Left-hand Whitworth threads
Anyone working on older British engineering will eventually meet a left-hand Whitworth thread: on turnbuckles, on shaft nuts, on machine tools. Spare parts are rare, so the thread gets recut. VÖLKEL makes 104 hand taps for it to DIN 352 in HSS-G, from BSW 1/8 x 40 LH to BSW 1" x 8 LH.
55° stays 55°
Left-hand Whitworth keeps its 55° flank angle and its rounded crests and roots. A UN tool does not replace it, not even when diameter and thread count happen to match. The details are on the right-hand BSW hand taps page.
Three-piece like the coarse thread
Taper tap with a six to eight thread lead, second tap with four to five, bottoming tap with two to three. The marking on the shank is the same as on right-hand taps: one ring, two rings, no ring.
Before the first cut
On old parts it pays to identify the existing thread first: flank angle with the thread gauge, thread count over one inch, diameter with the calliper. Only then is it clear whether it is BSW, BSF or an American series. Tap drill sizes are in the article calculate tap drill size, the signs of left-hand threads in the article identify and cut left-hand threads correctly.
All sizes at a glance
104 articles in 2 series. The article number links straight to the tool.
Hand Tap ISO 529 HSS-G left hand thread
| Threadnominal size | Tapping drillØ in mm | set of 3 pieces | Taper Form A | Bottoming Form C | Second Form D |
|---|---|---|---|---|---|
| BSW 1/8 x 40 LH | 2.6 | 84307 | 84307-1 | 84307-3 | 84307-2 |
| BSW 5/32 x 32 LH | 3.1 | 84308 | 84308-1 | 84308-3 | 84308-2 |
| BSW 3/16 x 24 LH | 3.6 | 84309 | 84309-1 | 84309-3 | 84309-2 |
| BSW 1/4 x 20 LH | 5.1 | 84310 | 84310-1 | 84310-3 | 84310-2 |
| BSW 5/16 x 18 LH | 6.5 | 84311 | 84311-1 | 84311-3 | 84311-2 |
| BSW 3/8 x 16 LH | 7.9 | 84312 | 84312-1 | 84312-3 | 84312-2 |
| BSW 7/16 x 14 LH | 9.3 | 84313 | 84313-1 | 84313-3 | 84313-2 |
| BSW 1/2 x 12 LH | 10.5 | 84314 | 84314-1 | 84314-3 | 84314-2 |
| BSW 9/16 x 12 LH | 12 | 84315 | 84315-1 | 84315-3 | 84315-2 |
| BSW 5/8 x 11 LH | 13.5 | 84316 | 84316-1 | 84316-3 | 84316-2 |
| BSW 3/4 x 10 LH | 16.5 | 84317 | 84317-1 | 84317-3 | 84317-2 |
| BSW 7/8 x 9 LH | 19.25 | 84318 | 84318-1 | 84318-3 | 84318-2 |
| BSW 1" x 8 LH | 22 | 84319 | 84319-1 | 84319-3 | 84319-2 |
Hand Tap DIN 352 HSS-G left hand thread
| Threadnominal size | Tapping drillØ in mm | set of 3 pieces | Rougher | Intermediate | Finisher |
|---|---|---|---|---|---|
| BSW 1/8 x 40 LH | 2.6 | 22006 | 22006-1 | 22006-2 | 22006-3 |
| BSW 5/32 x 32 LH | 3.1 | 22008 | 22008-1 | 22008-2 | 22008-3 |
| BSW 3/16 x 24 LH | 3.6 | 22010 | 22010-1 | 22010-2 | 22010-3 |
| BSW 1/4 x 20 LH | 5.1 | 22014 | 22014-1 | 22014-2 | 22014-3 |
| BSW 5/16 x 18 LH | 6.5 | 22016 | 22016-1 | 22016-2 | 22016-3 |
| BSW 3/8 x 16 LH | 7.9 | 22018 | 22018-1 | 22018-2 | 22018-3 |
| BSW 7/16 x 14 LH | 9.3 | 22020 | 22020-1 | 22020-2 | 22020-3 |
| BSW 1/2 x 12 LH | 10.5 | 22022 | 22022-1 | 22022-2 | 22022-3 |
| BSW 9/16 x 12 LH | 12 | 22024 | 22024-1 | 22024-2 | 22024-3 |
| BSW 5/8 x 11 LH | 13.5 | 22026 | 22026-1 | 22026-2 | 22026-3 |
| BSW 3/4 x 10 LH | 16.5 | 22030 | 22030-1 | 22030-2 | 22030-3 |
| BSW 7/8 x 9 LH | 19.25 | 22034 | 22034-1 | 22034-2 | 22034-3 |
| BSW 1" x 8 LH | 22 | 22038 | 22038-1 | 22038-2 | 22038-3 |
Tapping drill: drill diameter recommended by VÖLKEL (Technical Information “Tapping drill sizes”).
