Thread cuttingMy lathe came with the following thread cutting gears 24t x2, 32, 34, 36, 40, 44, 46, 48, 50, 52, 54, 56, 60, 66 & 96. The 50 is probably not original as it does not appear in the gear selection table. So it is likely to have been added at a later date for more thread options. Also when cutting threads the drive pin is shifted and the back gear lever operated to reduce the chuck speed. |
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| The gear selection
plate is marked Thread
Stud Comp & Screw Thread is the number of threads per inch. Stud is the first gear in the chain. Comp is used where two intermediate gears are used back to back to create the required gearing, otherwise just one gear is used as an idler. Screw is the gear on the end of the lead screw. Below is a picture of the gears used to cut a 20tpi thread. The selection plate shows Thread 20 Stud 36 Comp (blank) Screw 40 |
Note the middle gear is used as an idler so any size of gear that fits can be used. Also the gears are in one vertical line the gears to the right of the gear train are just used as spacers. |
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| Below is the lathe set
up to cut 56tpi thread. The selection plate shows Thread 56 Stud 36 Comp 56/32 Screw 96 |
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| Other threads can be cut using combinations of gears not shown in the table on the end of the lathe. The lead screw advances one inch for every 12 turns of the shaft. Using the ratio of the gears in the chain it is possible to calculate how many turns of the chuck is required to advance the cutting tool by one inch. | ||
| The Lot number of the Lathe is LOT -4-No 1623 |  |
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