Why scissors are a good candidate for MIM in the first place
A scissor handle isn't one simple shape. It's a finger ring, a bow, a shank that tapers toward the pivot, and on a ratchet scissor, a row of interlocking teeth, all as one continuous piece.
Producing that geometry by forging and machining means forging a blank, milling the ring profile, cutting the ratchet teeth, grinding the shank taper, then polishing. Multiple setups, multiple operations, and every one of them adds cost per unit that doesn't go away with volume.
MIM produces the ring, the bow, the taper, and the ratchet teeth in a single mould cavity. The finger ring's inside diameter, the ratchet tooth profile, the bow's cross section, all of that comes out of the mould already close to final shape. That's the real case for MIM here. Not that it's inherently better, but that a scissor handle happens to be full of the kind of small, repeated, moderately loaded features MIM is suited to.
The pivot is where MIM has to earn its keep
The finger rings and ratchet teeth are the easy argument for MIM. The pivot is the harder one.
Two things happen at a scissor pivot that a mould alone won't reliably solve.
The blade faces have to be flat and meet along their full length. Sintering shrinkage isn't perfectly uniform across a part. It depends on wall thickness, local geometry, and how the part sits during the sintering cycle. A scissor blade face that's off by even a small amount won't close cleanly against its mate. This is a surface that gets ground after sintering on essentially every MIM scissor built for actual surgical use.
The pivot bore has to hold a consistent, repeatable tension. A screw pivot or rivet pivot depends on a bore diameter that stays the same from the first part off the mould to the ten thousandth. Sintering shrinkage variation is the enemy here specifically. A bore that drifts even slightly out of tolerance changes how tight the scissor feels, and a batch with inconsistent pivot tension is a batch with inconsistent quality, which in a surgical instrument isn't a minor issue.
Both of these are solvable, and they're solved with secondary grinding on the blade face and precision reaming or broaching on the pivot bore, not left to the as sintered part. Any MIM supplier who tells you the mould alone handles pivot critical surfaces on a scissor hasn't built enough of them.
Ratchet mechanisms: where MIM's advantage is real, not theoretical
A locking ratchet scissor, used across hemostatic forceps style scissors and many general surgical scissors, needs its ratchet teeth to engage at a defined set of positions, cleanly, with no partial catches.
This is genuinely one of the strongest cases for MIM on a scissor. Cutting a ratchet tooth profile by machining means indexing the same cut multiple times per handle, on both handles, with the tooth pitch matching exactly between the two halves so they interlock correctly at every position. That's slow, and it's a real source of rejects if the indexing drifts even slightly between operations.
MIM produces the full tooth profile, pitch, tooth angle, and engagement depth, directly from the mould geometry, identical on every part, cavity after cavity. The tooth profile isn't a secondary operation at all in a well designed MIM scissor. It's one of the features that justifies the tooling investment on its own.
Material selection: it's not just "stainless steel"
Surgical scissors are almost always 400 series or precipitation hardening stainless. Most commonly 17-4PH for parts that need higher strength and good corrosion resistance after heat treatment, or 420 stainless for a harder, more wear resistant cutting edge, particularly if the blades are a separate hardened insert rather than part of the MIM handle.
The material choice affects the MIM process itself, not just the finished part's properties. 17-4PH in MIM form goes through a solution treatment and age hardening cycle after sintering to reach its final strength. That's an additional process step that needs to be specified up front, not added as an afterthought once tooling is already cut. A supplier quoting a MIM scissor handle without asking which heat treatment condition you need hasn't fully scoped the job.
What actually happens to a cutting edge
This is worth being direct about, because it's the one place MIM genuinely cannot replace conventional finishing.
A surgical cutting edge, the actual blade to blade shearing surface, is ground and honed to a specific edge geometry and surface finish. No MIM mould, however well designed, produces a functional surgical cutting edge as sintered. The mould can get the blade blank close to its final profile, but the edge itself is always a post sintering grinding operation.
This matters for how you should be evaluating a MIM scissor quote. If a supplier's pitch is that MIM eliminates machining, that's a claim worth being skeptical of on any scissor with an actual cutting function. The realistic pitch is that MIM eliminates machining on the handle, the ring, the bow, and the ratchet, and the blade edge still gets ground, the same as it always has.
Volume is still the deciding factor
Everything above assumes the volume justifies MIM tooling in the first place. A single scissor handle cavity, properly built for consistent dimensional control at the pivot bore and ratchet, isn't a low cost tool. It only makes sense once the per unit machining savings, multiplied across your annual volume, clear that upfront investment.
For a scissor design still in low volume production or early clinical use, forging and full machining remains the more sensible route. Not because MIM can't technically produce the part, but because the tooling cost has nothing to amortize against yet. This is the same volume threshold that applies to MIM generally, and a scissor handle doesn't change that math just because the geometry suits the process well.
The practical takeaway
MIM is a strong fit for scissor handles specifically because of what a scissor handle actually is. A ring, a taper, and on ratchet designs, a repeated tooth profile, none of which need to be perfectly flat or perfectly sharp on their own. The features that do need to be perfect, the pivot bore and the blade mating face, are exactly the features every serious MIM scissor supplier still finishes by grinding, not by trusting the mould alone.
The question worth asking a potential supplier isn't whether they can MIM a scissor. It's which features they're finishing after sintering, and how they're holding the pivot bore tolerance across a production run. A supplier with a real answer to that question has actually built these before.
At HongYing, we coordinate MIM tooling and production for surgical instrument components through our manufacturing partner network in China, alongside the secondary grinding, heat treatment, and finishing that a functional surgical scissor actually requires. If you have a scissor or similar cutting instrument design you're evaluating for MIM, send us the drawing and we'll walk through which features are realistic to mould and which will still need finishing.
Exceptional parts start with choosing the right partner, not just the right factory.
Frequently Asked Questions
Can MIM produce a functional surgical cutting edge? No. The blade profile can be moulded close to final shape, but the cutting edge itself is ground and honed after sintering, the same as on a forged blade.
What stainless steel grades are used for MIM surgical scissors? Most commonly 17-4PH, which is solution treated and age hardened after sintering for higher strength and corrosion resistance, or 420 stainless for a harder cutting surface.
Is MIM cheaper than forging for scissor handles? Only above a certain production volume. MIM tooling is a real upfront investment that needs enough units to amortize against. For low volume or early stage production, forging and machining is usually more economical.
Does MIM eliminate the need for a pivot to be machined? Not entirely. The pivot bore comes out close to final size from the mould but is typically reamed or broached afterward to hold the tight, repeatable tolerance a scissor pivot needs.
