The M8 size of Bonded Sealing Washers is dimensioned by BS 4518. The table below gives the dimensional row from the standard, followed by the installation notes for this type.
M8 Dimensional Row (BS 4518)
Thread size
Inner diameter d1 (mm)
Outer diameter d2 (mm)
Thickness s (mm)
Seal material
Max temperature (deg C)
Reference standard
M8
8.2
14
1.5
NBR
120
BS 4518
Common Applications for M8 Bonded Sealing Washers
M8 Bonded Sealing Washers are commonly specified for general-purpose load-spreading and locking under machine bolts.
Mating Parts for M8
A M8 flat washer pairs with a M8 bolt/screw and matching M8 nut.
Technical Drawing
Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.
Sends the selected values to the quote form below.
Request a Quote
The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.
Dimensions & Specifications (BS 4518)
Thread size
Inner diameter d1 (mm)
Outer diameter d2 (mm)
Thickness s (mm)
Seal material
Max temperature (deg C)
Reference standard
M4
4.1
8
1.0
NBR
120
BS 4518
M5
5.1
10
1.0
NBR
120
BS 4518
M6
6.1
12
1.5
NBR
120
BS 4518
M8
8.2
14
1.5
NBR
120
BS 4518
M10
10.2
16
1.5
NBR
120
BS 4518
M12
12.2
19
2.0
NBR
120
BS 4518
M14
14.2
21
2.0
NBR
120
BS 4518
M16
16.3
24
2.0
NBR
120
BS 4518
M18
18.3
26
2.0
NBR
120
BS 4518
M20
20.3
28
2.0
NBR
120
BS 4518
M22
22.3
30
2.0
NBR
120
BS 4518
M24
24.3
32
2.0
NBR
120
BS 4518
M27
27.4
36
2.5
NBR
120
BS 4518
M30
30.4
39
2.5
NBR
120
BS 4518
M33
33.5
43
2.5
NBR
120
BS 4518
M36
36.5
46
2.5
NBR
120
BS 4518
Materials & Grades
Select a material class to see the grades we supply it in. Each designation is listed with its ISO/EN, AISI/SAE, JIS and GB equivalents.
Third-party video, selected automatically for this topic. It is not produced by Engineering Hardware and is not a specification source — use the tables on this page for dimensional data.
Inside the plant
Manufactured in our own plant
This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.
01
Cold heading
Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail.
Head dimensions and under-head radius checked at set-up and per shift.
02
Thread rolling
Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch.
Go / no-go ring gauges to ISO 965 tolerance class 6g.
03
Heat treatment
Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it.
Core hardness and tensile tested per lot to ISO 898-1.
04
Surface treatment
Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list.
Coating thickness and neutral salt spray hours to ISO 9227.
Frequently Asked Questions
What clearance and tapping drill suit M8?
Use a 9 mm clearance hole (ISO 273 medium) for through-fixing, or a 6.8 mm tapping drill for a coarse M8 thread.
Which washer dimensions matter most for M8?
For a flat washer, the outside diameter (the bearing surface) and the thickness control how the load is spread under the head and how much elastic preload is preserved. The inside diameter must clear the bolt body but not be so large that the head bears mostly on the washer's outer rim.
What is the coarse-thread pitch of M8 for Bonded Sealing Washers?
For M8 the standard coarse pitch is 1.25 mm — this is the value used for Bonded Sealing Washers.
How do I request a quotation?
Use the technical drawing on this page to pick the exact configuration, then submit it with the quote form. We respond within one business day.
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