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"Knurling Made Simple" (preview)

Knurled surfaces are commonly seen on cylindrical parts such as
handles, knobs and rollers. Knurling is a process that creates a
pleasing, easy-to-grip geometric pattern on a part's surface.

When knurling, machinists apply a tool with two freely rotating
rollers that deform, or push, the material rather than cut it.
Creating a crisp, clean knurl on a lathe is easy if you follow these
suggestions.


‧ Understand the relationship between a knurling tool and the diameter
of the part to be knurled.

Some machinists get into trouble when they try to start a knurl over
an arbitrary diameter and find that the knurl doesn't track properly
by repeating itself in the previously laid grooves.

A proper diameter to knurl is any diameter that is a multiple of the
spacing, or distance, between the teeth of a knurling tool divided by
π (3.14159). The relationship is the same whether the knurl is diamond
or a straight knurl. However, you must measure the spacing of a
diamond knurl's teeth along the axis of the part or roller for the
relationship to hold true.

Suppose you want to impress a diamond knurl on a 1"-dia. shaft and the
distance between each tooth of the knurling tool measured, with
calipers, along the roller's axis is 0.060". The measurement is not
extremely critical in that ultimately you will determine the final
diameter by trial and error. However, the measurement will give you a
decent starting point.

Following the formula stated previously, 0.060 divided by 3.14159 is
0.019. Therefore, any multiple of 0.019 should provide a diameter for
a perfect knurl. For example, 0.019 times an arbitrary number such as
40 equals 0.760. In theory, then, if you turned a shaft to 0.760", you
should be able to create a perfect knurl.

However, because you want to knurl a 1"-dia. shaft, you have to find a
multiple of 0.019 that gets you close to 1", such as 52 ( 0.019 × 52 =
0.988). Based on experience, though, the chances of producing a
perfect knurl on the 0.988"-dia. shaft are not great. An error occurs
as a result of an imperfect measurement between the teeth of the
knurling tool, which isn't a big deal because ultimately you are going
to sneak up on a usable diameter. Therefore, begin by machining the
part about 0.010" larger than the calculated diameter.


‧ Lay a short test knurl by hand. ...

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www.proshoppublishing.com/articles.html

Best,
Joanna


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