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View Full Version : Feed rate for a 1/4 down sprial orsurd bit



teddy27
05-13-2008, 12:37 PM
I was wondering what would be the best feedrate for a down sprial bit cutting through 5/8 or 3/4 plywood?

Would you cut through it in two passes?

Gary Campbell
05-13-2008, 04:01 PM
Ted...
You dont say what machine you have or router vs spindle. Using a down spiral on plywood will tear up the bottom veneer significantly. If you use an up spiral it will do the same to the top. If you need a fairly good edge quality you should use a compression spiral. Your machine and router abilities will determine if you can cut in 1 or more passes.

Brady explains this better in this article: http://www.shopbottools.com/BradysTricks.htm
Gary

knight_toolworks
05-13-2008, 05:59 PM
it depends on the plywood. some cuts fine with either bit.

teddy27
05-14-2008, 09:38 AM
Gary,
I have an prt 48 X 96
no 4g upgrade.
I assume two passes are best?

Brady Watson
05-14-2008, 12:39 PM
Ted,
If you keep your move speed 2 IPS or less 2 passes might be OK. I personally like to cut 3/4" ply in 3 passes on an older PRT to avoid losing steps.

-B

jhicks
05-14-2008, 04:36 PM
Ted, we run a 2003 vintage PRt with mach controller and cut plywood most every day with a 5mm bit. We run at 160IPM, at 13,000 to 14,000 rpm on a 5HP spindle and generally get 20+ sheets per bit. Can go deeper and/or faster but have found this to be our safest sweet spot in MDF, prefinished ply, platform ply, and 13 ply so if it works and we dont have to worry about it, thats where we stay until proven otherwise.