Screwing nuts which are not perfect perpendicular on Z axis - industrial use 2

[AdrianTC]

Hello,

I'm having some serious problems in finding a solution for screwing flange nuts on bolts which are not perfect perpendicular because of construction tolerance with the other assembled part ( turbine actuators vs compressor housing bracket - 2 degrees in radius tolerance for bolts ). The position is perpendicular, industrial cycle, Rexroth screwdrivers, different types of programs used, different types of tools with no result.

 

[Screwman1]

What is the failure mode that you are getting from the parts in service? Both the bolts and nuts are allowed a certain amount of angularity in addition to the variation from the joint components.

 

[AdrianTC]

It's about final assembly line, where the rejected parts are somewhere at 5% because of this issue, the tolerance from the joint and screw i think its ok, the problem is that the nut sometimes doesn't fallow the pitch/lead on screw ( NOK screwing ).

 

[Tmoose]

"2 degrees in radius tolerance for bolts ".

If this means one or more of the screws are "leaning" because 2 holes are not concentric enough?

http://www.fluidpowersafety.com/images/4bolt_flange.gif

Are the parts made per the drawings?
If the parts are circular and have flanges are they forced to be "clocked" out of position.

If the positional accuracy is correct then I think the holes need to be a little larger.
What size are the bolt clearance holes?

http://www.metricmcc.com/catalog/Ch10/10-1040.pdf

 

[3DDave]

A good picture is worth 10000 questions.

 

[Jboggs]

The best solution is to attack the problem, not the symptom. Leaning screws and crooked nuts are not a problem. They are a symptom. Why are they leaning? Does your system not allow enough tolerance of actual position of "aligning" holes? Can you improve that alignment? I'll bet you can.

Also, is the requirement for which they are being rejected realistic, or is some bureaucrat exercising their "power"?

 

[byrdj]

for exacting aplications, you could use leveling washers

http://www.jwwinco.com/products/section11/gn350.3/

 

[racookpe1978]

Or a pair of bevel washers.

NOT as accurate as leveling washers, but less expensive. If the joint will be adequate with the lower accuracy solution, use it.

 

[Screwman1]

I'm not sure what is happening. If it's alignment then a dog point or MATthread would generally be the solution for automotive applications. How about using a Taptite screw and an untapped nut member and eliminate the possibility of cross threading?
We need to know better what the problem is, there are a lot of potential solutions, but they depend on the circumstances of the application.

 

[Tmoose]

I think McMaster Carr stocks most of these, but only in inch/Imperial sizes. -

http://i1040.photobucket.com/albums/b404/gsx800ho/slide show 1/Specialboltchart_zps0a6ff027.gif