Help on cutting accurate holes in plywood please

[mental4astro]

Hi all,

Finally I'm able to get my 17.5" project under way.

I need to cut a series of 50mm diameter holes into 15-30mm plywood. These need to be accurate as they will be holding the truss poles in place (there will only be three truss poles). Hole saws are no good- too big. I have both a drill & a router. Any suggestions?

Mental.

[DavidU]

The only way is to find a 50mm hole template and use a Pattern Follower router bit like the top one in the image.

[Ian Robinson]

A Dremel and suitable Dremel micro-routing and cutting tools will do the trick .

[bloodhound31]

Keep your tool speeds high, your feed rate low (watch out you don't burn it though) and your work firmly clamped in place so it can't possibly move.

Where you can, use a template or guide and if in doubt, test it first on a scrap piece of wood, the same material and thickness as you are going to use.

Baz.

[snowyskiesau]

Try a forstner bit.
Used in a drill press will make a very neat and accurate hole in timber.

[Waxing_Gibbous]

A good quality hole saw & high speed drill will work fine.
Remember to tape over the cutting area (front & back) to help avoid shredding the wood.


Snowyskiesau: A 50mm Forstner bit?! Blimey! My admittedly old and cranky DP will only just drive a 25.

[mental4astro]

Thanks everyone for your replies.

I know I don't have the capacity to handle a 50mm forstner bit.

For a pattern follower bit, wouldn't I need a substantially deep template to engage the bearing? Might be better to use a template for the router to trace, wouldn't it?

I've seen two types of templates/jigs for tight circle cutting: the 'Jasper Jig' type commercially made or DIY, and the circular hole template for the router's base to trace. Which would be a better option?

[mithrandir]

There is a "51mm" hole saw in my set. It is actually 2" as it is an imperial set. They weren't particularly cheap, but then no Sutton tools are.

Your local tool shop might also have metric ones if 2" isn't close enough.

You drill from one side most of the way through (until the pilot drill is all the way through), turn the timber over and finish from the other side. No surface splitting. 500rpm recommended max speed.

I'm sure you'd find other uses for the hole saws, like making wheels for toys, so you could amortise the cost.

[snowyskiesau]

Using a CNC router would be the best way. Can;t help with that though :)

[mental4astro]

I very much like Sutton tools. I have one of their drill sets, beautiful.

The aluminium poles I'll be using are 50mm (just how close to 50mm I find out on wednesday when I take delivery of it). These impirical hole saws might make the fit too sloppy I think, especially after sanding & finishing.

I've seen one and two arm hole cutters to fit a drill press. Are these also an option or would I be asking too much of these tools to cut through a lot of 15mm hardwood ply?

[mental4astro]

Mmmmm, CNC routers...:love::love::love:

Where would I get a 50mm forstner bit?

[snowyskiesau]

Carbatec (http://www.carbatec.com.au/cmt-tungsten-tipped-forstner-bits_c9081)
Timbercon (http://www.timbecon.com.au/products/forstner-style-bits-367_0.aspx)
McJing (http://www.mcjing.com.au/searchresult.aspx?keyword=forstner)

Prices vary as does quality. There are a number of styles of cutter, I don;t know which is best. McJing are probably the cheapest.

[DavidU]

You know what I would do (to save a lot of messing about) I would make an accurate drawing of what you want and take it to a water jet cutting place.
I do this a lot, the results are awesome.

[snowyskiesau]

Dave's right. Waterjet or laser cutting (or CNC router) will do a quick, accurate job on cutting the pieces to size and drilling all the required hole.

You'll need to be able to provide a suitable CAD file of what you want to cut/drill.