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Complete Guide To Cutting Glass.

There comes a time when every handyman wants to cut glass for some job around the house. A window needs a new pane, glass is wanted for a bookcase or cabinet. Here is all you need to know about handling and cutting glass. Keep this valuable article for future reference. - it's all simply explained here.
By Ray Lewhite

SAFETY NOTE You must protect your eyes by wearing safety glasses or goggles. Wear thick leather gloves when hacking out or handling glass.
Anyone can cut glass if they tackle it with knowledge and confidence. I have tried in this article to cover all the points of difficulty that you may come across. At the same time by following closely you'll learn all about glass you need to know, the tools, measuring, handling and how to use the cutter. But first, before I tell you how to cut a piece of glass, it will be as well to run through the short list of tools required.

You will need

A glass cutter
A straight-edge or T-square
A spring steel rule (Marked off in inches)
A flat bench or table
A jar of turps or white spirit
A one inch paint brush

Complete Guide To Cutting Glass Now I will explain these in detail.

Any glass cutter will work if handled correctly, but I prefer a metal shaft single wheel type of cutter, which can be obtained from your local hardware shop. This type of cutter usually has a removable spindle, should it be necessary to replace a wheel, the spindle can be tapped out with a small brad and a light hammer. A new wheel bought at the same shop for a few pence, can then be inserted. A glass cutter that is kept well oiled, and not left to rust on a shelf, should last many years, and no replacement wheel should be necessary.

Making a T-square

The straight-edge or T-square can be home made by using a length of hard timber. This should be about 36in. long, 2in. wide, and 3/16in. thick. The edges should be smoothed down with a piece of fine glass-paper, and the corners very slightly rounded. If small holes are bored along the straight-edge every 10in. or so, it will help stop the wood from warping.
If another short piece of timber, about 14in. x 2in. x 3/4in. is joined centrally across one end of the straight-edge to form a T-square, this will prove more satisfactory, as then all your glass can be cut squarely.
If a T-square is made up, it should be a firm job, and it is advisable to cut a notch each side of the straight edge into the crosspiece, to allow the glass cutter to traverse the full length of the glass(see Fig.1).
A pull out spring steel rule is the most useful accessory for measuring off. This should be marked off in inches, usually up to 72. The footage measure is never used in the glass trade and sizes should always be written down in inches.
The smallest unit of measurement is 1/8in.. So should the job in hand demand a more accurate size then 'full' or 'bare' of an eight is correct, For example, if the size required is 12 5/16in. then the glass size required is 12 1/4in. 'full,' or 12 3/8in. 'bare.'
The main reason for this is that most window frame rebates are made large enough to allow you to measure to the nearest 1/8in., thereby avoiding to many fractional sizes.
A fair amount of attention should be paid to the workbench or table that you are going to use. This should be as near flat as possible, and there must be no nail heads or other projections sticking up above the top of the table.
It is possible to cover the bench with a blanket or a similar piece of material, kept fairly taut to avoid wrinkles or folds in the cloth so much the better. But whether covered or not the bench must be kept swept clean, or your sheet of glass will get scratched or broken. Don't leave chips of glass laying on the bench - again you'll scratch the glass you are cutting.
A small jar of turps or white spirit and a small paintbrush are handy accessories to have. You'll need them if a small strip of glass has to be cut off the edge of a sheet or if a piece of plate glass needs cutting. More about that later.

Glass is made of various weights 24oz. being the most common. Eighteen ounce is used for picture frames, birdcages, cabinet doors and the like. Being light this glass does not put too much strain on the cabinet door hinges when the door is open.
Twenty four ounce is used in windows up to 36in. square, garden frames, greenhouses and most odd jobs about the home. Thirty two ounce should be used when a window exceeds 36in. square and on lean-to roofs where the runs exceed 18in. wide, or where the runs are fairly long and the glass is preferred in one piece so that there is no lap. Thirty-two ounce should also be used on large windows and door panels that are likely to get a lot of slamming, and for small shelves up to about 12in. x 6in. These incidentally should not be overloaded, as 32oz. is only half the thickness of 1/4in plate, which is the glass usually recommended for shelves.
Quarter inch plate should be used for shelves larger than 12in. x 6in., and for any shelf that is required to take the weight of jars and bottles. Quarter inch plate is also advisable for aquariums and any large picture window that exceeds 48in. square. If one wants a view uninterrupted by the waves and blemishes that are present in 32oz glass then 1/4in. plate should be used also in picture windows under 48in. square.

Complete Guide To Cutting Glass Measuring

Measuring correctly is more difficult than would appear at first sight. One must get the sizes right, and get them down on paper so that the cutter can understand them and cut the glass to the correct size.
Measuring should be tackled with the steel rule mentioned earlier. A tape measure tends to stretch with use, and is not reliable for accurate measuring. A 2 or 3ft. rule can be used where the sizes are less than the full measure of the rule, but if two measurements have to be taken, added together, then an allowance made for a between glass and window frame, a mistake can easily occur.
First ascertain that the opening to be measured is square, and that none of the bars are warped. If all is well, measure the exact distance between the top rebate and the bottom rebate (see Fig.2). Subtract 1/8in. to allow for a clearance between glass and frame, and write down the resulting size.
Measure the width of the frame in the same way. The result should be the glass size required. Check the width at top and bottom of frame and check the height at either side. Always measure height of frame first to enable the cutter to distinguish one size from the other especially when lining up certain types of glass which have distinctive patterns.
In the case of a rather large square or where there are some doubt as to whether the bar or bars are straight, a check should also be made at points between top and bottom, and left and right of frame, to ensure that bars are parallel. If a bar or frame is badly warped and the glass will not fit at both ends and centre, the frame should be measured 1in. oversize to allow for 'cutting in' freehand. I will explain this later in detail.
If you want to glaze or fix just one or two odd sized pieces of glass, and have to purchase these from your local glass merchant, then providing the frame has been measured correctly, cutting by you should not be necessary, but if you happen to have a few odd pieces of glass knocking around in the garden or shed, which you wish to use, then the instructions given here if followed correctly, will bring you satisfactory results.

Complete Guide To Cutting Glass Handling the glass

If you have a piece of glass large enough for the job in hand, lay this on the bench ready for cutting. The correct way to do this is to pick up the square of glass by placing one hand on each vertical edge, lift it off the floor, and then tilt it sideways so that the right hand is at the bottom and the left hand is at the top. In this position, walk across to the bench and place the glass against the front edge of the bench as near the centre of the glass as possible. The right hand should now be below the edge of the bench and the left hand should be about the same distance above(see Fig.3).
The right hand now lifts the bottom edge of the glass and pivots it on the front edge of the bench so that the top of the glass comes to rest flat on the bench. This should be done with care. The speed of this movement can be controlled by pressure of the right hand. However, the glass should be given its 'head' and not held back by the right hand except to ease the speed with which the glass falls. The glass can now be slid on to the bench, leaving about one inch overlapping. If the glass is dirty clean it thoroughly with a rag dipped in turps, or a moist leather and dry off. Then lay the straight-edge or T-square on the glass, and measuring from the left hand edge, move the T-square along until it comes to rest 1/16in. short of the required size measuring to the right hand side of the T-square. This 1/16in. is an allowance for the thickness of the shaft of the glasscutter.
Check the size at both the top and the bottom of the T-square and having made sure that this is correct, you can proceed with the cutting as follows. If however, the glass is out of square, then you must be trued up first by cutting about 1in. off the right-hand end, using the T-square of course. Then turn the glass so that this freshly cut edge is at the left hand side of the bench.

Complete Guide To Cutting Glass How to use the cutter

Take up the glass cutter between the first two fingers of the right hand (the business end on the same side of the palm). Place the first finger on the flattened place provided and the thumb underneath (see Fig.4).
Now reach forward and place the wheel of the cutter as near to the top of the glass as is possible without it actually going over the edge, close up against the right hand side of the T-square.
The left hand should be firmly pressed into the T-square, about halfway up the glass, care should be taken to see that the fingers of the left hand do not get in the way of the cutter.
Now taking care that the T-square does not move, exert a slight pressure on the cutter and, keeping it pressed firmly against the T-square draw it down towards you, completing the cut in one operation.
If the rule should move or the cutter fails to cut due to too little pressure, stop cutting and measure out again. Now cut the glass where the cutter missed the first time but on no account go over the same cut twice.
Having succeeded in making a cut on the surface of the glass, several methods are now available for opening the cut. The method used will depend on the size of the off-cut. (That's the piece of glass left after the required piece of glass has been cut.)
No hard and fast rules can be laid down for this, but the following will serve as a good guide : If the off-cut exceeds 12in. (method 1) the T-square should be moved from the glass, the glass lifted at one end, and the T-square placed immediately under the cut. The glass should be lowered gently on to the T-square (Fig.5). The piece of glass required (the cut size) should be pressed gently down on to the bench. This will cause the off-cut to be lifted clear of the bench. Holding the 'cut size' down firmly with the right hand held roughly central. This will create tension over the surface of the glass and cause it to snap along the mark made by the cutter. Separate the two pieces, remove the off-cut and stand it down. Pull the 'cut size' halfway off the bench and with a sliding motion turn the glass into position for cutting the width. At all times when carrying glass it should be held on edge and never carried horizontally.
,br> If the off-cut is less than 12in.wide (Method 2). then use the following method : Make the cut in exactly the same way, remove the T-square and place both hands under the edge of the glass with fists clenched ( one hand each side of the cut). The curled forefingers should touch the glass underneath and the thumbs press down on the top. The thumbs should be about 1in. either side of the cut line Now move the knuckles of the two little fingers in towards one another, at the same time exerting a slight upward pressure with the forefingers, and keep the thumbs held firmly on top. This will cause tension as in the first method and the cut should open along the mark.

If the off-cut is under 2in. wide (Method 3). the cut should be tapped from underneath with (the glass cutter (the part marked X in Fig.4). Only one tap need be made, providing this opens up the cut for about 1/2in. from the end. You can quiet easily see if the cut has opened. Then open the cut using method 2.

In the event of the off-cut being only a 1/4in. or less, the small paintbrush should be dipped into the white spirit and then run along the edge of the T-square before the cut is made. After making the cut, remove the T-square and swivel the glass around so that the 1/4in. off-cut overhangs the edge of the bench. Then take the cutter in the right hand, in the normal cutting position, and fit one of the notches over the off-cut, at one end. The notches are of different sizes, and the correct one to use is the notch which fits the glass comfortably. Push the cutter onto the glass until the front edge of the notch comes level with the cut line. Then maintianing a slight pressure in towards the glass, twist the handle of the cutter outwards and downwards until the glass opens along the cut. This will result in either the whole of the off-cut coming off, or a small piece coming away. If only a small piece breaks off, clean out the notch in the cutter and try again at the spot where the first piece broke away.(see Fig.7).

Complete Guide To Cutting Glass Obscured Glass

Obscured glass, called 'frosted' glass by most people, is made in many different patterns. When glazing or fixing the pattern should always be on the inside, no matter if the frame is being glazed from outdoors or in. The reason for this is that the rain brings down a certain amount of dirt, which lodges in the grooves that most patterns consist of, if the obscured glass is glazed with the pattern on the outside. With the glass glazed correctly this cannot happen.

To cut obscured glass, measure and handle in the same way as 24oz. making sure your cut on the the smooth side. Most obscured glass is about the same weight as 24oz.sheet. Extra care should when handling obscured glass, as this when cut tends to leave a sharp edge.
Plate and 1/4in. wired cast glass is cut in the same way as (18oz., 24oz., 32oz. or obscured) but the following points should be observed : When buying second-hand plate glass from car breakers , etc., make sure it is not 'toughened plate' unless it happens to be the exact size you require. 'Toughened plate' cannot be cut by any method.
Method 1 of cutting should be used when cutting plate, with the following addition : A brush of white spirit should be run down the edge of the T-square - on the glass - just prior to cutting, however large or small the off-cut should be.
Method 2 cannot be used for opening the cut when the off-cut is less than 12in. on plate, but another method is brought into use. Make the cut in the normal way, then slide the plate right onto the bench. Lift it slightly and place a pencil or brush handle immediately under the cut at the rear end. Then press down firmly on both sides of the cut as in Method 1, but with both hands near the pencil.
The notches in the edge of the cutter are not large enough for plate glass, when the off-cut is less than an inch or so a pair of pliers or pincers must be used. Glass pliers manufactured specially for the job can be purchased from the hardware shop and there's no doubt that these are the best tool for the job. But the amateur not wishing to go to this expense should be able to get by with a pair of pliers or pincers wrapped in a piece of rag. With the jaws of the pliers muffled this way, close the jaws over the edge of the off-cut in the same way as with the notches on the glass cutter and proceed in the same way. The edge of the jaws must come right up to the cut line (see Fig.8). When cutting wired cast glass, proceed as with plate, but after the cut lines have been opened it will be found that the wire holds the two pieces of glass together. To break the wire, swivel the glass around so that the off-cut overhangs the edge of the bench and, gently but firmly, move the off-cut up and down, the angle of the arc being small at first, but increasing as the wire give way. After three or four movements up and down the wire will break, and the off-cut will come off. Stand this down, and run a metal object over the wire spikes which are left protruding from the edge of the glass, to flatten them down. Extra care should be taken with wire cast as the spikes are very sharp.

Leather gloves should be worn when handling plate and wire cast, but I don't advise their use when actually cutting, or when handling sheet glass, unless you find you are getting too many cuts on your hands.
A few minor cuts and scratches cannot be avoided when handling glass, but these can be cut down to a minimum providing reasonable care is taken and the glass is not allowed to slip through the hands. On no account try to hurry. Take your time, and everything should be OK.

Cutting freehand

When a shaped piece of glass is required, It is not possible to use the straight-edge, of course, so a slightly different technique must be employed.
As mentioned earlier, sometimes the glazing bar may be warped, or it may be necessary to cut around an obstruction. If this is the case a cardboard template can be made, or the glass can be stood up in front of the frame and the edge of the rebate traced onto the glass with a wax crayon. The glass should then be taken to the bench ready for cutting freehand.
To do this, lay the glass so that the crayoned mark is parallel with the front edge of the bench, and take up the cutter as explained previously, now starting at one end of the crayoned line, push the cutter along the inside of the line, maintaining a slight pressure, and keep going until the other end of the glass is reached.
To keep the cutter steady, you may find it helps if you also hold the cutter with the left hand, by pressing the fingers onto the forefinger of the right hand. The second and little fingers of the right hand can be allowed to trail on the glass, this helps to keep the cutter at the correct angle. This should be approximately 45 degrees.
The cut is then opened up using Method 2.
If a cardboard template is taken of the shape to be cut, lay this on the bench, under the glass, and then follow the edge of the template with the cutter.
Please do not try to be too ambitious with cut-outs and sharp curves, as these are difficult to do, and a knowledge of just how much a piece of glass will stand before breaking is essential.
It is practically impossible to cut glass to a right-angle, and it will be found far more practical to design a frame whereby this shape is not required. The only other way out is to cut the glass into two pieces (A and B.Fig.9) and butt them together.

All this must seem a lot to remember but don't worry. Just pick out the section which applies to the job you have in hand and once having mastered the use of the glass cutter you can always turn for reference to this article at londonwidepainters.co.uk
Before attempting to cut the piece of glass required, try out your cutter on a old piece first and get the feel of it. And don't forget make sure the glass is clean and dry( with the exception of white spirit) before you start.
Now stop reading, go and dig out that cutter, give it a drop of oil, and you'll find that it really does work after all.



Fig.1
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Fig.5
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Fig.7-8
Fig.9
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