Metric thread milling issue

[danpayneuk]

Hi guys.

I recently tried machining a new component that needs two different threads thread milling.  One at 9/16 x 20, the other 22mmx1.  I am using 2 different thread mills for each thread.

I have done some research on this and even ran a test to make sure the thread milling worked. This was just for the 9/16 thread.  This one is fine and the info I put into fusion 360 produces the tool path expected.

The problem I seem to be having is with the 22mmx1 thread.

The hole was bored out to 21mm with a min/major difference of 1mm or 0.5mm if halved.  

However if I put any plus figure in the Pitch Diameter Offset, the tool path will produce a bigger diameter then needed. 

The pop up box says these figures need to be plus.  I have put a minus figure in and it seems to produce the right diameter but this seems to go against what fusion is saying.

The screen shots show the setting installed and the tool path produced.  I have added a 22mm circle so you can see the tool cutting deeper than it should.

Any help would be much appreciated.

[seth.madore]

Can you share your file, or recreate the same hole scenario in a dummy part?
Yes, Radial Offset values should be positive. Are you modeling the hole to the minor or major diameter?

[danpayneuk]

Hi @seth.madore it is modelled to the minor diameter (21mm)

I will try it in a new drawing and see what the outcome is.

[danpayneuk]

Does the same in a separate drawing all together. Minor Diameter of hole modelled to 21mm dia. Sketch of circle 22mm dia.

Thanks. Dan

[seth.madore]

Can you share that file, rather than the photo?

[mathew.hutton]

Hi @danpayneuk 

Is your hole modeled to 21mm diameter or 22mm? that might be where something is going wrong? 

If you attach your project that would help and we can investigate what's going on

Cheers

Mat

[mathew.hutton]

Hi @danpayneuk 

Sorry think my internet is running slow as it didn't load your reply saying you modeled it to 21mm. But as per my first message, if you can attach your model that would be great

Thanks

Mat

[danpayneuk]

Hi @seth.madore @mathew.hutton 

Yes modelled to minor diameter of 21mm.

https://a360.co/2LqprsU

Here is the model as requested.  

Thanks

Dan

[seth.madore]

There seems to actually be a bug. Define your flute length slightly greater than 25mm, or change your "Number of Teeth" to 24

With flute and teeth set to 25mm/25teeth I get an I/J value of 6.616

With flute and teeth set to 25mm/24teeth I get an I/J value of 5.75

[danpayneuk]

Hi @seth.madore 

I have tried adjusting no. of teeth. to 24.  This made a difference but still doesn't appear to provide the correct offset.  If I adjust the flute length to 26mm and leave teeth at 25 I am unable to click OK to complete the edit tool.

[danpayneuk]

Hi @seth.madore , @mathew.hutton 

Just a follow up from yesterday.  I am assuming from the replies that this maybe something software based.  Does that mean there is nothing I can do to resolve at present?

Many thanks

Dan

[danpayneuk]

Could an update on a way to solve this problem please be provided.  

I am unsure if the issue is a bug with the Cam, or simple error that can be rectified by myself.

Many Thanks

Dan

[seth.madore]

Sorry, I've not had sufficient time to dig into the actual cause of this issue.

For the time being, as a workaround, you can adjust the Radial Offset to a point where you feel it's close to what you are looking for. It's not elegant, and shouldn't have to be the case, but...yeah.

[danpayneuk]

@seth.madore Thats fine thanks.  Glad to know it is being investigated and luckily temporarily adjusting it should work.   Will get a program finished and put through the machine to check.

Thanks for spending the time to look.

Dan