Metric R8 Collets and Metric Drill Bits

[EmilioG]

I use quite a few metric drill bits. At my job we only have
Imperial R8 collets so I can't use my metric endmills.
I only need a few metric R8 collets but was wondering,
since metric R8's only come in 2-20mm sizes, will an 8.1mm
endmill fit in an 8mm R8 collet? How much room do these collets
have for odd size endmills? or do they make r8's in 8.1, 8.5mm etc...?
Thanks

 

[18w]

Emilio,
I have only seen metric collets in one mm increments and they do not collapse or expand to accept 8.1 for example. Your best alternative would be to put a R8 to ER collet chuck in the mill and then you could use all your metric drills and endmills in that holder with the appropriate collets. The ER system has a wide range of grip diameters within each collet. Only downside is you lose a little daylight between spindle and table. Because most of the world has long used the metric system there may be metric R8 collets out there but you would still need individual collets for every size.

Regards
Darrell

 

[Ebel440]

Just a suggestion but unless you have a lot of metric tools why not get standard and eliminate the problem I would think its easier and cheaper

 

[LEEQ]

I like the er collet solution. I use it. A metric set has no gaps in the gripping range, and can be used for any shank metric, or standard, drill bit or endmill ect.

 

[EmilioG]

OK, heres the answer, the shank is a fractional size, 8.7mm to fit into an 11/32" r8 collet.
These metric Guhring drill/mills have shanks made for either metric or imperial depending on the
size. Thanks. That makes more sense.