Help setting up a table saw

[ColeyS1]

I've got a sliding table saw (for ripping 10ft sheets) and also a normal fence. A while back I noticed it wasn't cutting very well so got out a micrometer thingy and first rotated the saw so it was in line with the sliding carriage then adjusted the fence so it was slightly wider as the wood exited.
My question is should I really have set the saw bang on parallel? (Front and back of blade) Using the sliding carriage, as the wood enters the saw blade it cuts beautifully but as soon as the wood touches the back of the blade it begins scorching- somethings obviously moved. I'm gonna remove the carriage and have a good butchers to see what might have moved (blades all fitted nice and clean) but am not too sure how much clearance, if any I should have on the fence/carriage.
I've got some 4 inch thick treads that need cutting for length so it'd be good if I didn't need to do too much to the ends.
Cheers

Coley

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[Newbie_Neil]

Does your fence extend past the end of the blade?

 

[marcros]

i would set it up parallel.

With wood, I would suggest a short fence, with panels a full length one. In both cases though, if it is not parallel it will cause problems.

 

[ColeyS1]

Does your fence extend past the end of the blade?

Neil it's adjustable

Last time I set it I had the fence a whisker (0.3mm ish) wider at the back.
I can rotate the motor so it lines up with the carriage it's that part that's rubbing the most.
Marcros, so bang on parallel is what you suggest ? From memory I think the riving knife is a tad wider than the blade so I set the fence to match so it didn't pinch.

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[marcros]

i would also recommend changing the riving knife to one that is a fraction wider than the saw blade body, but a fraction narrower than the teeth

 

[MARK.B.]

If the riving knife is wider than the blade would this not cause the slowing down and scorching as you are trying to force the cut ?

 

[ColeyS1]

Thanks guys I need to check some measurements and I'll let you know. Just pushed through a tread to check I wasn't dreaming and got this...

I cut an extra 15mm off and it still scorched so somethings amiss

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[ColeyS1]

Saw kerf 3.8mm,riving knife 3mm blade thickness 2.45- that's on the 400 diameter.

Saw kerf 3.2mm, riving knife 2.7mm blade thickness 2.3mm on 315 diameter.
It's kinda like you said would be best for riving knife thickness :|

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[Racers]

Lots of teeth on that blade is it clogging with sawdust and burning?

Pete

 

[ColeyS1]

Pete it's a freshly sharpened and doesn't seem to be clogging.

1.15mm out of parallel from front to back no wonder it's misbehaving! !!

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[Steve Maskery]

The alignment is one issue, the other is that your blade has too many teeth, I think. From the photo it looks as if that blade is intended for cutting laminates like MFC, rather than crosscutting timber.
I think your riving knife is right.
S

 

[Zeddedhed]

I've noticed with my saw that when ripping thick timber (75mm or over) it can often scorch like that at the beginning of the cut. For ages it puzzled me until i realised what was happening.

The cut was closing up fractionally BEFORE it got to the riving knife allowing a scorch (caused by the upcoming teeth at the rear of the blade contacting the timber). The scorch was not present along the length of the cut - just the very beginning. As soon as the riving knife came into play the problem was solved for the rest of the cut.

That said there isn't much that can be done if this is the cause - in your case the alignment is the obvious culprit. The tooth count does look high but I don't think it would cause scorch like in your photo, which is very localised.

I suspect that the poor alignment causes the initial scorch and the riving knife kicks in effectively widening the kerf enough to compensate for the mis-alignment.

Or i may be taking utter rubbish - it's quite late after all.

 

[ColeyS1]

I usually rip sheets with the same teeth count and still have the issue. If after realigning the saw and fence I still have issues with the scorch I'll try a blade with more teeth. Zeddedhed, I wound the blade down so it would reach the riving knife quicker but even just trimming off 15mm it still scorched.

Steve last time I adjusted it I mentioned you to my workmate. I told him you were the powertool/machine (workshop supremo )guru and that you probably cover setting up tablesaws in one of your dvds !?

So just to conform,I need to set it up as bang on 100% parallel as I can ?- firstly turning the motor/blade to suit the carriage, then adjusting the fence parallel to the blade ? I'll switch to another 400mm blade just to check the blade isn't distorted, remeasure, then try and figure out how the saw managed to move to being 1.15mm out :?

Appreciate the input guys. It's like having a load more knowledgeable people peeping over my shoulder sussing out the problem.

Cheers
Coley

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[siggy_7]

Generally the advice I have seen is that sliding tables should be set so that they move slightly away from the blade, this is for accurate cross cut work to ensure no second cut of the piece on the cross cut fence. Personally I have never bought into this way of thinking particularly if you are using the fence for ripping sheet goods, I always set my table parallel.

Nice looking saw by the way, wish I had something so industrial!

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