TRUBOR Stub Drills

[GreensandsParticipant @greensands]

Over the years I have acquired a useful range of TRUBOR HSS stub drills which are conspicuous by their notably flat cutting face. The one illustrated is 9/32 in diameter and marked 2 1/4 x 160 signifying drill length and I believe the cutting angle. My experience is that provided you put a pilot hole through first they are capable of producing a remarkably accurate hole, sometimes requiring light use of a reamer as a finish to provide a superior result.  I would be interested into hear of other peoples experiences in using them and to find out if they are still available. I would also be interested to hear the original reason for their existence and typical applications in general engineering.

[Anonymous]

Looks like a drill intended for sheet metal.

Andrew

[bernard towersParticipant @bernardtowers37738]

Ill go with that.

[Michael GilliganParticipant @michaelgilligan61133]

The horse’s mouth :

http://www.metalbor.com/

MichaelG.

.

My guess is that they are ‘SPOTWELD FACING DRILLS’ as featured on the ‘Specials’ list.

[JasonBModerator @jasonb]

The majority of spot weld drills have a small central point or pip and are then flat ended. They are flat so that you can drill away one layer and not the one behind which allows a new panel to be spot welded back in place. See first drill on Dormers list

Sheet metal drills are short as you don’t need the length if just drilling sheet. They also have the wider angle so that they don’t break through too quickly which can leave a trilobed hole.

[Michael GilliganParticipant @michaelgilligan61133]

Quite true, Jason … I was only picking something from the list on the website

Although, of course, they are happy to make non-standard items

MichaelG.

[old martParticipant @oldmart]

My Trubor drills are also stub length, but they differ from the first photo, The outside diameter is the full size with no relief at all. The tip angle is standard and they are specifically intended for sheet metal, particularly aircraft skins. The hole produced is always round, never lobed and the size range matches the rivets used, so full ranges are not available.

[Author]

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