Plunge milling square parts from round stock

Nov 05, 2026 Last reply: 4 days ago 4 Replies
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The finished parts are square pieces cut out of round stock, and the way the maker gets there is by plunging a Seco Turbo 10 straight down into a thick, curved segment of 1.7225 steel held in a machine vise. The spindle housing carries the HURCO and SR PLUS markings, and once the cycle runs, curled chips pile up across the vise and the machine table in impressive quantity.



The cutter holds indexable, replaceable inserts, and the economy of the setup is what stands out. The inserts are old ones no longer usable for square milling, and since plunging never touches their end cutting edges, inserts headed for the bin still cut well here.



Workholding got the same careful treatment. The maker machines clamping surfaces onto the part first and never grips the saw cut, having learned that a slightly slanted cut lets a part shift under heavy loads. With only two milling machines and no bandsaw freely available, that discipline seems worth the extra cycle time to me.



One trade-off shows up near the end of a pass: the material gets thin, pushes away, and the edges rub more than they cut, throwing small sparks from the cutting interface. On the tooling side, the maker moved from Sandvik to Seco after a tool representative went independent and started selling Seco, though Sandvik solid carbide drills, some older than ten years, still handle drilling and turning.


Those little flashes near the bottom of the cut caught my eye. Has the maker said what actually causes them? They look more like the tool rubbing than clean shearing, and I am curious whether that is just part of plunging into stock that thin or something a different pass depth would avoid.

Running inserts that would otherwise be scrapped strikes me as the cleverest part of this. Plunging leaves the end cutting edges untouched, so worn-out stock gets a second life at no cost. The trade-off is that those edges never earn their keep, which limits the inserts to work where plunging is the whole job.

A bandsaw might be worth borrowing for a job like this. Slicing that section off the round bar before it reaches the vise would trim mill cycle time, and with only two milling machines in the shop, freeing one up sooner has real value. Even occasional access to a saw could help.

The maker has addressed it. As the cut progresses the material gets thinner and pushes away, and then the edges rub more than they actually cut. That rubbing is what throws the small sparks from the cutting interface, so it comes down to the thinning wall rather than anything else.

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