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Spotting drill size

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br23/07/2021 15:11:08
697 forum posts
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If you want to drill a 6mm hole in a shaft, what size spotting drill should you use ?

bill

old mart23/07/2021 15:15:30
3316 forum posts
203 photos

Any size you like, it is only for making a spot.

Swarf, Mostly!23/07/2021 15:22:52
606 forum posts
62 photos

Hi there, Bill,

Just my two penneth - I'd say the 'spot' needs to be big enough to at least fully contain the chisel point on the first proper drill you intend to use.

Best5 regards,

Swarf, Mostly!

Steviegtr23/07/2021 15:26:44
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2225 forum posts
311 photos

I only have 6mm spotting drills but they work for most sizes. I guess a really small hole spotting may be difficult. The spotting drills i have are just from Starret holesaws. They have a very fine point so are ideal & much cheaper.

Steve.

JasonB23/07/2021 15:55:30
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21315 forum posts
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1 articles

Really depends on how you want to treat the hole.

A spoting drill can also be used to camfer the edge of the hole prior to it being drilled thus saving one operation in which case an 8mm min or preferably a 10mm 90deg spoting drill would be the best option so you don't have to deburr the entry side..

Larger still if you wanted a fully countersunk hole as the spotting drill can also pre countersink rather than going back after drilling with a CSK bit.

I would not really class the holesaw pilot drills as spotting drills, maybe 4-facet or split point but a bit long for spotting so may wander a bit. I mostly use an 1/8" one which does for starting holes upto about 5mm, 5mm one above that or 6mm carbide one in the CNC.

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