Low Cost Automation Tutorial

#130 Production Technology Improvement Course for Mechanical Designers - 14: Press Fit Assembly

Category : Automation elements technology

September28, 2012

Assembling bores and rods are classified into two assembling procedures based on the dimensional relationship between the two parts.

Bore & Rod Assembly

Here, the glossary of press-fitting that requires forces for assembly is explained.

[Table 1] Glossary of press-fitting work

Press-fit Glossary	Explanations on glossary and application examples	English terms
Static Press-fitting	Press-fitting procedure using static forces without impacts. Example: Press-fitting of punches into mold fixture bases.	Static press fit
Vibratory Press-fitting	Press-fitting procedure with vibrations applied. Example: Light press-fitting of easy to break parts.	Vibratory press fit
Impact Press-fitting	Press-fitting procedure employing impact effects. Example: Press-fitting of dowel pins and locating pins.	Shot fit Hammering fit
Push-fitting	Press-fitting procedure for o-rings, gaskets and springs where the parts are pushed into places along a shaft axis. Example: Press-fitting of E-type retaining rings and ball bearings into holders.	Push fit
Shrink-fitting	Assembly procedure of fitting shafts into bores where the bores are enlarged by heating. Example: - Used when high accuracy and high torque press-fitting is required. - For rotating cutting tools (end mills, etc.) to be mounted on shrink fit holders, fixing drive gear rims on hubs.	Hot press fit
Expansion fit	An opposite of the above where the shaft OD is made small by cooling, then inserting into the bore. Example: - For large parts and easy to break parts to avoid breakage by press-fitting. - For fitting and fixing of shaft bushings.	Cold press fit

Explanation on press-fitting procedures

- Press-fitting is a procedure to fit two parts of a shaft diameter and a bore diameter where a targeted interference is utilized by spreading by the parts fit.
- The surface pressure and friction of spreading this interference apart is applied as the press-fitting pressure. The way to apply this press-fitting pressure classifies the press-fitting operation.
- Obtaining of this press-fitting pressure requires some preparation operations with associated difficulties such as accurate locating of two parts and managing of gripping forces, but the press-fit pressure would commensurate the resultant parts combing reliability.

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