Get the reaming allowance and the pre-ream drill diameter for the hole you want, by material. Too little stock and the reamer rubs; too much and it cuts oversize.
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Request a Proposal โA reamer removes a small, controlled amount of material to achieve precise hole size and surface finish. Too little stock and the reamer rubs; too much and it overloads, produces a bell-mouthed hole, or breaks. This calculator gives the optimal stock allowance.
H7 (e.g., 10.000-10.015 mm) is standard with a quality reamer in good condition. H6 is achievable with carbide reamers and rigid setup. The reamed hole is never perfectly round -- expect 1-3 ยตm out-of-roundness due to spindle runout and uneven chip loading.
Boring heads are adjustable and can correct position error; reamers follow the existing hole. Use boring for position-critical holes (true position under 0.05 mm). Use reaming for high-volume, consistent-diameter holes where position is less critical.
Common causes: excessive spindle runout, built-up edge on the reamer, wrong stock allowance, misaligned tailstock or turret, and worn guide bushings. Check runout first -- a reamer floating in a worn collet will always cut oversize.
Enter the finished hole diameter. The calculator recommends the stock allowance and the pre-ream drill size. For critical holes, drill undersize, then bore to within reaming allowance, then ream -- this corrects position error before the reaming pass.
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Use the calculator freely. If the result points to a tooling or process problem, we can source the exact carbide tooling you need from vetted factories in China. Compare factory-direct pricing.
Before you commit to a spec, it helps to know what the market pays for it. These are real, publicly listed factory prices — not a quotation, and not a guess.
We source the tool families below direct from vetted Chinese factories, matched to the material and tolerance you just worked out. Every batch ships with its material certificate and dimensional record.
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PLANNING A REAMING OPERATION? Reamers are a low-volume, high-precision purchase where the supplier decides the result. See how to evaluate a reamer supplier.
Reaming only works if the allowance, the reamer tolerance and the drill that precedes it all agree. Send the hole tolerance and the material.