Thread: Enlarging a 54mm hole in plywood

Originally Posted by JillB

Hello, I have drilled a number of 54mm diameter holes in 15mm ply, and need to expand them to 55mm without wrecking the edges.

Can anyone please suggest some ways to go about this?

Normally a step drill wouldn't work in 15 mm material material but seeing the largest size is 55 mm it should work.
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Oh dear. I guess if you need to avoid split edges, you also need to maintain a perfect circle?
One way to do it might be to glue 2 or 3 of the waste plugs from the hole saw together and glue some coarse sandpaper to the perimeter. You'd mount it to a spindle such as a cup-head bolt and run it in a drill. Should be enough clearance in the waste pieces to allow them to fit even with the paper attached. If you could work out some way of using an extended spindle (eg a threaded rod) and hold the other side that would offer even more control.

Good Morning Jill

You are only enlarging the hole by 1mm; you obviously need a precise round hole with sharp edges or you would not have asked the question. Thus I doubt that any re-drilling or sanding technique would be sufficiently precise.

Perhaps you could consider drilling a 55mm hole in another piece of plywood and then use that as a jig or guide. Align the jig over an existing hole, clamp securely and then route out the hole using a strait cutter with a bearing.

Hope this helps

Cheers

Graeme

Buy a new piece of ply?

File it using a rasp and working to a fine file as you near the finished dia of 55mm
Edited JilliB tape around the hole so it doesn't break away score the radius which will help also

buy a 55mm forstener bit use the original cut out as support and centre it

use a trimmer make a stop guide first which only allows the cutter to remove 1mm

Many thanks, everyone, for all your great suggestions.

I have decided to go with graeme's suggestion with a template and a flush trim bit, but if that fails, I will take the yowie option and use a clean sheet of ply and drill them all again, this time the correct size

I think you have made the best choice.

The template and the flush trim bit worked like a dream. Thanks for the suggestion Graeme

best idea.

This is a stroke of genius I worked out one day that should work for you, lol

Set up a rebating bit so it is only taking of that 0.5 mm, you may need to talk to your 'good' hardware store guy to set this up. Then flip it and finish with a flush trim bit. Done.