Solid Carbide Spade Bit speeds

[intrepid]

I was given a small set of solid carbide spade bits. 1/8", 3/16", 1/4", 3/8", and 1/2". I plan to use for drilling broken taps that I know sometimes happens. What are the recommended speeds to use with these bits? I searched on line and found one chart which I could not understand.

 

[mmcmdl]

I use these in at work when I think they will work . Lots of oil , and the speeds decrease as the size increases . I always peck drill when removing anything hardened . I use the fine quill stop on the mill to step down a few thou for each down stroke . The drill WILL wander to the softer metal . I also always use a flat bottom carbide end mill to cut the broken tap/drill /endmill flat to start these spade drills . Can't tell you the exact RPMs but the machine will let you know . And these spade drills will chip , but they also keep cutting .

We have sizes that are just under the regular tap drill sizes and not the standard sizes as you mentioned . I go 5 to 10 thou under and pull the rest of the remaining threads out when re-tapping . Most of our dies are in the 45RC range and are a BIT** to re-tap . We also have an EDM sinker when needed .

 

[markba633csi]

I've used those on ceramic tile- just a few hundred rpm will do it

 

[intrepid]

I use these in at work when I think they will work . Lots of oil , and the speeds decrease as the size increases . I always peck drill when removing anything hardened

Thanks for the information. This is good to know. I suspect I will be using the smaller ones the most. So I'll keep the speed high and lots of oil.