Three ways to hold a cylindrical shank, three different reasons to choose them. The wrong question is “which is best”. The right question is what is standing next to the cut, and what the operation actually needs.
| Shrink fit | Hydraulic | Mechanical (ER, power chuck) | |
|---|---|---|---|
| Runout | Best | Very good | Good, depends on collet grade |
| Nose profile | Slimmest | Slim (3° versions) | Bulkiest — the nut is the limit |
| Damping | None — solid steel | Yes — oil chamber | Some, through the collet |
| Tool change | Induction unit, heat, cooling wait | Hex key | Wrench |
| One holder, many diameters | No — one bore, one diameter | Yes — reducing sleeves | Yes — collets |
| Cost per station | Highest (plus the machine) | Middle | Lowest |
Deep cavity work where the holder body would otherwise hit the wall. High rpm where every micron of runout shortens edge life. Anywhere the profile is the constraint rather than the price.
It needs a shrink machine, and every diameter needs its own holder. If you run five cutter diameters across three tapers, that is fifteen holders.
Reaming and finishing, where the oil chamber absorbs cutting vibration and it shows directly in the surface. Also any shop that wants good runout without buying an induction unit.
The part people underrate: reducing sleeves. One ø20 hydraulic holder plus a set of sleeves covers 3 to 16 mm. That is one holder instead of six. Mongtec sleeves run HY12S (3–8 mm), HY20S (3–16 mm) and HY32S (6–25 mm), with a coolant-channel version.
Roughing. High tool variety. Shops where holders get dropped. An ER32 chuck holds 2 to 20 mm with a box of collets and survives conditions that would make an expensive holder a bad investment.
If the nut is what hits the workpiece rather than the tool, ask for a mini nut version — smaller nose diameter, same collet.
Ask any supplier for the balance grade. Mongtec publishes G2.5 at 25,000 rpm across the shrink fit, hydraulic and HSK-A ranges. On the BT and BBT range it is G6.3/15,000 or G2.5/25,000 depending on the type. A holder without a published balance grade is a holder nobody wants to commit to.