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Regolamento - Glass bits have a spade-shaped carbide point

Mims - 27 Nov 2019 04:10:33
Oggetto: Glass bits have a spade-shaped carbide point
Glass bits have a spade-shaped carbide point. They generate high temperatures and have a very short life. Holes are generally drilled at low speed with a succession of increasing bit sizes. Diamond drill bits can also be used to cut holes in glass
, and last much longer.
PCB through-hole drill bits

A great number of holes with small diameters of about 1 mm or less must be drilled in printed circuit boards (PCBs) used by electronic equipment with through-hole components. Most PCBs are made of highly abrasive fiberglass, which quickly wears steel bits, especially given the hundreds or thousands of holes on most circuit boards. To solve this problem, solid tungsten carbide twist bits, which drill quickly through the board while providing a moderately long life, are almost always used. Carbide PCB bits are estimated to outlast high speed steel bits by a factor of ten or more. Other options sometimes used are diamond or diamond-coated bits.

In industry
, virtually all drilling is done by automated machines, and the bits are often automatically replaced by the equipment as they wear, as even solid carbide bits do not last long in constant use. PCB bits, of narrow diameter, typically mount in a collet rather than a chuck, and come with standard-size shanks
, often with pre-installed stops to set them at an exact depth every time when being automatically chucked by the equipment.

Very high rotational speeds鈥?0,000 to 100,000 RPM or even higher鈥攁re used; this translates to a reasonably fast linear speed of the cutting tip in these very small diameters. The high speed, small diameter, and the brittleness of the material, make the bits very subject to breaking
, particularly if the angle of the bit to the workpiece changes at all, or the bit contacts any object. Drilling by hand is not practicable, and many general-purpose drilling machines designed for larger bits rotate too slowly and wobble too much to use carbide bits effectively.

Resharpened and easily available PCB drills have historically been used in many prototyping and home PCB labs, using a high-speed rotary tool for small-diameter bits (such as a Moto-Tool by Dremel) in a stiff drill-press jig. If used for other materials these tiny bits must be evaluated for equivalent cutting speed vs material resistance to the cut (hardness), as the bit's rake angle and expected feed per revolution are optimised for high-speed automated use on fiberglass PCB substrate.

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Five Magic Phrases: Tips For Negotiating Like A Pro

By Jenna Glatzer

Those who are new to freelancing are often too afraid to ask for more than a client offers. Thrilled to be making any money at all, new freelancers typically agree to whatever figure is proposed. I was no exception to this rule
, but once Iíd built up my credits, I realized clients werenít about to offer me a raise if I continued to play the role of doormat.

Once a freelancer has some experience, the bottom line becomes more important. "Trivial issues" like prompt and appropriate payment start to matter when you depend on your home-business income to pay the bills.

Until youíve tried negotiating, you may not realize how much youíve been undercut. A clientís first offer is rarely the maximum amount he or she can actually afford to pay you; as is human nature, most will try to get good work at the lowest possible cost. Your job is to convince those clients that paying you a little extra for your piece will be worth it. How?

The answer may be simpler than you ever imagined: you just have to ask. In over four years as a full-time writer, Iíve gotten exactly what I asked for in every case except one-- and even in that case
, I was able to get the editor to spring for a 10% increase. In other words, every single time I got up the nerve to negotiate, I wound up with a bigger paycheck.

Remember that everything within a contract is fair grounds for negotiation; your goal should be to negotiate the highest fee, payable quickly after you complete the work, and terms that stipulate extra payment if extra work is required. You can also strike barter deals for the advertisement for your business, discounts on the clientís products
, etc.

Itís always slightly uncomfortable for a freelancer to ask for more than a client wishes to spend. But, with a few key phrases under your belt, you, too, can significantly increase your income.

The Magic Phrases

1. "That sounds a little low."

A timeless classic. This follows a golden rule: keep it simple. No matter what figure is proposed, just state those five words and then shut your mouth. Since no one can stand uncomfortable silences
, your tight lips will force the client to say something in response. Either he or she will make a new offer, ask you what you need, or tell you thatís the best they can do. If itís the latter, employ one of the next phrases.

2. "To make it worth my time, I would needÖ"

This one lets you take control of the situation. If youíve already figured out approximately how much time and effort this job will require, you should be able to determine how much you expect to be paid for it. Make sure that youíve done some research and that your figure is in the realm of what that particular market typically pays. (Asking for a figure thatís 20% more than their average payment for a job of your scope is reasonable; asking for 200% more is not.) Donít bother mincing your words; just state your figure and let the client decide whether or not to meet your demands.

3. "Considering the amount of (research
, time, material) required, can we agree toÖ"

You can end this open-ended statement with a higher fee.

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