What is in this group
| Family | Covers | Reach for it when |
|---|---|---|
| Tool holders | BT, HSK, CAT, VDI and Capto-compatible holders | The machine interface has to be matched and the tool located |
| End mill holders | Side-lock, shrink-fit and hydraulic holders | Runout at the cutting edge has to be minimised |
| Collets and chucks | ER, DA and TG collets, collet chucks, drill chucks | A tool shank has to be gripped, and the collet is a wear item |
| Workholding | Top pins, chuck jaws, fixture plates and clamping components | The workpiece has to locate the same way on every cycle |
Runout is the number that matters
Runout at the cutting edge is the sum of the holder taper error, the collet bore error, how the collet seats in the nut, and the tool shank itself. Each is small and together they are the reason a holder specified at 0.003 mm measures 0.015 mm at the tool.
That is why we quote assembled runout when the tool, holder and collet come from one source. It is the only figure that means anything in the machine, and it is why replacing a collet is frequently a more effective fix for poor finish than changing the cutting parameters.
- Check taper contact with marking blue; below about 85 percent the holder should be replaced
- Treat collets as consumables and replace them on an interval, not on failure
- Torque the collet nut to the manufacturer's figure rather than by feel
- Balance the assembly with the tool and nut fitted, not the holder alone
- Check for fretting or a polished band on the taper, which indicates movement under load
Gripping the tool against gripping the workpiece
The two halves of this group look similar and solve different problems. Tool holding locates the cutting edge relative to the spindle, so its error shows up as tool wear, chatter and surface finish. Workholding locates the workpiece relative to the machine, so its error shows up as size scatter and position error that no tool adjustment can correct.
Both are wear items. A locating pin, a jaw face and a collet all lose accuracy gradually, and in each case the loss is slow enough to be mistaken for a tooling problem.
In this group
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CNC Tool Holders
Precimill manufactures CNC tool holders in the standard machine interfaces: BT30, BT40 and BT50, HSK-A and HSK-E, CAT40 and CAT50, VDI for lathes, and Capto-compatible...
Read moreCollets and Chucks
Precimill manufactures ER, DA and TG collets to DIN 6499, together with collet chucks and keyed and keyless drill chucks. Collets are hardened and ground with runout...
Read moreEnd Mill Holders
Precimill manufactures side-lock end mill holders, shrink-fit holders and hydraulic chucks. Side-lock holders are the robust choice for heavy cuts, shrink-fit holders give...
Read moreWorkholding and Fixture Components
Precimill manufactures workholding components: top pins for locating and clamping, soft and hard chuck jaws, fixture plates, and clamping elements. Parts are made to...
Read moreFrequently asked questions
How do I know whether the tool or the holder is at fault?
Measure runout at the cutting edge. If it exceeds the tool's specification, the holder, collet or nut is the cause and changing the tool will not help. Chipping on a single flute while the others still have life is the clearest symptom of a runout problem.
What taper contact should a good holder have?
Around 85 percent of the taper length or better, verified with marking blue and distributed evenly. A holder with poor contact feels tight in the spindle but deflects under load, which appears as chatter and premature wear rather than as an obvious fault.
How often should collets be replaced?
Treat them as consumables with an inspection interval rather than replacing them on failure. A collet that has taken a set still grips, which is exactly why it stays in service long past the point where it is causing tool breakage.
Do I need a shrink-fit holder for finishing?
It gives the lowest runout and the best balance, so it is the right answer for precision finishing and small tools. For mixed low-volume work where tool sizes change constantly, a collet chuck or hydraulic holder is more practical and usually accurate enough.
Why does workholding affect size more than the tool?
Because the workpiece position relative to the machine sets the datum for every cut. A fixture that locates on a rough surface or a worn pin moves the part, and no tool offset can correct a position that changes between cycles.