Hi-Lok hole clearance
Hi-Lok hole clearance
(OP)
Can any one tell me if there are different clearances for holes in different materials i.e alum and titanium. Where can you find approved data on this?
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Hi-Lok hole clearance
RE: Hi-Lok hole clearance
If you need high interference fits with nominal dimensions, suggest using Radius Lead-In bolts which are designed for intereference fits.
Regards,
jetmaker
RE: Hi-Lok hole clearance
RE: Hi-Lok hole clearance
From my understanding, it is irregardless of material used. It all depends on the fatigue enhancement you want. However, something to keep in mind is that you are more likely going to damage a Titanium bolt if you are installing it in a tight interference fit in a Titanium or steel plate.
So, to summarize, if the bolt is not much harder than the material you are installing it in, go with a close ream or net fit. If you need the fatigue enhancement, perform an operation like coldworking or shot peening rather than a tight interference fit.
Regards,
jetmaker
RE: Hi-Lok hole clearance
1/ in light stainless skin panels if a hole is reamed to the same size as aluminum .. the panel will be distorted (damaged - if not cracked) by the time the fastener is installed.
2/ in difficult ares - thru heavy members (+.25 inch) the holes are usually larger because the fastener head will be damaged from installation impact by the time it is installed. .. also if direct impact on the head is not possible due to tight confines .. it will not be possible to install the fastener - the fastener has to be installed sufficiently so that several threads are protruding - otherwise the fastener cannot be drawn thru. holes in castings are usually reamed on the larger limit of the tolerance.
3/ Aluminum Hiloks in aluminum thin skins are usually tight because they almost always "spin" otherwise.
my 2 cents ..
RE: Hi-Lok hole clearance
Excellent contribution.
RE: Hi-Lok hole clearance
RE: Hi-Lok hole clearance
There are typically (4) types of structural fastener installations... I'll submit the following definitions for these catagories...
close-reamed = .0005--0.0015 clearance [hole shall be slightly larger than max true* diameter of a bolt, but still defined by very tight tolerance]
transition fit (-)0.0008-to-(+)0.0008 [nominal hole size equal to true* fastener diameter, +/- a small tolerance]
light interfernce fit = (-)0.0005-to-(-)0.0015+ [hole size guarenteed to generate interference with fstnr shank]
high interfernce fit = (-)0.0015-to-(-)0.0045 [hole size guarenteed to generate significant interference with shank, and require significant effort to drive-in]
Here are rules of thumb I have learned the hard way...
Use clearance or transition fit for applications as follows:
A) where ANY of the base material(s) have an SCC [stress corrosion cracking] threshold below 25KSI in the ST orientation.
B) material stack-ups of aluminum thicker/deeper than +2Dia thickness [simply to assure high quality fastener installation W/O having to hammer/press fasteners into tight holes in deep structure [can damage holes and fastener heads!!]
C) for any stack-up that includes (any) layer(s) of steel, CRES or titanium.
Use light interference for most jobs in SCC resistant aluminum materials for trade-off on installation of good quality fastening and fatigue performance. Note: use of Hi-Loks is probably Ok in light interference... but Hi-Tigue style HL would generally be easier and less damaging to install. SOMETIMES this stack-up can include titanium... but I don't recommend it without careful study of installation forces!
For heavy interference only use Hi-Tigue style Hi-Loks (variation on Hi-Lok design for smooth fit during interference installations) in aluminum structure ONLY... after considerable study of potential fatigue-durability benefits VS risks of installation damage (may require extreme force to drive into position)... and potential for SCC in [usually] alloys/tempers.
Regards, Wil Taylor
* true fastener diameter as defined by the fastener [or mnfctrs] specification
Regards, Wil Taylor
RE: Hi-Lok hole clearance
RE: Hi-Lok hole clearance
May be its useful: http
Regards
Fernando
RE: Hi-Lok hole clearance
gbowman
RE: Hi-Lok hole clearance
Usually the protcetive coating is damaged to some extent on installation and you can argue in some cases it is redundant for the normal life span. I do believe most manufacturers install Hi-Loks wet with their sealant of choice to provide some environmental isolation.