Does Mongtec sell standard expanding mandrels from stock?

No. Every Mongtec hydraulic expanding mandrel is designed and built to order around the customer's part drawing. That is what makes it accurate: the sleeve is made for one bore.

What bore tolerance does the part need?

A finished bore, IT7 or better on the clamping length. The expansion is small, at most 0.3–0.5% of the clamping diameter, so the bore has to be close to size before it is clamped.

Can one mandrel take several bore sizes?

Yes, with interchangeable sleeves on one body. A change of bore size within the part family is then a sleeve change, not a new mandrel and a new setup.

We use a pneumatic or mechanical expanding mandrel today. Can Mongtec replace it?

Mongtec mandrels are hydraulic. Send the part drawing and a photo or drawing of the mandrel you use now; Mongtec engineering tells you whether a hydraulic design suits the job before quoting. The main condition is a finished bore.

Do you supply customers outside Taiwan?

Yes. Mongtec quotes and ships to customers worldwide; shipping terms and payment are set out on the how-to-buy page.

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Custom Hydraulic Expanding Mandrels

Mongtec builds hydraulic expanding mandrels to order, around the customer's part drawing. A pressure screw pressurises oil inside the body, a thin-walled sleeve expands evenly around 360°, and the part is centred and clamped on its own bore — for gear grinding, gear inspection, external cylindrical grinding and finish turning. Each mandrel is designed for one bore, or as one body with interchangeable sleeves for a part family.

Send the part drawing for a quote →

Mongtec hydraulic expanding mandrel holding a helical gear for gear grinding

What Mongtec builds

Clamping principle	Hydraulic. A pressure screw pressurises oil sealed in the body and a thin-walled sleeve expands evenly around 360°.
Bore on the part	Finished, IT7 or better on the clamping length.
Expansion	Small by design — at most 0.3–0.5% of the clamping diameter. That is where the centring accuracy comes from.
Mounting	Between centres, on a spindle flange, or on a taper — designed for your machine.
Sleeves	One fixed sleeve, or interchangeable sleeves on one body for a family of bore sizes.
Typical work	Gear grinding, gear inspection, external cylindrical grinding, finish turning of sleeves, bushings, rings and thin-walled parts.

Mongtec flange-mounted hydraulic expanding mandrel with pressure screw — Flange-mounted Mongtec hydraulic mandrel. The pressure screw on the end face sets the clamp.

Why a hydraulic mandrel

Uniform contact. The part is held over the whole bore surface, not on three or six points, so it is centred on the bore it will run on.
Thin-walled parts stay round. Even pressure from inside does not distort a sleeve or ring the way jaw pressure does.
One datum for machining and inspection. The same bore locates the part on the grinder and on the gear tester.
Fast part change. Release the pressure screw, change the part, clamp again — no re-indicating.

How a Mongtec mandrel is quoted

You send the part drawing, the operation, the machine and how the mandrel will be mounted.
Mongtec engineering checks the bore, the clamping length and any interruptions in the bore — keyways, cross holes, splines — and proposes the design.
The design and the quotation are confirmed with you before anything is made.

Lead time is confirmed with the quotation for the design and quantity you order; Mongtec does not publish a standard lead time for made-to-order mandrels.

How hydraulic mandrels work, hydraulic versus mechanical, and good practice: Hydraulic expanding mandrels — the guide →

FAQ

Does Mongtec sell standard expanding mandrels from stock?: No. Every Mongtec hydraulic expanding mandrel is designed and built to order around the customer's part drawing. That is what makes it accurate: the sleeve is made for one bore.
What bore tolerance does the part need?: A finished bore, IT7 or better on the clamping length. The expansion is small, at most 0.3–0.5% of the clamping diameter, so the bore has to be close to size before it is clamped.
Can one mandrel take several bore sizes?: Yes, with interchangeable sleeves on one body. A change of bore size within the part family is then a sleeve change, not a new mandrel and a new setup.
We use a pneumatic or mechanical expanding mandrel today. Can Mongtec replace it?: Mongtec mandrels are hydraulic. Send the part drawing and a photo or drawing of the mandrel you use now; Mongtec engineering tells you whether a hydraulic design suits the job before quoting. The main condition is a finished bore.
Do you supply customers outside Taiwan?: Yes. Mongtec quotes and ships to customers worldwide; shipping terms and payment are set out on the how-to-buy page.

What to send for a quote

Mongtec designs each mandrel from four details. Email them to info@mongtec.com or use the quote form — we reply within one working day.

The part drawing with bore diameter, tolerance and length, and the face the part locates against.
The operation — gear grinding, gear inspection, OD grinding or finish turning.
The machine and the mounting — between centres, spindle flange or taper.
Runout required and batch size, so the design and price match the job.

Request a quote → · Shipping, Incoterms and payment for buyers outside Taiwan →

Special accessories → · Face drivers → · Hydraulic expanding mandrel guide →

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