Half & Full Flute design core drills

Full Flute or Half Flute Annular Cutters?

Different manufacturer of annular cutter have their own different design and geometry. But, the main two types of design are the Half Flute Annular Cutters and Full Flute Annular Cutters. Below article gives more details on Why Fully Flute Annular Cutters are technically much better than Half Flute Annular Cutters,

A full flute is an advanced design than the half flute. Some manufacturer produces half flute cutters only for their production cost cutting. The half flute has no advantage on drilling, In fact, it is an old technology compared to the full flute designed cutters. Many good manufacturers from Germany, UK and USA have only full flute designs. Please also check the websites of Milwaukee, BDS Maschinen, FE Powertools, DeWalt, Haugen, etc.

A. Why is a full flute better than a half flute?

1. When drilling deep holes, the flutes work as a track or travel for the chips to come out of the hole.Half & Full Flute design core drills

2. In full flute design, the chips can easily travel the complete length of the cutter and come out of the hole. Thus it does not block or jam the cutter.

3. In half flute the chips can travel only half distance, thus they very frequently block the or jam the cutter. Hence giving the poor life of cutter.

B. Why some manufacturer produce half flute design cutter?
Only and only for cost reduction by taking quality into risk.

C. Why some dealers encourage end user to buy half flutes?
Firstly because of ‘’superstitious!!’’. Secondly, no technical education and third, because they do not have other visible arguments to make to sell against the good quality manufacturer.

D. Why do professional manufacturers not manufacture half flute?
Because of its more than 15 years old technology and not an advanced technology.

E. What is the technical proof/reference to above arguments?
Click on this link for literature on drill bits and flutes, written by By Robert H. Todd, Dell K. Allen, Leo Alting


core drills drilling deep holes

Drilling Deep Holes With Annular Cutters I Drilling Deep Holes With Magnetic Drills

Drilling holes in thin plates with annular cutters and magnetic drilling machine is an easy task, but when it comes to drilling deep holes in thick plates from 60 mm to 110 mm thickness the task becomes a little tricky.

As per the geometry of the annular cutters, the spiral chips comes out of the hole with the help of the flutes made on annular cutters. But, while drilling deep holes the chips do not easily come out complete which results in annular cutter not performing or getting stuck.

In this video, we would like to demonstrate and give tips on how to drill deep holes with annular cutters and magnetic drill?

We are using a 90 mm thick steel plate (3 35/64 inches).

We are drilling with 22 mm (55/64 inches) diameter X 110 mm (4 21/64 inches) length tungsten carbide tip annular cutter.


While drilling more than 70 or 80 mm (3 5/32 inches) deep holes with a magnetic drill and annular cutter, there is always an issue that the cutter after certain depth does not cut or penetrate the material.

This is because the chips from the material are not able to travel outside of the hole and thus creates a layer of powdered chips between the cutter teeth and the surface of half made hole. This layer of powdered chips does not allow the annular cutter to penetrate.


For drilling deep holes the best way to have air compressor along. Once you feel the cutter does not cut, give reverse feed to the cutter and blow air inside the holes to remove the powdered chips.

Also, blow air on the tips of the annular cutter and also around the flutes of the annular cutter to remove the powdered or spiral chips.

Then, start to drill again.

Repeat the process until you finish to make the hole.

With this process, you can easily make deep holes and also increase your tool life.


Use external as well as internal lubrication while drilling deep holes.

We would recommend not using an ejector pin or pilot pin after you reach 60 mm (2 23/64 inches) deep because sometimes the ejector pin is too long to go upside into the taper and may also prevent the annular cutter to cut.

Step by step method to drilling deep holes with annular cutters.

Considering the plate thickness is 100 mm and hole to be made is 22 mm diameter.

Buy an annular cutter of minimum 100 mm long and 22 mm diameter, also don’t forget to buy the ejector pin of the same brand.

For 100 mm deep holes, we would always recommend you to buy TCT annular cutters rather than HSS annular cutters.

Set the RPM of the machine to 290 RPM. For deep holes, it’s better to use a magnetic drill with variable speed control.

Start to drill with a lot of external and internal coolant.

After drilling about 60 mm deep, we recommend you to completely remove the ejector pin and drill further without an ejector pin.

Whenever your feed gets harder to drill further, just give reverse feed, use the air compressor and blow air inside the hole removing all the powdered chips from inside the hole. Also, blow air on the tips of the annular cutter and flutes of the annular cutter.

Drill further, whenever its get harder to drill, follow above step.

With all the above steps you will be able to easily drill deep holes in metal.