- Updated 23 October 2023
IBM buckling rubber sleeves (or simply IBM buckling sleeves) is the provisional name for a tactile key-switch developed by IBM as a quiet, low-profile alternative to IBM membrane buckling springs for IBM's flagship keyboards outside of the buckling spring keyboards' primary domains. It was first employed on the IBM Personal System/2 L40SX laptop and its Model M3 numeric keypad option both released in 1991, then subsequently reused on Model M4-family Space Saver Keyboards and then modified for use on Model M6-family PS/Note, PS/55 Note and ThinkPad keyboard assemblies. Its use on portable computers was phased out by the late 1990s, however, Unicomp continued to produce this switch for its Model M4-based Mighty Mouse keyboards until the late 2000s
ASK - Revealed: The Story of the Model M4 family [accessed 2021-11-18].. A version of this switch was also employed on IBM's 1993-launched Model M7, M7-1, M8, M9 and M11 POS keyboards and keypads, and later POS keyboards and keypads that IBM introduced in the 2000s and Toshiba Global Commerce Solutions continues to make today.
|Keycap mount||Dual-clip (M3/M4/M4-1/small gauge M6/M6-1) or crosspoint (standard & medium gauge M6/M6-1)|
|Total key travel||3mm typical (depends on gauge)|
|Peak tactile force travel||1mm|
|Peak tactile force||~60gf (± 20gf)|
|Rated lifetime||10 million key presses minimum|
Specifications correct for IBM buckling sleeves employed by Unicomp as of 1999
Unicomp - The Mighty Mouse 84 Key [accessed 2021-12-31]..
IBM buckling sleeves key-switches are membrane driven and were seemingly derived from the same patents and/or copyright as membrane buckling springs as their host devices often cite 1984 as the copyright date. The sleeves are tactile and snappy and are of medium-heavy weighting just below buckling springs. They do not feature part-way actuation as a property - like membrane assembly or conductive PCB driven rubber dome switches, the user is required to bottom out to actuate, but the experience of doing so is different to rubber dome switches and even some conceptually similar buckling rubber sleeve based switches. The key differences:
- Compared to rubber dome switches, the rubber component (the sleeve element) sits externally from the assembly on top of a barrel plate and is used for providing tactility and return force for the keycap only - they play no part in direct actuation. Most non-capacitive rubber dome switches are required to play a role in bridging the connection with the sensing mechanism.
- For IBM sleeves, a rod on the keycap or a slider in the barrel (depending on implementation) provides a solid interface to the membrane assembly to close the circuit, meaning the mushy bottom-out feeling typically expected from low-end rubber dome key-switches is generally avoided
ASK - Revealed: The Story of the Model M4 family [accessed 2021-11-18]..
- IBM sleeves are outwardly-expanding conical-shaped instead of traditionally dome-shaped and are sculpted so that the rubber at the top rim of the sleeve buckles to rest aside the bottom rubber instead of all 'squishing' at the bottom.
- Unlike the conceptually close Mitsumi KPQ-type key-switches, IBM's design lacks the conductive rubber foot on the bottom of its actuation element (keycap rod or barrel slider), eliminating another possible element that could dampen a solid bottoming out feel.
IBM buckling sleeves exist in five distinct sizes and forms (referred to as gauges) suited for different key sizes.
|Standard||M3, M4, M4-1, M6, M6-1, M7, M7-1, M8, M9, M11, M-e||~12.5mm||~3mm||Most common|
|Alt-standard||M3, M4, M4-1, M6, M6-1||~12.5mm||~2.5mm||Originally used on M3/M4/M4-1 spacebars, early M6 & M6-1s may also use this for all keys|
|Medium-tall||M-e||~10mm||~3mm||Exclusively used on CANPOS & MCANPOS small keys|
|Medium||M6, M6-1||~11mm||~2.5mm||Typically for only function & nav keys, some use for all keys|
|Small||M6, M6-1||~6.8mm||~2mm||Exclusively small function & nav keys|
IBM buckling sleeves were manufactured to various colours, which could vary based on many factors such as year of production, OEM, sleeve gauge and the colour of the host keyboard. The following sleeve colours are known:
Grey was the first prominent colour of buckling sleeve element used from the beginning, in 1991. They were typically found in most pearl white (IBM's trade name for creamy off-white colouring on products) Model M3s and pre-Unicomp Model M4s and M4-1s, but can also be found in early Model M7 to M11 keyboards made by Lexmark and Maxi Switch as late as 1996. They have only been seen in standard gauge.
The black buckling sleeve element was an alternative to the grey sleeves, used for most raven black (IBM's trade name for black colouring on products) buckling sleeve keyboards. They were first found on Model M6 ThinkPad and PS/55 Note C52 keyboard assemblies introduced in 1992 in alt-standard and medium gauge. The following year, raven black Model M4-1s appeared with standard gauge black sleeves. This colour of sleeve can notably vary, with some examples becoming greyish and powdery likely due to age and/or wear.
Grey-pink coloured buckling sleeve elements can be found as the alt-standard gauge buckling sleeves used on a number of buckling sleeve keyboards' spacebars. They appeared as early as 1993 on the spacebars for Model M6 for Lexmark's OEM laptops and most pre-Unicomp Model M4 and M4-1 keyboards. For Models M4 and M4-1, grey-pink sleeves were eventually replaced by the blue translucent standard gauge sleeve.
The blue translucent sleeve element was a spacebar-only standard gauge sleeve that served as either an alternative or outright replacement for grey-pink alt-standard sleeve. It has been spotted as early as 1995 on Lexmark-made Model M4-1s but is primarily associated with Unicomp after they took over Model M4/M4-1 production from Key Tronic in 1998.
Clear translucent sleeve elements first began appearing as Model M6 and M6-1 keyboard assemblies' small gauge sleeves and Apple Newton X0044 keyboard's medium gauge sleeves. As early as 2000, Maxi Switch had introduced clear translucent standard gauge sleeves on IBM POS keyboards too. Afterwards, all buckling sleeve elements would be of this colour. In 2001, the IBM Model "M-e" CANPOS Keyboard introduced the final sleeve gauge - medium-tall - in clear translucent.
The original implementation of IBM buckling sleeves was introduced with the March 1991-launched
IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES [accessed 2022-06-14]. IBM PS/2 L40SX laptop and its Model M3 numeric keypad, originally manufactured by IBM US. The following year, the L40SX keyboard assembly was adapted for use as a desktop keyboard for the Model M4 (without TrackPoint) and M4-1 (with TrackPoint) Space Saver Keyboards (made by Lexmark until 1996). Key Tronic briefly produced M4s shortly after Lexmark's exit from keyboard production and Unicomp finally continued producing and selling a keyboard based on them called the Mighty Mouse until 2010. During the 19 years of production and sale, the switch design remained unchanged. The principal feature of this earlier type of IBM buckling sleeves is the keycap mount, which features two plastic clips on either side of the keycap that retains the keycap on the barrel plate. As described in Design, the keycap's central rod is used for actuation
ASK - Revealed: The Story of the Model M4 family [accessed 2021-11-18].. This implementation also exclusively uses standard gauge sleeves, even for the smaller-sized keys.
IBM buckling sleeves received its first and largest revision in February 1992 when the IBM PS/2 CL57SX was announced
Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13]., sporting a Model M6 based keyboard (made by IBM U.S.
ASK - Revealed: IBM Model M3 & M6 laptop buckling sleeves keyboards#CL57SX [accessed 2022-06-19]. and later Lexmark
Ardent Tool - PS/2 Model CL57 SX [accessed 2022-06-19].) that despite resembling the L40SX's featured a radical change in the switch's actuator design. Namely, the membrane assembly's contact points are now pressed on by a barrel-fixed slider instead of a rod on the keycap, and the keycap itself now has a more traditional form of mounting (crosspoint) that doesn't require clips on the edges. The barrel slider colour was at first brown, a defining feature of early Model M6s. Along with the keyboards used for the ThinkPads 700, 720 and 350 series, PS/note 182 and 425 series and PS/55 note N27sx and C52, these keyboard assemblies were usually designated Model M6 by IBM. Lexmark itself also used the M6 design for a number of its own laptop (Lexbook) keyboard assemblies and some laptop keyboards it made for other companies. All known M6 keyboards were produced by IBM U.S. (very early on) or Lexmark.
M6 was later supplanted by the Model M6-1 introduced in June 1993
ThinkWiki - ThinkPad History [accessed 2021-11-18]. with the IBM ThinkPad 500 series. The actual distinction between M6 and M6-1 is blurry as both keyboards use interchangable sleeve gauges and keycaps (depending on unit size), but over time, the barrel slider colour was first changed to black then its keycap stem mounting socket was altered to appear more solid. M6-1 was made widespread by what followed the ThinkPad 500, such as the ThinkPads 750 series, 360 series, 370C, 355 series, 755C series, Power Series 850, 365 series and RS/6000 Notebook 860. There are some other non-ThinkPad IBM laptops and Lexmark OEM designs that were M6-1 based too. M6-1 was produced by Lexmark and later Key Tronic
ASK - Revealed: The Story of the Model M4 family [accessed 2021-11-18]. starting 1995 Q4, however, these should not be confused with Key Tronic's own take on the buckling rubber sleeves design used on the ThinkPad 701C/701CS TrackWrite keyboard
micrex22 - ThinkPad Keyboards and Switches [accessed 2021-11-18].. Several lineages of M6 family keyboards have appeared that use different layouts and/or key sizes which have been described into six types. For the alphanumeric and modifiers keys, the M6 family typically used standard or alt-standard gauge sleeves (all M6/M6-1 types except IV) that are fully interchangable with M3/M4/M4-1 type. However, for the smaller function and navigation keys, medium gauge sleeves are now employed. A select few M6s may use medium gauge sleeves for the alphanumeric and modifier keys (namely Type IV M6/M6-1) and small gauge sleeves for their function and navigation keys (Type IV or VI M6/M6-1).
The mouse button type IBM buckling sleeve is a subtype of Model M6 type used for the mouse buttons on Lexmark Lexbook AR-10 (16mm trackball) and GS-20 (pointing stick) series laptop keyboard assemblies. Thanks to the AR-10, they appeared as early as March 1992
PC Mag - 31 Mar 1992 [accessed 2023-05-11]. License/note: accessed via Google Books.. The two buttons are positioned in between the left-side Ctrl and Alt keys and are labelled "M1" and "M2". The sleeve and keycap design are the same as M6's, with the only observed sleeve used being standard gauge. But the barrel slider is clearly raised compared to its standard counterpart. This reduces the possible travel, creating a more "binary" feel that one might expect from a mouse button switch.
The third implementation of IBM buckling sleeves was introduced in June 1993 with the Retail series of POS (RPOS) keyboards introduced for the IBM 4694 POS Terminal
IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-04-23].. These keyboards were namely the IBM Models M7, M7-1, M8, M9 and M11 produced by Lexmark and Maxi Switch. This type is barrel slider actuated just like M6 type but the barrel slider is black instead of brown. The keycap mount itself is unchanged and it's possible to mount M6 (and later M6-1) keycaps onto an RPOS keyboard with this type. RPOS keyboards only ever used standard gauge sleeves.
Late POS type buckling sleeves are the latest IBM buckling sleeves design and the only one still in production. When IBM shifted RPOS production from the Americans to the Far East in the early 2000s, IBM opted to alter the keycap design back to a rod-actuated design like M3/M4/M4-1 type but still with some differences. Instead of using two clips to hold the keycap in place, the rod itself acts as the clip securing the keycap in its barrel. Late POS type keycaps are known for being hard to remove without damaging them. Whereas early POS type buckling sleeves were produced by Lexmark (USA) and Maxi Switch (Mexico), late POS type was produced by XAC (Taiwan) and XSZ (China) during the IBM era. In 2008, IBM introduced the Modular series of POS (MPOS) keyboards
IBM - IBM SurePOS 300 machine type 4810 offer new point-of-sale keyboards [accessed 2022-06-19]. that were an evolution of RPOS designs and retained the use of late POS type buckling sleeves. In 2012, Toshiba TEC bought IBM Retail Stores Solutions
IBM - Toshiba TEC to Acquire IBM's Retail Store Point-of-Sale Solutions Business; Agreement Allows Both to Tap Growing Smarter Commerce Opportunity [accessed 2022-06-19]., forming Toshiba Global Commerce Solutions and seemingly taking production of RPOS and MPOS keyboards in-house. As with early POS type versions, RPOS keyboards only used standard gauge sleeves, however, IBM CANPOS and IBM/Toshiba MCANPOS keyboards use medium-tall gauge sleeves for their half-height keys.
M3/M4/M4-1 type host devices
- IBM PS/2 L40SX (M3)
- IBM PS/2 L40SX Numeric Keypad (M3)
- IBM Space Saver Keyboard & Numeric Keypad (M4/M4-1)
- Lexmark Quiet Touch Keyboard & Numeric Keypad (M4/M4-1)
- IBM Personal System/55 5535-ZAD (M3)
- SAIC Galaxy 1100 (M3)
- Unicomp Mighty Mouse (M4/M4-1)
M6/M6-1 type host devices
- IBM 8554 PS/2 CL57SX (Type I M6)
- IBM 5527 PS/55note N27sx (Type I M6)
- Lexmark AR10 OEM series (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- CompuAdd Express 325NXL (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- CompuAdd Express 325FTX (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- CompuAdd Express 425FTX (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- IBM 9552 ThinkPad 700 series (Type III M6)
- IBM 9552 PS/55 note C52 (Type III M6)
- IBM 2141 PS/note 182 series (Type II M6)
- CompuAdd Express 325FTX/425CXL (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- Hyundai Courier Spectra (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- IBM 9552 ThinkPad 720 series (Type III M6)
- Cube ProBook 425NTX (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- IBM 2618 ThinkPad 350 series (Type II M6)
- IBM 2618 PS/note 425 series (Type II M6)
- IBM 2603 ThinkPad 500 series (Type IV M6-1)
- IBM 9545 ThinkPad 750 series (Type V M6-1)
- Lexmark GS20 OEM series (Type II M6, with 'mouse button type' buckling sleeve driven mouse buttons)
- Lexmark Lexbook MB10 & MB15 (Type IV M6-1, with 'mouse button type' buckling sleeve driven mouse buttons)
- Tadpole SPARCbook 3 series (Type III M6-1)
- Lexmark Lexbook SE10 (Type IV M6-1, with 'mouse button type' buckling sleeve driven mouse buttons)
- IBM 7007 RISC System/6000 Notebook N40 (Type V M6-1)
- IBM 2620 ThinkPad 360 series (Type V M6-1)
- IBM 9545 ThinkPad 755C "early" series (Type V M6-1)
- Winbook XP series (Type VI M6-1)
- IBM 2619 ThinkPad 355 series (Type V M6-1)
- AST Ascentia 900N series (Type VI M6-1)
- IBM 2604 ThinkPad 510Cs (Type IV M6-1)
- IBM 9545 ThinkPad 755C "late" series (Type V M6-1)
- IBM 9545 ThinkPad 370C (Type V M6-1)
- IBM 6042 ThinkPad Power Series 850 (Type V M6-1)
- Tadpole P1000 series (Type III M6-1)
- IBM 2625 ThinkPad 365 series (Type V M6-1)
- Tadpole ALPHAbook 1 (Type III M6-1)
- IBM 7249 RS/6000 Notebook 860 (Type V M6-1)
- Apple Newton MessagePage Keyboard (Type IV M6-1)
- Tadpole SPARCbook 3000 series (Type III M6-1)
Early POS type host keyboards
- IBM Retail POS Keyboard w/ Card Reader (M7, 1993-2002)
- IBM Retail POS Keyboard (M7-1, 1993-2002)
- IBM Retail POS Keyboard w/ Card Reader and Display (M8, 1993-2002)
- IBM Retail ANPOS Keyboard w/ Card Reader (M9, 1993-2002)
- IBM Modifiable Layout Keyboard (M11, 1993-2002)
Late POS type host keyboards
- IBM/Toshiba Retail POS Keyboard w/ Card Reader (M7, 2002-2015)
- IBM/Toshiba Retail POS Keyboard (M7-1, 2002-2015)
- IBM/Toshiba Retail POS Keyboard w/ Card Reader and Display (M8, 2002-2015)
- IBM/Toshiba Retail ANPOS Keyboard w/ Card Reader (M9, 2002-2015)
- IBM/Toshiba Modifiable Layout Keyboard (M11, 2002-2015)
- IBM PS/2 ANPOS Keyboard with Integrated Pointing Device
- IBM CANPOS Keyboard
- IBM SurePoint 4820 Monitor Keypad and MSR Extension
- IBM/Toshiba Modular 67-Key Keyboard
- IBM/Toshiba Modular ANPOS (MANPOS) Keyboard
- IBM/Toshiba Modular CANPOS (MCANPOS) Keyboard
- IBM/Toshiba Modular 67-Key Keyboard with LCD Display
- ASK - Revealed: The Story of the Model M4 family [accessed 2021-11-18].
- Unicomp - The Mighty Mouse 84 Key [accessed 2021-12-31].
- theMK#1822 - donated photo. License/note: CC-BY-NC-SA 4.0.
- Jugostran#2852 - donated photo.
- IBM - THE IBM PS/2 MODEL L40 SX SYSTEM AND FEATURES [accessed 2022-06-14].
- Ardent Tool - IBM PS/2 Model CL57 SX System 8554-A45 and Features Announcement Letter (#ZG92-0165) [accessed 2023-07-13].
- ASK - Revealed: IBM Model M3 & M6 laptop buckling sleeves keyboards#CL57SX [accessed 2022-06-19].
- Ardent Tool - PS/2 Model CL57 SX [accessed 2022-06-19].
- ThinkWiki - ThinkPad History [accessed 2021-11-18].
- micrex22 - ThinkPad Keyboards and Switches [accessed 2021-11-18].
- PC Mag - 31 Mar 1992 [accessed 2023-05-11]. License/note: accessed via Google Books.
- IBM - IBM 4694 POS Terminal Model 001 Brief Description of Announcement, Charges, and Availability (#193-150) [accessed 2022-04-23].
- IBM - IBM SurePOS 300 machine type 4810 offer new point-of-sale keyboards [accessed 2022-06-19].
- IBM - Toshiba TEC to Acquire IBM's Retail Store Point-of-Sale Solutions Business; Agreement Allows Both to Tap Growing Smarter Commerce Opportunity [accessed 2022-06-19].
- ASK Keyboard Archive - P/N 65Y4044 (2011, IBM-RSS) [accessed 2022-11-30]. License/note: photos donated by theMK#1822, CC BY-NC-SA 4.0.
|2023-10-23||Revisions for IBM buckling rubber sleeve wiki page have been published - Added updated M6/M6-1 info and updated host devices list|
|2023-04-29||Revisions for IBM buckling rubber sleeve wiki page have been published - Add Colour section|
|2023-04-18||Revisions for IBM buckling rubber sleeve wiki page have been published - Properly attribute theMK for the P/N 65Y4044 photo|
|2023-02-02||Revisions for IBM buckling rubber sleeve wiki page have been published - Add section on mouse button type buckling sleeves found on Lexmark AR-10 and GS-20 laptops|
|2022-12-30||Revisions for IBM buckling rubber sleeve wiki page have been published - Add cover photo|
|2022-12-30||Revisions for IBM buckling rubber sleeve wiki page have been published - Change thumbnail from JPG to PNG|