Advice on drilling large holes thro ply.

[johnbs]

I'm contemplating making a fete game which goes by various names, including 'Jeu Gruyere'. It will involve drilling numrous holes through c 10mm ply, diameters in the range 40 to 55mm. I do have HSS hole-saws but I know from experience that they are slow and need de-clogging every five seconds or so. The hole finish needs to be pretty neat as well - I don't have a cnc router! Can anyone recommend a suitable drill-bit?

John
https://makezine.com/projects/the-game-of-jeu-gruyere/

 

[Spectric]

Can anyone recommend a suitable drill-bit

Not in 40 to 55 mm, to cut sheet goods you need a hole saw or fly cutter. The other method is to use a router with a bush and a jig which might give a cleaner edge but the hole saw is probably your best bet. Drill a 6mm hole where you want the larger hole and then with the hole saw drill from both sides so you do not get any breakout.

 

[Bingy man]

I would also use holesaws - my preference is starret and a hoover running with a crevice tool will help to clear out the sawdust and prevent burning. Clean the edges up with a sanding drum on a drill ..

 

[Fitzroy]

I find fly cutters a bit terrifying to use, and would only use in a drill press. I’d use a palm router and a template.

 

[John Brown]

I agree. Small router. Trammell, maybe?

 

[John Brown]

Just googled Jeu Gruyère. For that number of holes at that size I've jumped ship to the hole saw.

 

[Terrytpot]

Don’t forget that the reason your hole saw is slow and clogged easily is because the wood you cut has no means of escape as the blade is blocking its exit… simply drill one or two holes in the edge of the disc being cut out and the swarf/sawdust has a way to escape without slowing things down,over heating the blade and ultimately blunting it.

 

[gregmcateer]

Also, have a scrap piece behind to stop breakout. Sorry if that's sucking egg advice

 

[ChaiLatte]

I am curious why no-one has yet mentioned forstner bits. To me, they are the most suitable for a clean hole. Drill through from one side until the point breaks through, flip the piece over and complete the hole from the other side.

You could experiment by clamping the piece down and it might be possible to drill cleanly all the way through on one setting (use a depth stop so you do not damage the material below the piece being drilled and have to reposition it).

54mm is a standard size (2 1/8") in both measurement languages. 42mm (1 5/8") should also be a standard size.

Be aware that there are heaps of cheap forstner bits around that have a prong on the perimeter about the same size as the ripper on a Cat D11. They are probably the ones to avoid: you need the ones where the perimeter cuts like a knife

 

[recipio]

large drill bits soak up power and I once burned out a .motor in a drill press doing just that

Hole saws are crude tools and leave rough edges as s well as needing plenty of power.
The best option by far is a medium. Powered router with a good spiral bit using a template, either with a bush
Or bottom bearing, Use a grid drawn on the ply for reference

 

[Rewound]

Don’t forget that the reason your hole saw is slow and clogged easily is because the wood you cut has no means of escape as the blade is blocking its exit… simply drill one or two holes in the edge of the disc being cut out and the swarf/sawdust has a way to escape without slowing things down,over heating the blade and ultimately blunting it.

I agree this works quite well, although you do need to drill the waste holes very accurately so as to just touch where your hole saw will cut (on the waste side obviously)

best to have a a bit of waste material sandwiching what you are cutting to get a good finish - drilling / cutting holes accurately and neatly is a far from straightforward task

 

[Yorkieguy]

Don’t forget that the reason your hole saw is slow and clogged easily is because the wood you cut has no means of escape as the blade is blocking its exit… simply drill one or two holes in the edge of the disc being cut out and the swarf/sawdust has a way to escape without slowing things down,over heating the blade and ultimately blunting it.

That's what I've always done.

See pic.

 

[ChaiLatte]

The best option by far is a medium.

Thanks, I never knew Doris Stokes was into woodwork.

 

[John Brown]

Thanks, I never knew Doris Stokes was into woodwork.

She's good at drilling holes - how else do you think she gets through to the other side?

 

[Sideways]

I would make a simple template in mdf with a selection (3?) of hole sizes in it, then use this to guide cutting the actual holes with a 1/4 plunge router, 6 or 8mm straight bit and a guide bush.
Clamp the template each time and I would just go round and round inside the template with the router, gradually increasing the plunge to spiral downwards.
By the time your doing the third hole you won't need to lock the plunge depth. Just handhold it.

The holes in the template can be cut with a holesaw. The guide bush smooths out the textureof the sawn edge and will rout a better hole than the template.
Or, just draw holes with a compass and carefully rout to the lines freehand to make the template. Spend time getting these right and then these templated hole replicate super quickly.

Routed holes will be cleaner than anything, maybe even forstner cut, but without the cost of buying 3+ big forstner bits, which anyway work best in a drill press, not handheld drill.

 

[Spectric]

Or, just draw holes with a compass and carefully rout to the lines freehand

That sounds like a challenge, has anyone ever managed to do that or was that the challenge that resulted in the invention of guide bushes !!

 

[Sideways]

That sounds like a challenge, has anyone ever managed to do that or was that the challenge that resulted in the invention of guide bushes !!

I wouldn't suggest it if I thought it was particularly difficult.
I've made templates this way several times.
You can calculate and draw a circle diameter to make any finished hole size you want from any combination of cutter and guide bush you have that work together.
Use a 1/4" not 1/2" router. Mark with a 0.5mm tubular pencil.
Like a piece of woodwork decide to leave the line, or take the line.
Rough cut first and leave just a few mm inside the line then settle down and cut arcs sneaking up on the line then turning your workpiece so you are always holding the router in a position with good control, and cut another arc.
When you try it, you will discover why for shaving cuts that just remove a tiny amount of material, climb cutting with the router is a technique to learn, not something to dismiss just because it's not the conventional wisdom.

Big holes you can cut with a trammel bar, but 30-50mm handheld is the way.

And wear eye protection, you need to get close ish to the cutter to see clearly, but keep your face up and out of the line of fire. You are taking very fine cuts at the end so there is minimal stress on the cutter.

Let's say your template MDF is 10mm thick. Rout to the line but only 5mm deep.
If you mess up, you can flip the board and try again on the other side.
Pop a tiny hole through the board and draw matching circles on both top and bottom sides before starting to cut if you are worried about that.
When you have your good circle, use a flush bearing guided bit, top or bottom bearing, to flush trim the inside of the template to the 5mm deep section you've just completed.

 

[Spectric]

I find routers cut so quick that in the blink of an eye you have messed up so now for the sake of a quick jig I use guide bushes.

 

[HOJ]

Brilliant, this has really piqued my interest, for sure I will be making one for my great niece and nephew, that's my line of reasoning anyway!

From the the little "research" I have done, the hole's don't even need to be round, its more about the challenge of getting your balls up....the frame.

 

[James carter]

I got a cheap circle cutting jig/trammel from wnew . I think you can cut some quite small holes with it although I've not actually tried it . about 20quid on ebay