Milling cutters clamped with high stffness

A novel, highly precise way to clamp milling tools, and offering many advantages, has been developed by Franz Haimer.

A novel, highly precise way to clamp milling tools, and offering many advantages, has been developed by Franz Haimer.

The company offers a high-precision- (HG-) chuck which offers high precision and stiffness and which is nevertheless very slender.

These advantages are due to the design principle and the highly precise machining processes.

A quality component worth its extra money.

In machining metal, as usual in this country, the entrepreneurs trust more and more in costly machines and tools.

However, the important interface namely the tool-holders are often taken as an exception: function of these parts is often underrated and quality is not estimated very high.

It may be a mistake to save a few Euros in possibly higher investment costs, wouldn't you think so too ? It is surely true that the tool-holder influences the manufacturing result and the life of machines, spindles and tools very much so.

So an initially somewhat more expensive but higher quality solution could show in the end the much more favourable result.

As with all its products Franz Haimer rates quality and customer satisfaction highly.

For the collet chucks the development engineers have devised a completely new and patented design principle.

The basic body of the HG-chuck has an internal slightly tapered bore.

The collet chuck, having a slight external taper, is being drawn into this body from the rear.

In its final position it is retained practically by friction alone.

Contrary to conventional principles the tensional force in Haimer tool-holders is applied from the rear - and not via a nut from the front.

Therefore practically no torque is applied to the collet chuck.

It is true that it will tighten, however, the torsion applied otherwise directly onto the collet chuck does not exist.

Therefore tension is very centric and very precise.

Measured on the tool the Haimer HG-collet chucks attain a concentricity of max.

4 microns.

Thanks to the steep taper a very high transmission of power is applied.

A relatively low torque on the bolt is sufficient to effect high tensional forces.

These forces are in a range which is restricted otherwise to hydraulic collet chucks, called hydro-tension-clamping-chucks.

Stiffness of the tool clamping is achieved exclusively through metallic components.

Accepting body and the collet chuck are made of steel and also the milling cutter is made of steel or hard metal.

These components with sufficiently rigid wall thicknesses will not "water down" tension.

Stiffness is added to high precision - in addition the tool-holder is, seen in total, relatively slender.

The tool-holder can accept all types of milling cutters and drills with a shaft diameter of 2-20mm, provided the shaft is cylindrical with a tolerance of h6.

An excessive tolerance can make the chuck less effective.

However, it is of no importance if the shaft shows a clamping face or not.

It can at any rate have a Weldon face or any other bores.

Depending upon the tool diameter there exist collet chucks in three sizes HG 1,2 and 3 which can be replaced easily.

The Haimer precision collet chucks can also be used for milling cutters with internal cooling systems, without requiring an accessory e.g an additional sealing ring.

The collet chuck will seal through the type of slots incorporated.

The tightening bolt has a through hole so that the coolant can flow directly through the bolt and the complete tool-holder.

Coolant can also be provided laterally into the tool-holder via a threaded hole in the collet.

If no internal cooling is required, however, if coolant is required in front of the tool, the slots of the chuck may be opened towards the front.

Then the coolant can flow out on the chuck and then flow along the milling cutter to the front.

This action does not negatively affect precision of the chuck.

These clamping devices can be used in a versatile manner.

It is ideally suited for high-speed-machining, where low machining pressures are applied and where precision is a factor.

Also hard machining is an ideal field of application as concentricity is demanded and mostly a minute chip is removed.

Only the type of clamping is setting a limit.

Such a clamping based on friction will waste away the clamping power some time later.

Normally it is nevertheless sufficient to use the tool-holders for roughening too.

The pre-balanced tool-holders are available in SK40, SK50, with JIS (MAS/BT), in accordance with the Japanese standard and in HSK.

But it is not only the design principle that makes the precision collet chucks from Haimer that valuable.

The quality of the individual components will be noticed in the complete product.

The taper e.g is manufactured in the taper tolerance AT3 in order to save the spindle.

The chucks are externally TiN coated, which allows them to easily slide into the conical portions and allowing to exert high clamping powers.

The tightening bolt which is important for transmitting power, is only partially hardened to prevent rupture under high loads (please refer to the box too).

Claudia Haimer, Sales Manager at Haimer is placing the onus on high quality: "we are only delivering top quality articles, the taper and also the front bore is inspected 100 %." Quality is winning, this is what she feels.

"Anybody who has tested our system once will keep it and wants more of it." During the last four years this has become a winner in our product range.

We have sold last year almost 10,000 parts." An example of quality consciousness.

A small, however, important part of the tool-holders are tightening bolts.

Franz Ziegltrum, responsible at Haimer for Engineering and Quality Management says: "These bolts are geometrically relatively simple parts, which could be bought outside.

However, we did do this initially.

They were turned by a subcontractor in large quantities and then collected in a bulk case for hardening, where all the parts had been hardened through.

The components were cheap, but we had problems right from the start.

A tightening bolt which was hardened through ruptured.

This could have provoked a disaster, but we have reacted immediately.

From that day onwards we are producing the bolts ourselves and place an enormous onus on the quality of these parts.

This means the parts are turned in-house and before they are sent to hardening we connect the threaded pins so that the bolts can not be hardened through internally.

They are also masked at the very tight faces in order to prevent them from becoming brittle.

So we have the advantage that the tightening bolts are tough in important areas and they will not rupture.

Furthermore every batch is subjected to a crash test, however, they are not allowed to break at any time.

This is only one example how we try to offer utmost quality to our customers - even if this is costing a few Euros.

? Franz Haimer GmbH, Weiherstraáe 21, D-86568 Igenhausen, 0 82 57 / 99 88 -0.

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