I have to cut quite a few 0.25" holes in a 5mm checkerplate.
I am using a Kress router with a 0.25" ER collet.
Bought a new 1/4" drill bit for the job.
After the third hole the bit pulled out of the collet as the router was lifting out of the hole.
Of course the bit didn't get pulled completely out of the collet and as the machine was travelling to the next hole, the bit was spinning at 45 degrees along the plate.
Before I got to the emergency stop, both the bit and the collet were smoking hot.
The collet survived but the bit is blue top and bottom and, I presume, useless.
Of course it had to happen on a Saturday afternoon when the shops are closed.
I measured the shank and instead of being 0.25" it is 0.23
Apparently that is enough to allow the bit to slip in the collet.
Next time I will measure the shank to make sure it fits the collet but, since they are enclosed in a bubble pack, I could be buying several before I found a correct one.
Oh the joys of living in the bush NOT