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Cherry M8, MD and MJ

Contents

Cherry M8

Serie M8 is an ultra-low-profile keyboard switch series from Cherry in Germany. German M8 is fairly well documented: see the M8 schema for details. M8 switches use the 6 mm keycap mount, which is effectively a shorter version of the 8 mm mount used on Cherry MX.

M8 was divided into three subseries—M81, M82 and M84—according to the type of switch contacts used. M81 and M82 use solid metal contact prisms formed from gold and silver alloy respectively. These metal prisms were expensive to manufacture, and shortly before the introduction of Cherry MX, Cherry introduced a new lower-cost contact type based on gold-plated wire (see under MX for more details). This new contact type was used on German-made and US-made MX switches from the start, and it was introduced to M8 switches as subseries M84.

All M8 types offer 2.5 mm travel.

Configuration choices for this series include:

Cherry issued an end-of-life notification for M8 on the 31st of July 2013, and set the 31st of October 2013 as the last-buy date. A small quantity of M84A-0100 was obtained for Deskthority by Robin Bithrey of Cherry UK, while 20 models remained available up to that date. Only M82, M84, and M85 (a different but related series) were available by this point, with M81 being already discontinued.

Specifications

General

Note that the contact bounce time differs between the 1982 catalogue (2 ms) and the various M8 brochure scans, all of unknown age. Bounce time was not given in the 1998 catalogue.

Travel 2.5+0.2−0.3 mm
Pretravel 1.6±0.6 mm (linear)
1.3±0.6 mm (regular tactile)
1.4±0.6 mm (German postal tactile)
Bounce time 2 ms max (M81, 1982) or 5 ms max (brochure, all types)
Lifetime 10 million (momentary)

Electrical

Characteristic M81 M82 M84
Contacts Au Ag 26 Ni 3 solid prism Ag Pd 30 solid prism Au Ag 10, 3 µm plated wire
Switching current 100 mA maximum 100 mA maximum 10 mA maximum
Carrying current 500 mA
Voltage 28 V maximum 60 V maximum 12 V maximum
Contact resistance 200 mΩ max. initial (typical 25 mΩ)

Hirose Cherry M8

Separately, Hirose Cherry Precision in Japan made their own versions of M8 switches. These are themselves divided up into two separate subseries, M83A and M83S. Unlike German switches which were linear by default, Hirose M8 switches all seem to be tactile, although this was not advertised on the datasheet.

The relationship between German-made M93 and Japanese-made M83 is not known. Japanese-made M8 switches use Hirose’s own contact form, using a through-hole copper (or copper alloy) base plated in gold alloy, which stands in stark contrast to their datasheets which depict a structured solid alloy identical in form to that of American-made switches.

M83A

M83A appears to be the standard Japanese M8 switch. These switches exhibit a number of differences compared to their German counterparts. The most notable is the plunger planform, which appears to be designed for increased stability. This prevents an LED from being placed centre-edge as in German switches. Instead, the switch accommodates a miniature 2 × 4 mm rectangular LED in the rear-left corner. Travel is 2.5 mm as per German M8 switches.

M83S

M83S is the same size as M83A, but it reduces switch travel from 2.5 mm down to 1.5 mm. The raised areas on either side of the plunger are omitted. These switches so far have been found with black plungers. These have been found in the Epson PX-8 (for the function keys) and Yamaha QX21. In the former case, they are fitted with dust covers, unlike the MD switches used for the other keys.

Hirose Cherry MD and MJ

Hirose also produced two related series, offering greater travel. MD series extends the shell height from 6.7 mm to 7.3 mm, and the total height from PCB top surface to the top of the keystem by 0.5 mm from 10.6 to 11.1. Travel is increased to 3 mm. MD switches were used in the Epson PX-8 with angled keysems, although keystem angle was not a documented feature on the datasheet.

MJ series extends the shell height another 0.4 mm to 7.7 mm, and the total above-PCB height by 0.6 mm to 11.7 mm, providing a full 4 mm of travel.

Variants

See the M8, MD and MJ variants page.