Pocket Holes came out the Wrong Size

[James M]

Chose to pocket out some 7/16 inch (0.4375) holes for a game board rather than profile cut them with a 1/4 inch spiral down cut end mill. However, when I measure them they are actually ~27/64 inch (0.422).

How do you adjust the tool to reduce or eliminate that difference?

Thanks

[javabug]

Chose to pocket out some 7/16 inch (0.4375) holes for a game board rather than profile cut them with a 1/4 inch spiral down cut end mill. However, when I measure them they are actually ~27/64 inch (0.422).

How do you adjust the tool to reduce or eliminate that difference?

Thanks

Spiral end mills are generally undersized but not by much unless it's been resharpened. Tool deflection may also be a factor here. I'll just do a test pocket of the same size circle with a pocket allowance of -0.005 and make the allowance adjustment until you get to the desired size. Afterward, use the same allowance to regenerate the original toolpath.

[James M]

The end mill has not been re-sharpened as far as I know. You raise a valid point in that I should have done some test holes and then added an allowance. Thanks for your reply.

[rb99]

Measure the actual bit to see what size it is.

[knight_toolworks]

there is slop in your machine and downcut tend to make things a bit off size anyway. if yo want exact holes it is lays best to make a test hole measure it and adjust the tollbooth.