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Performance Details
The use of self-tapping inserts has significant
advantages over pre-tapped holes, moulded-in inserts and wire
thread inserts. They eliminate close tolerance holes required
for tapping directly into the base material, damaged tools
and low productivity resulting from moulded-in inserts and
the time consuming process of placing wire thread inserts
into pre-tapped holes.
The use of a self-tapping insert can result
in a reduction in thread size required because of the insert's
large effective shear surface saving material and reducing
cost and weight.
External Thread Interference
For a work-piece made of a light alloy, this
diagram illustrates clearly that whilst correct hole sizes
are important for product reliability, the Ensat 302 achieves
almost maximum pull-out with only 30% external thread interference.
Pullout Resistance
In light alloy, the self-tapping steel insert
resists a pullout force in excess of the yield point of an
8.8 grade bolt.
Installation
Procedure
- Drill hole to correct diameter, countersink if necessary.
- Screw the Ensat onto the driving tool with the cutting
slot or cutting hole pointing downwards.
- Ensure that driving stud engagement into the Ensat does
not exceed half the height of the cutting slot or hole
- Ensure that the insertion tool and Ensat are perpendicular
to the hole.
- When using a production driver, the rotating shell must
rest against the externally visible stop pins in such a
way that it is driven round clockwise by the pins.
- Set depth control, where applicable, to 0.1/0.2mm below
the surface of the receiving material.
- Apply reasonable downward pressure whilst driving the
Ensat into the material to 0.1/0.2mm below the surface.
- Finally back the driving tool out of the Ensat. In the
case of a production driver the friction lock will be released
automatically, the hand tool will require the hexagon nut
to be held as the drive is reversed.
Avoid "bottoming" the insert or using excessive
torque as this may strip the insert out or reduce pull-out
loading.
Most insertion problems arise from incorrect hole size, poor
tool maintenance or bad insertion techniques. Adequate trials
should always be carried out before moving to production.
Samples and low volume applications
A hand tool is available for use with a tap
wrench.
For field repair or initial tests, a nut
and bolt can be used. Ensure best possible alignment of the
insert in relation to the hole.
Hole size
calculation
Whilst 30% thread engagement will normally
give almost maximum performance, the most appropriate hole
size will vary according to the type of receiving material
and the type of insert to be used.
Example: Hole size for light alloy with tensile
strength of 280 N/mm2 for M8 insert type 302 is 10.8 - 11.0mm,
for M8 insert type 307 is 11.1 - 11.2mm.
If difficulty is experienced in installation, it is possible
to take the next hole size up without a detrimental effect.
However, this should always be established by tests prior
to production.
Hole design
Self tapping steel inserts can be installed
into drilled or core holes. Countersinking gives a neat finish
and the addition of a counter bore will facilitate insert
location during installation.
A = Minimum section for through hole.
B = Minimum depth of blind hole.
Minimum Wall
Thickness:
The wall thickness S is dependant upon the
hardness and strength of the material being used.
General recommendations:
Cast iron: S = 0.30 to 0.50 D
Metals: S = 0.25 to 0.50 D
(D = outside dia. of the insert)
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profile
sample/quotation