How To Cut 1/4" Plate Mirror?

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cjmst3k

cjmst3k

SGF, Supreme Grumble Framer
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Anyone know how to cut down a medium sized 1/4" plate mirror? Only time I've tried, I frayed the edges.

I ordered a 1/4" plate mirror in the wrong size. Luckily it's a straight edged (non beveled). I usually have the distributor cut the mirrors for me, but for framing glass I use a Fletcher 3100.

Thanks!
 
I use my Fletcher glass cutter. I would not try to cut off less then 1". One thing that I find helps is to squirt the surface with lighter fluid or kerosene before scoring. Remember only 1 score, you are not cutting the mirror, just scoring it.
 
To run off say less than a couple of ", you probably need glass breaking pliers (for leverage).
These might not normally be found in most frame shops, esp those with wall cutters.
The jaws are about1/4" wide and very flat when opened to that size.

Best advice I can make is if you haven't done this before, phone any nearby glazier, explain your dilemma, and ask if they can pop in for a nominal fee / favour, and do the one cut for you.

If you need to cut it yourself, and need to take off a few " or more, do this . . .

Cut on flat bench, lay mirror face up.

Have a hand glass cutter and pencil ready at hand.

Mark your size either side of the mirror face, using a square or straight edge, make you score on the marks.

Lift the glass at the cut near you, with the glass on the bench a couple of "s, and stick the pencil under the score at the edge.

Holding your palm on the larger piece near the score, push down on the small trim piece with your thumb, and as long as you cut is sweet, it should run along the cut fine.

You can rub the edge with a medium grit 120 - 180 or so sandpaper to take the sharp edge off.

If you have a small low value piece of thicker glass somewhere in the shop, have a practice on that first.
 
Or...after you make your score on the mirror, lightly tap the score line from below, starting at the end of the mirror and working up to the top. Tap lightly with the brass ball end of your glass cutter, if using an old Fletcher type, or the just the end of the glass cutter. The score line should "run" with the light taping. Just remember to tap lightly...just hard enough to start the "run". Snap off the edge. If you do not have a pair of "grossing" pliers (used by stain glass artist) you can grab the edges of the glass that are less than 1/2" to be cut off with a pair of pliers that have a flat edge. Grab the edge and snap down.
 
Yes, glass-breaking pliers are very helpful for cutting thick glass. Make sure your cutting wheel is fresh, clean, and well lubricated first. Remember, the lighter and smoother the score, the cleaner the break.

It's a good idea to score the coatings on the back of the mirror, directly behind where your score will be on the front. Doing that before scoring to cut would avoid the occasional problem of uneven edges on the coatings.
 
Pictures of tools.....

Thought I'd share pictures of grozier (grossing) and running pliers with you. These are two tools that help in trimming 1/4" - 1/2" off of glass and mirrors.



grozier pliers.jpg Grozier pliers

[FONT=Arial, Arial, Helvetica]To groze, hold the pliers curved side up, using a rolling motion to gently scrape the glass edge against the serrated teeth. Use the tips in a chewing motion to nibble glass away, including deep inside curves.[/FONT]
running pliers1.jpg Running pliers

Position the running pliers over the score line. Squeeze. The pliers can be positioned from any direction; it works full circle.
 
The honed angle of a glass cutter is different for thicker glass than for SSB. You may have better results with an angle greater than 120 degrees and I am not sure if you can easily buy them for a post mounted cutter (though they are readily available from glazier suppliers as a hand held cutter. (www.crlaurence.com) )

Also, Fletcher-Terry has an excellent website and has clickable links to a section with pointers on cutting glass (and especially thicker glass). Proper lubrication of the cut, honed angle of the cutting wheel, depth of score, and finally proper "break out" either using a rod or cut running pliers will help.

I think you are not using enough pressure and lubricant for your initial cut and your cutter is not making a deep enough score.

I disagree completely with the "tapping" advice. It only makes for "scalloped" areas on the cut where the tap was made.

Also, the break out should be started at the side of the mirror/glass where the cut ENDS.
 
Thanks Rob. At my class in Vegas, I will and do address the 1/4" factor and the type of cutting wheel. The best to use for mirror is the low angle wheel (sharper) that is used for "art glass". If you are selling more than 4 mirrors a year, and even cut down one, the $10 investment is worth your time and money.
Or you can do what I do and specify that all of my cutters be that style.... they work just fine on SSG. They will take less pressure and leave a finer score than the utility wheels on wall cutters.

Scoring through a "float" of kerosene is a talent, in that it muffles the sound and you can't tell if you have made a successful score or not. Better to dip the wheel into the kerosene then shake off the excess. The wheel will be lubricated for at least the next 10 cuts as you chop up those 48x96 plates into the desired 11x14s. :D
 
ditto on the glass shop...we have lots of mirrors cut at the local shop and they in turn send us some business
 
These are the pliers you need . . . http://www.crlaurence.com/productimages/R/RD1932_772.gif

Grozing and running pliers are too specialised for general running of such glass cutting use.
The above pliers will allow trimming of a few mm on picture framing glass too.

Tapping under the score is handy to start a run, but finish with fingers, pencil under, or (above) pliers. A scalloping look would occur if you do it all along, but not the first 1/4" or so to get a start.

Honestly, any good cutter will do, angles aren't terribly important. Just nice and smooth, and a dip of 'three in one' oil before going to the glass helps keep a score open.

Never heard of the mirror flaking at the back unless scratch through it, should just break perfectly clean. Adhesion of the backing materials should see a perfect clean edge. We get mostly Guardian mirror over here, but even cheaper imported mirror glass has always seemed the same in adhesion quality.

By now you've probably cut it, or had a glass company over, so hope it turned out ok.
 
Thanks for all the advice. I gave it a shot tonight. I never knew about the pencil trick, but that helped for most of it. When breaking the score it did take a curve to the edge about 2/3 the way to the end. I've been able to get the remainder off - and though a little rough, I think it'll look fine once under a frame, even when looking on an angle. If not, I can order another.

Thanks again for the tips!!
 
The pencil is the key. Score the clean mirror on the wall cutter with a newer, clean and oiled wheel. DO NOT SCORE TOO DEEPLY! Carefully transfer the mirror to a work table, face up. Lay a pencil directly under the score and apply pressure to the offcut piece at the corner. There is no snap, just a graceful run of the score. Practice makes perfect. Sand the edges to make the mirror more stable. A ground edge mirror is much safer than one with a course cut edge.

On a related topic, We use safety tape from CRL on every mirror we frame. Mirrors, especially big ones, can be dangerous. Safety First!

Peter
 
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