topic Metric thread forms wrong!! in Fusion Design, Validate & Document Forum

Metric thread forms wrong!!

HughesTooling — Sat, 28 Jan 2017 19:40:08 GMT

I'm pretty sure the metric thread forms are wrong. I'm making a mould tool to make M10 nuts. I've made a lot of unscrewing mould tools over the years and the thread on the OD of the core needs to be the same form as the ID of a nut (same form as a tap). When I section a female thread in Fusion the form looks all wrong, the ID and OD are correct for mid limits but the pitch diameter is wrong.

Here I've sketched the correct form using data from HERE, the section is a male thread made by Fusion.

Metric thread form. You can see here the thread should be more truncated at the core than at the OD.

Example file attached.

Mark

Re: Metric thread forms wrong!!

HughesTooling — Sat, 28 Jan 2017 11:56:22 GMT

Looking at the metric thread data XML file, all the information is correct so the fault must be the way Fusion is using he information!

Mark

Re: Metric thread forms wrong!!

HughesTooling — Sat, 28 Jan 2017 13:18:38 GMT

I made a couple of mistakes in my first post but can't edit. I should have said female thread not male. Quoted below and corrected.

@HughesTooling wrote:

I'm pretty sure the metric thread forms are wrong. I'm making a mould tool to make M10 nuts. I've made a lot of unscrewing mould tools over the years and the thread on the OD of the core needs to be the same form as the ID of a nut (same form as a tap). When I section a female thread in Fusion the form looks all wrong, the ID and OD are correct for mid limits but the pitch diameter is wrong.

Here I've sketched the correct form using data from HERE, the section is a female thread made by Fusion.

Metric thread form. You can see here the internal thread should be more truncated at the core than at the OD.

Example file attached.

Mark

Re: Metric thread forms wrong!!

Anonymous — Sat, 28 Jan 2017 13:38:59 GMT

@HughesTooling

HughesTooling wrote:

Metric thread form. You can see here the internal thread should be more truncated at the core than at the OD.

Example file attached.

The land at the minion diameter will be determined by the thread % (75% vs 50%), which is determined by the tap drill size. But what you are seeing is a pitch diameter discrepancy right?

I'm trying to wrap my head around this and figure out how that could even happen.....

Re: Metric thread forms wrong!!

HughesTooling — Sat, 28 Jan 2017 14:01:21 GMT

@Anonymous wrote:

@HughesTooling

@HughesTooling wrote:

Metric thread form. You can see here the internal thread should be more truncated at the core than at the OD.

Example file attached.

The land at the minion diameter will be determined by the thread % (75% vs 50%), which is determined by the tap drill size. But what you are seeing is a pitch diameter discrepancy right?

I'm trying to wrap my head around this and figure out how that could even happen.....

The point I was really trying to make is the land at the top of the female thread is bigger than the the land on the ID on female threads Fusion is making. And you are correct the reason is because the pitch diameter is incorrect.

I found I could use Press Pull and offset the faces of the helical surfaces by 0.098mm to correct the problem for now. Looking at what I've ended up with Fusion's male threads look correct it's just the female ones that are wrong.

Corrected female thread with male thread.

Mark

Re: Metric thread forms wrong!!

HughesTooling — Sat, 28 Jan 2017 14:31:25 GMT

It looks like they've might have the P/8 and P/4 around the wrong way! 1.5/8 = 0.1875 and 1.5/4 =.375

Mark

Re: Metric thread forms wrong!!

Anonymous — Sat, 28 Jan 2017 14:37:40 GMT

I think you are right! Those are reversed.

Re: Metric thread forms wrong!!

paul.clauss — Sun, 29 Jan 2017 17:30:41 GMT

Hi @HughesTooling

I think you are right as well. I logged FUS-30218 with our development team about this issue and will keep you updated as I have more information to share. Please let me know if you have any questions!

Re: Metric thread forms wrong!!

mroek — Sun, 29 Jan 2017 20:29:21 GMT

If it is indeed just a reversal of those two parameters, it should be a real quick fix.