Clearance for various hex head nuts and bolts 1

[mit227]

Does anyone know where I may find values for the clearances needed to assemble hex-head fasteners?

For instance, if I have a M6 hex head nut that is going in a plastic molded piece, how large should I make the diameter of the cavity so that the technicians may assemble the nut in place?

 

[CoryPad]

What you need is the outer diameter of the socket used to tighten the nut. You take the maximum socket outer diameter and add a small factor (like ~ 0.5 mm) to allow for free spinning.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[desertfox]

Hi mit227

I think the machinery's handbook gives clearances around hex head fasteners for assembly purposes.

regards

desertfox

 

[dgowans]

Machinery's Handbook does have a table for wrench clearances, although a quick glance at my copy didn't show anything about metric fasteners.

Cory's suggestion is completely valid. Take a quick walk around your shop and start measuring the tools your technicians will use to assemble your products. Tell them what you're up to and you may learn something about how they plan on assembling your creation that can help you with the design. At the very least they'll know you were thinking of them during the design phase rather than just throwing something over the wall and saying "build this!"

 

[CoryPad]

The 26th Edition of Machinery’s Handbook does show wrench/socket clearances on page 1511 that were obtained from the SAE Aeronautical Drafting Manual. They used a clearance of 0.030 inches (0.762 mm), which is a little large in my opinion.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[drawoh]

mit227,

ASME Y14.5M-1994, the dimensioning and tolerancing standard, shows how to analyze clearance holes and position tolerances to ensure your parts can be assembled.

JHG

 

[mit227]

thanks a lot everyone,

I'll have to look into the Machinery's Handbook. Anyways, I am doing this for my technicians, I just didn't want to bother them every couple of hours with these kind of questions and wondered whether there was a chart.

Once more thanks again

WJM

 

[Dave K]

The chart in the 26th edition is for metric? my 23rd edition only has a chart for inch sizes

-Dave
Everything should be designed as simple as possible, but not simpler.

 

[KENAT]

mit, you need the simplistic data of how big the socket and/or wrench heads are.

You then need to allow for the fact that the size and location of the bolt hole vary and that hence the position of the bolt head will move. Depending on your application they may move a little or a lot, depends on the tolerances of the part(s) involved. This is what drawoh is telling you.

Cory, depending on not just the sizes but the relevant postional tol/coaxiality of the bolt holes the .03 doesn't sound generous to me.


KENAT, probably the least qualified checker you'll ever meet...

 

[Tmoose]

The variation amongst socket wrenches ( 6 vs 12 point, premium vs no-name import among other things ) likely to be pretty extreme. using the M Hdbks clearance for an open end wrench is likely to be good enough for a socket, if a socket can even be used.