Metric Collets gripping inch tools: too sloppy?

[Frogblender]

Can I use a "13mm" ER20 collet to grip a 1/2" tool?

My 3/8" collet is definitely 0.375, so a 3/8" tool is snug. But a 13mm collet is .512"... is that too sloppy to hold a 1/2" tool? I know collets have a "grip range", but I want a tighten-and-go solution, without having to check for runout.

[ger21]

I have some ER32 collets that actually say 12-13mm that I use with 1/2" tools, but prefer 1/2" collets as they are slightly smaller. But 1/2" is closer to 13mm than 12mm, so they should work fine.

[mc-motorsports]

ER collets have a "clamping range", best bet is to grab a catalog that shows the clamping range for the collets from the manufacture. But you'll most definatly be fine, some manufactures are + a few, - a few, others are +0, -.040".

MC

[Superman]

I agree with mc-motorsports
The ER type collets work on the spec on the collet ie 12-13mm. As mc-motorsports states 0 to -0.04"(1mm). This will clamp a 1/2" shank securely, but put in a 12mm shank and you are at the collets' limit, ( would be best to use an 11-12mm )

Similarly a 7/16" shank (11.1125") should not go into a 10-11mm collet
( you may need a hammer )
The ER uses the entire outer taper to "squeeze" the whole collet around the tool-shank

The DA type uses a double angle on the front area of the collet to collapse it against the tool-shank, the acceptable range for this type is 0 to -0.02"(0.5mm), any more and tool runout is a major issue. The front of the collet is the only area that is collapsed around the tool.

DA type collets IMO are only good for drills, reamers etc but trueness should be checked before running.

[Geof]

Half inch is 12.7mm which is fine to grip in a 13mm ER Collet with a qualification; I have found that high helix cutters taking heavy cutters can slowly pull out of ER collets.