120° HSS-COBALT SPOT DRILL SET 4 PCS 6, 8, 10, 12mm, Nc Spot Drill Hss Carbide Stub Center Bits 60 90 120 Degree, SPOTTING DRILL SET 5 PCE 90DEG HSS-COBALT TiNite, M42 HSS High Speed Steel Titanium Plated Spotting Drill Bits Set Round Shank 90 Degree Drilling Tool, Spot Drill HSS Co Cobalt NC Center Bit 60 90 120 Degree, Carbide Spot Drill NC Spotting Drill Set, Woodworking Metalworking & Multipurpose Drill Bits China Supplier Factory
120° HSS-COBALT SPOT DRILL SET 4 PCS 6, 8, 10, 12mm Specifications
Material:High-speed Steel(HSS-CO Cobalt)
Titanium Coating Drill Bits;
Length:Approx.45mm /1.8in
Size:1/4in (6.5mm), 5/16in (8mm), 3/8in (10mm).
Applications
General workshop and trade drilling
Workshop, maintenance and trade kit
Fitters, fabricators and tradies
The purpose of spot drilling is to drill a hole that will act as a guide for drilling the final hole. The hole is only drilled part way into the workpiece because it is only used to guide the beginning of the next drill process. Nc Spot Drill Hss Carbide Stub Center Bits 60 90 120 Degree
What is the purpose of a spot drill bit?
A Spotting Drill aims to make a tiny divot to precisely pinpoint the centre of a drill while starting a plunge. However, some machinists use these tools for a different purpose — chamfering the top of drilled holes.
When do I need to use a spot drill? M35 HSS Cobalt NC Center Spotting Drill Bit Titanium Coated
Is it necessary to use a spot drill every time a precise hole has to be drilled? Its function is to guarantee that the hole is situated correctly. The brief spot exercise is quite stiff, and the spotting action is unlikely to deviate. When using a carbide drill or a screw machine length drill, spotting is usually unnecessary. Because carbide is stiffer than HSS, the drill will travel where it is pointed. Most manufacturers advise against using a carbide twist drill or an insertable drill because the carbide is easily chipped in the dimple. Screw machine length twist drills are substantially shorter and less prone to flex. In general, avoiding spot drilling will save you much time. Purchasing a screw machine length twist drill set is worth the investment. I hardly ever utilize jobber length pieces. Sometimes a jobber length drill is required because the hole is too deep for a screw machine drill. In that instance, you may either start the twist drill with a spot drill or drill the shallow section of the hole with a screw machine length before switching to the more extended drill. You’re facing a tool change either way, so it’s six of one and a half dozen of the other. DIN333 Type A HSS Pilot Center Drill Bit for Lathe Machine Centering Pilot Drilling
A spot drill has a small flute length and a precise tolerance point geometry.
It is critical to understand that a spot drill has no land or body relief and is NOT intended to drill beyond the depth of the point angle, which is adequate to drill a detent or “dimple” in the workpiece.
Spot drills are used to increase the precision of secondary drill operations. However, if the spot drill diameter is more significant than the final hole size, they can also be used as a chamfering tool. HSS DIN333A Metal Centre Drill Bit for Rotary Tap / Router 60°
Ideally, the spot drill diameter should be around 70% of the ultimate drill diameter. The point angle of the spot drill should be more than or less than the point angle of the final drill.
In hardened steel, spot drilling is not suggested.
Contacting the corners of the carbide drill before the middle point in the hole opening may result in corner chipping.
Using a spot drill with an angle less than the drill tip angle WILL result in “blown off” drill flutes.
Never use a 90-degree spot drill followed by a 140-degree drill point! M2 TiN Coated HSS Centre Drill
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SIZE
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Diameter
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Total Length
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Flute Length
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Cutting Angle
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3.0
|
3
|
46
|
12
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60° / 90° / 120°
|
|
4.0
|
4
|
55
|
14
|
60° / 90° / 120°
|
|
5.0
|
5
|
62
|
16
|
60° / 90° / 120°
|
|
6.0
|
6
|
66
|
18
|
60° / 90° / 120°
|
|
7.0
|
7
|
70
|
20
|
60° / 90° / 120°
|
|
8.0
|
8
|
79
|
22
|
60° / 90° / 120°
|
|
9.0
|
9
|
84
|
24
|
60° / 90° / 120°
|
|
10.0
|
10
|
89
|
26
|
60° / 90° / 120°
|
|
11.0
|
11
|
95
|
28
|
60° / 90° / 120°
|
|
12.0
|
12
|
102
|
30
|
60° / 90° / 120°
|
|
13.0
|
13
|
102
|
32
|
60° / 90° / 120°
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