Bandsaw ripple

[LarryS.]

Hi all


I’ve just cut a piece of 18th or 19th century battleship on my bandsaw for my next door neighbour to remove sections with nails so he can turn it.

Halfway through the cut the bandsaw started making a low droning noise and when I finished the cut I can see it coincides with a ripple effect on the cut.

Anyone got any idea what has happened ? I did tighten the blade not long after the droning noise started but that made no difference

And b fire anyone suggests it , it is a Tuffsaws blade !

Any help appreciated


Paul

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[marcros]

what tpi was the blade?

 

[LarryS.]

3/8ths blade 10 tpi


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[marcros]

my thoughts are that the tpi on the blade was too high, and the feed rate was too fast. If it is a lack of tension, you tend to get a banana shaped cut. you normally work on having 3 teeth in the wood at a time, so 3-4 tpi for inch stock. You obviously can't get much less than that, so for thicker timber you need to go with the same 3-4 tpi blade and a nice slow feed rate.

 

[Sgian Dubh]

3/8ths blade 10 tpi

Two to three TPI on a 1/2" to 3/4" wide blade would be my choice for a cut that deep. Big gullets carry the dust away better. The most likely cause of the flutter and droning noise is gullets chock full of sawdust meaning that even though the teeth might still be trying to cut there's nowhere for the sawdust created to go so you end up with something that's effectively a band of solid material that's a mixture of steel and chips. Slainte.

 

[LarryS.]

Ah ok thank you both, looks like I need another blade then, and to be fair I love an excuse for buying more tooling. !


Paul


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[ED65]

What's the way to manage a cut like this with a blade that isn't ideal? Can you get away with lowering the feed rate to a crawl to give the smaller gullets plenty of time to clear?

 

[Peter Sefton]

What's the way to manage a cut like this with a blade that isn't ideal? Can you get away with lowering the feed rate to a crawl to give the smaller gullets plenty of time to clear?

No I am afraid that just makes the blade rub and get hot which in turn ruins the blade. Less teeth and bigger gullets are required.

Cheers Peter

 

[Sgian Dubh]

What's the way to manage a cut like this with a blade that isn't ideal? Can you get away with lowering the feed rate to a crawl to give the smaller gullets plenty of time to clear?

To add to Peter's comment, my experience is that even if you go very slowly with a too fine toothed blade each gullet tends to get so tightly packed with chips or dust that they don't drop out efficiently and they're still there when that tooth and preceding gullet come around again, i.e., there's still nowhere for new chips to go as the tooth tries to cut. Some wood species are worse than others for this, e.g., resinous wood species tend to choke up the gullets more than non-resinous woods, and wetter examples of a wood species tend to choke the gullets more than a drier example. It's not a perfect correlation, but there is that tendency. Slainte.

 

[ED65]

Thanks gents.

 

[Robbo3]

A 12" (300mm) cut is possible with a 6TPI blade if you do it at a sensible speed.

This was the first of two similar cuts which saved me having to change the blade. However you get long stringy shavings rather than sawdust (the same with a chainsaw) when you cut along the grain.