Thread: Cutting a 90mm diam circle

Back in my day we would use a hand held hole saw after all that's what they were made for.

and time and tide marches on.

hi rod1949, in this instance the hole had to be an exact 90mm diameter, and perfectly round My hand tool skills are no way even close to doing this

Dengue, I recieved this link in an email from Woodsmith this morning.

I haven't watched it all but I thought it may be of interest here.

Oversized Holes Made Simple | Woodsmith Tips

Sacrificial piece for the job is a good idea but I think you would need
to do some judicious clamping of the whole workpiece.

The other ""rig"" is also called a trepanning tool.

Thanks Fred, most interesting, but mostly applicable to smaller holes. It involves expanding an existing hole with a rabbet bit, then finishing off with a pattern bit. It limits the the size you want to a combination of the original hole diameter, and multiples of the width of the rabbett.

The biggest hole I can drill is 40mm, so using that method to expand to 90mm can be done, but would take a long time.

At this stage I am inclined to give the two pronged knuckle duster you recommended in one of the early posts a go, but very slowly and carefully.

Hello,

You can get decent 2 sided sticky tape from Bunnings or $2 shop.

You could use that to stick down both the remnant circle and the "product piece" with the hole in it onto some sacrificial board and then use a router circle jig. Both pieces will stay firm on the final cut.

Bill

In the end I used a circle cutter on my drill press like the one Big Shed recommended, in the interest of time. It was only a single cutter, so a bit unbalanced. I have had it for over 30 years, but never game to use it previously. It cut a very neat hole in the 9mm thick MDF, but it was a nerve wracking experience when you think of what could go wrong.

This article was very informative, and worth reading the comments at the end. I like the idea of marking the extremities of the cutter with fluorescent paint, and putting up a temporary perspex shield in case any of the parts come loose.

I still prefer the circle cutting jig for a router.

Thanks for all the helpful comments above