Is the size of the nut correspond one-to-one with the size of the wrench?
Thread Content
This post was last edited by jmdc on 2019-10-12 at 12:11. Is the size of the nut matched one-to-one with the size of the wrench? For example, can an M12 nut be tightened using either an 18mm wrench or a 20mm wrench? How can one determine what size wrench to use based on the size of the nut? Also, is the size of the hex head on the hex head bolt the same as the size of the nut that matches it? Also, are there any **standards** for the total length of the bolt and the length of its threaded portion, or can it be whatever length one wants to buy or use?
Please refer to several common nut standards such as GB/T6170 and GB/T6175; for example, for M12 nuts, the standard value under the S standard is 18 mm, and a wrench with a size of 19 is required. 20 is not a standard size; if the S value of the nut is too small and the opening of the wrench is too large, it is very likely that the nut cannot be tightened. For bolt length and thread length, please also refer to the relevant standards.
When used properly, wrenches and nuts must match each other one-to-one. However, in practical use on site, it’s not necessarily the case; adjustable ratchets or homemade wrenches are acceptable as long as they can be fitted onto or used to tighten things. There are standard requirements for thread length; it can be extended as needed. If it exceeds the standard requirements, of course, the standard long bolts can also be shortened through cold cutting.
The ratio between the wrench and the bolt is generally 1.5 times; for example, a wrench needed for an M20 bolt is of size 30. The length of the bolt is usually determined based on actual requirements. For instance, bolts of size M16 are used for DN40, DN50, and DN80 connections, but due to differences in flange thickness, different lengths of bolts are required. Additionally, the length varies depending on whether an 8-shaped blind plate is used or not. Generally, bolts used on the inlet flanges of safety valves are longer. Bolts of the same specification used on pipe flanges differ in length from those used on heat exchangers.
Yes, generally a 18mm wrench is used; a 19mm one can also work, but it may easily damage the corners of the hex nut
Wrenches come in fixed wrenches and adjustable wrenches. Fixed wrenches match nuts by size, while adjustable wrenches can be adjusted; they vary in length, and the opening of the wrench also has certain limits – small wrenches cannot be used with large nuts. Bolts come in fully threaded and partially threaded types, and the standards vary as well. Check the standards for the length of the bolt and the length of its threads. Threads also come in different precision grades; in short, once you look at the relevant standards, everything will become clear.