Hotplate & Stirrer

Overhead Stirrers Accessories

<h2>What Are Overhead Stirrer Accessories?</h2>
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Overhead stirrer accessories are modular components that attach to an overhead stirrer motor unit to adapt it for specific applications, vessel formats, and chemical conditions. The core accessories are impellers (the mixing head), drive shafts (which connect the motor to the impeller), chuck or collet adapters (which secure the shaft in the motor's output), and support stands with clamps or crossbar assemblies that position the motor above the vessel at the correct height. Additional accessories include vessel holders and clamp stands for securing round-bottom or Erlenmeyer flasks during mixing, PTFE sleeves for shaft sealing in closed-vessel applications, and digital speed display controllers that retrofit onto analog motor units. Because overhead stirrer motor chucks accept shafts within a defined diameter range (commonly 6 mm, 8 mm, 10 mm, or 12 mm), confirm shaft diameter compatibility with the motor before ordering any impeller-and-shaft combination. Before ordering any accessory, confirm three things: motor chuck bore diameter, required shaft length for your vessel depth, and whether the impeller geometry matches the flow regime your application needs.
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<h2>What You Will Find:</h2>
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<ul>
<li>Stainless steel and PTFE (Teflon&reg;) propellers compatible with overhead stirrers for a variety of mixing applications.</li>
<li>One-line propellers designed for efficient agitation in low- to medium-viscosity liquids.</li>
<li>Paddle propellers with flat holes for enhanced fluid circulation and blending performance.</li>
<li>Centrifugal impellers that promote radial flow and effective mixing of liquid samples.</li>
<li>Four-arm propellers available in stainless steel or PTFE for versatile stirring across diverse laboratory workflows.</li>
</ul>
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<h2>How to Choose Overhead Stirrer Accessories</h2>
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Impeller geometry
Impeller type determines mixing regime and is the primary accessory selection decision. Propeller impellers (two- or three-blade marine propeller) generate axial flow, drawing fluid from above and directing it downward, suited for general liquid blending, cell suspension, and low-viscosity mixing. Paddle and anchor impellers sweep tangentially near the vessel wall, appropriate for high-viscosity materials that resist axial flow. Dispersing disc impellers (flat disc with serrated edge or teeth) generate radial high-shear flow for emulsification, pigment dispersion, and fine particle suspension. Ribbon impellers are used for highly viscous, thickening batches where conventional impellers fail to move material from the vessel walls.
Shaft length and diameter
The shaft length must extend from the motor chuck to the correct immersion depth in the vessel. Standard lengths range from 200 mm to 600 mm; longer shafts are available for deep vessels or pilot-scale bioreactors. Shaft diameter must fit within the motor's chuck bore (confirm before ordering). Thicker shafts (10 mm to 12 mm) are more rigid and reduce wobble at high speed; thin shafts (6 mm) suit small-volume vessels and lower-torque motors.
Material: stainless steel vs. PTFE
Stainless steel (316L is preferred for chemical resistance over 304) is the standard for shafts and impellers in aqueous buffers, culture media, alcohols, and mild organic solvents. PTFE shafts and impellers are required for corrosive acids, bases (concentrated NaOH, HCl, HF), halogenated solvents, and any application where metal ion contamination of the sample must be avoided. Stainless steel and PTFE impellers are not interchangeable from a torque-transfer standpoint; PTFE is softer and suitable for lower-torque applications.
Support stands and clamps.
Support stands must be rigid enough to prevent shaft wobble at maximum operating speed. Confirm that the stand's vertical travel range accommodates the vessel height plus the motor unit. Crossbar clamp assemblies allow the motor unit to be raised and lowered without removing the shaft from the vessel. Heavy-duty stands with a wide base footprint are recommended for motors above 40 Ncm and for operation above 500 rpm.
Chuck and collet adapters
Motors accept shafts with a specific bore range. Collet adapters reduce or increase the effective chuck bore to fit a different shaft diameter. Confirm the motor's chuck diameter (manufacturer-specific) and the shaft outer diameter before ordering a collet or chuck adapter; a mismatched fit can cause shaft slippage during mixing.
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<h2>Specifications Context</h2>
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Impeller diameter should be 30 to 50% of the vessel inner diameter for most mixing regimes. A blade diameter that is too small leaves dead zones at the vessel wall; too large generates excessive shear and can damage shear-sensitive samples. For autoclave-compatible setups, confirm that the shaft, impeller, and any sealing sleeve are rated for 121 degrees C steam sterilization. Shaft straightness should be verified at the stated operating speed; a bent or unbalanced shaft generates vibration that compounds with any sample viscosity increase to stress the motor bearings.&nbsp;
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Looking for the right propeller for your process? Explore our overhead stirrer accessories and <a href="https://mbpinc.net/contact-us">reach out to the MBP team</a> for a quote today.

Overhead Stirrer Accessories

Optional propeller, stainless steel centrifugal impeller

The IPS2050-P-S2 by Benchmark Scientific is a 316 stainless-steel centrifugal impeller propeller (400 mm length, 90 mm diameter) for the Benchmark Scientific OS-20L and OS-40L overhead stirrers, designed for mid- to high-speed mixing in small-mouth, round-bottom flasks.

Length

Diameter

Shaft Diameter

Material

Manufacture

Optional propeller, stainless steel one line

IPS2050-P-S1 by Benchmark Scientific is a 316 stainless steel one-line (single flat-blade) propeller, 400 mm long with a 60 mm blade diameter and an 8 mm shaft, designed for low-viscosity, mid-to-high-speed mixing on the Benchmark OS-20L and OS-40L overhead stirrers. The single-blade axial flow pattern suits rapid buffer homogenisation, reagent dissolution, and suspension maintenance in aqueous process fluids up to 20 L capacity.

Optional propeller, stainless steel paddle with flat holes

IPS2050-P-S3 by Benchmark Scientific is an optional stainless steel flat paddle propeller with 3 flat holes for the Benchmark IPS2050 OS-20L and OS-40L overhead stirrers. Designed for gentle, mid to low-speed mixing, its paddle geometry minimizes shear stress — suited for fragile cell suspensions, viscous samples, and slow-dissolution applications where the standard 4-arm propeller would cause damage or foaming.

Optional propeller, Teflon 4 arm

IPS2050-P-T4 by Benchmark Scientific is a PTFE-coated (Teflon) 4-arm propeller for the Benchmark™ OS-20L and OS-40L overhead stirrers — 300 mm total length, 65 mm propeller diameter, 6 mm shaft. Designed for mid to high-speed mixing of corrosive acids, bases, and solvents where metal or plastic propellers are not suitable.

Optional propeller, Teflon centrifugal impeller

IPS2050-P-T2 by Benchmark Scientific is a PTFE-coated centrifugal impeller measuring 350 mm long with an 85 mm open diameter and a 6 mm shaft, designed for mid-to-high-speed mixing on the Benchmark OS-20L and OS-40L overhead stirrers. The centrifugal open-blade disc geometry is optimised for small-mouth round flasks and corrosive solvent applications where a paddle propeller cannot enter the flask neck and metal-free fluid contact is required.

Optional propeller, Teflon one line

The IPS2050-P-T1 by Benchmark Scientific is a PTFE-coated, single-line propeller (350 mm length, 70 mm blade diameter, 6 mm shaft) designed for low-viscosity, mid-to-high-speed mixing. Compatible with Benchmark OS-20L and OS-40L overhead stirrers, it suits buffer prep, dissolution studies, and solvent-based mixing in research labs worldwide.

Optional propeller, Teflon paddle with flat holes

IPS2050-P-T3 by Benchmark Scientific is a PTFE-coated flat paddle propeller with three holes, measuring 350 mm long with a 68 mm blade diameter and a 6 mm shaft, compatible with the Benchmark OS-20L and OS-40L overhead stirrers. The flat-hole paddle geometry produces low-shear axial flow for gentle to mid-speed mixing of corrosive, protein-containing, or foam-sensitive fluids where metal-free contact and minimal turbulence are required.

Hotplate & Stirrer Accessories

<h2>What Are Hotplate and Stirrer Accessories?</h2>
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Hotplate and stirrer accessories are supplementary components for single-position and multi-position hotplate stirrers that improve temperature accuracy, expand vessel compatibility, enable reflux setups, and maintain equipment in working condition. The most important accessory for research-grade hotplate use is an external temperature probe, which monitors actual solution temperature rather than hotplate surface temperature, which can be 20 to 50 degrees C higher than the liquid in the vessel. PTFE stir bars in standard cylindrical, oval, octagonal, cross-shaped, and polygon geometries allow matching of bar shape to vessel type and mixing requirement. Support rods and clamp assemblies secure condensers, separating funnels, and other glassware above the hotplate for reflux chemistry. Magnetic stir bar retrieval wands recover stir bars from flasks without contaminating the solution. An external temperature probe is the single most impactful hotplate stirrer accessory: without one, you are controlling plate temperature, not solution temperature, and the two can differ by 20 to 50 degrees C.
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<h2 dir="ltr">What You Will Find:</h2>
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<ul>
<li data-section-id="dpsp0x" data-start="25" data-end="139">Temperature sensors for compatible GHS-series hotplate stirrers, available in standard and glass-coated designs.</li>
<li data-section-id="yvvor4" data-start="140" data-end="248">Sensor support stands and clamps for secure positioning of temperature probes during heating applications.</li>
<li data-section-id="hdqu1" data-start="249" data-end="353">Support rods and clamp sets for mounting laboratory apparatus and accessories above hotplate stirrers.</li>
<li data-section-id="rtdv85" data-start="354" data-end="446">Magnetic stir bars, including standard and pivot ring styles, for efficient sample mixing.</li>
<li data-section-id="1hl26tt" data-start="447" data-end="560" data-is-last-node="">Chemically resistant clamp set options featuring inert PTFE construction for demanding laboratory environments.</li>
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<h2>How to Choose Hotplate and Stirrer Accessories</h2>
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External temperature probes
Confirm probe type compatibility with the hotplate stirrer model: most digital hotplate stirrers accept either a PT1000 resistance temperature detector (RTD) or a Type K thermocouple, and these are not interchangeable between models. The probe is inserted directly into the solution and feeds temperature data back to the PID controller to maintain the solution (not the plate surface) at the setpoint. Probe length and sheath material (stainless steel, glass, or PTFE) should be matched to the vessel size and chemical compatibility requirements.
PTFE stir bars: geometry and size
PTFE stir bars are available in cylindrical, oval (egg-shaped), octagonal, cross (X-shape), polygon, and ring geometries. Cylindrical bars are the most common general-purpose format. Octagonal bars provide more turbulent mixing in flat-bottomed vessels than cylindrical bars. Cross-shaped bars improve mixing in round-bottom flasks by preventing the bar from riding the wall. Ring or hoop bars are used for mixing around fixed probes or frits inside the vessel. Stir bar length is selected to match vessel diameter, typically 30 to 50% of vessel inner diameter.
Support stands and clamp sets.
Support stands (rod-and-base assemblies) mount above or adjacent to the hotplate to hold condensers, addition funnels, thermometers, and other glassware in reflux setups. Confirm rod diameter compatibility with the clamp set (most lab glassware clamps fit 12.7 mm or 16 mm rods). Weighted bases provide stability for tall assemblies. Crossbar assemblies allow horizontal positioning of clamps at adjustable heights along the support rod.
Magnetic stir bar retrieval tools
Stir bar retrievers are magnetic wands encased in a non-contaminating sleeve (PTFE or glass) that attract and remove the stir bar from a vessel without inserting fingers or metal into the sample. Available as handheld wands or bench-mounted extractors. An essential accessory for labs processing multiple samples per day, as losing track of stir bars is among the most common minor equipment management issues in bench chemistry.
Replacement sensors and calibration weights
Temperature probes degrade after repeated heating cycles or chemical exposure; replace probes showing drift against a calibrated reference thermometer. For hotplate stirrer models with external calibration weights (balance verification), confirm the weight set is OIML or ASTM traceable for regulated workflows.
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<h2>Specifications Context</h2>
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PTFE stir bars should be inspected regularly for chipped or worn PTFE coating. Bare metal exposure from a chipped bar contaminates the sample with metallic particles and alters the bar's magnetic coupling properties, resulting in reduced mixing efficiency or bar stall at lower speeds. Discard and replace any stir bar showing PTFE damage. For regulated lab environments (GMP, ISO 17025), maintain a stir bar inventory log and retire bars on a scheduled basis. External temperature probes rated for immersion in aqueous solutions should be verified against a calibrated reference thermometer at least annually; probes showing more than 1 degree C deviation should be recalibrated or replaced.&nbsp;
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Looking for that one missing piece to complete your setup? Browse our accessories collection and <a href="https://mbpinc.net/contact-us">reach out to the MBP team</a> for a friendly quote today.

Optional Rod for Hotplate/Stirrer (H3770 Series)

H3770-ROD by Benchmark Scientific is an optional support rod that mounts onto the H3770 series hotplate/stirrer to provide a vertical attachment point for lab clamps, condenser mounts, burette holders, and overhead accessories during heated stirring operations.

Optional Temperature Probe (H3770 Series)

The H3770-TP by Benchmark Scientific is an optional external temperature probe for the H3770 series digital hotplates (H3770-H and H3770-HS). It connects directly to the hotplate's microprocessor to enable sample-temperature control rather than surface control, maintaining ±1°C accuracy. Compatible with the H3770-H hotplate and H3770-HS hotplate stirrer; not compatible with the H3770-S stirrer-only model.

Rod for Hotplate/Stirrer

H4000-ROD by Benchmark Scientific is the support rod for the H4000 series hotplate, stirrer, and hotplate-stirrer units (H4000-H, H4000-S, H4000-HS), providing a vertical mounting point for thermometer clamps, temperature probe holders, and condenser clamps during heating and stirring operations. Available as a replacement or spare for the rod included with the H4000-HS, compatible with Benchmark's H4000 ceramic-surface hotplate series.

Stir Bar, 1"x5/16"

The PTFE Magnetic Stir Bar 1 inch x 5/16 inch Series by Across International is a PTFE-coated magnetic stir bar measuring 1 inch × 5/16 inch (25.4 × 7.9 mm). The PTFE coating is chemically inert to acids, bases, and solvents and withstands autoclave sterilization. Suitable for 50–250 mL beakers and flasks on any standard magnetic stir plate. Available in pack options from MBP. Available models: H4000-BAR, H4000-BAR-10.

Stir Bar, 1"x5/16", pack of 10

Stir Bar for use with IPS7101

Replacement magnetic stir bars for the Benchmark IPS7101 High-Capacity Magnetic Stirrer (HCS) series. Two sizes: IPS7101-BAR-100 (100 mm) and IPS7101-BAR-150 (150 mm × 24 mm). Select by vessel diameter.