We bought a used router and are newbies.
We want to cut letter backs for channel letters out of .040.
Does this need to be adhered to a backer? Our hold down system is clamps.
Could someone recommend a bit and bit speed?
you won't only need a special bit, but you'll need an oil lubricant which doesn't only cool and greases the alluminium as it cuts, but applies it with pressure. If you are using a multicam, you can use the actual router to drill into the base. Now these bits are actually hollow, and if you use your nugget, you can buy a pump and some pressure pipe and do your own vaccuum table. Boss did it in his 'spare time' wrote off a night but saved himself a few grand.
Belin Router bits #33635 1/4" CED 5/8" Cutting length approx $35.00. If you have a nice surface board already maybe it's MDF. Use transfere tape and cover the surface. Get some 3M spray Glue and spray the top of the tape, rest the aluminum (Masked) on top of that and walk on top of it and maybe even use some heavy transformers to hold down for about 15 minutes before you start ripping away. Hope that helps. Oh and that bit will cut threw that aluminum like butter. CAll 321.757. 3232 for some suggested speeds. I would think about 9,500-12,000 rpm's @ 1 inch/sec
Belin spiral upcut bits leave a clean edge. Use a 1" bead foam sacrificial board on your table. It's cheaper than dirt and won't create drag or noise from the bit. Clamp the aluminum to the sacrificial board (and your table base) with a dozen 2" spring clamps. Buy the plastic ones from your local 99 cent store and you won't have to duck for cover when you accidentally drive through one. Simple and cheap.