metal dust collection

[Toronto_Nomad]

Hello all

After seeing a video on you-tube, i am going to take a shot at building a dust collection system for my shop (i do almost exclusively metal work). Sanding and grinding make a hell of a mess and i would love to deal with it, but unless your willing to crank out thousands for one designed for metal your kind of screwed (most are for wood and using them for metal is a fire ball waiting to happen)

My plan is to use a Thien style collector power by a large metal blade blower (similar to the ones used in a house furnace) built inside a fully sheet metal housing. My issue before starting is trying to figure out the min airflow (CFM) i am going to need to make it work as the metal and stone dust is a lot heavier than wood dust. Love this site and have learned a bit so far but have yet to locate the info i need (doesn't mean its not here, i just joined and there is a LOT of info on this site). I'm hoping someone can help or point me in the right direction to be able to figure out what CFM i will need so I don't waste time and money using a blower not strong enough.

Thanks in advance, and now back to hunting the site