Category Archives: Threads

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Thread identification guide

Posted on by JCA
04
Apr

Thread identification guide

STEP 1

Determine if the thread is tapered or parallel/straight.

Measure the thread with a caliper at the beginning and the end. If the diameters increase for a male end or decrease for a female end, the thread is tapered. If it is the same value the thread is straight/parallel.

STEP 2

Determine the thread size and type. Imperial sizes are normally common fractions ¼”=0.25”.

Measure the outside diameter OD for male and inside ID for female threads.

If the thread is tapered measure the diameter of 4th or 5th full thread.

The diameter measurement obtained in this step may not be exactly the same as the listed nominal size for the given thread. This variation is due to manufacturing tolerances.

STEP 3

Determine the pitch for metric or the amount of threads per inch (T.P.I) for imperial sizes.

In both cases Thread pitch gauges can be used.

TPI 28 27 24 20 19 18  16  14  12 11.5 11 8
Thread pitch (mm) 0.91 0.94 1.06 1.27  1.34  1.4  1.59  1.81  2.12 2.21 2.31 3.18

Check for any markings on fitting or equipment which may be a clue to thread type. Country of origin may provide a clue.

Europe (DIN,BSP), America (NPT, JIC, UNO, ORFS), UK/Australia (BSP), Japan (JIS).

www.caetool.com

. All, Calculators, Threads

Thread runouts

Posted on by JCA
17
Nov

Thread runouts for metric ISO threads

DIN 76-1

For fine threads the dimension of the thread runout is chosen according to the pitch P.

1)As a general rule, apply if no other entries are given.

2)IApply if a shorter thread runout is necessary.

3)Apply if a longer thread runout is necessary.

www.caetool.com

. All, Calculators, Threads

Minimum thread engagement depth

Posted on by JCA
09
Apr

Minimum thread engagement depth

The table shows, for differents materials, the minimum engagement depth of a threaded hole (L) to enable the screw fails before the thread of the hole.

So, it is needed to define previously, the characteristics ot the screw:
– ISO Standard Thread (available from M1 to M36)
– Property class
– Thread pitch (fine or coarse)

Finally, the table also shows, the rest of dimensions that the hole should have, according to DIN 77 norm:
– Surplus thread length
– Thread total length
– Thread runout
– Hole total length

If the result of the cell is a “-” (dash), means that the holed material resistance is lower than the screw material, and in consequence, the thread of the hole will fail before the screw.