Why bandsaw blade snapped?

[peps1]

Hi guys,

Just switched out my wood cutting blade and had the new blade snap on me (SuperTuff Carbon in 14tpi 3/8”) while cutting a small bit of 12mm plexi????

Wondered what part of my saw set-up could have been the problem?

 

[AndyT]

My guess is that the powered saw got hot and melted the plastic onto itself, so gripping the blade tight and snapping it.
Cutting plastic with power tools needs more chip clearance than wood (the chips tend to stay attached rather than falling free) and a very carefully controlled rate of feed.
I suggest you use a handsaw for the other cuts!

(Similar precautions apply to drilling holes - I once had a job where I had to drill hundreds of holes into sheets of perspex - it was all too easy to get the feed rate wrong and weld the bit to the work.)

 

[Jensmith]

Too much tension on the blade?
Too fast a feed rate for the depth? It's a pretty fine tpi. I have one and you have to feed slowly on thicker material.

 

[Steve Maskery]

If the break is at the weld, I'm sure Ian will say Sorry and fix it for you. If the break is elsewhere it's not a weld problem. Have you lowered the speed of the machine? You need to do so for plastic as it melts otherwise causing all sorts of problems.
Did the blade just snap or was there some advance warning that something else wasn't right? The machine talks, you know.

When you say the workpiece was "small" what do you mean? It wasn't so small that it got caught in the throat plate was it? That could cause a jar enough to snap a blade.
S

 

[peps1]

Cutting plastic with power tools needs more chip clearance than wood (the chips tend to stay attached rather than falling free)

Awww the joy of misinformation on the internet, had read plastic and sheet metal needed smaller tpi then wood.

Too much tension on the blade?
Too fast a feed rate for the depth? It's a pretty fine tpi. I have one and you have to feed slowly on thicker material.

Hard to know about tension, as it has no tension meter built in.....just tightened till i had less then 4 or 5mm of total play.

 

[peps1]

If the break is at the weld, I'm sure Ian will say Sorry and fix it for you. If the break is elsewhere it's not a weld problem. Have you lowered the speed of the machine? You need to do so for plastic as it melts otherwise causing all sorts of problems.
Did the blade just snap or was there some advance warning that something else wasn't right? The machine talks, you know.

When you say the workpiece was "small" what do you mean? It wasn't so small that it got caught in the throat plate was it? That could cause a jar enough to snap a blade.
S

Yes, was at the weld......no waning, just a ping!

I meant small as in thickness, as the same blade had been cutting the same plexi and thicker Phenolic board the other day and had no problem at all.

Think it is much more likely to be something iv done the a flaw with the blade

 

[Anima]

Speak to Ian at Tuffsaws about your saw settings and blade type and see what he says. If the blade was the problem then he will sort it free of charge, if not you get some free advice.

Just be glad you didn't get hurt. There was a thread on here a couple of months ago showing a broken blade and it looked deadly.

 

[peps1]

Will mention it to Ian and see what he says, need to get a bunch more blade from him anyway!

 

[Lons]

while cutting a small bit of 12mm plexi????

Hi

12mm thick acrylic isn't "small". It's actually pretty hefty stuff to cut and my guess would be that you've overheated the blade on the previous job and it's finally given up the ghost at what is often the weak point, the weld. Phenolic sheet is pretty tough as well depending on the type you used. As Andy said, it melts and fuses together if cutting speeds are too fast and exerts a hell of a strain on the blade or drill bit. Smells a bit as well :lol:

The company I managed in a past life used to sell and fabricate ICI Perspex and polycarbonate so I have a little experience. Out of interest, what are you making with 1/2" acrylic?

Bob

 

[peps1]

what are you making with 1/2" acrylic?

A Etching tank for etching PCB ferric chloride...........was giving me really nice clean cuts till it went.

 

[hammer n nails]

2 or 3 wheeled bandsaw if its a 3 wheel one the blades snap, ian told me that as i had a carbon blade in my bandsaw but he was as good as gold and changed it for me