HSS Titanium Coated Twist Drill Bit 1.5-12mm Set
A twist drill is a metal rod of a specific diameter that has two, three or four spiral flutes running most of its length. Two-flute drills are for primary drilling, whereas three- and four-flute drills are only for enlarging cast or punched holes in a production situation. The section between the two flutes is called the web, and a point is formed by relief grinding the web to an angle of 59° from the drill's axis, which is 118° inclusive. This forms a sloped cutting edge at the edge of the flute, which is called the lip. A twist drill is very inefficient at the point because the web leaves scant exit space for debris (called swarf) and because the point has a low surface speed compared to the periphery. For this reason, a good scheme for drilling larger holes is to first drill 1/4" or less and then follow with the drill of the desired diameter.
Package & Shipping:
- Free shipping all over the world
- 13pcs Twist Drill Bit
- To Korea, Japan : it take about 7-10 days
- To USA, CA, Spain, France, Poland, Belgium, Portugal, United Kingdom, Germany, Italy and Netherlands: it take about 12 - 20days
- To other European countries and Ukraine,Belarus,Russian Federation: it take about 15-30 days
- To other countries: it take about 20-35 days
Specification:
- Type: Twist Drill Bit
- Material: High Speed Steel
- Coating: Titanium
- Set 1.5-6.5mm Including: 1.5mm 2mm 2.5mm 3mm 3.2mm 3.5mm 4mm 4.5mm 4.8mm 5mm 5.5mm 6mm 6.5mm
- Set 2-12mm Including: 2mm 2.5mm 3mm 3.2mm 4mm 5mm 5.5mm 6mm 8mm 8.5mm 10mm 10.5mm 12mm
More About Twist Drill Bit Set
In addition to creating the cutting lips, the flutes provide a place for the swarf to be drawn out of the hole. The spiral expedites this, but the flute becoming impacted with swarf is always a niggling problem. For this reason, a twist drill must be constantly cleared; that is, completely withdrawn from the hole. If you do this frequently, the swarf will be flung away, but if you wait too long, you will have to stop the drill and manually clean the flutes. Clearing is much easier with a drill press than with a drill motor. Wood is a poster child for quickly impacting a twist drill, so even more frequent clearing than with metal is necessary. This problem can be somewhat ameliorated by now and then applying wax or spraying silicone to the drill.
Fractional size twist drill assortments are commonly offered in sizes between 1/16" and 1/2" in 1/64th inch increments. Number drills cover sizes between the fractional diameters below 1/4". Numbered between 1 and 80, they cover sizes from .228" (#1) down to .0135" (#80). Letter drills cover sizes between the fractional diameters from 1/4" to 1/2". An A drill is .234" and a Z drill is .413" diameter. This is somewhat confusing because the number series becomes smaller from 1/4" as the numbers increase and letter series get larger from 1/4" as the letters increase. Twist drills are also offered in metric sizing, so just about any diameter desired can be obtained.