Reaming pilot holes

[RainbowsParticipant @rainbows]

Anyone know of a chart for finding the size of drill for reaming various holes? Wikipedia says 0.2mm undersize for soft materials (does that include mild steel?). Was looking for a second opinion.

And tonight I carefully picked out a 25/64" drill for reaming a 10mm hole then used a 12mm reamer by accident. First time I reamed on a drill so I didn't really realize how much speed it would cut with.

[RainbowsParticipant @rainbows]

[Neil WyattModerator @neilwyatt]

Reamer must have enough material to bite, or it will rub and get blunt, ~10 thou seems to work for me. Yes, soft materials will include mild steel in the context of reaming.

Neil

[mechman48Participant @mechman48]

I find that using a drill 1/64" less produces desired results, but anywhere between 10 -15 thou should suffice for mod.eng. needs.

George.

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