Instructions
Grinding, Pg. 4 OF 4
wheel), have a slight at on the tip, and a tip angle of less
than 90°.
Tools used on lathes such as the Sherline will do all their
cutting at the tip of the tool because they don’t have the
horsepower for 1/4" (6 mm) cuts.
We don’t recommend using oil stones to improve the edges.
After a few minutes use with an occasional dab of cutting
oil a properly sharpened tool will hone itself in.
The nal sharpening to a tool should take place with the
wheel cutting the cutting edge of the tool from the top of
the tool to the bottom when using bench grinders.
These instructions include a great deal of information about
how to do what should be a simple operation, but these are
very complex instructions to write because we are trying to
tell you how to control your hands, not a simple machine.
Incidentally, the reason we call a tool a right handed tool
when the cutting edge is on the left is because it is designated
by which way the chip leaves the cutting tool. Cutting tools
such as left or right handed tin snips are also designated
in this manner because the cut-o falls to the left or right.
The left hand tools are ground the same as right, in the
same order with the angles reversed.
Boring Tools
Side View
Bottom View
FIGURE 13—Typical boring tool.
Boring tools are the most dicult to grind. They should
always be made as rigid as possible. Tool angles around
the “tip” can be the same as any cutting tool, but clearances
of the tool body have to be considered carefully. A tool
ground with enough clearance for a nished hole may not
have enough clearance to start with when the hole has a
smaller diameter. If you have to bore a hole in a part that
has a lot of work in it, have a tool ready to use that’s been
checked out on a piece of scrap.
Form Tools
Form tools are used to create a shape the same as the tool.
To grind form tools, a pattern of the nished shape should
be at hand and there should be some possibility of success
with what you have to work with. You can’t grind a 1/8"
(3 mm) groove into your tool 1/4" (6 mm) deep with a 1/2"
(12 mm) wide wheel.
Shape of part
desired
Step 1 Step 2
A B
Form
Tool
FIGURES 14A—A typical form tool made by a custom toolmaking
shop, and 14B, a home shop method of achieving the same
nished shape in two steps with a tool that can be ground on a
bench grinder.
This type of tool is usually made by Tool and Cutter
specialists that have high shop rates using precision grinders,
diamond dressers, and a large variety of wheels available
to them.
All is not lost if we have a good pair of hands with a good
mind driving them! We can use the grinding wheel corners
on our $50 grinder and generate the shape 1/2 at a time on
each side of the tool and still get our job done.
Form tools don’t need any top relief (hook) to work. Use
low spindle RPM and steady feed rates to prevent chatter.
The width of a form tool should never exceed three times
the smallest diameter of the nished part.
Like any skill, tool grinding is one that has to develop
with time. It is also the skill that allows you to go one step
beyond the average hacker.
Thank you,
Sherline Products Inc.
High-Speed Steel Bits Available from Sherline
PART
NO.
DESCRIPTION
11950 H.S. Steel, Cutting Tool, Right
11960 H.S. Steel, Cutting Tool, Left
11970 H.S. Steel, Cutting Tool, Boring
1200* H.S. Steel Internal Threading Tool
3005 H.S. Steel 1/4" Square Tool Blank
3005B H.S. Steel Tool Blanks (5-Bulk)
3007 H.S. Steel Set (Right, Left, Boring)
*NOTE: the Internal threading tool is very dicult to make
on just a bench grinder. If a precision thread is required, we
recommend you buy our P/N 1200, which is pre-ground
to the proper shape.