Finger Protection While Grinding

 Grinding lots of glass pieces often leads to a number of small cuts on the tips of your fingers. There are several things that can be done to reduce these cuts and the tenderness that comes from lots of grinding.

Various methods of protection are used.

Altering the fingers used to press the glass to the grinding bit.

Gloves –  It is not recommended that you wear gloves around rotating machinery. There is too much risk of injury, even on a small grinding machine. Some of the alternatives to gloves include plasters (band aids), masking tape, electrical tape.

Finger protection you can buy include rubber finger protectors, finger tip pads, finger caps (as used in counting money).

Other tools are made to hold the glass such as the grinder cookie

and Nick's Grinder's Mate 

Prevention
The sore fingers are usually caused by tiny cuts from the glass. So, all these methods are ways of putting something between the glass edges and your fingers. More importantly, you need to think about your practice if you are getting sore fingers while grinding.

The first thing is just to lightly grind all the way around the piece. This can be quick, and should use minimum pressure. This to is to take the sharp edges off the glass.  You can do a simple, light grind all the way around the piece. This removes the extra sharp edges that often remain after breaking the glass.

You can go a step further and do a light arris around the piece. This is just lightly holding the glass at about 45degrees to the grinding bit and going all the way around on all sides. This does not take off the shape of the piece, but gives a more rounded feel to the piece.

An illustration of the effect of holding the glass at an angle to the grinding head, although it need not be so much.

If you have to press hard to achieve the effect you want, it may be that your grinder bit is badly worn. It may also be that you need to have a coarser bit to achieve the amount of grinding that you need.

You should not be pressing hard in any case. This will wear out bearings on the motor and reduce the life of the bit.  Let the grinder do the work. Many people seem to put huge pressure on the piece to grind away the waste more quickly, but this is actually counter-productive. Less pressure means less fatigue, less chipping at the edges, fewer broken pieces, and most importantly, fewer cuts to the finger tips.

You should use medium pressure to allow the diamonds on the grinding bit to do the work. This will be about the same pressure as scoring the glass.  Fine work requires a fine grit, removing a lot of glass requires a coarse bit, not more pressure.  

If you frequently have to remove large amounts of glass, you need to review the accuracy of your cutting. You should not be relying on the grinder to do more than tidy your cuts.

Remedies
There are several remedies to relieve the soreness:

Cucumber melon
Vitamin E
Tea tree oil
Germolene
Antibacterial hand lotion 

Glass Grinder Maintenance

by Stephen Richard

Glass grinders are often the main machine used in stained glass.  They are important machines to many of us and so need proper maintenance and use to give us long service.  This note is about the things you need to keep in mind about maintaining the grinder.

Glass grinders are very handy tools. They mainly consists of a spinning diamond coated cylinder (the bit) extending above a grid surface that can rapidly and accurately grind glass to the desired shape.

Don't purposely cut glass large with the intention of grinding. Ideally no grinding would have to be done. It should be used only for minor adjustments or for grinding tough-to-cut inside curves.

Cleaning

The water reservoir should be emptied each day after use.  It is not advisable to have standing water in your grinder for some health reasons, avoiding unpleasant smells, and as moving a grinder with water risks damaging the grinder’s motor and other equipment and materials in the studio.  Even if you do not move your grinder about, the water needs changing just as frequently as the glass grit needs removing.  Some people line their reservoir with aluminium foil to catch the grinding residue.  This may not be possible on all grinders, but does reduce the effort of cleaning the grit from the bottom of the reservoir.

Ensure you clean your sponge (if the grinder uses one) when cleaning out the reservoir.  If you do not clean it regularly, it will become hard and stop bringing water to your grinding head.

The accumulated glass grit should be cleaned out with scraper or paper towel and disposed of in the waste, not down a sink.  The glass grit is relatively heavy and will become solid and block your drains.  If you have a garden, the glass grit is a good soil modifier, by helping the drainage.  Without regular cleaning, the glass grit will accumulate and restrict the flow of water to your grinding head.

Clean any plastic eye shield with running water, as rubbing it will scratch the surface.

Ensure there is water in the reservoir before starting any grinding, but do not over fill as the excess water could get into the motor. Empty the reservoir at the end of the day's use. 

Grinder Head Maintenance

Wear - There seem to be two main indications of wear – chipping of the glass, and slow grinding.  There are a number of reasons that may cause the grinder to chip the glass surface and not all are indications of wear. Some of the things to check are:

• Too much pressure will cause the glass to chip.  It may be that you are pressing the glass into the grinder head too hard. The grinder head should do the work. Firm rather than hard pressure should be applied. If the grinder motor slows, it is an indication that far too much pressure is being applied. It will also lead to cuts on your fingers. Run the glass lightly against the grinder all the way around to remove any overlooked sharp shells on the glass.  Then light pressure will not cut your fingers while grinding.

This shows some finger protection being used to protect fingers from cuts.

• Grit size has an influence on the way the edge appears.  It is possible that you may be using too coarse a grit on the grinder bit/head. The coarser the grit is, the larger the chips will be taken off the edge surfaces. Smaller grits take smaller chips off the edges, and so are less obvious.

• New bits can be a source of chipping.  Oddly, new bits can cause chipping. If it is a new bit that is causing the chipping, consider dressing it. New bits often need to be dressed – removing protruding diamonds, or cleaning and exposing new ones on a worn bit. To dress the bit you can grind some scrap glass, brick, or use a dressing stone to lightly grind some of the abrasive material away. This most often settles the bit and avoids chipping.

• A worn or damaged grinder bit/head can cause chipping.  Inspect your bit carefully for smooth areas showing that the diamonds have been worn away. Also look for dents, and other irregularities on the surface, indicating that the bit is damaged. Any dents or smooth places on the bit cause a vibration that is similar to a tiny hammer tapping the edge of the glass.

This range of possible causes shows that chipping of the glass is most often comes from the way the machine is used rather than the grinder head needing replacement.

Lubrication

Water for the grinding head.  Insufficient water supply can reduce the life of the grinder head.  If there is too little water reaching the head to lubricate the diamonds and keep the glass cool it can reduce the life of the grinder head, by overheating it too. If you are getting a white paste or a powder on or near the glass, you need to increase the water supply. This may indicate a low water level, too much grit in the reservoir or sponge clogged preventing sufficient water reaching the grinding head.

The white reside on the grinding head shows there is insufficient water reaching the grinding surface

Use Vaseline or other grease on the shaft and grub screw.  Smooth any corrosion from the shaft with fine wet and dry sandpaper and lubricate the shaft. Periodic removal of the bit and lubrication of the shaft should be part of the regular maintenance of the grinder.  Also ensure the grub screw is kept clear of glass grit by putting some Vaseline in the recess.  This keeps the threads and the slot for the alan key from clogging up with glass grit.

Removing the Head

The first step in removing the grinding head is to loosen the grub screw that fixes the head to the shaft. This is often full of glass grit, so clean the recess for the alan key first. I do this by using a needle or other thin sharp object to clear out all the glass powder from the recess in the screw and the threads.  When clean, insert the alan key as far as possible and while holding it in turn the key in an anticlockwise direction.  If it will not move, you need more leverage.  If the alan key simply spins in the recess, you need a stud bolt remover tool. 

This is a tool that many mechanics and tool shops have. It is normally square or triangular. It is used by drilling into the broken off bolt. The tool is tapped into the hole and then with a wrench/spanner the grub screw is loosened. In the case of the grub screw the recess is already there so you only need to hammer the removal tool into the alan key recess and proceed as normal.

The more modern and safer method is to use a tool with a reverse thread on it. This means that as you turn anti-clockwise, the tool thread bites into the recess and brings the grub screw out.

If the grinding bit is already seized, the method of removal is based on how fast it is stuck. If there is a bit of movement around the shaft when the grub screw is removed, you can probably remove it with simple tools. First use very fine wet and dry sandpaper to remove all corrosion and roughness from the upper, exposed part of the shaft. Put a thin film of lubrication or penetrating oil on the shaft and then you can hold the top of the shaft tight with smooth-jawed pliers while you twist the bit. Be careful not to mark the shaft or you will create another obstacle to removal of the bit. Alternatively, while pulling up on the bit, you can tap the top end of the shaft gently with a plastic hammer to shake the bit loose.  Be careful with this method as the shaft is directly connected to the motor and excessive pressure can damage the motor.

If this does not work, remove the grid and turn the dried grinder upside down and spray WD-40 or other penetrating oil to the bottom of the grinder bit.  This should be left for a few days with renewal of the penetrating oil every half day. Then try the methods above to free the bit from the shaft.

If the bit is still firmly stuck, you will need a small wheel puller to get the bit off the shaft.  Small wheel pullers are available from most DIY or mechanics suppliers.  They are often called faucet pullers.

Once you have the bit off, smooth any corrosion from the shaft with fine wet and dry sandpaper and lubricate the shaft. Periodic removal of the bit and lubrication of the shaft should be part of the regular maintenance of the grinder.

Adjusting height

If your grinder bit is too low or too high the diamond surface will not grind the whole of the glass edge. This can lead to chipping of the surface of the glass at the edges.

A good practice is to start with the bit as high as possible to allow for differing thicknesses of glass. As high as possible is with the bottom of the diamonds just below the platform of the grinder. This will ensure that you can deal with varying thicknesses of glass without immediate adjustment. You can then lower the bit as it wears.

This bit is only just high enough for this style of grinding

An example of  the right height,although too much pressure is being applied

Here the head is only just low enough to catch all the glass. 

Be certain that you secure the grinding head with the grub screw facing the flat part of the shaft.  Failure to do that will both mark the shaft, making removal difficult, and potentially allow the shaft to spin while the head remains stationary.

This shows the minimum level for 3mm glass

Of course, you need to ensure there is adequate water reaching the grinding bit to avoid overheating the glass, and to keep the dust from grinding from getting into the air.

Care in Use

Lubrication

Water is the primary lubricant.  It washes the grit from between the diamonds and keeps the head cool.  It also cools the glass, of course.

You can buy an additive for the water – often called a diamond coolant – which is intended to provide a kind of lubrication for the diamonds. This may also extend the life of the bit, but is not necessary.

Grinding head/Bits

The diamond bit must be kept wet to prevent glass dust from developing and being inhaled.  Also, importantly, it keeps the bit cool and so avoids overheating the bit and extends its life.  There are several grits available. "Fine" grinds slower but leaves fewer chips out of the glass. "Coarse" grinds very fast but leaves larger chips. "Standard" is a central compromise.

Shaft

Smooth any corrosion from the shaft with fine wet and dry sandpaper and lubricate the shaft. Periodic removal of the bit and lubrication of the shaft should be part of the regular maintenance of the grinder.  The maintenance is not only on the shaft but also on the fixings. Putting a dab of Vaseline or thick grease into the grub screw socket will help keep it clear of the glass residue. 

Pressure

It may be that you are pressing the glass into the grinder head too hard. The grinder head should do the work. Firm rather than hard pressure should be applied. If the grinder slows, it is an indication that too much pressure is being applied.  That kind of pressure also puts a lot of wear on the bearings of the motor.

Extending the life of your grinder bits is a matter of recognising that you should not force the glass into the grinding head. Excessive pressure against the head heats the bit and allows the diamonds to become free of the binding material, so reducing its life. 

If the grinder is not taking glass off fast enough for your purposes, you should put a coarser bit on the grinder, rather than press harder. The bits do come in a variety of grits. Try out some different grits to find the one that works best for the speed at which you want to remove the glass.

Maintenance routine

A maintenance routine for your grinder is a practice that will reward you with longer lives for your grinder heads and the machine itself.  A sample routine might be like the following:

Daily

Empty the water reservoir 

Clean out all the glass grit 

Clean the eye shield

        

        Weekly

Inspect the bit for wear. Adjust up or down or replace
Inspect that grub screw is free of glass grit. Clean and re-fill with Vaseline
Check head moves freely up and down on shaft.  Tighten the grub screw after.