Printed from Kezuriba (kezuriba.net/en/threads/m30/)
M30×3.5
ISO metric coarse threadNominal diameter 30 mm, pitch 3.5 mm. Tap makers recommend slightly different drill sizes, so they are listed side by side.
Thread angle 60°. H1 (basic thread engagement) = 0.541266P = 1.894. The pitch diameter is where the thread ridge and groove are equally wide. For cutting taps, pick a drill that lands inside the 6H tolerance of the minor diameter D1. Enlarged to show the shape; proportions are not to scale.
⌀Tap drill size for cutting taps (maker recommendations)
For internal thread class 6H. Values as given in each maker’s technical data (mm).
| Maker | Recommended drill | Notes | Source |
|---|---|---|---|
| OSG | 26.5 | min. 26.3, 6H max. 26.77 | [3] |
| Nachi (Nachi-Fujikoshi) | 26.5high-performance drill 26.6 | [5] | |
| Yamawa | 26.6 | [4] |
Forming (roll) tap drill sizes differ by maker and product line; see the Japanese page for the table.
⌇Basic dimensions
| Nominal (major) diameter d | 30 |
|---|---|
| Pitch P | 3.5 |
| Pitch diameter d2, D2 | 27.727 |
| Basic minor diameter D1 (nut), d1 (bolt) | 26.211 |
| Fundamental triangle height H = 0.866025P | 3.031 |
| Basic engagement H1 = 0.541266P | 1.894 |
Basic dimensions are theoretical values without tolerance. Try other pitches with the thread dimension calculator.
⬡Bolt and nut sizes
| Item | mm | Confidence |
|---|---|---|
| Hex bolt width across flats s (ISO-based JIS, main body) | 46 | 1 source (reference)[8] |
| Hex bolt width across flats s (old JIS, annex) | 46 | 1 source (reference)[9] |
| Hex nut width across flats s (ISO-based JIS, main body) | 46 | Agrees in 2+ sources[8][10] |
| Hex nut width across flats s (old JIS, annex) | 46 | 1 source (reference)[11] |
| Hex nut height m (style 1, max.) | 25.6 | 1 source (reference)[10] |
| Socket head cap screw head diameter dk (max.) | 45 | Agrees in 2+ sources[12][13] |
| Socket head cap screw head height k (max.) | 30 | Agrees in 2+ sources[12][13] |
| Hex socket size s (hex key size) | 22 | Agrees in 2+ sources[12][13][8] |
| Hex socket depth t (min.) | 15.5 | Agrees in 2+ sources[12][13] |
⊙Clearance holes and counterbores
| Item | mm | Confidence |
|---|---|---|
| Clearance hole d′ for socket head cap screws | 33 | 1 source (reference)[12] |
| Counterbore diameter D′ for socket head cap screws | 48 | 1 source (reference)[12] |
| Counterbore depth H″ (head sits below the surface) | 32 | 1 source (reference)[12] |
| Counterbore depth H′ (head slightly proud) | 28 | 1 source (reference)[12] |
| Clearance hole, class 1 (JIS B 1001) | — | Not confirmed |
| Clearance hole, class 2 (JIS B 1001) | — | Not confirmed |
| Clearance hole, class 3 (JIS B 1001) | — | Not confirmed |
| Spotface diameter for hex bolts and nuts (JIS B 1001) | — | Not confirmed |
Socket-head values are from the reference table of JIS B 1176; clearance-hole classes are from JIS B 1001. The two standards give different clearance holes for some sizes.
≋M30 fine threads
| Size | D1 range (6H) | Recommended drill (cutting tap) |
|---|---|---|
| M30×2 | 27.835 – 28.21 | OSG 28 / Nachi (Nachi-Fujikoshi) 28 / Yamawa 28.1 |
| M30×1.5 | 28.376 – 28.676 | OSG 28.5 / Nachi (Nachi-Fujikoshi) 28.5 / Yamawa 28.6 |
📚Sources
Most sources are Japanese technical documents from the tap and fastener makers.
- iwata-fa.jp https://www.iwata-fa.jp/contents/assets/pdf/technicaldata/2022_tec_other_13.pdf
- nbk1560.com https://www.nbk1560.com/images/ja-JP/product/technical_data/meternezi_NBK/meternezi_NBK_1.…
- osg.co.jp https://www.osg.co.jp/media_dl/technical/file/drill_hole_size.pdf
- yamawa.com https://www.yamawa.com/Portals/0/images/download/holesize/jp/technical-contents-15.pdf
- nachi-fujikoshi.co.jp https://www.nachi-fujikoshi.co.jp/dcms_media/other/2501-12.pdf
- baer.tools https://baer.tools/en/blog/core-hole-dimensions-for-screw-taps-everything-you-need-to-know
- orist.jp https://www.orist.jp/technicalsheet/98015.PDF
- eg.aktio.co.jp https://www.eg.aktio.co.jp/wp-content/uploads/R3T_1-5_TONE_bolt_nimen.pdf
- tsurugacorp.co.jp https://www.tsurugacorp.co.jp/img/usr/pdf/B00000.pdf
- fabory.com https://www.fabory.com/en-GB/p/01103300001
- static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_nut_NBK/rokkaku_nut…
- jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2363.pdf
- farnell.com https://www.farnell.com/datasheets/11699.pdf