KA Series Single Standard Worm Gear Reducer_0052_01

KA Series (WPKA) hollow bore worm gear reducer

The WPKA is a hollow-shaft worm gearbox; the driven shaft is inserted directly into the output bore, thereby eliminating the need for an output coupling and saving 80–150 mm of axial installation space. It covers sizes 50–155, with bore diameters ranging from Ø20 to Ø70 mm and speed ratios from 10:1 to 60:1. It serves as a direct replacement for SEW-Eurodrive WA-K, Bonfiglioli VF-K, and Motovario TA-K hollow-shaft units, and is utilized in Australia for screw conveyors, agitators, and conveyor head shaft drives.

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Description

The fastest way to eliminate output-side coupling failures in an industrial worm drive is to remove the coupling entirely — and the KA Series (WPKA) hollow bore worm gear reducer does exactly that. Where the standard WPA presents a solid output shaft stub that requires a separate coupling to connect to the driven machine, the WPKA output passes straight through the worm wheel hub as a precision-bored hollow shaft, accepting the driven machine shaft directly. The driven shaft slides into the bore, engages via a standard DIN 6885 key and setscrew, and the WPKA sits directly on the machine — no coupling, no coupling guard, no alignment shims, no intermediate bearing housing. The axial length saved at the output side is typically 80–150 mm depending on frame size, and the eliminated coupling represents one of the top three sources of planned maintenance downtime in shaft-drive worm gearbox installations across Australian manufacturing facilities in Sydney, Melbourne, Brisbane, and Perth. Covering centre distances from size 50 to 200, bore diameters from Ø20 mm to Ø80 mm, and gear ratios from 10:1 to 60:1, the WPKA is specified across packaging, food processing, material handling, and agricultural machinery throughout Australia. Manufactured to ISO 9001:2015, designed per AGMA 6034, and supplied by Ever-Power Worm Gear Reducer Co., Ltd. (Australia), 27 Harley Crescent, Condell Park NSW 2200.

KA Series WPKA hollow bore worm gear reducer shaft-mount right-angle drive — Ever-Power Australia

Key Specifications & Parameters — KA Series (WPKA) Hollow Bore Worm Gear Reducer

All parameters per ISO 9001:2015, AGMA 6034, and DIN 3975 gear quality specification. Bore tolerances to H7 per DIN 286.

Size Ratio Range Centre Dist. A (mm) Hub Width AB (mm) Overall Length B (mm) Height H (mm) Bore Length HL (mm) Output Bore Ø (mm) Weight (kg)
50 10:1–60:1 175 105 107 180 50 Ø20 7
60 10:1–60:1 195 120 117 210 60 Ø25 10.5
70 10:1–60:1 234 140 131 243 70 Ø30 14.5
80 10:1–60:1 264 160 144 273 80 Ø35 22
100 10:1–60:1 322 190 175 340 100 Ø40 36
120 10:1–60:1 385 230 200 405 120 Ø45 63
135 10:1–60:1 435 260 212 455 135 Ø60 80
155 10:1–60:1 507 302 312 490 135 Ø70 114

What Is the WPKA Series and How Does the Hollow Bore Work?

WPKA hollow bore worm gear reducer bore detail and keyway
WPKA worm reducer shaft-mount installation with torque arm

In the WP family model code, K denotes the hollow output shaft configuration. The WPKA is therefore a K-output (hollow bore), A-base (foot-mount) worm reducer — maintaining the same cast-iron housing and four-bolt foot-mount base as the WPA, while replacing the solid output shaft stub with a through-bore machined to H7 tolerance through the centre of the worm wheel hub.

The hollow bore engagement works as follows: the driven machine shaft is inserted into the WPKA output bore until the keyway slots align. A standard DIN 6885 parallel key is inserted, and a locking setscrew in the bore hub clamps the assembly. A torque arm bracket — supplied with each WPKA — is then bolted to the housing face and pin-connects to the machine frame, reacting the rotational moment of the housing without requiring any additional mounting feet or base plates. This torque-arm arrangement is the standard shaft-mount configuration used across Australian screw conveyor drives, mixer shaft drives, and grain auger applications where mounting a gearbox base plate is either impractical or impossible due to machine geometry.

The WPKA inherits the WPA housing geometry — meaning its rated output torque and thermal power at each frame size and ratio are identical to the WPA. The hollow bore replaces only the output shaft stub; the worm wheel, worm shaft, bearings, and sealing are unchanged. The critical distinction between the WPKA and the WPKS (its heavy-duty hollow-bore counterpart) is the bore length (HL): WPKA bore depths range from 50 mm (size 50) to 135 mm (size 155), compared with 130–390 mm for the WPKS — the WPKA is the standard-duty hollow bore unit, appropriate for shaft engagement lengths within the WPA torque rating; the WPKS is specified for heavy-load, long-bore-engagement applications.

WPKA vs WPA vs WPKS — Which Hollow-Shaft Specification Is Right for You?

Feature WPA (solid shaft) WPKA (standard hollow bore) WPKS (heavy hollow bore)
Output connection Coupling to driven shaft Direct bore onto driven shaft Direct bore, longer engagement
Bore depth HL (size 100) N/A (solid shaft) 100 mm 250 mm (+150%)
Axial footprint saving None 80–120 mm vs coupling 80–120 mm vs coupling
Shock load tolerance Standard (coupling absorbs) Standard — WPA-class housing Higher — WPS-class bearing
Best for Any motor shaft via coupling Light–medium shaft loads Heavy shock, long shaft engagement
Torque arm required No Yes (included) Yes (included)

Manufacturing Quality: Bore Precision and Material Specification

The hollow output bore is the most dimensionally critical feature of the WPKA, as any bore-to-shaft clearance or angular misalignment directly transfers as torsional shock to the worm wheel hub. The following manufacturing controls ensure bore integrity:

  • Bore Tolerance H7 per DIN 286: The output bore is finished to H7 tolerance — for a Ø40 mm bore (size 100), this means +0 to +0.025 mm over nominal. This provides a clearance fit of approximately 0.010–0.045 mm onto an h6-tolerance driven shaft, ensuring full key engagement without fretting between bore and shaft.
  • Single-Setup Boring: The bore is finish-machined in the same CNC fixture setup as the housing bearing bores, ensuring the output bore axis is parallel to the worm wheel shaft axis within 0.02 mm/100 mm. Axial misalignment above this level would cause uneven keyway contact under torque and premature bore wear.
  • Keyway Dimensions per DIN 6885: Keyway width, depth, and length tolerance follow DIN 6885 Part 1 (Form A parallel key) standards. This ensures that standard Australian-market parallel keys sourced locally will fit correctly without re-machining.
  • Worm Wheel Material (ZCuSn10Pb1): The tin-bronze worm wheel through which the bore passes is produced from a single-piece casting with no internal joints or welds, ensuring full structural integrity of the hub wall surrounding the bore even when the bore is at maximum diameter relative to the hub OD.
  • Housing: GG25 Cast Iron: The same cast-iron housing specification as the WPA provides the structural rigidity to resist the bending moment from the torque arm reaction force without housing distortion at rated load.
WPKA hollow bore worm reducer complete assembly with torque arm

How to Select and Install the WPKA Hollow Bore Worm Reducer

Selection:

  1. Confirm Driven Shaft Diameter: The bore diameter must match your driven machine shaft. Standard WPKA bore diameters are Ø20–Ø70 mm as listed in the spec table. Non-standard bore diameters (e.g., Ø38 or Ø42 mm) are available as factory custom options with a 2–3 week lead time — specify at time of order.
  2. Calculate Required Torque and Select Frame Size: WPKA rated output torques are identical to the WPA at the same frame size. Apply service factor (SF 1.25–2.0) to your design torque and select accordingly. For continuous shock loading (e.g., grain auger starting under full load), consider upgrading to WPKS at the same frame size for its deeper bore engagement and heavier bearing arrangement.
  3. Confirm Bore Length Coverage: Verify that your driven shaft’s engagement length into the bore (the length of shaft inside the WPKA hub) is at least 1.2 × the bore diameter — the minimum engagement length for reliable key torque transfer per DIN 6885 recommendations. For Ø40 mm bore (size 100, HL=100 mm), the minimum engagement is 48 mm. If your shaft does not extend sufficiently into the bore, specify the WPKS for its longer bore depth.
  4. Size the Torque Arm: The maximum output torque multiplied by the housing-to-torque-arm-pivot distance gives the torque arm pin load. Ensure the machine frame can accommodate the torque arm pin load in shear at the pin attachment point.

Installation:

  1. Shaft Preparation: Clean the driven shaft of any burrs, paint, or surface rust in the engagement zone. Apply a thin film of anti-fretting compound (e.g., Molykote G-n or equivalent) to the shaft surface before sliding the WPKA onto the shaft.
  2. Key Insertion: Insert the DIN 6885 parallel key into the shaft keyway first, then slide the WPKA bore over the shaft and key simultaneously. Never force the WPKA with a hammer — if resistance is felt, check for keyway misalignment or a burr on the key edges.
  3. Setscrew Torquing: Tighten the bore hub setscrew(s) to the specified torque — typically 10 N·m (M8 setscrew) to 25 N·m (M12 setscrew) depending on frame size. Torquing to specification is critical: undertorqued setscrews allow axial slip of the reducer on the shaft under cyclic loads; overtorqued setscrews can crack the hub wall on smaller frame sizes.
  4. Torque Arm Installation: Mount the torque arm bracket to the housing using the supplied M10 or M12 bolts torqued to DIN 912 specification. Connect the free end to the machine frame via the rubber-bushed pivot pin supplied. Confirm 3–5 mm of free movement at the pivot before clamping — this prevents binding under thermal expansion of the machine shaft during operation.

Accessories We Also Supply: Torque arm replacement rubber bushes, DIN 6885 parallel keys (standard and oversized), anti-fretting compound (Molykote G-n), shaft locking assemblies (shrink disc option for zero-clearance mounting), replacement oil seals (NBR and Viton), and IEC motor adaptor flanges for input side. Contact Ever-Power Australia for pricing.

Applications of the WPKA Hollow Bore Worm Reducer Across Australia

The WPKA’s shaft-direct mounting is particularly valued in Australian industrial and agricultural applications where the driven shaft is exposed and accessible but the machine frame cannot accommodate a conventional foot-mount gearbox base:

Sector & Location Application WPKA Size / Ratio
Grain Handling (QLD, NSW, SA) Screw auger shaft drives, grain conveyor head shaft Size 80–120, 20:1–40:1
Mixing (Sydney, Melbourne) Agitator shaft drives, ribbon-blender shaft mounts Size 70–100, 30:1–60:1
Packaging (Sydney, Melbourne) Conveyor roller shaft drives, turntable shaft mounts Size 50–80, 20:1–40:1
Water Treatment (Perth, Adelaide) Sludge scraper shaft drives, filter-press shaft mounts Size 100–135, 40:1–60:1
Agricultural Machinery (WA, VIC) Irrigation boom pivot shaft, seeder metering shaft Size 60–80, 30:1–60:1
WPKA hollow bore worm reducer product range all sizes Ever-Power Australia

What Australian Customers Say About the WPKA Series

★★★★★

“Replaced three WPA units on our Sydney conveyor line with WPKA 80s. The hollow shaft mounts directly on the conveyor head shaft — we went from three coupling alignments per year to zero maintenance on those drive connections. The 80–100 mm saved on each conveyor section was genuinely useful for our layout redesign.”

— Alex P., Mechanical Engineer, Sydney NSW

★★★★★

“WPKA 100 at 40:1 on our grain auger head shaft in Queensland. The torque arm bolts straight to the machine frame and the WPKA sits directly on the auger shaft — no separate bearing, no coupling. Clean install, runs quietly. Second order placed after 14 months of trouble-free operation.”

— Tim W., Grain Handler, Darling Downs QLD

★★★★☆

“WPKA 70 units on our ribbon blender agitator shafts in Melbourne. Self-locking at 30:1 means the blades stay put when power is off — no drift. Would be 5 stars but one bore needed minor cleaning of a burr before the key would seat fully. Easy to fix but worth noting for incoming inspection.”

— Rachel T., Maintenance Engineer, Melbourne VIC

★★★★★

“We fit WPKA 60 units to our irrigation boom pivot shafts in WA. The hollow shaft directly on the pivot shaft is far simpler than the old coupling-and-bracket arrangement we ran for years. With self-locking at 60:1 the boom stays exactly where we leave it. Ever-Power supply is reliable and pricing is excellent.”

— Don M., Irrigation Manager, Geraldton WA

Why Choose Ever-Power for WPKA Hollow Bore Worm Reducers in Australia?

Ever-Power Worm Gear Reducer Co., Ltd. (Australia) at 27 Harley Crescent, Condell Park NSW 2200 stocks WPKA units across all eight frame sizes in standard bore diameters for 5–10 business day dispatch. Custom bore diameters are available in 2–3 weeks. Our engineering team provides free bore engagement confirmation and torque arm sizing for your specific shaft arrangement. Learn more at About Us. Technical reference at worm-gearbox.top.

Frequently Asked Questions — KA Series (WPKA) Hollow Bore Worm Gear Reducer

1. What is the minimum shaft engagement length required in the WPKA bore?+
The minimum shaft engagement length for reliable torque transfer via key is 1.2 × bore diameter, per DIN 6885 key engagement guidelines. For a Ø40 mm bore (size 100), minimum engagement is 48 mm; for Ø70 mm (size 155), minimum is 84 mm. The WPKA bore depths (HL) listed in the spec table represent the maximum available engagement length. If your shaft only extends partially into the bore due to machine layout constraints, confirm the actual engagement length meets the minimum before ordering the WPKA — if it does not, the WPKS (deeper bore HL) or a shrink disc engagement option should be specified.
2. Can a shrink disc be used instead of a key to mount the WPKA?+
Yes — a shrink disc engagement is available as a factory option for WPKA bore sizes Ø35 mm and above (sizes 80–155). The shrink disc applies uniform radial clamping pressure across the full bore engagement length, generating a friction torque capacity approximately 20–30% higher than an equivalent keyed connection, with zero clearance and therefore zero backlash at the bore-shaft interface. Shrink disc engagement eliminates keyway machining in the driven shaft and prevents the fretting corrosion that can develop in a key-fit connection under cyclic reversing torque. Specify “shrink disc” at time of order with the driven shaft diameter — Ever-Power supplies a matched shrink disc from stock for all standard WPKA bore sizes.
3. Is the WPKA rated to the same output torque as the WPA at each frame size?+
Yes — the WPKA shares the identical internal worm shaft, worm wheel, and bearing arrangement as the WPA at each frame size. The hollow bore replaces only the external output shaft stub; the gear centre rated torque is unchanged. The rated output torque at each ratio and frame size is therefore the same for WPKA and WPA. The output shaft stub torque rating of the WPA becomes the bore wall shear torque rating of the WPKA — both are calculated at the same point (the worm wheel hub) and are therefore the same value.
4. How do I prevent the WPKA from migrating axially along the shaft during operation?+
The bore hub setscrew(s) provide the primary axial retention, clamping the WPKA against the shaft. For additional positive axial location — required in applications with sustained axial force at the output, such as vertical shaft drives or thrust-loaded agitators — mount a shaft collar with a hardened face on the driven shaft on either side of the WPKA bore hub. For horizontal shafts with minimal axial loading, the setscrew is usually sufficient provided it is torqued to specification and re-checked at the 200-hour run-in inspection.
5. When should I choose WPKS over WPKA for a hollow bore application?+
Specify WPKS over WPKA when: (1) your driven shaft is long enough to extend into a deeper bore — the WPKS bore HL is 30–250 mm deeper than WPKA at the same frame size, providing proportionally greater torque transfer area; (2) the application involves heavy shock loads (grain auger starting under full load, crusher feeder drives, heavy reversing agitators) where the deeper bore engagement and WPS-class bearing arrangement of the WPKS provides better resistance to bore fretting and output bearing failure; or (3) the application requires the maximum possible bore-to-shaft contact area for high-cycle fatigue resistance. For light-to-medium smooth duty, the WPKA is fully adequate and costs approximately 8–12% less than the WPKS at the same frame size.
6. What are the Australian Standard requirements for torque arm attachment in food processing facilities?+
For food processing environments in Australia, the torque arm must comply with AS 4024.1 machinery guarding requirements — primarily, the torque arm pin and bracket must be guarded or recessed to prevent operator contact with the rotating housing and bracket during machine operation. The rubber bush in the torque arm pivot absorbs minor vibration and prevents metal-to-metal contact at the pin, but is a consumable part — inspect annually and replace when cracking or hardening of the bush is observed. For stainless steel torque arm options (required in washdown-intensive dairy and meat processing applications), specify at time of order. Stainless steel torque arm kits are available for WPKA sizes 70–155.

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