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### Metric Helical Coil Threaded Insert Hole Data

Metric Hardware Specification Charts and Tables

Metric Helical Coil Threaded Insert Hole Data per. ASME B18.29.8M - 2005

Each nominal threaded insert size is standardized in five lengths, which are multiples of the insert's nominal diameter. These are 1, 1.5, 2, 2.5, and 3 times nominal diameter. Each nominal length is the minimum through-hole length (material thickness), without countersink, into which that insert can be installed. The nominal insert length is a reference value and cannot be measured. Actual assembled length of the insert equals nominal length minus 0.5 pitch to minus 0.75 pitch, with insert installed in a basic STI threaded hole. Assembled length cannot be measured in the insert's free state.

(1) The minimum drilling depths allow for

a) countersinking the drilled hole to prevent a feather edge at the start of the
tapped hole.

b) 0.75 to 1.5 pitch of insert set-down to allow for maximum production tolerance.

c) Dimensions are shown for both plug and bottoming taps. Plug taps 8 mm
and smaller have a male center, and the drilled hole depth dimensions allow for
this length (one-half of the diameter of the bolt).Calculation of minimum drilling
depth dimension G is as follows:

- Plug taps 8 mm and smaller, G = insert nominal length + 0.5 × nominal bolt diameter + 4 pitchs for tap chamfer + 1 pitch for tap end clearance + 1 pitch allowance for countersink and maximum insert set-down.
- Plug taps larger than 8 mm, G = insert nominal length + 4 pitchs for tap chamfer + 1 pitch for tap end clearance + 1 pitch allowance for countersink and maximum insert set-down.
- Bottoming taps, G = insert nominal length + 2 pitchs for tap chamfer + 1 pitch for tap end clearance + 1 pitch allowance for countersink and maximum insert set-down.

countersink

holes with insert set-down of 1.5 pitch maximum (See Fig. 1.).

The dimension T = insert nominal length + 1 pitch.

(3) Thread diameters are calculated as follows:

- Pitch diameter, min. Pitch diameter, min. of nominal thread 2 · H
_{max} - Pitch diameter, max. Pitch diameter, max. of nominal thread 2 · H
_{min} - Major diameter, min. Pitch diameter min. 0.649519 · P
- Minor diameter, min. Pitch diameter min. 0.433013 · P
- Minor diameter, max. Minor diameter min. tolerance

where H_{max} and H_{min} and tolerance is selected from the appropriate
data provided in ASME B1.13M with basic major diameter equal to the minimum
major diameter of the STI thread.

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