I've just had a bespoke mirrored bathroom cabinet installed. The mirrors have had holes drilled for the knobs, and one of the holes has a white mark around it and generally doesn't look very clean. The mark is visible even when the knobs are in place.

The cabinet maker tells me "such a white mark around the cut out in the mirror is normal. It's very difficult to cut through the mirror with a very clean cut".

Is my cabinet maker correct, or should I ask for a new mirror?

See pictures:

enter image description here.

bad hole in mirror

  • 8
    Drilling glass without damaging it certainly is difficult. There are special bits for cutting glass, and it should be done on a drill press, not by hand, to ensure a perfect right angle without any cracking or oblong holes. Glass is far less forgiving than wood when it comes to drilling holes. As RedGrittyBrick says, however, part of the cost of the mirror is paying professionals who have the skills and proper tools to do it correctly.
    – user4302
    Commented Oct 3, 2017 at 15:26
  • 5
    With the right drill bit, taken slowly and run wet, with suitable backing behind the workpiece, I would expect to do a better job than that myself, depsite only having drilled glass a handful of times. For small holes this type work
    – Chris H
    Commented Oct 3, 2017 at 15:27
  • 7
    There are crack repair glues (like for automotive windshields) that you can use to greatly reduce the appearance of those chips. Commented Oct 3, 2017 at 18:06
  • 8
    I suggest asking the glass maker for larger handles to hide the cracks.
    – Pere
    Commented Oct 3, 2017 at 18:24
  • 2
    @Harper: Some people make it look easy - getting the hole started smoothly and in the correct place looks kinda tricky though. Anyone who does this professionally ought to do it well or not at all. Commented Oct 3, 2017 at 19:12

3 Answers 3


I used to work for a company that built machines that drilled these holes (though we did it in much larger pieces, usually 3/4" to 2" thickness). It's not a hard process, it's slightly expensive, but it's doable. The process is basically as follows:

  • Use two diamond-tipped drill bits to cut the hole (one above and one below);
  • Use a water-jet to push water through and around the bit to cool the glass;
  • Clamp the glass on a tight space (vibration relief);
  • Spin the bits opposite each other at a high RPM;
  • Bring the bits together and cut into both sides of the glass at the same time;
  • Make sure not to smash (read: "crash") the bits together;

In the situation where vibration cannot be controlled, and you don't have an upper and lower bit, the manufacturer would typically use an ultra-low RPM (like, 20-30 RPM) which avoids the vibration. This takes longer to cut a hole, but avoids problems.

With ultra-thin material (1/8"-1/4") we would use a direct water-jet, we would literally push water at 60,000 PSI and blow a hole straight through the glass. This is done by backing the glass with a solid (usually metal) surface with a hole for the jet-stream.

You should end up with a clean-cut hole, and no scarring or scoring - minimal fracturing. We used to build these machines, and this type of scoring is very unusual and indicates a faulty machining process. Your cabinet maker likely has one of these machines quite possibly from us or a different company.

This is a defect (it actually looks like the mirror wasn't adequately cooled, so it fractured). It's plain-and-simple, this is a manufacturing defect, and you can probably convince them to send you a new one.

However, I would avoid that altogether.

While this may be unsightly right now, here's how I would fix it (usually for less than $2.00 at a nearby hardware or crafts store):

  • Go to a local hardware store and buy plastic (or nylon) washers (you want plastic/nylon so that it doesn't interfere negatively with the glass, handle or paint), you want the OD (outer diameter) to be slightly larger than the total size of the issue, and the ID (inner diameter) to be slightly (but not much) larger than the bolt on the handle, you'll want a small thickness;
  • Get a small bottle of whatever colour touch-up paint you like (probably black to match the handles), these plastic washers often come in gray, white or black (what you'll find depends on the hardware store), make sure it's a water-based paint (certain oil and lacquer based paints will have a negative reaction with the plastic/nylon washer or the handle), and type that is used on model cars should work fine;
  • Paint both sides of the washers;
  • Place the washer between the handle and the mirror to cover-up the defect;

If done right, you should be able to eliminate the defect area visibility entirely, and you should end up with a visually pleasing result. Depending on the theme of your bathroom, you may opt to get a larger OD on the washer and use an "accent colour" ('hot rod red', for example) to make it "pop" and get a more unique look.

  • @SimonKatz It should help reduce the visual displeasure, and if you do it right you can add your own "style" to the room, just make sure to get the plastic or nylon, that is extremely important. :) (It also fixed the issue without needing to get involved with a back-and-forth war with the manufacturer, because I'm certain they'll continually try to pawn it off on you.) Commented Oct 3, 2017 at 23:08

Is my cabinet maker correct

They are right that drilling clean holes in glass is more difficult than in wood or steel.

In my opinion, they are not right to say that visible cracking around the hole is normal.

They are a professional and part of the price they charge is for having the skill, experience and tools to do the job better and quicker than you can. The hole on the right suggests they can get an acceptable result at least 50% of the time. In my opinion, they should have factored into their price the cost of wastage in redoing work where needed.

should I ask for a new mirror?

That's up to you. If you are going to stare unhappily at that defect every time you use that cabinet then you should get it fixed now.

enter image description here

How you do this is a matter of negotiation - because you probably don't have a written contract that specifies explicitly what constitutes an acceptable hole in the mirror.

  • 2
    Judging by the pictures the chipping is hidden by the door handles in normal use. Unless it's severe enough that the handle wobbles - in which case I'd want a replacement on that ground - out of sight out of mind probably should apply. Commented Oct 3, 2017 at 15:07
  • 5
    @Dan, if you look carefully at the top photo, you can see the cracking is visible in the reflection of the back end of the left hand handle. In my personal subjective opinion it is minor which is partly why I wrote that doing anything about it is "up to you". Different people have different ideas about what is OK. Commented Oct 3, 2017 at 15:11
  • Thanks, I didn't notice it in the first picture before you pointed it out. Commented Oct 3, 2017 at 15:15
  • @RedGrittyBrick Thanks, that helps me think about it more clearly. Not sure yet what I'll do. :-)
    – Simon K
    Commented Oct 3, 2017 at 17:43
  • This is why I like doing things myself. Professionals are in a hurry because it affects their profits. Drilling a neat hole in glass is easy if you take your time. You are actually grinding your way through the glass. If you do it very slowly with very moderate pressure you don't need all the cooling and you won't cause shatter damage. As others have said you need to do it from both sides (true for all materials, it stops tear out) and a jig to keep you square helps.
    – Peter Wone
    Commented Oct 5, 2017 at 14:11

The level of cracking you're showing on the left is not normal. There is some roughness around the hole on the right which is generally normal. Actually, the hole on the right is, more or less, what it should look like when you drill a mirror or any glass. This is one of those skills that takes practice to become consistently good at.

As for replacing the mirror, that's your call. If it bothers you, then replace it now as another commenter said, you'll be happier for it. From what I can see in the pictures, I don't think that it is structurally unsound. Meaning, I don't think it will break under normal use due to the mediocre quality of the hole.

  • 1
    Yup, I fouled up when I was typing. Thanks for catching it. I've edited the answer.
    – Haendler
    Commented Oct 3, 2017 at 21:50

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