|697 forum posts|
If you want to drill a 6mm hole in a shaft, what size spotting drill should you use ?
|old mart||23/07/2021 15:15:30|
|3316 forum posts|
Any size you like, it is only for making a spot.
|Swarf, Mostly!||23/07/2021 15:22:52|
|606 forum posts|
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.
2225 forum posts
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.
21315 forum posts
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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