Pilot hole for Tapered Pipe Thread-1

【英】困ったときの知恵袋詳細

Thread Mills Pipe Threads Trouble ShootingHow to useSpecification of toolsBasic Knowledge

Can you give me some advise for machining a Rc (PT) 1/4-19 tapered internal thread with a threading length of 8.7 mm? I am machining with a carbide helical cutter 080153 X 19 R. I got good results using a tapered pilot hole. Could you tell me the reason for recommending the taper hole when processing a Rc (PT) 1/4-19 R? I would like to put this in my processing manual.

When processing a Rc 1/4-19 taper thread with a taper pipe taps you gradually start cutting the thread with the cutting chamfer end of the tap at the smallest diameter. The tap continues cutting the complete taper thread until the tap reaches the tapered reference diameter position where the diameter becomes the largest.
When using a helical cutter #080153X19R, it is possible but not recommended to process a tapered thread with a straight pilot hole. However, the cutter processes all the threads from the bottom of the thread to the inlet of the hole where the tapered diameter becomes largest in a single rotation around the diameter of the threaded hole . If you use a tapered helical cutter in a straight hole, the extra cutting load may chip the cutter, please refer to the explanation on the attached PDF file for details.

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