What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The marking format of the thread mark is: Thread code - thread tolerance zone code (pitch diameter, top diameter) - screw length l) Tolerance zone code is represented by numbers plus letters (inner thread with uppercase letters, external thread with lowercase letters) , such as 7H, 6g, etc., it should be specially pointed out that 7H, 6g, etc. represent thread tolerance, while H7, g6 represent cylinder tolerance code. 2) The length of rotation is specified as short (represented by S), medium (represented by N), and long (represented by L). In general, the thread engagement length is not marked, and the thread tolerance zone is determined by the medium engagement length (N). If necessary, add the screw length code S or L, such as M20-5g6g-L. When special needs are required, the value of the screwing length can be indicated, such as M20-5g6g-30.
Heat treatment broadcast quenching and tempering HB220-270, nitriding HRC>65 foreign use titanium carbide coating method to improve the corrosion resistance of the screw surface, but according to reports, its wear resistance is not good enough. A series of measures have been taken abroad to improve the wear resistance and corrosion resistance of the screw. One way is to use highly wear-resistant and corrosion-resistant alloy steel. Such as 34CrAlNi, 31CrMo12 and so on. There is also a method of spraying Xaloy alloy on the surface of the screw. This Xaloy alloy has high wear and corrosion resistance.
In the prior art, there are two ways to feed the screws of the locking screw machine, the air blowing type and the air suction type. The air suction type is suitable for relatively small screws. If the screw size is larger than M2, smaller than M5, and the length-diameter ratio is larger than 1.4, the air-blown screw machine can be selected.
Washers are divided into: flat washer-C, large washer-A and C, extra large washer-C, small washer-A, flat washer-A, flat washer-chamfer-A, steel structure high Strength washer, spherical washer, cone washer, square bevel washer for I-beam, square bevel washer for channel steel, standard spring washer, light spring washer, heavy spring washer, internal tooth lock washer, internal serrated lock washer, External tooth lock washer, external tooth lock washer, single ear stop washer, double ear stop washer, outer tongue stop washer, stop washer for round nut.
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