Helpful guide to the Metric to Fractional Interchange with today’s most popular sizes.

This winter are you planning on assembling an on-board tool kit for your Perkins marine engine? Or maybe a field service kit for your Deutz in a screening plant? Here’s a way to save time, weight, space, and money: use selected standard sizes and metric size sockets interchangeably.

Listed below are common interchanges that are safe to use and will insure a snug fit. As a precaution, try not to exceed 5 thousandths difference in size to avoid rounded-off head bolts.

Standard Fractional Size

Metric Size

Difference in Thousandths

15/64

6

.002

5/16

8

.003

7/16

11

.004

5/8

16

.005

3/4

19

.006