Large Screw or use a washer

[BraunP]

Hello great knowledge of this forum. I have a simple question, where I work, we assemble stuff. We have 2 options with out product one with a 6-32 thru hole and one with a 10-32 thru hole. We use the same bracket for both parts that has a 6-32 threaded hole. Now the issue that has come up is, is using a 6-32 screw with a washer for the 10-32 bracket equivalent to drilling out the hole to a 10-32 and using a 10-32 screw.

Personally I really don't see an issue with using the washer method. it does reduce the number of unique screws. that's about it.

there is little force on the screw, so material strength does not need to be factored in.(if the screw experiences 2 lb of force, that would be a lot)

Hardware like screws and washers are not inventoried so there is no worry about messing with that.

If you have any other questions let me know.

 

[ctopher]

I always use some type of washer.
Scroll down to washer info:
Link

Chris, CSWA
SolidWorks '15
SolidWorks Legion

 

[BraunP]

so in terms of functionality, there is no difference from what you linked.

 

[KENAT]

Depending what type of screw your design is optimized for, could use a flanged version of a socket head to avoid separate washer

http://www.mcmaster.com/#92235A504

Flanged button heads also available - but on 6/32 the hex is a bit small and prone to stripping especially if someone uses a ball end wrench.

"is using a 6-32 screw with a washer for the 10-32 bracket equivalent to drilling out the hole to a 10-32 and using a 10-32 screw"

Obviously not, but if your application doesn't see any load the 6-32 and associated clamp force generated is adequate then I don't see the problem.

I end up using undersized fasteners with unloaded off the shelf items all the time to minimize the different types of screw used in assemblies (or because the good folks that supply a lot of off the shelf stuff with mounting holes don't believe in allowing for tolerances in mating part).

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[ctopher]

is using a 6-32 screw with a washer for the 10-32 bracket equivalent to drilling out the hole to a 10-32 and using a 10-32 screw

With no load, probably no difference. I can't say without knowing the design.
I have seen screws snap (without a load designed into it) by simply changing to a smaller screw because the engineer thought it would be either more convenient or make more space on the part.
Whatever the design is, you need to figure out the screw size based on the load it will see.

Chris, CSWA
SolidWorks '15
SolidWorks Legion

 

[BraunP]

so it seems like I was not thinking crazy. I will stick to the washer since it sees little to no force, and we already use that screw and washer in other parts of the build, so adding another type of screw will just increase the size of the BOM and not really give any benefit.

Thank you for your help on this matter. I know it was a simple question, but it was appreciated.

 

[KENAT]

DFMA proponents might suggest that eliminating components and the associated process steps might be worth it - especially if the washer is fairly small (<.5" per the consultant our former Manufacturing Engineering Director made us endure) so difficult to handle.

Posting guidelines faq731-376

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(probably not aimed specifically at you)
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[tbuelna]

....We have 2 options with out product one with a 6-32 thru hole and one with a 10-32 thru hole. We use the same bracket for both parts that has a 6-32 threaded hole....

How do you install a 10-32 UNF screw into a 6-32 UNC threaded hole?

Using a 6-32 UNC screw in the larger diameter hole designed for a 10-32 UNF screw and using an oversize washer to bridge the gap seems rather amateurish. If a 10-32 screw will fit, then I would suggest the correct approach would be reworking the mating part to accept the 10-32 screw so that everything looks like it belongs. You and your company should take some pride in the products you produce. Do what's best rather than what is cheapest and most expedient.