measuring screws - question from a non-DT tech !

TechZoe

New member
Science technician trying to reassemble a trolley which has half its screws/bolts missing - hoping someone here can help me out !

I've got couple of the correct screws, but will need to buy some more. Please could someone explain what measurements I need to take, and how to translate that to something I can search ebay for ? I've tried googling but still didn't understand :laughing:

Thanks !screws.jpg
 

tcadmin

Administrator
Staff member
Science technician trying to reassemble a trolley which has half its screws/bolts missing - hoping someone here can help me out !

I've got couple of the correct screws, but will need to buy some more. Please could someone explain what measurements I need to take, and how to translate that to something I can search ebay for ? I've tried googling but still didn't understand :laughing:

Thanks !View attachment 11

Ignore the American half of this video but when they get to metric it explains everything you should need to know...
In short. the M number is the diameter of the thread, eg M5 would be 5mm dia.
The thread pitch number is the measurement between the each 'peak' of the thread.
Hope this helps.
 
An easy way to compare thread pitches is to hold the known good thread alongside the test thread and try to slide them apart. If the pitch is the same they will drag or lock. If not they will skid over each other.
Alternatively place them side by side and look where they touch against a light background. You'll be able to see if they mesh showing that they are the same pitch.
 
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