Stacking TCT saw blades

[Chubber]

I am not asking people to approve/condemn this idea, my Dewalt 7845 saw does not have an arbor long enough to support a dado stack but were I to mount two 18 tooth flat top ground blades with the teeth 'nested' with a thin card washer between, I could in theory cut a near 5mm slot in one pass, solely in a box joint cutting arrangement.

I shall continue to use a router for housing joints.

Have I missed something, indeed has anyone here tried it?

 

[ChaiLatte]

In the same spirit in which you ask the question, you might do well to look at the specifics of what bona fide dado stacks do.

In particular, I do not think they use cardboard, but use a metal washer/shim of a specific thickness. The (minimum) thickness of that shim would be related to how much a tooth overhangs the plate of the blade.

I would guess (and this is what you would have to verify) that it would be undesirable to have the tooth of one blade exactly touching the plate of the other blade. To me, there needs to be a small gap to account for any static wobble in either blade as well as any side-to-side vibration when in use.

 

[rob1693]

Take a look at steve maskerys jig for box joints using single blade, I made one not that complicated

 

[robgul]

IIRC Keith Brown Rag n Bone on YT has 6mm kerf blade on a table saw . . . that seems a safer option to me.

 

[Deadeye]

I am not asking people to approve/condemn this idea, my Dewalt 7845 saw does not have an arbor long enough to support a dado stack but were I to mount two 18 tooth flat top ground blades with the teeth 'nested' with a thin card washer between, I could in theory cut a near 5mm slot in one pass, solely in a box joint cutting arrangement.

I shall continue to use a router for housing joints.

Have I missed something, indeed has anyone here tried it?

Agree you'd need a metal washer and the teeth not to touch the adjacent blade. Otherwise I'd say fine - Matthias Wandel has a clip doing exactly this https://woodgears.ca/shop-tricks/dado.html

 

[JSW]

I wonder what would happen if the two blades were to slip, at 3000rpm

 

[Distinterior]

I wonder what would happen if the two blades were to slip, at 3000rpm

My thoughts exactly....!

 

[Jacob]

One blade wobble saw? People used to make up their own wobble washers.
Not sure why they are deprecated.
I've got a wobble saw unit which is too fat for the saw arbor but works brilliantly on the spindle. It's a cheap version of the Omas and very easy to adjust precisely.
https://www.ukworkshop.co.uk/threads/spindle-moulder-groovers-v-wobble-saw.97104/

 

[ChaiLatte]

I wonder what would happen if the two blades were to slip...

The 'if' in the above phrase implies a probability of an event happening.

The probability of one or both blades slipping in a double blade setup would have some relationship to the probability of a blade slipping in a standard single blade setup.

Hence, a starting point for your thoughts exactly would be to estimate that probability for the single blade case. Write down, for instance, how many board feet of lumber you have sawn and the number of blade slips you have had.

If that number is too low for reasonable conclusions to be drawn from it, consider extending your data pool to any item that uses a similarly-retained blade (like angle grinders, tile cutters, etc.).

Once you have a ball park figure, it would need some well-reasoned arguments concerning how that probability would be increased with two blades and the amount by which it would be increased.

Perhaps after calculating the risk, a person could mitigate that risk by insisting that the spacer be no thinner than that which allows clearance between two exactly adjacent teeth.

 

[JSW]

Perhaps after calculating the risk,

I considered the risk a couple of years ago after watching Matthias' youtube vid, it got filed away in the memory warehouse under "Things you REALLY don't want to try"

 

[Spectric]

'nested' with a thin card washer between,

This might prevent you from tightening the fixing nut, ie it starts off as appearing to be tight but due to compression of the cardboard could soon become loose and therefore dangerous. You would need a steel shim and an arbour long enough to fully take both blades and allow the fixing nut to be fully threaded on and not just by a few threads.

 

[Bingy man]

A simple thought is that the dewalt saw is designed for a single blade ,surely the additional weight of the 2nd blade would unbalance the motor leading to increased vibration and additional stresses on the arbor, motor and the blade .

 

[Chubber]

One blade wobble saw? People used to make up their own wobble washers.
Not sure why they are deprecated.
I've got a wobble saw unit which is too fat for the saw arbor but works brilliantly on the spindle. It's a cheap version of the Omas and very easy to adjust precisely.
https://www.ukworkshop.co.uk/threads/spindle-moulder-groovers-v-wobble-saw.97104/

I have in the past used a Kity wobble saw set, but it leaves a visibly curved cut noticeable in cuts over 10mm wide

 

[Chubber]

A simple thought is that the dewalt saw is designed for a single blade ,surely the additional weight of the 2nd blade would unbalance the motor leading to increased vibration and additional stresses on the arbor, motor and the blade .

I feel it would make little difference to the main centrifugal forces in as much as a 48 2.6mm tooth blade spins a lot more metal about than an 18 tooth 2.6 blade.

 

[Chubber]

This might prevent you from tightening the fixing nut, ie it starts off as appearing to be tight but due to compression of the cardboard could soon become loose and therefore dangerous. You would need a steel shim and an arbour long enough to fully take both blades and allow the fixing nut to be fully threaded on and not just by a few threads.

Yes I see that and agree.

 

[Jacob]

I have in the past used a Kity wobble saw set, but it leaves a visibly curved cut noticeable in cuts over 10mm wide

But you'd never see it unless squinting down the open end of the slot?

 

[MW24]

Depending on the kerf size you're looking to achieve, CMT do thick kerf blades on Amazon. Sure they're probably for sale elsewhere too.
Only 180mm diameter so you'd sacrifice a little cutting depth, and you'd have to remove the riving knife, but shouldn't be an issue given it'd be for grooving cuts.

https://amzn.eu/d/6JKVcLQ

 

[bp122]

Generally speaking, the kerf width of blades has a major effect on the work done on the timber.

The larger saws with a dado stack have extra oomph to deal with the extra power requirement dictated by the overall kerf width. The smaller saws may not. So doing what you are trying to do, for the same depth of cut, you will be overloading the motor with a wider blade.

You are better off using a cross cut sled and making multiple cuts using stop blocks or the "kerfmaker" gadget (I didn't understand how to use it, but some people do like it)

 

[Orraloon]

I will try and bust a few misconceptions here. Having a dado stack I have never noticed blade slip and the worst that would happen if they did may be a couple of chipped blade tips. The rotation direction actually tightens the nut. That said 6mm kerf blades are available for saws with a standard short arbor so it would be the smart thing to get one. The nut is sure to have enough thread then.
My saw is built to take a dado but it's only 2 HP. Seeing as dados are usually are not all that deep power is not a problem.
Actually if those 6mm kerf blades had been around years ago I would have got one instead of the dado stack I have. 1 blade to install and perhaps 3 passes at most to get the width of an entire stack. Lot less messing about.
Anyhow to the question by Chubber. Provided the nut is fully on the arbor thread and the shim/washer is not compressible I can not see a problem with it.


Regards
John

 

[wiley198]

Personally, I hate risk. The dewalt table saw is not meant to be used with more than the single blade, so I would not take the risk. Especially as that risk will only increase the cut made by a kerf width.

I would use a jig and a single blade or a router. You get the job done. It may take a little longer, but you decrease the risk.