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A batch of hard-ground steel balls is ready for lapping when its size spread, remaining allowance and surface condition all fall within the limits agreed for the next stage — not simply when grinding is finished. Sending a batch on too early is one of the most common reasons lapping cycles grow longer while the number of accepted balls stays flat.
This guide covers the transfer decision itself: how to judge a batch, what to record at handover, and how to compare process trials. For what each process does and how lapping parameters affect roundness and finish, see our steel ball lapping process guide.
Grinding and lapping need a defined handover, and it must state more than "how much allowance is left". It must also state how that allowance is expressed. Does the figure on the drawing or route card mean the reduction in ball diameter, or the stock removed from each side of the surface? The two must never be mixed.
A handover record should include at least:
Material grade, batch number and heat-treatment condition
Current size distribution and target size range
Roundness or sphericity results
Surface condition and any defects found
The allowance planned for later stages, and its measurement basis
For case-hardened low carbon steel balls, the process engineer must also check the planned material removal against the final case-depth requirement. A route developed for through-hardened balls cannot be applied directly. See case-hardened carbon steel balls: hardness and case depth for how case depth limits the material that can be removed, and AISI 1010/1015 precision grades for how this affects achievable precision.
If lapping cycles for the same product are getting longer, compare this batch's handover record with the last batch that passed, before adjusting the lapping machine. How incoming geometry and lot spread affect lapping is explained in our lapping process guide; the steps below focus on finding which change caused the problem.
Read the inspection results separately. Better surface roughness does not mean the size spread within the batch now meets requirements. A batch that passes on diameter may still have surface defects.
Then run a controlled trial. Keep the original process as a reference, change conditions according to a plan, and record processing time, size change and the reasons for any rejects. If the abrasive, pressure and load are all changed at once, you cannot tell which change made the difference, even if the result improves.
When comparing two grinding or lapping set-ups, agree on one set of acceptance criteria first, then run both with representative incoming balls.
| Record item | Question it answers |
| Incoming record | Are the material, size distribution, hardness and surface condition comparable between the two trials? |
| Inspection before and after | Which items improved? Did any new rejects appear? |
| Actual time used | Beyond machine running time, how long did loading, unloading, cleaning, inspection and rework take? |
| Accepted output | How many balls met the same acceptance criteria? |
| Repeat batch result | Does the result hold with another representative batch? |
If the review points to a machine decision, start with our guide on how to choose a steel ball grinding machine.
When the review points to hard grinding and size correction, see the 3M7480 Vertical Steel Ball Grinding Machine, with a published ball diameter range of φ3–20 mm.
When the balls are already hard-ground and need lapping or superfinishing, see the 3ML4780D Vertical Steel Ball Lapping Machine, with a published ball diameter range of φ3–25 mm.
These ranges are for initial screening. Actual suitability depends on the incoming balls, allowance, target quality and process configuration.
When you contact RISHENG, send one incoming inspection record and your finished-ball acceptance requirements, and tell us your hardest problem: long processing time, wide size spread, surface rejects or low accepted output. This tells us whether the existing process needs adjusting or whether new equipment is the right step.
Check three things against the limits set for lapping: the size distribution across the batch, the remaining allowance on the smallest balls, and any surface defects. If any one of them is out, review the batch before it enters lapping.
An average can hide balls that are still oversize next to balls already close to the lower limit. Lapping removes material from every ball, so the undersize-risk balls fail even when the average looks right.
Material grade, batch number and heat-treatment condition; current size distribution and target size range; roundness results; surface condition and defects found; and the allowance left for lapping, stated as either diameter reduction or stock removal per side.
Use the same acceptance criteria and comparable incoming balls, change one condition at a time, and compare the number of accepted balls and total cost per accepted ball, including handling, cleaning, inspection and rework, rather than machine time alone.
