The subject of the invention is drilling cutting tool of wood industry for preparing holβ3 πainly in wood and in the like sort , which holas can be U3βd as blind- or through holes for fastening together wooden cons ructions , furniture, toys, etc . and which has essentially a cylinder-shaped .drilling body which is rotable around the longitudinal axis by way of fixation of bore rod and on the cutting frontal area of said drilling body there is one or more πain cutting edge/s/ which refine/s/ t e bottom o-f. the hols and which has /have/ swar -lead ng sur acβ/s/ which i3 /are/ situated behind one or πore main cutting edge/s/ and is /are/ continuously rising and reaches the bac -side of the drilling body.

Drills suitable for producing blind- or through holes hare been known for a long time in wooden industry, but said drills are suit¬ able for holes of low depths only and the surface quality of hole casing is not satisfactory either. The technical book "Faforgacsolό ^* szerszamok" /Lϊiiszaki Kiadό, 1984/ writes about drills which are suitable for producing holes of such kind. The drill according to the invention can be classed among the family of cylinder-boring machines by classification of this . echnical book.

The disadvantage of the previously introduced forms generally is that the swarf is lead by the cutting edges into so narrow room where said swarf is accumulated and can cause such a clogging by the local heaping that the edge often burns off or peeling off.

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The formation and the pitch of the known 3hell bits's spiral 3hape is not suitable for assuring the transport of the swarf outwards the hole. The .mown shell bits fill in the whole cross soction of the hole, so the transport of swarf is hindered, so they are not fit for continuous operation. She accumulation of 3warf in the hole could be elimina ed.only by lifting the drill several times during operation, so the efficacy was very low.

The aim of this invention i3 to produce a wood industrial drilling cutting tool where the cutting edges are easily available due to the structural development and as a result of this, they can be graund by machine, said tool leads the swarf outwards the cutting room continuously without the risk of accumulation and clogging and therefore said tool is suitable for producing deep holes and gaps, too, during continuous operation.

Shis invention solves this probleπ by producing such wood indust¬ rial drilling cutting tool, which has concave curved swarf leading surfaces seeing from the direction of the bore rod, furtheron a swarf lifting spiral is formed on the bore rod as the continuation of the swarf leading surfaces.

The further characteristic of the invention is that the bore rod side part of the swarf-leading surface fits essentially to the ' back-surface of the drilling body along the centre-line curved line which is parallel with the main cutting edge.

The swarf lifting spiral and double-spiral is made advantageously of the material of the bore rod.

The swarf-li ting spiral can be spring steel with triangle-, or

paralβllogra cros3-section.

The bore rod of the cutting tool is formed advan geously as a LIor3β-cone to which a drilling- nnexe i3 connected which has a spiral or double spiral exterior surface and which can be fixed in drilling machine.

The advantageous formation is where the bore rod is fixed by right-hand thread to the drilling-annexe which has spiral or double-spi¬ ral ex erior surface and which can be fastened in drilling machine. finally, it i3 also characteristic that on the bore rod a trun¬ cated cone-surface is formed which stands out of the drilling body's back surface and which reaches the threaded part of the bore rod.

Purtheron the invention is made known based on it3 embodiment in the examples by the help of the figures which are:

Pig. 1. - Side-view of the wood industrial drilling cutting tool

Pig. 2. - Side-view of the cutting tool according to Pig. 1. turned by 90° compared to said Pig. 1.

Pig. 3. - Top view of the cutting tool according to Pig. 1.

Pig. 4. - Swarf lifting double spiral with paralellogram cross- -sec ion

Pig. 5. - Swarf lifting double spiral with triangle cross-section

Pig. 6. - An embodiment of a bore rod with threaded part which can be fastened in the drilling annexe

Pig.7. - Side view of another formulation of a spiral.

The wood industrial cutting tool which can be seen on Pigβ. 1 - 3 consists of drilling body /l/ and cylinder- or cone-shaped bore rod /2/ which serves for clamping the drilling body. On the front surface /3/

of the drilling body /l/ which makes the machining process and the cutting, cutting edges /5/ - which machine the casing of the hole - and main cutting edges /4/ - machining the bottom of the hole - are situated. Por example the main cutting edges / are situated on one diameter of the front surface /3/ in a single line and they divide the drilling body /l/ in two equal part3 in two cutting bodies /δ/ which are formed on two sides of main cutting edges /4/ turning by 180° compared to each-other. The front surface /3/ is perpendicular

I to the rot tio axis of the drilling body /l/.

Seen in the rotation direction there is one-one practically one-quarter sector shaped open area /!/ in order to secure the con¬ tinuous leading out and the automatic elimination of the swarf. The one -quarter sector shaped open areas /7/ make possible that the swarf which, forms in no matter how much quantity should leave the area of the main cutting edge /4/ of the cutting tool. The swarf is pushed out of the main cutting edge's /4/ area by the swarf which forms continuously, but later.

Behind of every main cutting edge /4/ there is swarf leading sur¬ face /9/ which raises continuously and reaches the back surface /8/ of the drilling body /l/.

Prom the front surface /3/ of the drilling body /l/ a centralised guide-tip /ll/ is formed ih the ^* middle ^* ,-.wBioli goes beyond the plane determined by cutting edges /5/.

At the advantageous embodiment of the wood industrial cutting tool according to the invention the two main cutting edges /4/ which machine the bottom of the hole reache the cutting area of the centra-

lized guide tip /ll/. In order to realise it, the side /lβ/ - which surrounds inwardly the opean areas /7/ - of the cutting body /6/ is under achined in a way marked by dotted lines.

The undermachining along the side /14/ serves the purpose that main cutting edges /4/ should approach as better as possible the mid-line of the drill and hereby the smoothest possible hole-bottom can be forned.

The traditional wood industrial drilling cutting tools have narrowing cro3s-section as a" result of undermachining of the side /lβ/ along ^; straight line and said narrowing cross-section leads to the thickening of dwarf jjust forming. At the formation of this in¬ vention the swarf-leading surface /9/ is formed in a way that the 3warf-leading surface /9/ which approaches the back surface /8/ archedly turns to the root of the bore rod along the mildly curved line /lβ/. This way the continuous failure-free swarf-stream can be assured.

The single or double spiral /15/ formed as a continuation of the arched 3war -leading surface /9/ which fits to the root of bore rod /2/, serves the further elimination of the swarf from the hole. The single or double spiral /15/ can be made of the material of bore rod /2/ and can also be spring steeel with a triangle- or paralello- gram cross-section.

The spring steel can be fastened on the bore rod /2/ of the cutting tool or on the drilling annexe /17/ in a Imown way.

The spiral /15s/ or the double spiral can also be formed on drilling annexe /17/ which is separated from the drill and which τsan

be clamped in the drilling machine. In 3aid drill-annexe /17/ the bore rod /2/ of cutting tool can be formed as Morse-cone or thread¬ ed 3han . '.Then it i3 formed as threaded shank on the bore rod /2/ a cone-frustruπ type surf ce is formed from the back surface /8/ of drilling body /l/ till the threaded part.

The most important advantageous characteristics of the wood in¬ dustrial cutting tool according to the invention are as follows:

The formir-g of the swar -leading surface makes possible the con¬ tinuous throwing-out of the swarf. The spiral or dαuble-spiral which has smaller diameter than that of the hole loosen continuously the thickening swarf and makes possible the drilling of deep gaps even without lifting the tool.

A separated exterior spiral-surface drilling annexe can be used also for different cutting tools. Hereby it is not necessary to buy more, outwardly spiral formed cutting tool when wishing carpentry, but only one suitable drilling annexe is sufficient. of. By the help of the cutting tool "this invention wood, plastic and even leather can be worked especially advantageously.

The advantageous revolution number at 100 millimeter hole 0 is

600 revolution per minute, at 200 millimeter hole 03000 revolution per minute.