crazy spoil board fire.

[knight_toolworks]

I don't know why this happened. Was testing hole size in some 3/4" pdf that had a white laminate on it. it was a 1/4" downcut end mill at 1ips because I wanted the holes accurate. I cut the hole checked the size went back to aspire to change the tool path a bit to loosen the hole up when I see a glow coming from the hole as the machine was just starting the next test hole. I grabbed a bottle of water but turned off the dc but not the vac.I had to move the sheet to make sure it was out as it was still smoking. Now See why it had spread fast.
it was a 3/8" hole and I was using a inside profile cut a climb and a regular.
http://www.talkshopbot.com/forum/attachment.php?attachmentid=30242&stc=1

[jerry_stanek]

Using a down cut is a good way to start a fire

[Gary Campbell]

Plus 1 to what Jerry says. 2 types of bits start fires.... Broken and downcut

[curtiss]

So is there a way to keep a spark out of the dust collector system ?
What precautions should be taken with the dust collector ?

So upcut bits for holes are better?

I sometimes just mark the holes with a downcut bit and use a drill later...

[knight_toolworks]

if you drill or jam bit yes. but this was a 3/8" hole and I have done many sun holes with a downcut. if it was dull I can see that has happened but it was not a dull bit the only time I had issues cutting pdf was when the bit was really dull. this was one hole with a profile cut and a sharp bit. I was afraid of tearing the face with a upcut. I seldom cut laminated material so it is odd for me.

[jerry_stanek]

There no room for the chaff to go and it is heating up as a 1/4 inch bit is always in basically the same spot in that size hole

[knight_toolworks]

I have done it and 1/2" holes quote often as long as I am not drilling and not doing it on 1" material. this time was strange the bit was not even darkened like what happens when it starts getting dull. almost all my mdf cuts are with downcut bits and I never have issues unless the bit is dull and even then I have some warning with shavings packed in and really hot. this was one hole with a sharp bit ramped in.

[Gary Campbell]

All of that, and yet it still started a fire. Predictable when using downcuts with laminate or melamine.

[knight_toolworks]

All of that, and yet it still started a fire. Predictable when using downcuts with laminate or melamine.
thats what I Was thinking. I have only cut it a few times. I just cut it with a upcut and the surface was fine. I have this new customer they have two big cnc machines one with 2 heads and one with two beds and 8 heads. they are so busy they throw stuff my way. this was one sheet of th laminated pdf that was lamest 10' long when done and two rows holes they wanted tight. I got the first cut all setup and was testing hole size. it was rushed cause the pickup guy came early and then this happened.

[JimDav]

What is pdf? I thought it was just a typo for mdf but it is repeated multiple times here. The only pdf I know is an extension for a computer file type.

[knight_toolworks]

should be mdf frigging spell checker the computer one and the human one (G)

[JimDav]

should be mdf frigging spell checker the computer one and the human one (G)
That's what I thought really, but then thought just maybe, it was some kind of new product after seeing it a few times.