Thread: Metric Timber and Router Bits

Standard metric roundover bits at Carbitool

CARB-I-TOOL - Router Bit and Accessories Catalogue - NOVEMBER 2015

Not sure i agree with your basic premise. You don't need exact size bits to match metric sheet goods, just adjust the cuts to suit. In your example, a 1/4 inch bit will only be "out" about 1/3 of a millimeter, and the nominal sized sheet goods will likely vary by more than that. Even if they don't, just adjust depth of cut a small fraction to get the effect you want. We are wood working, not engineering! Take a leaf from boat builders book - the old saying applies here "Builders build houses to the nearest inch, engineers build machines to the nearest thou', boat builders build boats to the nearest boat". Adjust to the work at hand, not to the ruler.

CMT make Ovolo roundover bits in whole number metric radii of 4, 5, 6, 8, 16 and 19 mm
they also make beading bits (like the Ovolo bit, but with a bottom bearing) in sizes 2, 3, 8, 16, and 19 mm

there will be other sizes from other manufacturers, but it's unlikely that the Green shed will carry them

Originally Posted by RossM

boat builders build boats to the nearest boat

I wonder what would happen if they rounded down

Originally Posted by RossM

Not sure i agree with your basic premise. You don't need exact size bits to match metric sheet goods, just adjust the cuts to suit. In your example, a 1/4 inch bit will only be "out" about 1/3 of a millimeter, and the nominal sized sheet goods will likely vary by more than that. Even if they don't, just adjust depth of cut a small fraction to get the effect you want. We are wood working, not engineering! Take a leaf from boat builders book - the old saying applies here "Builders build houses to the nearest inch, engineers build machines to the nearest thou', boat builders build boats to the nearest boat". Adjust to the work at hand, not to the ruler.

Hey Ross, I agree somewhat, woodworking is not a precise thing. However I"m trying to make tight inset joints (almost a mortise) with semi-circular ends (i.e. the bit diameter). Using a 1/4"r tool doesn't quite do the job neatly and requires a bit of hand sanding. I make small relatively intricate tings and having the right tools just makes it a lot quicker and easier.

Maybe I should just apply the 'Boatbuilders' principle - OMG!!!

Thanks guys, I'll check out those links above^^^. Material from the 'big green shed', anything that cuts I look elsewhere.

God may very well have made mankind but everything else is made in that place NNE of us!!

Originally Posted by Toohard

Hey Ross, I agree somewhat, woodworking is not a precise thing. However I"m trying to make tight inset joints (almost a mortise) with semi-circular ends (i.e. the bit diameter). Using a 1/4"r tool doesn't quite do the job neatly and requires a bit of hand sanding. I make small relatively intricate tings and having the right tools just makes it a lot quicker and easier.

that changes the situation somewhat.

You're not so much rounding 12 mm thick material, but cutting a matching round-over to match a round bottom slot.

Not sure of what you can buy at Bunnings, Home Hardware, Mitre10, et al, but CMT (and other router bit makers) make Bull nose and Round Nose bits that match. In your case, 9.5 mm and 12.7 mm bits would seem to be suitable for 12 mm thick material.

I think it is up to the likes of us to order metric bits from carbitool and other suppliers. Manufacturers will fill demand so metric bits will become more easily available once enough consumers stop thinking some imperial bit is close enough.

Sent from my SM-G935F using Tapatalk

Originally Posted by DaveVman

I think it is up to the likes of us to order metric bits from carbitool and other suppliers. Manufacturers will fill demand so metric bits will become more easily available once enough consumers stop thinking some imperial bit is close enough.

Sent from my SM-G935F using Tapatalk

I completely agree. The range of metric tooling is somewhat limited from what I can see. Even European manufacturers like CMT concentrate heavily on imperial sizes. It doesn't make much sense to me but then again I'm very used to metal working tools which is very well served in both metric and imperial sizes. FGS we even are still buying routers with 1/4" and 1/2" collets!! OK some manufacturers do supply metric collets too but try and buy a tool that fits those. IMHO all routers should come standard fitted with ER11 or ER16 collet chucks - then you could use whatever size by simply changing the collet. Suppose one could go buy one of those hideously expensive Musclechuck gizmos.

Indeed. The lack of routers having ER collets is bluntly inconceivable... why are they not even an option? Why?

It makes zero sense.

I have a new whizz bang router motor from PWS for the lifter (oh boy is it a beauty) and Im lucky in that a company does sell ER collets for the spindle... but this shouldnt be a one-off solution, but a standard. This is it: Collets, Nuts and Toolholders

Same with Drill Press chucks and lathe chucks for tailstocks..... all drill bits come with METRIC sizes and even the big ones are 10mm METRIC end sized.

One buys METRIC router bits, but they have IMPERIAL sockets. Why? Why?

Jeez, its not as if the USA, Liberia and Burma are the powerhouses of manufacturing any more.... even those in the US that still make tooling must be thinking of changing over.

I think the Germans could lead the way but they never seem to address the shipping and be cost effective so it doesn't happen. When the Germans or Swedes control the entire chain then we see glimpses of what they could deliver.
The USA is increasingly shrinking in importance and their failure to go metric is a significant part of that. The EU almost banned non metric. They do have strict requirements and eventually they probably will ban non metric.

Burma has a program to go metric and catch up with rest of the world. Overtaking muddled Britain in the process.

And lets be honest. No one cares what Liberia does. It has a GDP of $2billion total and survives thanks to foreign aid. Basically all its imports are from metric countries and most of the economy is subsistence farming with 80% below the poverty line.

Sent from my SM-G935F using Tapatalk

Originally Posted by woodPixel

all drill bits come with METRIC sizes and even the big ones are 10mm METRIC end sized.

I thought most smaller drill bits were shanked to the same size as the drill, while in the larger sizes, the common shank sizes are 3/8" and 1/2"


BUT, perhaps more importantly, a drill chucks uses a different type of "grip" compared to a router collet.

Originally Posted by woodPixel

One buys METRIC router bits, but they have IMPERIAL sockets. Why? Why?

I suppose the short answer is that that you're not prepared to pay the asking price for bits with 6, 8, 10 or 12 mm shanks. (CMT make them.)


But what I don't really understand your "frustration" that the common standard for router bit shanks is 6.35 and 12.7 mm. A standard is a standard, users shouldn't need to worry what it is.
I'm sure I could go to many sports or industries where an accepted "standard" doesn't make sense in some measurement system.

Who cares what the shank size is?? Imperial is the standard and it makes no difference to the cutting end.

I don't hear people complaining that car wheels are still in inches or that recipes still use cups and teaspoons.

I complain about recipes being in cups and teaspoons all the time! But this is a woodworking forum so didn't think it was the appropriate audience to air my grievances about that.....

I hate trying to have to measure our 137.456423mLs of milk to make something nice for dinner... and how do you get a 2/3 teaspoon of butter? The recipe doesn't saw to melt it, and scooping it out creates air pockets so it isn't exact... its an outrage! there needs to be an investigation!