{"id":7893,"date":"2026-10-08T07:03:27","date_gmt":"2026-10-08T07:03:27","guid":{"rendered":"https:\/\/chinametalfoundry.com\/?p=7893"},"modified":"2026-10-08T07:03:27","modified_gmt":"2026-10-08T07:03:27","slug":"casting-machining-allowance","status":"publish","type":"post","link":"https:\/\/chinametalfoundry.com\/ja\/blog\/casting-machining-allowance\/","title":{"rendered":"Casting Machining Allowance: How Much Stock to Leave, Process by Process"},"content":{"rendered":"
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A casting machining allowance of 3 mm instead of 5 mm looks like a drafting detail. On a 185 kg gray iron housing run at 1,200 pieces a year, that 2 mm gap moves about $25,000 \u2014 and setting it the other way, too little stock, is how a casting that already passed inspection turns into weld repair or scrap after the first cut.<\/p>\n<\/div>\n

This guide covers how casting machining allowance is specified under ISO 8062-3:2023<\/strong>, typical stock values by process and casting size, what that stock has to absorb before a surface actually cleans up, and a cost model you can run on your own part. Standards practice here follows published foundry references from the \u7c73\u56fd\u92f3\u9020\u5b66\u4f1a<\/a> and the North American Die Casting Association<\/a>, with the cost figures taken from Supro MFG production records.<\/p>\n

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Same part, two conditions: the rough as-cast skin on the left is what the machining allowance has to remove.<\/figcaption><\/figure>\n

What Casting Machining Allowance Actually Buys You<\/h2>\n

Casting machining allowance is the layer of metal left on every surface that will be cut, measured from the as-cast surface to the finished surface. It is not a tolerance and it is not draft. Tolerance describes how far the as-cast dimension can wander; allowance is the reserve you give the machinist so that wandering never leaves a patch of black skin in the middle of a sealing face.<\/p>\n

That reserve does three jobs at once:<\/p>\n