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LMT has introduced a solid monoblock tool holding solution that overcomes some of the problems experienced when using a more traditional spring-based tool holding collet.

The new TER solid holder enables the maximum transmission of spindle speed, torque and feed rate to the cutting tool.

Through the new solid holder, tool life can be increased by up to 300 per cent with added precision available to the cutting process by maintaining run-out at the tool tip within three microns TIR.

Developed and patented by the Bilz division of LMT, the TER shrink collet, now available through LMT UK of Meriden in Coventry, is a straight replacement (DIN 6499) for the traditional spring-based collet used in a chuck and driven tool holder for the direct clamping of tools by the shank in the machine tool spindle.

The TER can be used on tool shanks between 3mm and 20mm in diameter and will be accepted by normal collet holders without the need for a sealing disc.

By changing over to the TER shrink collet from a traditional collet system at a customer for both rough and finish machining on a 10-axis Index G 200 turning centre, rough machining time using a 10mm shank tool was reduced from 75 seconds to just 30 seconds and finish machining with a 6mm shank tool was reduced to 17 seconds.

Owing to the higher rigidity of the tooling setup, cutter life was increased from 500 to 1,500 parts on both rough and finish cycles.

The shank of the tool is secured in the TER holder by heat shrinking, a quick-acting thermally based process normally taking less than 30 seconds to accomplish.

This has the effect of creating a single unit of tool and holder to ensure maximum rigidity and stability between the machine spindle and cutting tool.

Its replacement of the spring collet/chuck arrangement overcomes several disadvantages when using this more traditional method to mechanically grip the shank of the tool.

Collets are prone to progressive wear and damage if not monitored and exchanged on a regular basis and, in certain cases, will allow the tool to skid under cutting conditions or even drop out of the spindle.

Centrifugal force from the rotating tool can also encourage tool slip by relaxing the spring collet while any run-out at the cutting edges of the tool causes uneven wear, noise, vibration and degraded levels of surface finish on the component.

As a general rule, for every 10 micron TIR of run-out at the tool tip, the life expectancy of the cutter should be reduced by around 10 per cent.

The use of shrink-fit technology provides not only a quick, fool-proof and positive method of mounting or dismounting a drill, milling cutter or tap with its holder but also creates an advantage that is particularly noticeable as spindle speeds are increased.

The cutting tool shank is positioned over the bore in the TER solid holder.

The nose section of the holder is heated via an induction coil until the tool shank drops into the tool holder, aided by the clearance created by its thermal expansion.

The cutter is then gripped tightly as the holder rapidly cools and contracts onto the tool shank.

Tool removal is just as simple by reheating the holder.

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