Spot drills are used to create a small indent prior to drilling with a twist type drill, the indent acts as a location point and guide for a larger diameter drill to follow minimising the risk of deflection. Spot drills differ slightly from centre drills as they are usually on a nominal shank and do not have the smaller pilot diameter that a centre drill has.

In conclusion, Spot drills and centre drills are both useful tools for creating holes in metal. However, they have different purposes and advantages. Spot drills are more accurate and help to prevent the secondary drilling cycles from wandering. Centre drills are used to drill support holes in the workpiece for a lathe centre and create a starting point for a larger diameter hole. The best way to choose between a spot drill and a centre drill is to consider the purpose of the drill bit, the hole size you require and what machine you are working on.

In this blog I will help to differentiate between the two and help you make the right choice when selecting the best tool for your application.

Before drilling a hole or preparing to use a live (revolving) or dead centre on a lathe, it’s common to use a spot drill or centre drill to ensure accuracy for the drill or centre. Spotting drills and centre drills may have similar characteristics, but they are intended for two different purposes.

The spot drill is a good tool to have in your arsenal, its function is no longer limited to the drilling of pilot holes. In addition to this, it is possible to use them as a chamfer mill and various angles are available. The angles can be 60°, 90°, and 120° and can be used for a wide range of processes, including:

To create their bendy microprocessor, the researchers teamed with a group at PragmatIC Semiconductor to create a bendable version of the Cortex M0+ microprocessor, which was chosen for its simplicity and small size. To make their chip, (which includes ROM, RAM and interconnections) the team used amorphous silicon fabricated (in the form of metal-oxide thin-film transistors) onto flexible polymers.

Centre drills are mainly used to create a hole in the centre of a workpiece. This hole will act as a guide/support for a revolving or dead centre and in some case a starting point for the hole to be drilled with a larger drill diameter.

For expert advice on choosing the right drill for your application, please contact our technical team on 01924 869 615 or email salescutwel.net.

In the first iteration of their PlasticARM, the researchers put the registers used by the CPU in a reserved part of RAM, and only 128 bytes of RAM were used. The resulting microprocessor was bendable, but it was neither efficient nor fast. Also, it did not have any programable memory. But the researchers note that they are just beginning. They suggest their work thus far has shown that it is possible to make viable flexible microprocessors, which means that eventually, it could be possible to print them onto clothes and other wearable devices at very low cost. They estimate that trillions of objects in the coming decades will be outfitted with processing power, including chips that can tell you if the milk is sour, shirts that can measure body fluids to be processed by your smartphone, and labels you can paste onto to your skin to warn others of your mood. The possibilities will be constrained only by the imagination.

Microprocessors power a wide range of products, but what they all have in common is their stiffness. Almost all of them are made using silicon wafers, which means that they have to be hard and flat. This inability to bend, the researchers with this new effort contend, is what is preventing the development of products such as smart clothes, smart labels on foods, packaging and even paper products. To meet that need, the team has created what they describe as the PlasticARM—a RISC-based 32-bit microprocessor set on a flexible base. In addition to its flexibility, the new technique allows for printing a microprocessor onto many types of materials, all at low cost.

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Excellent for Steel, Stainless Steel and Aluminium whilst also suitable for Hardened Steel up to HRc55, Titanium & Cast Iron.

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Centre drills come in two common types, Type A (DIN 333-A) this has 60-degree chamfer and Type B (DIN 333-B) that has two chamfers, a front 60 degree and secondary 120-degree chamfer. Centre drills are commonly available in Metric or BS (British Standard Imperial) sizes.

Centre drills are first choice for predrilling when using revolving or dead centres in the tailstock on manual or CNC lathe.

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More information: John Biggs et al, A natively flexible 32-bit Arm microprocessor, Nature (2021). DOI: 10.1038/s41586-021-03625-w Journal information: Nature

As mentioned above, a spot drill has multiple uses, the main use is spotting prior to drilling, this process increases the accuracy of the secondary drill. If the drill being used is not self-centring, then spot drilling is a must as it will minimise the risk of drill wander. Spot drilling will improve tool life and improve surface roughness. It’s worth noting that self-centring drills do not require spot drilling.

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A centre drill (which can be made from HSS or Carbide) can be used to drill a starter or guide hole in many different material types such as cast iron, aluminium, copper, steel, and stainless steel. Centre drills have a short and stubby design, this eliminates the risk of deflection making them the perfect tool for pre-drilling applications. When pre-drilling for a lathe centre, accuracy is key as the hole will ultimately keep the job aligned and stable during the machining process.

A centre drill has a slightly different geometry than a spot drill, they are shorter, with a tapered, or cone shaped end that is much smaller in diameter than the shaft of the drill. The smaller diameter is used as guide and creates clearance for the tip of lathe centre. A centre drill can also be used as a countersink to allow countersunk screws to sit flush with the surface.

Unlike centre drills, spot drills can be used for multiple applications such as spot drilling, chamfering, countersinking, V grooving and engraving. They are available in HSS or Carbide with different point angles, most commonly 90° or 120°.

A team of researchers at ARM Inc., has developed a 32-bit microprocessor on a flexible base which the company claims could pave the way to fully flexible smart integrated systems. In their paper published in the journal Nature, the group describes how they used metal−oxide thin-film transistors along with a type of plastic to create their chip and outline ways they believe it could be used.