Hi-Lok Sizing
Hi-Lok Sizing
(OP)
I have a task where I have to pick grip lengths for Hi-Lok fasteners. What is the best way to calculate the correct length? We have a requirement that two threads be showing past the nut. What confuses me is all the possible tolerance stackups of the material and fastener and the spec tells you what the max and min grip length can be calculated. I don't have must experience with this and I know is a standard calculation that has been done a zillion times in the past.
Thanks
Mark
Thanks
Mark





RE: Hi-Lok Sizing
Individual practices vary at different companies, but that method is pretty standard.
RE: Hi-Lok Sizing
There is a specific Go/No-go dimension for Hi-Lok Pin protrusion measured at the Collar.
Textron sells special Hi-Lok Go/No-go gauges, but gives the dimension in the fastener installation manual.
The specific data for the fasteners can be had at their web site.
http://www.textronfasteningsystems.com/aerospace/
RE: Hi-Lok Sizing
RE: Hi-Lok Sizing
As SuperStress stated every company has their own specification for this. Allow for nominal and some part tolerance. Washers can always be added to the nut stack up to allow for varying grip lengths. Just be careful not to let the nut shank out. It is very difficult for the mechanic to remove a fastener of this type if there is no hex drive recess in the tail of the fastener. This may result in the fastener spinning during fastener removal and will mechanically and thermally damage the hole.
But obviously don't make the grip length too short so that you have threads in bearing. We usually kept the grip length out of the drawing requirements and mandated the mechanics actually grip the fastener during assembly or repair to allow for any tolerance build ups for the actual fastener installation.