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Washers · Trade series (vulcanised fibre washer)

M4 Insulating Fibre Washers Dimensions

Controlling dimensions to Trade series (vulcanised fibre washer), with tolerances and fit.

M4 Insulating Fibre Washers dimensions to Trade series (vulcanised fibre washer): inside diameter 4.3 mm, outside diameter 9 mm, thickness 0.5 mm.

Inside diameter
4.3 mm
Outside diameter
9 mm
Thickness
0.5 mm

Figures are nominal values from the governing standard. Confirm against the tolerance class for your application before machining or ordering.

M4 Insulating Fibre Washers Dimensions reference image

Dimensional data for M4 Insulating Fibre Washers. Selection is by nominal bolt size rather than by thread, so the controlling figures are the ones in the row below together with the fit and tolerance the mating feature requires.

M4 Dimensional Row (Trade series (vulcanised fibre washer))

For bolt sizeInner diameter d1 (mm)Outer diameter d2 (mm)Thickness t (mm)Dielectric strength (kV/mm)Max temperature (u00b0C)MaterialMoisture
M44.39.00.510105Vulcanised fibreHygroscopic u2014 indoor use

Mating Parts for M4

A M4 flat washer pairs with a M4 bolt/screw and matching M4 nut.

Custom manufacturing · Made to drawing

Need insulating fibre washers in a size this table does not list?

This page covers M4 insulating fibre washers. Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

Custom washer manufacturingSend a drawing

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.

Dimensioned line drawing of M4 Insulating Fibre Washers to Trade series (vulcanised fibre washer). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.
Inner diameter d1 (mm)
4.3
Outer diameter d2 (mm)
9.0
Thickness t (mm)
0.5
Dielectric strength (kV/mm)
10
Max temperature (u00b0C)
105
Material
Vulcanised fibre
Moisture
Hygroscopic u2014 indoor use
Sends the selected values to the quote form below.

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The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

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Specification
Business Information

Dimensions & Specifications (Trade series (vulcanised fibre washer))

For bolt sizeInner diameter d1 (mm)Outer diameter d2 (mm)Thickness t (mm)Dielectric strength (kV/mm)Max temperature (u00b0C)MaterialMoisture
M33.27.00.510105Vulcanised fibreHygroscopic u2014 indoor use
M44.39.00.510105Vulcanised fibreHygroscopic u2014 indoor use
M55.310.00.810105Vulcanised fibreHygroscopic u2014 indoor use
M66.412.00.810105Vulcanised fibreHygroscopic u2014 indoor use
M88.416.01.010105Vulcanised fibreHygroscopic u2014 indoor use
M1010.520.01.010105Vulcanised fibreHygroscopic u2014 indoor use

Applications & Industries for M4 Insulating Fibre Washers

The sectors that buy Insulating Fibre Washers, and the duty each one buys them for. Stocked from M3 to M10 (nominal bolt size).

Industries that specify Insulating Fibre Washers

  • Food & pharma equipment Non-marking, non-contaminating washers in washdown areas.
  • Electrical & electronics Insulating and isolating fixings in panels and boards.
  • Chemical & process Chemically resistant seating under a fastener.
  • Machine building & OEM Setting bearing area on soft alloy, plastic and oversized holes.
  • Timber & construction Large-diameter washers that stop pull-through in softer material.
  • Rotating & vibrating plant Spring, tooth and wedge types that maintain or lock bolt tension.

Typical applications

  • protecting a soft or finished surface under a head
  • insulating a fastener electrically from the panel
  • separating dissimilar metals to break a galvanic cell
  • maintaining bolt tension in a joint that settles
  • spreading clamp load over a soft or oversized bearing face
  • protecting a painted or plated surface under a turned nut

Service conditions to specify against

Marine and coastal
Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
Hardness matters
Under a high-strength bolt a soft washer embeds into the joint and preload is lost — specify a hardened washer for structural bolting.

Full application guide: where Insulating Fibre Washers are used, how to specify them, and the cases they are wrong for

Video: M4 Insulating Fibre Washers Dimensions

45° Wedge Washer Product Overview & Best Practices

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.

  1. Wire rod feeding into a cold heading machine
    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.

  2. Thread rolling machine producing bolt threads
    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.

  3. Baskets of bolts staged for heat treatment
    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.

  4. Zinc plated bolts in a treatment basket
    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

Which washer dimensions matter most for M4?

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 M4 for Insulating Fibre Washers?

For M4 the standard coarse pitch is 0.7 mm — this is the value used for Insulating Fibre Washers.

What clearance and tapping drill suit M4?

Use a 4.5 mm clearance hole (ISO 273 medium) for through-fixing, or a 3.3 mm tapping drill for a coarse M4 thread.

Is M4 Insulating Fibre Washers suitable for electronics and small mechanisms?

M4 Insulating Fibre Washers is in the micro range and is widely used in electronics, instrument enclosures and small precision mechanisms. Watch the over-torque margin — micro joints strip easily.

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.