Forged Worm Shafts & Worm Blanks
A worm drive achieves large reduction ratios in one stage, at the cost of sliding contact along the whole tooth flank. That sliding makes surface durability the governing design factor.
Forged worm shafts achieve large single-stage reduction ratios through sliding rather than rolling contact, which generates heat and demands surface durability. They are case hardened to 58–62 HRC in 20MnCr5 or EN353 with thread forms ground after hardening.
- Shaft diameter
- 20 mm – 150 mm
- Length
- Up to 1,000 mm
- Materials
- 20MnCr5, EN353, EN19
- Case hardness
- 58 – 62 HRC
- Thread form
- Ground after hardening
Forged Worm Shafts & Worm Blanks at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Shaft diameters 20 mm to 150 mm
- Case hardened to 58–62 HRC
- Thread form ground after hardening
- 20MnCr5 and EN353 grades
Sliding Contact, Not Rolling
Unlike spur gears which mostly roll, a worm slides against its wheel along the entire flank. That sliding generates heat and demands surface hardness plus effective lubrication, which is why worm shafts are case hardened and ground.
- Sliding rather than rolling contact
- Heat generation from friction
- Case hardened and ground flanks
- Lubrication is critical
Thread Form Accuracy
The worm thread form determines contact pattern with the wheel. A poor pattern concentrates load on a fraction of the tooth face, accelerating wear dramatically. Form is ground after hardening and verified against the drawing.
People also ask
Why do worm drives run hotter than gear drives?
Because contact is sliding rather than rolling along the whole tooth flank, converting a larger share of transmitted power into friction heat.
What causes worm gear wear?
Inadequate lubrication for the sliding contact, incorrect contact pattern concentrating load, or insufficient surface hardness on the worm flank.
What reduction ratios do worm drives achieve?
Large ratios in a single stage — commonly 5:1 to 100:1 — which is their principal advantage over spur and helical gearing.
Topics covered on this page
- worm shaft
- worm gear
- sliding contact
- case hardening
- reduction ratio
- contact pattern
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
Why are worm shafts case hardened?
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Worm drives slide rather than roll, generating heat and wear that only a hard, ground surface resists adequately.
What material is used for worm shafts?
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20MnCr5 and EN353 case hardening grades, giving a hard flank over a tough core.
Do you grind worm threads?
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Thread form is ground after hardening and verified against the drawing contact pattern requirement.