日本語

Printed from Kezuriba (kezuriba.net/en/threads/m27/)

M27×3

ISO metric coarse thread

Nominal diameter 27 mm, pitch 3 mm. Tap makers recommend slightly different drill sizes, so they are listed side by side.

Tap drill, rule of thumb (d − P)
24.00 mmMaker recommendations below
Minor diameter D1 range (6H)
23.752 – 24.252 mmKeep the hole inside this range[4][5][3]
Pitch diameter d2 (basic)
25.051 mmd2 = d − 0.649519P
M27 basic profile and dimensions (schematic)
external thread (bolt)major dia. d = 27pitch dia. d2 = 25.051minor dia. D1 = 23.7526H range 23.752–24.252 (tap drill target)P = 3H160°

Thread angle 60°. H1 (basic thread engagement) = 0.541266P = 1.624. 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).

MakerRecommended drillNotesSource
OSG24min. 23.8, 6H max. 24.25
[3]
Nachi (Nachi-Fujikoshi)24high-performance drill 24.1[5]
Yamawa24.1[4]
Calculate tapping RPM for this size →

Forming (roll) tap drill sizes differ by maker and product line; see the Japanese page for the table.

⌇Basic dimensions

Nominal (major) diameter d27
Pitch P3
Pitch diameter d2, D225.051
Basic minor diameter D1 (nut), d1 (bolt)23.752
Fundamental triangle height H = 0.866025P2.598
Basic engagement H1 = 0.541266P1.624

Basic dimensions are theoretical values without tolerance. Try other pitches with the thread dimension calculator.

⬡Bolt and nut sizes

ItemmmConfidence
Hex bolt width across flats s (ISO-based JIS, main body)411 source (reference)[8]
Hex bolt width across flats s (old JIS, annex)411 source (reference)[9]
Hex nut width across flats s (ISO-based JIS, main body)41Agrees in 2+ sources[8][10]
Hex nut width across flats s (old JIS, annex)411 source (reference)[11]
Hex nut height m (style 1, max.)23.81 source (reference)[10]
Socket head cap screw head diameter dk (max.)40Agrees in 2+ sources[12][13]
Socket head cap screw head height k (max.)27Agrees in 2+ sources[12][13]
Hex socket size s (hex key size)19Agrees in 2+ sources[12][13][8]
Hex socket depth t (min.)13.5Agrees in 2+ sources[12][13]

⊙Clearance holes and counterbores

ItemmmConfidence
Clearance hole d′ for socket head cap screws301 source (reference)[12]
Counterbore diameter D′ for socket head cap screws431 source (reference)[12]
Counterbore depth H″ (head sits below the surface)291 source (reference)[12]
Counterbore depth H′ (head slightly proud)251 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.

≋M27 fine threads

SizeD1 range (6H)Recommended drill (cutting tap)
M27×224.835 – 25.21OSG 25 / Nachi (Nachi-Fujikoshi) 25 / Yamawa 25.1
M27×1.525.376 – 25.676OSG 25.5 / Nachi (Nachi-Fujikoshi) 25.5 / Yamawa 25.6

📚Sources

Most sources are Japanese technical documents from the tap and fastener makers.

  1. iwata-fa.jp https://www.iwata-fa.jp/contents/assets/pdf/technicaldata/2022_tec_other_13.pdf
  2. nbk1560.com https://www.nbk1560.com/images/ja-JP/product/technical_data/meternezi_NBK/meternezi_NBK_1.…
  3. osg.co.jp https://www.osg.co.jp/media_dl/technical/file/drill_hole_size.pdf
  4. yamawa.com https://www.yamawa.com/Portals/0/images/download/holesize/jp/technical-contents-15.pdf
  5. nachi-fujikoshi.co.jp https://www.nachi-fujikoshi.co.jp/dcms_media/other/2501-12.pdf
  6. baer.tools https://baer.tools/en/blog/core-hole-dimensions-for-screw-taps-everything-you-need-to-know
  7. orist.jp https://www.orist.jp/technicalsheet/98015.PDF
  8. eg.aktio.co.jp https://www.eg.aktio.co.jp/wp-content/uploads/R3T_1-5_TONE_bolt_nimen.pdf
  9. tsurugacorp.co.jp https://www.tsurugacorp.co.jp/img/usr/pdf/B00000.pdf
  10. fabory.com https://www.fabory.com/en-GB/p/01103270001
  11. static.nbk1560.com https://static.nbk1560.com/images/ja-JP/product/technical_data/rokkaku_nut_NBK/rokkaku_nut…
  12. jp.misumi-ec.com https://jp.misumi-ec.com/pdf/fa/2015/p1_2363.pdf
  13. farnell.com https://www.farnell.com/datasheets/11699.pdf