Heat Treat Before or After CNC: Stock Leave

Heat treat before or after CNC is really a sequencing question. Quench and temper can move a part. Leave stock, finish after, or buy prehard and cut slower. The wrong order is how a perfect green part comes back as scrap.

How Much Stock Do You Leave When You Heat Treat Before Finish Machining?

On most precision parts, rough first, heat treat, then finish. Titans of CNC answers that exact shop question in One Tiny Mistake Just Cost $50,000…. Nathan asks how many thousandths to leave before heat treat and stress relief. Titan's rule of thumb for a solid piece is about 0.030 in on surfaces; thin or warp-prone geometry may need 0.050 to 0.100 in so you can rough and finish after. He also says call the heat-treat house with the model and print. They have seen your alloy a thousand times.

Heat Treat Before or After CNC: What Changes

Rough, treat, finish is the usual path when the drawing calls for a hardened condition and tight sizes. Fictiv's heat treatment guide for steel and aluminum puts it plainly: leave stock so you can correct distortion and set critical dimensions after the furnace. On hard steel the last pass may need grinding or EDM rather than a conventional mill.

Buy already hard can win on short runs. Titan notes that for small 17-4 jobs he will buy H900 or H1150 stock and machine it slower with the right tools instead of sending a green blank out and back. That matches the annealed-versus-prehard choice on 4140 annealed vs prehard. Soft stock cuts faster; prehard skips a heat-treat loop and the warp risk that comes with it.

Aluminum 6061 and 7075 are often already in T6 when you buy them, so another heat-treat cycle after machining is rarely the default. Ask us when you quote if the temper or aging note on the drawing needs a process DigiForge does not run in-house.

How It Shows Up in a Quote

Our CNC quote is built from stock, setup and programming, machining time and detected features. A rough-treat-finish route adds a second machining setup (and often a grind) after heat treat. Hard machining from prehard stock may raise tool time but cut the logistics loop. Either path beats inventing a single-pass green finish that the quench will throw out. For material picks on shafts, see 4140 vs 1018. For what else moves the number, see what actually drives the cost of a CNC quote.