Discussion on Lasers

Your recent discussion regarding lasers has prompted me to post on this list. I’ve had 20+ years experience with lasers from simple diode based pointers to high-powered that will easily cut 3/4" steel plate. I wrote a short piece for a couple of other lists that I’ll copy here that primarily deals with safety issues.
 
Many people regard a laser as just a bright red flashlight. Sadly, this is far from the truth.
 
A laser emits an extremely concentrated beam of radiated energy in the form of light. The radiation in some hand held lasers is equivalent to that of direct sunlight. While that initially doesn’t sound disturbing, consider looking straight at the sun for just one second and also remembering what the sun can do to your skin in a few hours.
 
A hand held laser pointer is designed to project a collated beam a significant distance. The reason that none of them have permanent on/off switches is they are intended to be momentary devices. Quilters have adopted them as a stylus type tool, seemingly without concern for any danger.
 
It is true that most laser pointers will not cause immediate permanent eye damage, even when viewed directly, however the long term exposure of reflected radiation has not been sufficiently studied yet.
 
Lasers are classified by the amount of radiation emitted. Most pointers in the USA are class IIIa. Some of those that are very inexpensive ($5 - 10) have such poor quality control that they really fall into the class IIIb designation, which is more powerful.
 
Most American schools, universities, and government facilities have banned all class III lasers along with all of Australia, Great Britain, and some other European countries, due to excessive radiation. A conservative measure that should make you realize someone has serious safety concerns.
 
Quilters who are staring at the reflected beam for hours at a time are clear off the charts for expected usage of a laser. A beam that is so powerful that it can be projected for miles is being used to go only inches, so it never really disperses its energy.
 
There are several ways to protect yourself:

1. If you have not yet purchased one, look for a lower power class II laser. They are easy to spot as class II has a yellow "Warning" label while class III has a red "Danger" label. If you are buying online, be sure to ask first.
2. If you already have one, place a restriction over the aperture, such as a piece of black tape with a pinhole in it. This is prudent for both class II and III
3. To be really safe, buy the special laser protection glasses. I personally would not wear them, but they are available
4. Use patterns that are printed on dull paper to reduce reflection
5. Rest your eyes often. Be careful to take a minute to let your eyes readjust to natural light before attempting any activity that could be harmful or dangerous without good vision

Please don’t let this discourage you from using a laser, but if you’ve read this far you’ll have a better understanding to provide you with safeguards and prudent use.

Table Levelling

It is precisely the behaviour of the machine when you stop moving it that indicates whether the table is "level" or not. In the early days we used to use a spirit level, and I even heard of one customer using surveyors’ equipment to level the table. But now, as I said, we rely on what the machine is doing to indicate whether the table is adjusted correctly for the machine. The energy chain exerts its own tiny forces, you see, so "level" becomes an ideal concept.

Move the head to one end of the table and test the behaviour by nudging it back and forward across the table. You’re looking for a consistent amount of roll in each direction proportional to the force of your nudge. You’ll find it easier to wind the feet up and down if you first move the machine to the other end of the table (which you will have to do anyway to get that end of the table right). Keep testing at each end of the table until satisfied. The middle should look after itself if the ends are OK, although this area is more important than the ends because that’s where you do most of the work. If the machine still rolls off at the middle, you’ll have to sacrifice the ends to justify the mean (middle). If your machine stands on carpet, you’ll probably find you have to do this a couple of times until the pile settles.

For longways adjustment we developed "the rubber band test" (purists only). Take one large rubber band and put it around the spool pin on top of the machine. Now use it to drag the machine in one direction and note the stretch in the band required to keep the machine moving at constant speed. Now reverse the direction. You’re looking for the same stretch in both directions. The rubber band is a primitive force gauge.

Dismounting Your Nolting from its Table

There are four steps to this process ... BUT FIRST: DISCONNECT THE POWER

1. Extract the telephone jack from the rear encoder (press clear plastic clip on the side) 
   
2. Unscrew the cover plate of the on/off switch and separate the push-together connector inside
   
3. Using a quilting pin or similar ease apart the cheeks of the last and second-last links of the energy chain. The last link is an anchor block that is firmly attached to the trolley where it should remain. Grasping the chain further up and twisting it should separate the links at the anchor block. The freed chain may be laid out straight along the throat space and tucked behind the needle bar.
   
4. Partially extract the removable axle pin from the left end of the cloth roller - enough to be able to lift the roller out and slide it off the fixed axle at the other end then remove it from the throat space of the machine. The machine is now free to roll off its carriage. Use a rubber band to capture the side encoder wheel as it emerges from the trolley track and hook the rubber band over the track lock on the right side of the machine. This will protect the delicate encoder from knocks.
   
5. In replacing the machine on the trolley the reverse steps apply. When you come to reconnect the energy chain it is a good idea to lead the encoder wire back under the chain to stop it interferring with the back axle.