how big spindle for drilling holes

[DanOSB]

what would the minimum size for spindle to use for drilling the holes on mild steel

would 1.5 horsepower be plenty to use for drilling 1/2 inch holes maybe some angular cutter/rotabroach bits?


Thanks
Dan

[WSS]

Dan,
Tomorrow I will be drilling 11/16" holes in 1/2" A36 with a annular cutter. I will double check the HP but I think it is 1HP, it is a dayton for sure. I have no problems with these holes. I can do the hole in 9 seconds with with plenty of down feed. I have not seen your gantry, but I think you might have to go slower due to down force. With that in mind you could probably get away with 3/4HP? Also consider 90vdc, as you can infinitely vary the speed and they have good torque curves (in your range 1/8-1/4HP).

[DanOSB]

the gantry is very very beefy for that machine

does ur drill have a gear reduction?

i plan to use those vdf spindle (same stuff they use for router) i saw one local for sale (1.5 horsepower) so im considering grabbing that setup and use it for my big cnc whenever i finally finish it.. been working on it lots lately..

i am glad i actually bought 2nd cnc machine and use it to cut parts for the main cnc machine

[WSS]

Dan,
I should clarify that I will do these an a radial drill. A small one but designed for the task. I have not tackled a drill on our gantry yet (you first!). The 1.5HP vdf, how is the speed varied? How about down pressure? I have seen the router type CNC run but I a have not really paid close attention.

WSS

[DanOSB]

im no vfd expert myself.. but i beleive they can go 400 rpm or something which is slow enough for drilling metal i beleive..

speed is varied by VFD driver im not exactily sure how it works but it can adjust the speed via mach tell how many rpm i want and it will rotate that much rpm..