topic Re: Checking countersink screw fitting - flush and tight? in Fusion Design, Validate & Document Forum

Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Wed, 03 Aug 2022 14:53:58 GMT

Hello! I'm working on a simple project that incorporates a standard hex drive, countersink metal screw from McMaster-Carr, part 92210A619. This is going into a ¼" piece of metal. And I have two questions: how do I check if the screw will fit flush given my design of the receiving hole in a metal plate; and how can I be certain that a part with a tapped 3/8-16 hole, affixed to the underside of said plate, will have no gap or wiggle/rattle? I've inserted a 3d model directly from McMaster-Carr into my model, and have attached it here. Thanks for your help!

Re: Checking countersink screw fitting - flush and tight?

davebYYPCU — Wed, 03 Aug 2022 15:45:25 GMT

I have no access to the file at the moment.

Install the screw into the plate with Joint and Contact Set, for seating, with section view,

check that the full working depth of the thread as supplied is available below the plate,

could be the run out of the thread will not secure a tight fit.

Might help....

Re: Checking countersink screw fitting - flush and tight?

stiller.design — Wed, 03 Aug 2022 15:57:37 GMT

@jimlaffertyphoto I had a look and the screw doesn't fit due to it has a different angled countersink hole.

If you want to assemble the plate with the screw you have to make the plate a component (click the body in the browser -> create components from bodies) that said I strongly recommend to look the HOLE command which is has most of the standard countersink holes covered.

If you find this helpful please accept it as a solution

Re: Checking countersink screw fitting - flush and tight?

etfrench — Wed, 03 Aug 2022 18:35:18 GMT

The McMaster-Carr screw model has chamfered edges so you can't just use the diameter of the screw for the top of the hole.

Create a sketch then project the screw to the sketch. Extend the sides of the screw to the top. Measure the distance between the extended lines' endpoints. Enter that distance in the Hole dialog. Joint the top of the screw to the top of the hole. Check for Interference (There should be none).

Re: Checking countersink screw fitting - flush and tight?

etfrench — Wed, 03 Aug 2022 18:45:44 GMT

To check the fit, Offset the top line in the sketch .25". Use that line to split the body of the screw. If the threads extend into the top of the screw, it will tighten.

I suspect you will want to use the next size smaller screw😁

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Thu, 04 Aug 2022 03:16:43 GMT

Thank you, and thanks to everyone who replied. Here's what's confounding to me... the screw head has a chamfer of 82 degrees, and when chamfering my hole, I used 41 degrees as the edge chamfer (82/2). I just used the Hole command and will compare results.

Re: Checking countersink screw fitting - flush and tight?

davebYYPCU — Thu, 04 Aug 2022 04:23:01 GMT

Try 49 degrees, for that chamfer, because it is being measured from screw top face, and not the axis.

The underside object will need a counterbore to make the screw do the tightening required.

However it is more convenient to insert the screw, and combine cut it out of the Plate, keep tools, to avoid the Maths. Delete Face will get you to what @etfrench says.

File returned with combine cut demo.

Might help...

Re: Checking countersink screw fitting - flush and tight?

stiller.design — Thu, 04 Aug 2022 07:25:17 GMT

the angle of the chamfer can be 41 or 49 depending on the reference. so you better use the HOLE command or make a sketch of the sinkhole. I dont recommend using chamfer here for many reasons (unstable, not necessary ect)

Re: Checking countersink screw fitting - flush and tight?

stiller.design — Thu, 04 Aug 2022 07:27:59 GMT

@etfrench I prefer to use McMaster's technical drawings for reference. most of the time this will help you to figure out what hole size ect you will need.

Re: Checking countersink screw fitting - flush and tight?

etfrench — Thu, 04 Aug 2022 07:51:54 GMT

The thickness of the material should be greater than the height of the head. The 6mm thickness in the OP's file is less than the height of the head (5.94mm). (Will 60 microns make a difference?) It's OK for .25" material. If you use the diameter of the head from McMaster-Carr drawing, the screw will not fit flush by .004".

Re: Checking countersink screw fitting - flush and tight?

stiller.design — Thu, 04 Aug 2022 09:55:26 GMT

@etfrench 0.004" is about 0.1mm and this is even without accounting for manufacturing tolerances. unless you look very2 hard you want see a difference IMO

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Thu, 04 Aug 2022 15:02:29 GMT

Yeah, I assumed this as well, but I'm dealing with making the plate part, and it's designed to unite with an off the shelf screw already in play, so I can't change the screw to suit the design... and it doesn't have to sit full flush. Frankly it could sit just shy of 1mm out and be fine.

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Thu, 04 Aug 2022 15:09:09 GMT

I am referencing McMaster's tech drawings BTW. Maybe saying that exposes that I don't fully understand what I'm looking at, which would be fair 🙂 But I got the head depth (5.94mm), the head diameter (19.84mm), and the head angle (82 degrees) all from the tech PDF.

As a side note, just to make sure I'm being clear... this is a ¼" plate in which I'm trying to recess a chamfered hole. The hole won't be threaded, and should be just large enough that the threads from the a 3/8-16 screw can pass through. The hex drive screw will sit in the chamfered hole, the head nearly flush to the plate... under the plate will be a metal box with a tapped 3/8-16 hole, and this metal box needs to sit flush with the underside of the plate once the screw is tightened, so that there's no play or rattle.

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Thu, 04 Aug 2022 15:23:52 GMT

Here's the hole parameters I'm entering...

Re: Checking countersink screw fitting - flush and tight?

etfrench — Thu, 04 Aug 2022 17:13:11 GMT

Those numbers should work fine. .375" is only 9.52mm.

Re: Checking countersink screw fitting - flush and tight?

davebYYPCU — Thu, 04 Aug 2022 22:33:46 GMT

Frankly it could sit just shy of 1mm out and be fine.

If you don’t know the finished height, you are wasting time.

Put a screw into the box, and wind it down to the physical stop, unwind one turn (or what suits).

Measure the distance from the box to the top screw face, place the screw in Fusion at that height from the underside of the plate, and Combine Cut the plate.

No fussing about threads not tight in the end result.

There are many ways to get the right chamfer, all based on the height of the screw standing out of the box, and referenced from bottom of your plate.

Might help....

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Fri, 05 Aug 2022 02:19:31 GMT

OK, I'm open to the idea that I am completely wrong in my assumptions, but isn't it the case that, assuming the threading on the screw *at least* terminates at the bottom of my plate... or, if the screw sits even a little higher (.25mm), so that the threading sits above the bottom of my plate... that I'm then guaranteed to get a tight fit, assuming the lower box which has 3/8 female receiver has threading flush with its top surface, or even countersunk a little? I just thought that we have some knowns and following them it should work... in other words, the beveled hole in which the screw head sits needs to merely: 1) match the head angle, 2) sit high enough above the bottom of the plate, which can be a spectrum of heights, provided it's a shorter distance than what is covered by the threading.

Re: Checking countersink screw fitting - flush and tight?

davebYYPCU — Fri, 05 Aug 2022 03:50:16 GMT

Don't assume anything, measure it.

You bolt has quite a lot of interfering transition between the lower countersink, and usable thread.

The interfering face highlighted blue, will / does / must interfere with the bottom object thread.

Creating a section sketch allows for the top of bolt to top of good thread, to be measured, and it is 9mm.

File updated.

Might help.....

Re: Checking countersink screw fitting - flush and tight?

jimlaffertyphoto — Fri, 05 Aug 2022 15:49:23 GMT

OK, thanks for that heads up.