BIG Daishowa Cutting Tools — Complete Product Guide
Summary
BIG Daishowa is a Japanese precision tooling company headquartered in Osaka, Japan, with US operations based in Hoffman Estates, Illinois. The parent entity is Big Daishowa Seiki Co., Ltd. Their Swiss subsidiary, BIG Kaiser, handles distribution and engineering support across Europe and North America and is the name most US machinists encounter when buying boring heads or hydraulic chucks through MSC or a regional distributor.
This is not a broad-line tooling company. BIG Daishowa doesn't compete with Kennametal or Sandvik on carbide insert grades. Their domain is toolholding and precision boring — and in that domain they are genuinely category-leading. If a shop is fighting runout on a tight-tolerance bore, or a spindle interface that's chattering, BIG Daishowa is usually the first name a process engineer reaches for.
The thing they're most known for globally — including with machine tool builders — is the BIG-PLUS dual-contact spindle interface. It's a de facto standard on CAT and BT-taper machines for shops that need simultaneous face and taper contact. If a VMC's spindle says "BIG-PLUS compatible," BIG Daishowa invented that.
What BIG Daishowa is best for
- Precision boring — EWN and EWB digital boring heads for finish bores and close-tolerance ID work. This is the core of what they do.
- High-precision toolholding — Mega New Baby hydraulic chuck, shrink-fit holders, milling chucks for applications where runout matters. Sub-0.0001" TIR is achievable with their top-tier holders.
- Dual-contact spindle interfaces — BIG-PLUS CAT40, CAT50, BT30, BT40, BT50. If you're running an existing CAT or BT spindle and want better rigidity, BIG-PLUS holders are a bolt-in upgrade where the spindle supports it.
- Tapping — Mega Synchro Tapper holders for rigid tapping where synchronization error is a real problem.
- Swiss and small-diameter work — their micro-boring and toolholding lines go down to very small diameters where most other boring head makers don't have a catalog entry.
If you're cutting steel all day on a job shop VMC with no tight-tolerance bores, BIG Daishowa probably isn't your first call. If you're holding ±0.0002" on a bore diameter or chasing chatter out of a long boring operation, it's exactly where you want to look.
Brand architecture
BIG-PLUS (spindle interface system)
BIG-PLUS is a simultaneous dual-contact taper system — the holder contacts both the taper and the spindle face at the same time. This improves rigidity and reduces axial runout compared to taper-only contact. It's licensed to machine tool builders worldwide and is compatible with existing CAT/BT spindles that are BIG-PLUS ground. BIG-PLUS holders work in standard CAT/BT spindles (taper contact only); standard holders do NOT get dual-contact benefit in a BIG-PLUS spindle.
EWN and EWB boring heads (precision boring)
- EWN series — digital fine-boring heads with a built-in micrometer scale. Adjust boring diameter without removing the head from the spindle. Available in a range of diameters from roughly 0.2" to several inches. The digital readout on the head shows the offset directly — no counting dial clicks.
- EWB series — similar digital boring head concept, positioned for larger bore diameters and roughing/semi-finish applications.
- These are the tools that put BIG Kaiser on the map in aerospace and die-mold shops. A machinist who's used an EWN head once rarely goes back to a non-digital boring head.
Mega New Baby Chuck (hydraulic toolholder)
A hydraulic-expansion chuck. Clamp a tool shank by applying hydraulic pressure through a set screw — the bore closes uniformly around the shank. Typical runout: under 0.0001" at the nose (manufacturer claims sub-3 micron TIR). Works with straight-shank end mills, drills, reamers. Gripping force is high and the damping effect of the hydraulic sleeve reduces vibration in finishing cuts. The "New Baby" suffix refers to the slim-nose geometry — reaches into pockets other hydraulic chucks can't.
Mega Synchro Tapper
A floating tap holder with synchronized torque control for rigid tapping. Compensates for small synchronization errors between spindle and feed axis. Useful on older machines where the rigid tapping sync isn't tight, or on taps where a broken tool is expensive.
HMC Shrink-Fit Holders
BIG Daishowa's shrink-fit line. High-interference fit, short gauge length, excellent runout — comparable to competitors like Haimer or Sandvik's shrink line. Requires an induction heater to load and unload tools.
Toolholder lines — interface options
BIG Daishowa makes holders in CAT40, CAT50, BT30, BT40, BT50, and HSK (HSK-A63, HSK-A100) interfaces. Their BIG-PLUS versions are marked clearly in the catalog. Not every holder style is available in every interface — check the current catalog for what's stocked in your taper.
Precision spec cheat sheet
| Product | Typical TIR (at nose) | Notes |
|---|---|---|
| Mega New Baby Chuck | < 0.0001" (3 µm) | Hydraulic, slim nose |
| HMC Shrink-Fit Holder | < 0.0001" (3 µm) | Requires induction heater |
| EWN Boring Head | Adjustable in ~0.00005" increments | Digital readout on head |
| BIG-PLUS vs. standard CAT40 | 30–50% rigidity improvement | Spindle must be BIG-PLUS ground |
| Mega Synchro Tapper | Compensates ±0.003" sync error | Application-dependent |
These are manufacturer spec starting points. Actual runout depends on spindle condition, holder seating, and tool clamping practice.
When to use BIG Daishowa vs. alternatives
- vs. Haimer: Haimer is the other precision-toolholding reference brand. Haimer's shrink-fit and toolsetting equipment are arguably more common in European shops. BIG Daishowa's hydraulic chuck (Mega New Baby) has a stronger following in US aerospace shops. They're comparable in quality — the choice often comes down to distributor relationship and what your shop already owns.
- vs. Kennametal / Sandvik toolholding: Both make decent Capto, HSK, and CAT toolholders, but toolholding is not their core competency. BIG Daishowa's precision holders will outperform a general-catalog shrink-fit holder from a carbide-insert company on runout-sensitive work.
- vs. Parlec / Lyndex-Nikken: US-market toolholding brands that are competitive on price. BIG Daishowa is typically more expensive, but the EWN boring head line and BIG-PLUS interface have no direct equivalent in that tier.
- vs. Sandvik CoroBore / Kaiser boring heads: BIG Kaiser (BIG Daishowa's own subsidiary) is the direct competitor to Sandvik's boring head line. The EWN digital head is the BIG Kaiser answer to Sandvik's CoroBore 825/826 line. Both are credible; machinists who've used both tend to split on preference.
Related articles
- Toolholder selection guide — CAT, BT, HSK, Capto interfaces
- Boring bars catalog — precision boring heads and adjustable tooling
- Shrink-fit toolholding — setup and runout specs
- Hydraulic chucks — setup and gripping force
- Machining tight-tolerance bores — boring vs. reaming
- CAT vs. BT vs. HSK spindle interfaces
Ask 4man
BIG Daishowa's catalog is organized by interface and application, not by material — which makes it hard to navigate if you're starting from a print tolerance. Give 4man your bore diameter, tolerance, and spindle interface, and it'll suggest the right EWN head range or hydraulic chuck size with a source citation.