1, thread cutting:
General calculation method? Here is the bottom hole diameter calculated by the tooth height ratio (%) of about 75%, which is also the most commonly used calculation method. Specifically: bottom hole diameter (S)= internal thread major diameter (D)- pitch (P)
How to calculate different tooth height rates? There are metric threads and English threads (calculated by English system, including American standard threads):
Metric thread? S=D-%*P/76.98
English thread? S=(D-%*0.0 1299/TPI)*25.4？ Here TPI refers to the thread per inch (Note: American thread D= size code, English thread needs to be calculated after conversion in metric, American and English thread standard manuals). )
2, extrusion thread:
General calculation method? This also refers to about 75% thread engagement: S=D-P/2.
How to calculate the engagement degree of different threads? Like trimming, there are two kinds: metric and imperial:
Metric thread? S=D-%*P/ 147.06
English thread? S=(D-%*0.0068/TPI)*25.4 (Note: American thread D= size code, and British thread is calculated after conversion according to metric, American and English thread standard manuals. )
(1) The bottom hole of the thread on the workpiece should be chamfered, and both ends of the through-hole thread should be chamfered.
(2) The position of the workpiece fixture should be correct, and the center line of the threaded hole should be placed in a horizontal or vertical position as far as possible, so that it is easy to judge whether the tap axis is perpendicular to the workpiece plane when tapping.
(3) At the beginning of tapping, put the faucet as straight as possible, then tap the faucet hard and turn the wringer. When cutting in 1-2 turns, carefully check and correct the tap position. Generally, when cutting 3-4 threads, the tap position should be correct. In the future, just turn the wrench, and don't put pressure on the tap, otherwise it will damage the thread profile.
(4) When tapping, the wrench should turn around 1/2- 1 2 every turn, so that the broken chips can be easily discharged and the phenomenon that the cutting edge is caught by the chips can be reduced.
(5) When encountering an airtight screw hole, be sure to exit the tap and remove the chips in the hole.
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