- Joined
- Aug 11, 2021
- Messages
- 5
I am an amateur - perhaps what I am asking about is a dumb question to most machinists.
I am experiencing something strange when I drill holes in Threaded Rod to make a Reloading Die (sizer)
using my 9" ENCO Bench Lathe.
I drilled a starter 'guide' hole thru a 1 inch long piece of threaded Rod with a 1/4 inch drill.
The hole measured 0.249", as expected, with my calipers. No problems.
I was going for a 0.318" hole.
So - I put an "O" drill in the chuck and drilled it out. Came out 0.326" - not 0.316" !!!!
I tried AGAIN, but this time I used the smaller 5/16" drill into the 1/4" pre-drilled hole....
it came out 0.324" - NOT 0.313" !!!!
So - I thought my Lathe is out of alignment (Runout). But the Main Chuck lines up
with the Tailstock Chuck (using very small center drills in each). ? ? ? ?
NOW - here's the rub....I tried AGAIN with a piece of threaded rod, again pre-drilled with
a 1/4" drill. THEN I enlarged the hole one letter drill at a time until I got to the
"O" drill... NOW the hole measures 0.318" - What I wanted to begin with !
Does anyone know why the first two holes would come out seven thousandths larger (or more)
than they should have ? I cannot see why that would be. The drills check out in size with
my calipers.
DoctorBill
I am experiencing something strange when I drill holes in Threaded Rod to make a Reloading Die (sizer)
using my 9" ENCO Bench Lathe.
I drilled a starter 'guide' hole thru a 1 inch long piece of threaded Rod with a 1/4 inch drill.
The hole measured 0.249", as expected, with my calipers. No problems.
I was going for a 0.318" hole.
So - I put an "O" drill in the chuck and drilled it out. Came out 0.326" - not 0.316" !!!!
I tried AGAIN, but this time I used the smaller 5/16" drill into the 1/4" pre-drilled hole....
it came out 0.324" - NOT 0.313" !!!!
So - I thought my Lathe is out of alignment (Runout). But the Main Chuck lines up
with the Tailstock Chuck (using very small center drills in each). ? ? ? ?
NOW - here's the rub....I tried AGAIN with a piece of threaded rod, again pre-drilled with
a 1/4" drill. THEN I enlarged the hole one letter drill at a time until I got to the
"O" drill... NOW the hole measures 0.318" - What I wanted to begin with !
Does anyone know why the first two holes would come out seven thousandths larger (or more)
than they should have ? I cannot see why that would be. The drills check out in size with
my calipers.
DoctorBill