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How to measure the thread of a chuck

How to measure the thread of a chuck

How to measure the thread of a chuck

How to measure the chucks's thread


What kind of thread does my lathe have, how to measure it, which chucks are good and which ones to buy? here is the answer!

In Europe there is a tendency to produce lathes with an M33x3.5 mm connection, because it is a DIN standard.

This standard is also standardized by many import brands.
Nevertheless, there are many machines with unified unions or in inches. Know the size of the thread of the machine you own
Therefore it is essential to be able to choose spindles, pads, etc.

 

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Check the lathe instructions, here you should find the size of the attack. If not, ask who has sold you the lathe: you should certainly know how to give these
information.
But if you can not find the thread size of your lathe, here's how you can measure it (you need to get a ventesimal or digital caliber): measure the diameter and the pitch, or the distance between the ridges of the fillet helix.

(It is important to consider that the thread Ø is always a couple of tenths less than the nominal thread diameter, for example, if we measure the thread M33 x 3.5 mm we will find the Ø of about 32.8 mm).


In table 1, we report the metric threads (ISO or S.I. thread, international system) most used on lathes.

 

Metric threading table

 

Table 1. Metric threads
Ø in mm Dist. thread crest  Metric size
18 2.5 M18 x 2,5
20 2 M20 x 2
20 1.5 M20 x 1,5
24 3 M24 x 3
25 2 M25 x 2
30 1.5 M30 x 1.5
30 3.5 M30 x 3.5
33 3.5

M33 x 3.5 DIN 800

 

In table 2, you will find the threads in inches (inches or imperial system): in this case the pitch is not measured between two ridges, but it is easier to count the number of ridges in a space of 1 inch, ie 25.4 mm.

 

 

Imperial thread table (in inches)
Table 2 - Imperial thread
Thread diameter tpi or pitch in mm
Ø in mm Ø in inches No. pithc per inch (tpi) Dist. thread crest Inch thread sizes
12,700 1/2“ 20 1,27 1/2 inch x 20 tpi
19,050 3/4“ 16 1,59 3/4 inch x 16 tpi
19,050 3/4“ 14 1,81 3/4 inch x 14 tpi
19,050 3/4“ 10 2,54 3/4 inch x 10 tpi
22,225 7/8“ 14 1,81 7/8 inch x 14 tpi
25,400 1“ 12  2,12 1 inch x 12 tpi
25,400 1“ 10 2,54 1 inch x 10 tpi
25,400  1“ 8 3,18 1 inch x 8 tpi
28,575 1 1/8“ 12 2,12 1 1/8 inch x 12 tpi
28,575 1 1/8“ 7 3,62 1 1/8 inch x 7 tpi
31,750 1 1/4“ 8 3,18 1 1/4 inch x 8 tpi
38,100 1 1/2" 6 4,23 1 1/2 inch x 6 tpi
38,100 1 1/2“ 8 3,18 1 1/2 inch x 8 tpi

 

We have a number of adapters at your disposal to allow you to mount the spindles on your lathe.

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Important note

When screwing the spindle, make sure that it fits perfectly; otherwise, the spindle will not rotate on the axis
and this is very dangerous (This problem concerns low quality products).

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