Cutting a clean circular groove?

[GrahamRounce]

Hi again. I need to cut a nice clean circular groove about 35mm dia, 2 or 3mm thick, maybe 4 or 5mm deep, with no centreing hole in the middle.

I searched the inet for a special tool with no luck, then scratched my head, and now I'm thinking of grinding a flat bit to be something like this (put your shades on to avoid dazzlement from the draughtsmanship).....

...then setting the pillar drill to it's highest speed (as the bit will probably tend to jump around without the centreing spike) and gently gently slowly slowly lowering it.

I'm willing to give this a try, but before I do, I've learned here that there's not much that doesn't have an existing thing or method for doing it, so....
.... anybody know of one?

Thank-you,

 

[George_N]

Hi Graham, I don't understand when you say circular groove...your drawing looks more like a blind hole. If you give us a bit more detail about what you want to do, we will have a better chance of helping.

 

[JonnyD]

You could do it with a router guidebush and template and a 3mm bit. You would need to take light cuts and do the 5mm deep in about 3 passes to avoid the router bit snapping.

cheers

jon

 

[Jonzjob]

Or use a Dremel Router. They do very small router bits.

 

[nanscombe]

Are you a lathe user?

Is what you've got to make a groove in something you could mount, and spin, in a lathe perhaps?

 

[wobblycogs]

Perhaps use a hole cutter without the centre guide (saw it off a cheap one maybe). Would be easier than making a spade bit for it I think. What you making though?

 

[AndyT]

Would it be possible to drill a 35mm flat-bottomed hole (eg by using a Forstner bit) and then glue in a 30mm-ish disk, same thickness as the depth of the hole?

You could cut the disk using a hole cutter of suitable size mounted in a pillar drill, or if you needed the centre pilot, hot-glue a bit of scrap on, just to take the pilot drill.

 

[GrahamRounce]

Amazing! I was scratching my head for ages....

I think a hole cutter would be a bit coarse, and unfortunately it won't go on a lathe, and I need (ie: in an ideal world, 'would like'!) the original wood in the middle part, but I should have thought of the router/dremel way. I'd need to practice lowering/raising the router/dremel without leaving a trace bulge, but I'll give it a go.

Thanks for all the suggestions - I'll post a pic if I can make it work.

 

[nanscombe]

If only there was a picture of the Bosch 35mm Diameter Wood Plug Cutter.

 

[Tom K]

I wonder if this would cut wood?

http://www.tool-net.co.uk/p-347648/tool ... drill.html

 

[cgw59]

Hi,
A quick search on the internet revealed that Bosch make a 35 mm plug cutter, In the past I have used a similar if not slightly smaller plug cutter to achieve the same same result, just need to clamp the work piece firmly and with the bit in a pillar drill a high speed and slow feed is what is required to ensure a clean cut , if the centre does break away you always as someone else said use hot melt to refix it.
hope this is of some help.
p.s. a few practice cuts on some scrap will let you get a feel for the speed and feed before attempting the real thing.

 

[Jonzjob]

We still have no idea as to what it is you are trying to do Graham.

Any chance of some more gen???

 

[nanscombe]

Doing a search, on another topic, turned up this. Dakota Circle Hole Cutter.

Ok, it's got a drill in the middle but ... since the height of centre drill is adjustable, could you stick (with double sided tape or the like) a sacrificial piece of wood at the centre point?

Drill into that and remove it when finished.

Oh, it says 40mm - 200mm but I wonder if it could go as low as 35mm?

 

[ondablade]

Interesting one this, got me digging around.

I've done a bit of messing around before grinding strange profiles on spade bits, and always found they work well, but don't last very long. It's important to grind in a good clearance angle on the cutting edges though, and make sure everything else has clearance or it will burn/tear instead of cutting cleanly.

It's quite likely that your idea would work. One risk is that it might be inclined to vibrate, a good cutting edge and lots of speed and a slow feed should help this.

If you need something a little robust something like a tank cutter could well be OK, again subject to correct grinding of the cutting edges. If taken gently on a decent drill press it should be OK without a centre drill as they are made to cut metal - but beware of breaking through.

http://www.tool-up.co.uk/shop/diy/PRI400.html

http://www.handytools.co.uk/acatalog/Ha ... s_536.html

A plug cutter (cheaper ones anyway) doesn't always cut that cleanly, and might need a lot of grinding if you need a specific section of groove.

http://www.amazon.co.uk/Toolzone-8Pc-Wo ... B002NH4234

Turns out that Lee Valley Tools in Canada do an option similar to the Dakota one, it might be possible to get one from Axminster as they sell their tools. They give a very good mail order service too, it's no problem to order from their web site: http://www.leevalley.com/US/wood/page.a ... 42316&ap=1