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Blacksmiths drills are just like ordinary twist drills except that their shanks are made smaller. This is so they can be held in drills with limited chuck capacity. This is usually about 1/2 inch or 12mm. For this reason they usually start at sizes just bigger that that of the shank. They are usually shorter than a conventional twist drill of the same diameter.
They can be made of drill rod or high speed steel.
fig set of blacksmiths drills
Making blacksmiths drills
most large twist drills have soft shanks whether they are tapered or parallel. These can be held in a three jaw chuck by holding them just below the bottom of the flutes and turned down using a carbide bit.
fig turning a twist drill into a blacksmiths drill
Blacksmiths drills are really useful for drilling holes in wooden blocks to make a stand to hold tools. It is quite important that the hole is just larger than the diameter of the tool or else the tool will keel over too far.
Another use is where a very long drill is required a blacksmiths drill can be fitted in a hole in the end of a long round bar and held with grub screws.
Sometimes the hole required might be smaller than the smallest blacksmiths drill but standard twist drills can be cut down achieve the same result. In this case it might not be possible to use grub screws instead the drill can be soft soldered in.