In a message dated 3/1/04 12:24:37 PM Eastern Standard Time,
ryoung@navcomtech.com writes:
<< Problem with using an end mill is that you have to hold it centered on the
hole. Extra setup, and it's tough to do on a drill press, virtually
impossible by hand.
>>
Not at all difficult, even by hand.
If we have a 5 / 16 thread bolt with a regular allen/phillips or slotted head
that needs to be below the surface and the part we are drilling does not need
threaded, do the following:
Drill a 21/64 hole( 1 size above 5/16 ) all the way through the part
Drill a hole a size or two larger than the head of the bolt, drill until the
head of the bolt is almost below the surface.
Use a end mill equal to or slightly smaller than the drill above. Continue
with the end mill to clean the bottom of the hole up. The hole from step 2
holds the end mill from walking. Drill until the head is just below the
surface.
The only additional setup is changing the bits in the drill. In small
numbers this isn't a factor. If we were making many parts a core drill would
be the
answer. ( this is a stepped drill that makes a pilot hole and a counterbore
in one shot)
Another alternative is to drill a 21/64 hole and use a countersunk bolt.
Step 2 would be used but we would drill until the countersunk screw is below
the
surface.
Harold
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