6m6 dowel pin (+4/+12), Hole H7 (+0/+12) is preferred for sliding (tight) to tapping (light press) fit. If you want a good press fit for an 6m6 dowel pin you will have to go with a hole size 6P7 = 6 -8/-20. Easy to remember P/p stands for "Press" on dowel pins. If you would like to use a 6H7 reamer (common size) than stone it lightly to make certain you get the type of press fit you want. A brand new 6H7 reamer comes with a tolerance of +5/+10. A brand new 6P7 reamer has a tolerance of -10/-15.
Thanks juergenwt. This will be used as a stop pin for a small device with low torque applied, so will need a good press fit. Thanks for the tip! And, thanks to all of you for the input.
Um, so for press fits the actual force required to do the pressing/resisting pull out may be more important than sticking to some standard tooling based on arbitrary fit classes. Additionally the stress imparted to the parts in so doing.
Appropriate fit for SST into MIC-6 aluminum may be different from appropriate fit for high grade steel into high grade steel.