On aircraft the hole typically fails before the fastener

1. Hole Quality for aircraft mechanics brought to you by Mechanic's Toolbox Software - makes your job easier. www.mechanicsupport.com

2. A poor quality hole will fail the joint It's not how strong the rivet or bolt that matters - it's how strong the joint is. A poor hole will fail the joint and leave the fastener loose.

3. A poor quality hole will fail the joint Smoking Rivet - the rivet hasn't failed - but the hole has! "With a loose rivet, all we have is a hole in the airplane with some trash rattling around in it, and it always enlarges the hole."

4. A poor quality hole will fail the joint Joint failed at a stress far below published strength data due to metal fatigue. Proper hole preparation retains strength.

5. A poor quality hole will fail the joint "You can calculate stress all you want but if the hole is shaped like an hour glass or a pear it won't perform like you expect it to."

6. Feed and Speed Feed is the feed rate, or when hand drilling, how much pressure you put on the drill. Speed is the spindle speed or how fast the drill bit is rotating. Too much feed and speed dulls your drill bit and makes holes like the one above. Speed kills - slow down

7. Clean the Hole Deburring tool for cleaning the backside of the hole

8. Size the Hole Drill slightly undersize and ream to proper size. Reaming cleans the hole surface.

9. Cold Work the Hole for optimum fatigue strength 1. Hole filling rivet 2. Mandrel Expansion - http://www.fatiguetech.com Cold working the hole improves the surface finish and places the hole boundary under compression. Aircraft grade rivets are designed to expand against the hole boundary and compress the surfaces.

10. Measure the Hole Hole plug gauge for accurate hole measurement

11. Open Holes Increase Stress by 3 times. Plugging holes only increase the stress 2 times. 1/3 less stress! Plug the Hole

12. Mechanic's Toolbox Software for the Mechanic Saves you time and money www.mechanicsupport.com