{"id":3111,"date":"2026-11-09T08:32:52","date_gmt":"2026-11-09T00:32:52","guid":{"rendered":"https:\/\/skypumold.com\/dowel-pin-holes-tooling-plates-fixtures\/"},"modified":"2026-11-09T09:51:44","modified_gmt":"2026-11-09T01:51:44","slug":"dowel-pin-holes-tooling-plates-fixtures","status":"publish","type":"post","link":"https:\/\/skypumold.com\/pt\/dowel-pin-holes-tooling-plates-fixtures\/","title":{"rendered":"Dowel Pin Holes: Fits, Tolerances and Drawing Callouts"},"content":{"rendered":"

Dowel pin holes in tooling plates and fixtures are usually reamed to H7 and paired with hardened m6 pins, which gives a transition fit. The pin is normally tight in one plate and sliding in the mating plate, and fixtures that are loaded often use one round pin and one relieved pin. This article explains these fits, the hole tolerances behind them, and how to call out dowel holes clearly on your drawing.<\/p>\n

\"Stepped
A stepped base plate with counterbored screw holes. Dowel pins are added when a plate must return to an exact position.<\/figcaption><\/figure>\n

Screws Clamp, Dowels Locate<\/h2>\n

A clearance hole for a screw is deliberately larger than the screw, so a screwed joint can shift before the screws are tightened. A dowel pin fits its hole with almost no clearance, so it fixes the position. On a well-designed assembly, screws provide the clamping force and two dowel pins provide the location, so only the dowel holes need tight tolerances. We covered screw holes in our article on tapped and counterbored holes in tooling plates<\/a>.<\/p>\n

Pin Tolerance and Hole Tolerance<\/h2>\n

Metric hardened dowel pins are commonly ground to m6, and the hole is reamed or ground to H7. Elesa+Ganter notes that a dowel pin in an H7 location hole gives a transition fit (Elesa+Ganter<\/a>). For a sliding fit, a g6 pin in an H7 hole is a common choice (Wevolver, ISO 286 H7 chart<\/a>). The ISO 286 limits for common sizes are shown below, in micrometers (\u00b5m).<\/p>\n\n\n\n\n\n\n\n\n
Nominal size (mm)<\/th>\nHole H7<\/th>\nPin m6<\/th>\nPin g6<\/th>\n<\/tr>\n<\/thead>\n
over 3 to 6 (e.g. \u00d84, \u00d85, \u00d86)<\/td>\n0 \/ +12<\/td>\n+4 \/ +12<\/td>\n\u221212 \/ \u22124<\/td>\n<\/tr>\n
over 6 to 10 (e.g. \u00d88, \u00d810)<\/td>\n0 \/ +15<\/td>\n+6 \/ +15<\/td>\n\u221214 \/ \u22125<\/td>\n<\/tr>\n
over 10 to 18 (e.g. \u00d812, \u00d816)<\/td>\n0 \/ +18<\/td>\n+7 \/ +18<\/td>\n\u221217 \/ \u22126<\/td>\n<\/tr>\n
over 18 to 30 (e.g. \u00d820, \u00d825)<\/td>\n0 \/ +21<\/td>\n+8 \/ +21<\/td>\n\u221220 \/ \u22127<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

An m6 pin in an H7 hole can be slightly loose or slightly tight, which is why the fit is called a transition fit. The whole hole tolerance is only 12 to 21 \u00b5m, so dowel holes are drilled undersize and then reamed, bored or ground. SPIROL stresses that a reamer cannot correct a crooked or out-of-round drilled hole (SPIROL<\/a>). If you use pins with a different tolerance, state the pin on the drawing so the hole can be matched to it.<\/p>\n

Tight in One Plate, Sliding in the Other<\/h2>\n

A common arrangement is a firm fit in one plate and a sliding fit in the mating plate. The pin stays in the first plate, and the second plate can be lifted off and put back without forcing. If the pin is tight in both plates, the plates have to be pressed apart, which can damage the holes and the pin. You can achieve this with:<\/p>\n