Part Number: 1230
Weight: 0.14 lb
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- Combined drill and countersink
- Sizes 1, 2, 3, 4 & 5
- High speed steel
- 60° included angle
- Right hand cutting direction
This set includes five different sizes of combined drills and countersinks, commonly called center drills. They are used to produce a center hole on a workpiece for turning between centers.
Center drills are also used to start drilled holes. Because they are very stiff they don't have a tendency to wander.
The set is high speed steel and includes sizes 1, 2, 3, 4, and 5. These are 60 degree center drills with a right hand cutting direction. Each center drill countersink is made of ground high speed steel for good wear resistance with a hardness rating of Rc 58 - 60.
Combined drills and countersinks, commonly called center drills, are used to produce a center hole on a workpiece for turning between centers. Center drills are also used to start drilled holes. Because they are very stiff they don't have a tendency to wander.
Here are the sizes of center drills.
Here is a little treatise written by J. W.
Early about center drills:
|| 2 3/4"
The center drill is only for putting a starting mark on the work piece
so that your conventional drill will start easy without walking or
grabbing. If your finish drill is going to be 1/4" then I would use a #4
center drill which has a 1/8" diameter of the drill point and a 5/16"
diameter body. With a 1/4" hole in order to avoid a push up burr when
finish drilling the center drill shoulder should enter the part until
the outer diameter of the resulting chamfer is about .270 to .280 in
diameter giving a nice burr free chamfer to the hole after finish
drilling. When drilling a hole that is going to be tapped then your
outer chamfer should be .030 greater than the nominal diameter of the
thread in order that no starting burr will be present on the part
surface to be filed down or hand deburred.
||#1 through #5
||1 1/4" through 2 3/4"
||1/8" through 7/16"
||3/64" through 3/16"
||Rc 58 - 60
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