I have an electric drill with a 10mm chuck.

I need to drill a 12mm hole in concrete.

I need to buy a masonry drill bit with a 10mm shaft and

a 12mm .....what's it.

I've tried searching eBay and Google but can't find anything.

I think the problem might be I'm not using the right search words.

Does anybody know what these things are called or where I would find one for sale online.

Lazada sells drill bits try a search on there.

http://www.lazada.co.th/10150mm-long-sds-plus-rotary-hammer-concrete-masonary-drill-bore-bit-round-shank-intl-4379785.html

Drill 2 x 10mm holes and you can save the 8mm left over in your toolbox for the next time you need a hole.

You're looking for a "reduced shank" drill bit.

Shank 10mm to fit your chuck. Tip to be 12mm to suit your requirements.

However, you probably won't find them.

You'll find that if you get a 10mm masonry drill, you'll be able to get a bigger hole by wiggling the drill round while drilling. Drill over length, then retract to half way out and start to exert pressure in a circular motion.

Unless you require an exact 12mm hole for a specific purpose, my method will make the hole big enough to use a 12mm rawl plug or whatever.

thanks GsxrnG,

Your right they don't have 12mm reduced shank for sale but

a 10mm will do the job as you say.

Most towns will have a machine shop somewhere. If you can buy a 12mm bit ask someone to lathe down the shank to 10mm. 5 minute job should only cost a few baht.

As an alternative perhaps you could by and fit a 13 mm chuck to replace the 10 mm one and then you can fit drill bits of 1/2 inch any time.

Good idea,

My drill is black and decker.

Do I need to buy a chuck of the same brand or are they universal.

Universal. Have a look at this as an example:

http://m.ebay.co.uk/itm/171062380695

You're looking for a "reduced shank" drill bit.

Shank 10mm to fit your chuck. Tip to be 12mm to suit your requirements.

However, you probably won't find them.

You'll find that if you get a 10mm masonry drill, you'll be able to get a bigger hole by wiggling the drill round while drilling. Drill over length, then retract to half way out and start to exert pressure in a circular motion.

Unless you require an exact 12mm hole for a specific purpose, my method will make the hole big enough to use a 12mm rawl plug or whatever.

s-l225.jpg

Reduced shank bits are not too difficult to find. This one was from DoHome

I paid 75 baht today for a Meta Masonry Concrete 12 mm drill bit. One of the Bosch Drills I have is a 10mm shank. More fun was buying more Netafim drip irrigation tape and pipe for my wife's little farming project in a Buriram Village. The reducing shank masonry drill bit might be widely available at any tool shop or larger builders merchant store in Thailand.

The shanks on masonry bits are normally soft, unlike HSS drills. Another option is to buy a 12mm bit and carefully file or grind 3 flats on the shank to fit a 10mm chuck.

Your drilling machine is designed to drill till diam. 10. It's not advised to 'modify' the drill if you consider seriously the lifetime of your machine. 2 mm is a huge difference in torque.

If you need 12 you should go to SDS or SDS max drilling machines with appropriate drills.

For a few holes I would consider to borrow the machine.

I spoke English this morning with Mr. Wattana Armornmannant the current sales Department Manager of Hitachi Power Tools Thailand and his Japanese supervisor, Mr. Wataru Hama the managing director of Hitachi Koki Power Tools while they assisted expats and Thai home builders in Buriram at a family owned tool shop. Mr. Wattana had previously been employed by AEG Tools and started with Robert Bosh Tools in Thailand. I had brought in a Hitachi 18Volt garden hedge trimmer for a free adjustment by the normal technicians and some women hired for a special event who seemed very familiar with shaft and tool lubrication. The women were not aware that Hitachi Tools had purchased Metabo Tools in 2015, yet Mr. Wataru Hama was very aware of the European made tools now owned by Hitachi.