This article is the consequence of a rather surprising feedback comment in March relating to the purchase of a Toyo oil-filled glass cutter left at the Tempsford Stained Glass web site.
Tempsford Stained Glass were given 4 out of 5 stars and the following feedback:
Impressed by the quick delivery of this product but there was no information about how much oil to use.
To begin with I guffawed with laughter but later I began to understand that sometimes it is the little things in life that cause us trouble and confusion. My experience of Tempsford Stained Glass is 5 out of 5 so I dedicate this article to the author of that feedback comment.
A companion posting to this one is Lubricate Your Cutter Wheel where I chatter about the different lubricants people are using with their glass cutters.
The Olden Days
I will deliberately restrict what I write about the “bad old days” because it’s not so relevant to what we’re doing nowadays. Nevertheless there are some aspects that are still applicable.
Roll the clock back a century and your glass cutter would be a small diamond (or sapphire) glued to the end of a stick. Losing that little diamond could be a problem! You will find out more about such glass cutters if you pay a visit to the Gutenberg Project and look for a book called Stained Glass Work: A text-book for students and workers in glass by Whall. It is free, available in a variety of electronic formats and is a fascinating insight into the profession almost exactly a century ago.
As we move forward in time we get to the still-commonplace cutters which all have a small wheel at one end, often some “teeth” just above, then a handle and finally a ball at the top. A quick explanation for the teeth and ball is needed because their purpose is not obvious to a novice…
The ball at the top is used to “help”, “chase” or at least “start” a score line cracking by means of tapping underneath the score line. It’s hard to describe and demonstrate the process in text, and it takes some practice to achieve reasonable results reliably, but at the end of this article I give you a web link to understand the tapping method by watching a video (or three).
Incidentally, not all glass cutters have the ball at the top. Have a look in eBay, searching for “Shaw glass cutter” for examples of these traditional cutters. The “blue Shaw cutter” is, I think, a popular first choice. You’ll also see from the picture in this posting that I have a couple of modern glass cutters that do not have this ball. You will find a link at the bottom of this posting where you can see others and even watch a short video about glass cutters.
The teeth of a glass cutter were particularly useful in the days before glass grinders and grozing pliers of the kind we use nowadays. The teeth allowed the glass worker to “nibble away” the edges of the glass piece. The rough edge produced by this method is not a problem for traditional leaded lights but often will be for the copper-foiled method.
The differently sized gaps between the teeth allow for different thicknesses of glass or different techniques. The only time I have ever seen anyone use these teeth was on television where an “authentic” restoration of a stained glass panel was being undertaken.
And finally, when the glass worker got their glass to about the right size they could then make use of a scythe sharpening stone – something you can still buy from good stained glass suppliers. You should realise that nibbling the edges of a piece of glass with those teeth and using a scythe stone are time consuming and “risky” compared to the use of modern tools. They needed to be good at their craft in those days!
I should perhaps mention that glass cutters with a stainless steel wheel wear out quickly and tungsten carbide wheels last longer, for reasons explained in my previous Lubricate Your Cutter Wheel posting. Some have replaceable wheels and some do not.
And it may also be useful for me to mention also that you also need an oily rag (I have one in a little tin) or a little pot of cutting oil to lubricate these cutters before each use.
You can still get these “traditional” cutters and in the country where I live the “Shaw” brand is still quite popular. The traditional cutters still get used in some specialised tools such as circle cutters.
But, if you’re new to stained glass I recommend you jump straight to using a “modern” tool – an oil-filled cutter. This is not to say that a traditional glass cutter will not be useful but you’ll find it easier and more convenient to start with an oil-filled cutter.
Oil-Filled Glass Cutters
On the right you will see a picture of most of the common styles of oil-filled glass cutter available today. I will make some comments about each one in turn.
At the left is the cheapest of my glass cutters. It is from China and you can see it has no ball at the top and is slowly leaking cutting oil where the wheel is. I have used several of these cutters (and have given a few away too) but not all of them leaked like this one. This glass cutter is half full of oil and to fill it you have to unscrew the wheel-end of the cutter. The only problem I have ever found is that the lack of a metal ball at the top means that I can not use it to break glass using the “tapping” method – something that I recommend you only use when absolutely necessary because it tends to cause “wobbly” breaks, sharp “flares” and other problems when done badly. If you are strapped for cash then this is a perfectly good modern glass cutter to begin with.
Perhaps the most popular oil-filled cutter is the “standard” pencil-grip Toyo cutter (second from the left). I have found this cutter to be very reliable and long-lasting, it doesn’t leak, it holds a decent amount of oil (and is almost full) and the metal cap can be used for the “tapping” method of breaking glass and it is this cap you must remove to add more oil. This is the cutter I use most of the time. But, some people, particularly those with limited strength or painful ailments like arthritis, may find the next two cutters more usable.
The third from the left is a K-Star pistol grip cutter and is of a similar style to a Toyo pistol grip cutter. This cutter has a massive capacity for cutting oil and the one in the picture is about half full. Notice that there is a ball at the end of the handle for breaking glass using the tapping method and it’s this ball that you remove to re-fill the reservoir. I must confess that I don’t use this cutter very often because it “feels wrong” when I hold it and use it. By contrast, a friend with arthritis prefers this style of cutter because it does not hurt her wrist.
On the right of the picture is a tiny little cutter which nestles between your thumb and pointing finger. It is the Toyo Thomas Grip cutter. Notice that this cutter has a very small capacity oil reservoir and no tapping ball. Unscrewing the top of this cutter allows you to re-fill the oil reservoir. I don’t often use this glass cutter but I do find it particularly useful for curvy shapes.
Cutting Head Sizes
Did you notice that the Chinese cutter had a “wider” cutting head and that the other three were much shorter in profile?
A reason to choose a wider cutting head is if you mostly cut straight lines, simply because there’s a long surface along which the cutting head can more accurately slide along a ruler edge. For curves and free-hand work the shorter cutting heads are more convenient, not only because they can follow a curved ruler edge more accurately but also because they just seem to “feel right” -surely a completely irrational subjective reason!
Cutting Head Replacement
If you find your glass scoring is getting unreliable and the glass cutter has been used for a long time then it may be time to use a replacement cutting head. They cost almost as much as the whole glass cutter but your savings will come from producing fewer bad breaks and in turn less scrap glass!
At the bottom left of the picture you will see a replacement cutting head. It has a screw on the side. To replace the cutting head you unscrew and remove the old cutting head and then fit and re-screw the replacement with the screw pointing “forwards”. Nothing could be simpler.
Oh, and save the little screw before disposing of the old cutting head – you never know when you might need it!
And finally, a word of caution – the oil’s wicked to the cutting wheel by a little thread-like wick. Don’t remove the wick or the cutting wheel will either not get lubricated or the oil will simply flood back out.
An example replacement cutting head is shown that the bottom of the picture. Be sure to buy a replacement head that’s suitable for your cutter!
Filling an Oil-Filled Cutter
How you put oil into an oil-filled cutter depends on the model. The Chinese example (on the left) can be re-filled by unscrewing the cutting head and filling the reservoir with cutting oil. The two examples (in the middle) can be re-filled by unscrewing their ball-shaped caps. The little cutter on the right can be refilled by unscrewing the “handle” part at the top.
To avoid spillage and waste, use a cheap disposable pipette or syringe, for which you’ll see an example at the bottom right of the picture. Fill the cutter almost to the brim or just add a little. It’s your choice.
If you find the cutter has started to leak, dismantle and reassemble the parts. Some cutters have little rubber ring seals – check they are not broken.
Choosing a Cutting Oil
You have a choice of whether or not to use a cutting oil, as well as a choice as to what to use as your cutting oil. Here’s a quick summary:
- Petroleum-based oils – often kerosene or paraffin or a mixture
- Vegetable oils – beware of oxidation causing gumming-up
- Water-based – supposedly “environmentally friendly”
- Dry cut – some people don’t use any lubricant
You can either buy an expensive “glass cutting oil” thinking (or being told) it is somehow special or better, or you can use a “generic” cheaper alternative that is probably the same thing. Have a look at my Lubricate Your Cutter Wheel posting for a detailed discussion about who’s using what, why they use it and much more!
Don’t trust me to tell you everything and don’t trust my opinions as being the best. Do some more research. For example, here are a couple of nice places to visit. Other people’s opinions also matter, and the videos are worth watching.
And here is the first of a series of videos about tapping score lines. I could be argumentative about the terminology used sometimes but I will not be so because they’re nice helpful videos. I would only comment that I find it’s accuracy of the tapping rather than the softness of touch that makes for decent score line breaking by the tapping method.
Until Next Time
Thank you for reading this posting. I hope you found it useful or at least interesting.
My next posting will probably explore devitrification because I see plenty of people on the Internet seem to be confused about what devitrification actually is (and is not).
I don’t have all the answers, but here’s a teaser from my previous posting to get you thinking:
A clean cutting oil is a simple hydrocarbon mixture which will cleanly evaporate or “burn off” within a kiln – but we are told this can cause devitrification. However the use of other “contaminants” such as Glastac or White Glue (PVA) are routinely used and also “burn off” – but we are told these are not a risk for devitrification. This all looks rather self-inconsistent to me. We want facts not superstition and hearsay!