Pitted and spalled teeth
Surface fatigue pitting, frosted micropitting, and larger spalled craters on the tooth flanks. We regrind or recut to restore the profile and finish.
Houston, TX ยท Pinion gear repair
Pinion Gear and Pinion Shaft Repair
The pinion is the small, fast turning gear that does the hard work in a drive. It is the driving member that meshes with a larger gear, a bull gear, or a girth gear, and it carries the highest tooth contact stress in the set because it takes more load cycles per revolution than the wheel it drives. When a pinion goes bad, the whole machine stops, and that is exactly the kind of part we handle every day at Solution Gear Co. in Houston. We cut, regrind, reverse engineer, and replace pinion gears and integral pinion shafts, and we do all of it in house at 8449 West Belfort Ave.
We repair, regrind, reverse engineer, and remanufacture pinion gears and pinion shafts at our Houston shop. The pinion is the small driving gear that meshes with a larger gear, bull gear, or girth gear, and we rebuild it stronger than OEM with free shipping both ways and free inspection.
Most pinions we see are either a separate gear pressed or keyed onto a shaft or an integral pinion shaft with the teeth cut directly into the bar. Both fail in predictable ways, pitted and spalled teeth, scoring from lost lubrication, worn bearing journals, fretted keyways and splines, and outright tooth breakage from overload. We do not just patch the symptom. We measure the gear geometry, inspect the shaft and journals, and rebuild the pinion to run true against its mating wheel. If you also need the wheel side touched, our gear cutting shop handles bull gears and girth gears in the same building.
Distance is never an issue. We offer free shipping both ways, free pickup and delivery including crating and rigging, and a free inspection before any work begins. Send us the pinion or the whole reducer, and we will tell you what is wrong with it. See the industries we serve and the brands we rebuild, then send us your part.
What a pinion gear does and why it fails first
In any gear set the pinion is the smaller of the two meshing members and almost always the driving one. Because it has fewer teeth than the gear it turns, every tooth on the pinion engages far more often than every tooth on the larger wheel. More cycles under the same contact load means the pinion wears, pits, and fatigues sooner. This is why, in a bull gear and pinion mud pump drive or a ball mill girth gear and pinion drive, it is usually the pinion that comes out for repair while the big wheel still has life left.
The most common thing we see is pitting. Repeated rolling and sliding contact pushes the surface past its fatigue limit and small cavities open up on the tooth flanks. Micropitting frosts the surface and slowly changes the profile, while macropitting and spalling tear out larger chunks and get loud fast. Right behind pitting is scoring or scuffing, where the oil film breaks down and the mating teeth weld and tear at the microscopic level, leaving radial scratch marks. Abrasive wear from dirty oil simply thins the teeth until the profile and backlash are gone. The worst case is a broken tooth, usually a bending fatigue crack that started at the root fillet and finally let go under shock load.
Pinion shafts, bearing journals, and thrust
An integral pinion shaft is more than the teeth. The bearing journals, seal areas, keyways, and splines all have to be right for the gear to mesh where it should. We see plenty of pinions whose teeth are still serviceable but whose journals are worn undersize, whose keyways are fretted oval, or whose splines are rounded over. A pinion that floats on a worn journal will not hold mesh alignment, and bad alignment is what drove the tooth damage in the first place.
Mounting matters too. A straddle mounted pinion is carried by bearings on both sides for stiffness, while an overhung pinion hangs off two bearings on one end and deflects more under load. Helical pinions add a thrust component that has to be carried by the bearings, and if that thrust path is not handled the pinion walks and the contact pattern shifts to one end of the tooth. When we rebuild a pinion shaft we restore the journals to size, recut keyways and splines true, and confirm the bearing and thrust arrangement is correct so the new teeth do not repeat the old failure. If the bearings themselves are gone we handle that through our bearing repair work in the same shop.
How we cut, regrind, and reverse engineer pinions
A new pinion starts as a turned blank. We cut the teeth in the soft state by hobbing or shaping, then heat treat. Most industrial pinions are carburized and case hardened or induction hardened to put a hard, wear resistant case over a tough core, commonly in the high fifties to low sixties on the Rockwell C scale. After heat treat we precision grind the bearing journals and the tooth flanks to clean up the small distortion that hardening always introduces, which is what gives a rebuilt pinion a finish and accuracy that often beats the worn original.
When the teeth are only mildly worn or pitted, regrinding the flanks can restore the profile and surface without cutting a whole new gear. When the part is too far gone, or there is no drawing and no replacement to be had, we reverse engineer it. We capture the module or diametral pitch, pressure angle, helix angle, tooth count, lead, and tooth profile, and we call out the core material, case depth, surface hardness, and core hardness separately so the new pinion matches the original metallurgy, not just its shape.
- Gear cutting of new pinions and pinion shafts from blank to finished part
- Tooth regrinding to recover pitted or scored flanks without a full recut
- Reverse engineering when there is no print and no OEM part available
- Shaft repair of journals, keyways, splines, and seal areas
- Full reducer rebuild when the pinion failure damaged the rest of the unit
Pinion drives across Houston industry
Houston runs more pinion drives than almost anywhere in the country, and we rebuild for all of them. In the oilfield, mud pumps use bull gear and pinion sets, herringbone gears, and jackshafts that take a beating and come out for rebuild after years of duty. Refineries and petrochemical plants run pinion driven reducers on pumps, compressors, fans, and agitators. Cement and lime plants, steel mills, sugar mills, mining operations, marine drives, and pulp and paper mills all depend on pinion to gear and pinion to girth gear meshes to move heavy loads.
Because we ship free both ways and pick up and deliver with our own crating and rigging, it makes no difference whether your plant is in Pasadena, Baytown, Deer Park, or two states away. Here in town we lean on free local pickup and delivery since Houston is home base. Learn more about our oil field and mining equipment work, or just send us the pinion and let us inspect it for free.
What we repair and rebuild
What we fix.
Scored and scuffed flanks
Radial scoring from lubrication film breakdown and metal to metal contact. We recover the surface and confirm the root cause before return.
Broken and cracked teeth
Bending fatigue cracks at the root fillet and teeth lost to shock overload. We cut a new pinion when the part cannot be saved.
Worn bearing journals
Pinion shaft journals worn undersize so the gear no longer holds mesh alignment. We build up and grind back to size.
Fretted keyways and splines
Egged out keyways and rounded splines that let the pinion slip or float. We recut them true to restore a tight fit.
Thrust and mounting damage
Helical pinion thrust that walked the contact pattern to one end of the tooth, plus straddle and overhung mounting issues.
Missing prints and obsolete parts
No drawing and no OEM replacement. We reverse engineer the geometry and metallurgy and make a new pinion.
Failed reducer after a pinion let go
Collateral damage to bearings, housings, and the mating gear when a pinion failed. We rebuild the whole unit in house.
Common questions
What plants ask us.
What is the difference between a pinion gear and a regular gear?
In a meshing pair the pinion is the smaller member and is almost always the driving gear. The larger member is the gear, wheel, bull gear, or girth gear. Because the pinion has fewer teeth, each tooth engages more often per revolution, so it carries more load cycles and tends to wear and fatigue before the larger wheel does.
Can you reverse engineer a pinion with no drawing?
Yes. This is routine for us. We measure the module or diametral pitch, pressure angle, helix angle, tooth count, lead, and profile from the worn part, and we specify the material, case depth, surface hardness, and core hardness so the new pinion matches the original both in shape and in metallurgy.
Do you repair the pinion shaft as well as the teeth?
Yes. On integral pinion shafts we restore worn bearing journals, recut fretted keyways and splines, and refinish seal areas, then grind everything true. A pinion that floats on a worn journal will not hold mesh, so the shaft work matters as much as the teeth.
Is it cheaper to regrind a pinion or cut a new one?
It depends on how far gone the teeth are. If the wear and pitting are mild we can regrind the flanks and restore the profile, which costs less than a full recut. If the teeth are spalled, broken, or worn past the limit, we cut a new pinion. Our free inspection tells you which path makes sense before you spend anything.
How far will you ship to repair a pinion?
Anywhere. We offer free shipping both ways plus free pickup and delivery with our own crating and rigging, so distance does not change the price. In the Houston area we use local pickup and delivery since this is our home base.
Send us your pinion for a free inspection
Free shipping both ways, free inspection, and an up to a 24 month warranty on every rebuild. Tell us about your unit and we reply fast, often the same day.
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