I tend to think it would get moved out of the way.This then leaves the operator with only one real choice- extra vigilance.Various reasons have been put forward as to why the idea is unsound.Please bear in mind that this is what I wanted to ask in the first place.At no time have I said 'this is safe', I said 'what do you think?' The reasons put forward for this practice not being safe are as follows.
The strain on the spindle nut will be too great and the blades could slip.
I really cannot see a difference in torque needed between blades and blades and chippers.
The blades could slip and teeth could fly.
Good point and equally relevant to dados and chippers. They can collide.
Blades only will not allow clearance of waste.
This one worried me the most as it seemed the most plausable point so far.
Sorry to repeat myself but from an engineering standpoint if it is ok to use the two outside blades of the dado together then unless there is a fundamental alteration in the design of my other blades two, three, or more blades seem to act the same as one or two. I have not found any problem in short test pieces but I concede that it could happen in say a sheet of plywood.I have only tried a few times and believe me if I thought anything was coming loose I would not be doing it. As for the suggestion to use a radial arm saw I regard this machine as second to the spindle moulder in being dangerous. I have owned one for 20 years and tend to use it for cross cutting only and then very rarely since buying a chop saw.
Yet using dado's is accepted with this machine. If you want to live dangerously use one for ripping. You are a braver man than me.If the mods want to lock this topic I do understand as it is getting a little heated. Anyway I will continue to experiment (carefully) but I am willing to listen to alternative viewpoints as they appear.
 

Jake

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Like I said, apologies for believing you could be a troll. It is clear that you're not, just very brave.

In the history of this site, it is unlikely a troll could choose a better topic, apart from possibly the woodrat/leigh debate, and that made me more suspicious than I should have been! It was also a joke, in part, albeit not the most polite one. Anyway, apologies again.

I still think you're a bit nuts to mess around like this for the sake of a few tens of pounds!
 
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Anonymous

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I brick it every time i turn my new table saw on with the 1/8th blade in it.

I made a box joint jig today tho!!!! YAY!

I've been using one for about 4 days now...

With ALL this experience on a table saw that I have, I still dont get the troll ref.

:)
 

MikeW

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harry":2708cf3k said:
...snip snip...
Blades only will not allow clearance of waste.
This one worried me the most as it seemed the most plausable point so far.
Sorry to repeat myself but from an engineering standpoint if it is ok to use the two outside blades of the dado together then unless there is a fundamental alteration in the design of my other blades two, three, or more blades seem to act the same as one or two...
Ah harry, it's not heated, maybe spirited or passionate, definitely it began from different POVs as to whether the question was a genuine one. I took it from your having posted 30+ messages prior to the one in question that you were genuine.

From an engineering viewpoint, the wider the outer blades are spaced the greater amount of blade contact to the wood. This transfers more force from the blades (more teeth making contact at any given moment) to the wood and therefore increases chance of harm via kickback. The effect of a thinner, deeper cut (the chippers) does not apply as much force as the number of teeth engaged caused by using "regular" blades.

Also, blades made for general use are of lighter gauge in general with more flex.

That said, there is no significant increase of danger in using the two outer dado blade stacked. Danger increases as the width and depth of cut increases.

But then again, I'm a crazy american.
 

SlimShavings

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Guess this must be one of them scary "murican things". As an "murican" i use one almost every day. I would never stack several blades together. Blades, especially carbide blades have teeth that are wider than the body. even if you offset them you are putting them in a pinch. And as was stated before your in danger of having the teeth knockin on each other. Small bits of carbide slung at 3600 RPM can be lethal.

Dado is same if you approach it with one thing in mind. patience.
Your wood should be straight and square and the bigger or deeper the cut the slower you should go. About the biggest cut I ever take is 3/4 wide and 1/2 deep. and I make two passes. THe first pass may not clean out the dado completely. As the wood may ride up slightly as you pass over the dado blade. I use one pusblock and one hold down push block like you would use on a shaper or jointer.. Also a zero clearance insert
THere are different kind of dado sets also. Some have positive rake and some negative rake. I use a negative rake on the radial arm and positive rake on the table saw.
Once you become familiar with it . Its as safe as any other woodworking operation. Just be patient and go slow and it will work fine. in fact I have one table saw and one radial arm that are set up especially for those operations.
 

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This is actually an interesting thread: I have never cut dados, as the sets are, as far as I understand, effectively 'outlawed' under european/UK safety regs, and I just assumed there was good reason for it - and of course, as a result, our smaller 'hobby' saws are often not capable of mounting a set. If a groove is needed, it's out with the router.

That said, what is the specific danger with a dado set that is not present with a normal blade? I have just checked the HSE sawbench leaflet, and it doesn't detail the issue. In the spirit of a more complete understanding of what makes for danger and what doesn't, I'd like to learn why it is perceived as too dangerous 'this side of the pond'. My suspicion is that it's to do with the necessity of guard removal.

(Coversely, in answer to the original question, I just wouldn't do it, for 2 reasons: a) I'd be terrified of 'tooth arguments', and b) I like to use the right tool for a job - particularly when the tool's a 'man-muncher' like a TS.)
 

woodshavings

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The "official" dado blade for the Dewalt 720 Radial Saw comprises of just two blades with overlapping teeth. The width of cut is varied by changing the distance between the blades. The blade is expensive though, with two versions at about £230 each and only adust in the range 6 to 12 mm or 10 to 19.5mm.

I have a Freud Dado set ( with chippers) that I occasionally use on my 720. It works fine and fits within the guarding system. However, I only use the 720 for cross cut.
 

jasonB

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Shady, the main reasons are as you say the crown guard & riving knife will have to be removed thus leaving the blade ungaurded unless you have an overhead gaurd and riving knife that can be set below the top of the blade.

Secondly as all new saws have to be fitted with an electronic blade brake to stop the blade within 5 secs, the additional momentum of the dado will damage the brake and take longer to stop than the required time.

My saw only has a short arbour so I couldn't use a dado even if I wanted to, don't fancy one in my radial arm either. But I do have a 150mm Omas wobble saw that I use in the spindle moulder which works well.

Jason
 
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