3M™ Bayonet to 40MM NATO (RD40x1/7) Adapter

This prototype design for a 3M™ bayonet to 40MM NATO (RD40x1/7/DIN) gas mask thread. Designed to help cross compatibility of commercial off the shelf (COTS) filters with other manufacturer’s respirators, during this PPE shortage, should be compatible with any RD40x1/7 filter canisters.

If you do not have access to 40MM (RD40x1/7) filters, you can use the following adapters to step down to COTS filter cartridges from these companies below:

40 MM NATO to 3M™ Filter Adapter
https://www.thingiverse.com/thing:4245358

40MM NATO to Scott® 742 Series Filter Adapter
https://www.thingiverse.com/thing:4347531

40 MM NATO to MSA® Bayonet Filter Adapter
https://www.thingiverse.com/thing:4265715

40MM NATO to MSA® Comfo Classic Filter Adapter
https://www.thingiverse.com/thing:4267676

40MM NATO to Honeywell/Honeywell North® Filter Adapter
https://www.thingiverse.com/thing:4268775

40MM NATO to Honeywell Sperian® Filter Adapter
https://www.thingiverse.com/thing:4297348

40MM NATO to Honeywell Safety Sperian® /Survivair™ ValuAir® (Bayonet) Filter Adapter
https://www.thingiverse.com/thing:4345345

40MM NATO to AOSafety® Threaded Filter Adapter
https://www.thingiverse.com/thing:4273365

40 MM NATO to AOSafety® R5700 8051 Bayonet Filter Adapter
https://www.thingiverse.com/thing:4265538

40MM NATO to Portwest® Bayonet Filter Adapter
https://www.thingiverse.com/thing:4273464

40MM NATO to Moldex® 7000/9000 Series EasyLock® Bayonet Filter Adapter
https://www.thingiverse.com/thing:4275446

40MM NATO to Secura BC Bayonet Filter Adapter
https://www.thingiverse.com/thing:4294187

40MM NATO to JSP® Force™8 Filter Adapter
https://www.thingiverse.com/thing:4294203

40MM NATO to Delta Plus M3000 Mars Series Filter Adapter
https://www.thingiverse.com/thing:4311197

40MM NATO to Delta Plus M6000 Jupiter Series Filter Adapter
https://www.thingiverse.com/thing:4311200

40MM NATO TO GOST 8762-75 Threaded Filter Adapter
https://www.thingiverse.com/thing:4321450

40MM NATO to Draeger X-plore® Filter (3000/5000 Series) Adapter
https://www.thingiverse.com/thing:4329276

40MM NATO to ENHA Rockman 7300 Series Filter Adapter
https://www.thingiverse.com/thing:4329610

40MM NATO to Sundstrom SR Series Filter Adapter
https://www.thingiverse.com/thing:4338105

40MM NATO to Milla EURMASK® ETNA (Bayonet) Series Filter Adapter
https://www.thingiverse.com/thing:4342320

40MM NATO to Milla EURMASK® (Uno/New) Series Threaded Filter Adapter
https://www.thingiverse.com/thing:4342343

Alternatively, if you cannot source COTS filters, search thingiverse, there are a number of other DIY filter cartridge designs to mate to other major manufacturer, 3M/MSA/etc. respirator's attachment system.

Part Description:

3M_BAYONET_TO_40MM_NATO_ADAPTER_GEN1.stl
Initial model release, requires o-ring or gasket inside female side 40MM NATO threads to ensure proper seal.

3M_BAYONET_TO_40MM_NATO_ADAPTER_GEN2.stl
Gen. 2 features the following changes: (1) chamfers added to 3M bayonet to filter mating surfaces to reduce sharp edges that could result in wear on 3M bayonet, (2) redone chamber from underside OD to wrench flats to reduce printing overhang supports, and (3) added engraved markings on exterior periphery to ID adapter.

3M_BAYONET_TO_40MM_NATO_ADAPTER_GEN3.stl
Gen. 3 features the following changes: (1) reworked the 3M bayonet to filter mating surfaces to ensure positive engagement against OEM 3M gasket durometer, and (2) redone chamber from underside OD to wrench flats to completely printing overhang supports on wrenching ears.

Disclaimers/Risks:

1.) Use Proper Gaskets
Requires 40 mm OD gasket or o-ring on the underside bayonet to ensure proper seal maintained between cartridge and threads.

2.) Perform Proper Negative Pressure Test
Follow SSPs established by your institution or workplace for further guidance. But in general, don your respirator, adjust straps till taught against face, ensuring no obstructions around the periphery of the seal against face either due from hair, facial hair, or otherwise. Exhale deeply. Cover all inhalation ports. (Typically, most full face or half face respirators have two filters, so cover those intake ports with your hands. If your running only one filter, ensure the opposite port has filter cap in place.) Now inhale deeply. The mask should suck tightly against your face without any air leakages. Re-test if adjustments are required at gasket/o-ring interfaces at the adapter.

3.) Use At Own Risk – Temporarily Solution Only Until Supply Chain Normalizes
3D printing materials are not resistant to many solvents, are water soluble, and degrade when exposed to chemicals, heat, and UV/sunlight. 3D printing this adapter is only a temporarily ad-hoc solution against biological contagions. In addition to using a properly calibrated 3D printer, due to tolerances of adapters, if possible perform hot nozzle pass on all exterior surfaces, to reduce surface porosity. Highly recommended users apply a thin layer of polyurethane clear coat on all exterior surfaces, spray or dip based methods, to help resiliency and durability for repeated sterilization and to reduce fomite transmission in printed infill layers. Once supply chains return to normal, users should purchase OEM OSHA/NIOSH/EN standard approved respirators, adapters and accessories for their institution and workplaces.

Dev. Notes:

04/11/2020 - Initial model release. In work, pending 3D printing community support for any fitment and model revisions.

04/13/2020 - Revised model based on feedback from 3D printing community. The following changes have been made: (1) chamfers added to 3M™ bayonet to filter mating surfaces to reduce sharp edges that could result in wear on 3M™ bayonet, (2) redone chamber from underside OD to wrench flats to reduce printing overhang supports, and (3) added engraved markings on exterior periphery to ID adapter.

04/26/2020 - After getting my hands on a physical prototype, thanks to jlwatchman, updated model to with 3rd revision by removing all overhang support on underside of wrenching ears, changed workflow of female side geometry, with greater thicknesses to ensure positive engagement with OEM 3M™ gasket durometer, recessed pocket thickness increased past ramp, and ramp height increased to ensure proper compression against gasket. Note using different durometer gasket material on the 3M™ bayonet design may result in greater or less friction during engagement than original 3M™ 6895 Replacement Inhalation Port Gasket.