Wexmar provides centerless grinding services for round parts that need tighter diameters, better roundness, or finer surface finishes than turning alone provides. Our in-house centerless grinder sits on the same floor as our CNC lathes and Swiss machines, so pins, shafts, dowels, and bushings can be turned and ground without leaving the building. Buyers looking for a centerless grinding machine shop or centerless grinding near me in the Northeast can send complete jobs to our Canastota, New York shop near Syracuse.
What centerless grinding is
In centerless grinding, the part is not held on centers or in a chuck. Instead, it rests on a work rest blade between a large grinding wheel and a smaller regulating wheel. The regulating wheel controls the part's rotation and, in through-feed grinding, its travel across the wheel face. Because the part is supported along its length and ground on its own outside diameter, centerless grinding produces consistent diameters and good roundness, and it does so quickly. Through-feed grinding moves straight parts continuously past the wheel. In-feed, or plunge, grinding handles parts with shoulders or heads by bringing the regulating wheel in to grind a set length.
When a buyer needs centerless grinding
- Dowel pins, locating pins, and guide pins with tight diameter tolerances
- Shafts and rods for bearings, bushings, or seals that require a fine finish
- Turned parts that need a size band tighter than turning holds economically
- Hardened parts that must be finished to size after heat treatment
- Bar stock that needs to be ground to a precise diameter before further machining
Wexmar equipment for turned and ground parts
We run a centerless grinder in-house alongside a surface grinder, our CNC lathes, and our Swiss machines. A typical routing turns the part on a Mazak or Doosan lathe or a Maier MLK-32 Swiss machine, leaving grind stock on critical diameters, then grinds those diameters to final size. Hardened parts are heat treated through qualified outside processors that Wexmar manages, then returned for grinding. Our centerless grinder is suited to small and medium diameter round parts; tell us your diameter and length and we will confirm fit. See our CNC turning page and the machine list.
Typical tolerances and finishes
| Feature | Typical turned | Typical centerless ground |
|---|---|---|
| Outside diameter | ±0.0005 to ±0.001 in | ±0.0002 in; tighter by review |
| Roundness | 0.0005 in | 0.0001 to 0.0002 in |
| Cylindricity / taper | 0.0005 in over length | 0.0002 in over length |
| Surface finish | 32 to 63 Ra | 8 to 16 Ra |
| Hardened material | by hard turning | ground after heat treat |
Values are typical and depend on part length, diameter, material, and hardness. Very long or very small parts are reviewed individually.
Designing parts for centerless grinding
- Leave the ground diameter as the largest diameter on the part where possible, for through-feed grinding
- Add small chamfers at the ends so parts enter the wheels smoothly
- Specify roundness and finish only where they matter functionally
- If a part has shoulders, expect in-feed grinding and allow a small undercut at the shoulder
Centerless versus cylindrical grinding
Cylindrical grinding holds a part between centers or in a chuck, which suits parts where a ground diameter must be concentric to center holes or to another feature. Centerless grinding supports the part on its own outside diameter, which is faster and gives excellent roundness and size control, but it does not reference a separate axis. If your print ties a ground diameter to a datum through runout or concentricity, send it along and we will confirm the grinding route before quoting.
Materials
We centerless grind carbon and alloy steels, hardened alloy and tool steels, 300-series, 400-series, and PH stainless, Nitronic 50, brass, bronze, and some nickel alloys. Aluminum, copper, and plastics can be ground with the right wheel selection, though many soft materials hit their tolerances by precision turning alone.
Quantity fit
Through-feed centerless grinding is efficient at production volumes because parts flow continuously past the wheel. It also handles short runs of pins and shafts when a tolerance requires it. Grinding small prototype lots is common when a turned diameter needs one final step.
Inspection deliverables
Ground diameters are measured with calibrated micrometers and gages, and roundness and cylindricity are verified on our Brown & Sharpe CMMs when required. We provide dimensional and CMM reports, AS9102-format first articles, material certifications, heat-treat certifications from outside processors, and heat-lot traceability. See our CMM inspection page.
Getting a quote
Include ground diameters, tolerances, finish, hardness, and quantity on your drawing. You can upload a drawing for an instant estimate, and a human estimator confirms every quote. Call (315) 400-2654 or email ron@backwell.com, Monday through Friday, 7 a.m. to 4 p.m. Eastern.