- Joined
- Feb 1, 2016
- Messages
- 67
Thought I would stick this in as a general knowledge posting.
When I worked in the tapered and mis-located hole room (jig bore room). Also on the horizontal boring mills we all had sets of cutters to produce standard size pin holes. Usually for dowel pins for tooling plates or tooling balls. So in a specific size we would have.
Center drill (one size worked for several of the following).
Drill 1/32 below finish size.
Boring end mill (this is a circle ground with 2 deg. back taper end mill sized .010 below finish size).
Chucking reamer (held by the last 1/4 to 1/2 inch of the shank so it would not try to bore).
These reamers were selected from a pile for their exact size and were for slip fit, and press fit.
The boring end mill didn't need to go the full depth of the hole, only 1/4 or so to align the reamer.
Occasional a couple of tens more were needed from the reamer so a carbide insert in its holder would be rubbed down one flute along the reamer to raise a burr that would take out just a bit more. To bring it back it would be spun backwards in a drill chuck and a medium india stone held against the side.
You'll note I didn't say anything about using these in lathes since its hard to get the boring end mill on dead center. But I did use end mills that broke a tooth or were otherwise junk to hand grind clearance away from all but one tooth and use that as a boring bar for short holes.
Jim
When I worked in the tapered and mis-located hole room (jig bore room). Also on the horizontal boring mills we all had sets of cutters to produce standard size pin holes. Usually for dowel pins for tooling plates or tooling balls. So in a specific size we would have.
Center drill (one size worked for several of the following).
Drill 1/32 below finish size.
Boring end mill (this is a circle ground with 2 deg. back taper end mill sized .010 below finish size).
Chucking reamer (held by the last 1/4 to 1/2 inch of the shank so it would not try to bore).
These reamers were selected from a pile for their exact size and were for slip fit, and press fit.
The boring end mill didn't need to go the full depth of the hole, only 1/4 or so to align the reamer.
Occasional a couple of tens more were needed from the reamer so a carbide insert in its holder would be rubbed down one flute along the reamer to raise a burr that would take out just a bit more. To bring it back it would be spun backwards in a drill chuck and a medium india stone held against the side.
You'll note I didn't say anything about using these in lathes since its hard to get the boring end mill on dead center. But I did use end mills that broke a tooth or were otherwise junk to hand grind clearance away from all but one tooth and use that as a boring bar for short holes.
Jim
