DOWEL PINS AND EXTRACTABLE DOWELS Dowels are solid pins, usually precision ground to narrow


limits to permit accurate fitting, they are traditionally used to hold parts together in a fixed alignment, relying on the tightness of fit to stay in place.


Some applications for solid pins require clearance or transition fits on at least one of the components to be fastened. There are three factors that determine the size of hole needed:


< The tolerance on the dowel < The tightness of fit needed < The hardness of the components into which the dowel is to be fitted


TOLERANCES AND FITS


Our range standardises on m6 tolerance, which corresponds to the ISO and DIN standards*. The m6 tolerance is a ‘plus tolerance’ range and is normally used for interference fits. Also available are the minus tolerance ranges, h7 and h8.


HOLE TOLERANCE GUIDE Hole material


Interference fit Transition fit


Clearance fit


Hardened steel


Pin Ø less 5 microns Pin Ø less 2 microns


Pin Ø plus 25–60 microns


FITTING DOWELS INTO BLIND HOLES


When a dowel is interference-fitted into a blind hole, it increases the pressure of the air trapped in the hole. It is recommended that the dowel should have an air release flat ground along its full length to prevent the dowel being ejected under the pressure of compressed air, or bursting the component into which it is driven.


MATERIALS** Through hardened steel


Mild steel, unhardened Stainless a2 Stainless a4


*See page 37 for full details. **Other materials are listed under ‘special pins’. See page 38 for material compositions.


Mild steel


Pin Ø less 25 microns Pin Ø less 5 microns


Pin Ø plus 25–60 microns


Aluminium / zinc / brass Pin Ø less 35 microns Pin Ø less 5 microns


Pin Ø plus 25–60 microns


100Cr6, WS 1.3505 hardened and tempered to HV 550-650


WS 1.0718 (9SMnPb28) WS 1.4305 or 303S31 WS 1.4571 or 316S11


E: sales@technifast.co.uk W: www.technifast.co.uk


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