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Where have you used Button Head Cap Screws in machine tooling design?

 

The Holo-Krome web site says this about Button Head Cap Screws (BHCS)

“This product is designed for light fastening applications only.  Do not use it in critical high strength applications where a socket head cap screw should be used.”

 Another site, Coburn-Myers says something similar. 

Has a similar thread design as a socket head cap screw.  However, the dome-shaped head is wider and has a lower profile than a socket head cap screw.

Used when a wider bearing surface or a smoother, more finished appearance is desired. Button head cap screws do not afford the strength of socket head cap screws and are designed for light fastening applications. They are not recommended for critical, high-strength applications.”

 

So, I think “cut little button” when I think of BHCS.  I also think lower profile. 

 

Button Head Cap Screws are good for mounting Weld Spatter Guards made of sheet metal.

 

I have used BHCS for mounting sheet metal to a plate or block.  Such as mounting weld spatter guards or putting together an electrical box.  They are good for these applications because they have a bigger diameter head and… well, they are “cute as a button” !

 

This Name Tag, made of sheet metal, is mounted with Button Head Cap Screws.

 

I have also seen them used for clamping.  But in most applications, this isn’t recommended because they just aren’t as strong and there are other fasteners that work better …

 

 

(A) Pan, (B) Button (Dome), (C) Round, (D) Truss (Mushroom), (E) Flat, (F) Oval (Raised Head)

 

 

 

 

So where have you seen BHCS used in machine design?  Was it a good application?

To learn more about screws, including how they are made, their history, and the drive types, (you know, like screw driver types… Phillips, Flat, Hex, etc.)  check out Wikipedia.  The grand poobah of knowledge. 

Speaking of Wikipedia.  Did you know that Rentapen’s RAPid Tooling Components are listed on Wiki?

Speaking of screws…

Remember our talk about Shoulder Screws?  Well I posted the question on linked in and found that as an axle or pivot point is their most popular use. 

Scott N. says he uses them for precision alignment…

“I build fixtures to hold parts to be machined. I need to bolt the fixture in place accurately every time. So I use, say 3/8″ mounting holes in the fixture and 3/8″ high precision shoulder bolts which are slightly undersized from a true 3/8″. Then, my fixture is mounted square and secure within probably .001″ every time and I can machine my parts precisely. I use the same theory in mounting my parts on the fixture. When I start machining, I know the parts will not shift several thousandths as it would with a typical threaded bolt in a clearance hole.”

And thanks to Randall W. for his contribution…

” Once upon a time, there were stripper bolts and shoulder screws. Stripper bolts were used as stripper guides in dies and were not of very good accuracy in diameter or length. Shoulder screws were real accuracy, both in diameter and length. What is now called shoulder screws are really stripper bolts. Diameters are .001-.005 undersize and length is all over the map.

To use a shoulder screw as a pivot, it should be buried one half the diameter of the screw into the support block or used as a pin across a yoke. This is to prevent the screw breaking at the undercut area at the shoulder. To provide an accurate clamping or precision positioning along the length of the screw, the screw(s) needs to be machined .005-.010 under nominal length to ensure cleanup. Be sure to measure the screws you have if you want an accurate bearing fit because you’ll need to use a tighter press fit to squeeze the bushing down to the correct size or have the screws plated to increase the diameter.”

And thanks to Barry P. who says that sometimes bushings should be used with the shoulder screw.  

“An axle for a wheel, cam follower or bushing…. The bushing could be added to the pivot slide application to reduce friction and galling… The bushing acts as a very low profile wheel to reduce wear from linear movement in a slot. In particular when the slot is in an aluminum plate. You make the bushing a wear item instead of the plate.   I have done this in end of arm tooling where you don’t have room for a cam follower.”

Thanks for all the great participation from the Engineers in the LinkedIn Machine Design Group!

 ‘Til next time…

The Queen

 PS

If you liked this conversation, be sure to sign up using the form on the right-hand side of this web page if you haven’t already.  Then you will receive an email notification the next time a Weld Fixture Design Lesson is posted.  And leave your ideas for using Button Head Cap Screws in the comments section below! 

 

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