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I am encountering an intermittent error with fillet on screw threads. Any thoughts?

Question asked by Andrew Pierce on Aug 28, 2014
Latest reply on Sep 2, 2014 by Andrew Pierce

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I have created a part and threaded each end according to 6 5/8" API Regular Left Hand thread specifications. I attempted adding a fillet to both crest edges of the threads on one end of the part with one fillet feature and received a rebuild error. I then applied the fillet to only one edge and received no error, so I created a second fillet for the other edge and still no error. Strangely, when adding the fillet to the threads on the opposite end of the part with the same geometry I am able to re-use the first fillet feature for the corresponding edge with no error. However, if I use the second fillet for its corresponding edge at the other end, I recieve a rebuild error. I even tried making a third fillet for the remaining edge and still get the error. It seems that this error is only present intermittently as I have created similar threads on other parts with no errors at all using only one fillet, and somtimes I will get this error when I first try to fillet and on later attempts I won't. Thanks in advance for any help.

Jerry Steiger Aug 29, 2014 5:56 PM

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Andrew,

It could have something to do with the way the fillet ends on one end or the other. Or it may just be that fillets are a bit touchy. I haven't noticed it in a while, but back in the good old days I had lots of trouble with fillets that wouldn't pattern, fillets that wouldn't mirror, fillets that worked if you started them on one end but not the other, fillets that worked if you selected some of the edges without tangent propagation and then made another fillet of the same value for the rest of the edges, fillets where a variable radius with all the same value worked when a constant radius wouldn't...

Jerry S.

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Kelvin Lamport Aug 28, 2014 8:37 PM

Can you post the part, or at least some images, to show what you are describing?

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Andrew Pierce @ Kelvin Lamport on Aug 29, 2014 9:45 AM

Ok I am posting some screen captures of what I am encountering. The first shows the error that occurs when attempting to use a single fillet (Fillet1) for both edges of the thread on the TOP end of the part. The second and third show no error when using two seperat fillet features, one for each edge on the TOP end. The fourth shows no error when re-using Fillet1 for the corresponding edge on the BOTTOM end of the part. Finally, the last shows the error that occurs when re-using Fillet2 for the corresponding edge on the BOTTOM end. I have also attached a screen capture of a part containing the female version of the same thread geometry, both edges are rounded using a single fillet feature.

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Jamil Snead @ Andrew Pierce on Aug 29, 2014 11:24 AM

Try unchecking tangent propagation and see if that helps.

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Andrew Pierce @ Jamil Snead on Aug 29, 2014 2:37 PM

Thanks for the suggestion, however turning off tangent propgation caused all the fillet features to fail with the previously mentioned error.

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Lenny Bucholz Aug 29, 2014 11:37 AM

Add the fillet to the sketch of the V shape, but it needs to be less than half of the crest at the major dia., but it may be because of the tapered thread?

1 question, why the fillet?

You will never get one if this is turned on a lathe or if you use a die, plus it add alot of detail that slows SW down.

you can call it out on the drawing with a note.

but if you are growing it then yes you would need it modeled.

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Andrew Pierce @ Lenny Bucholz on Aug 29, 2014 2:41 PM

The rounding of these edges is part of the API standard. I could simply not include the rounds in the model becuase these parts are being manufactured from a much older drawing currently. I am simply modeling parts to update a product catalog with three dimensional models. That being said, I would still like to know what the issue is here. It is strange that it works sometimes and not others.

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Lenny Bucholz @ Andrew Pierce on Aug 29, 2014 2:54 PM

So have you tried to modify the ones that work to the currents size that doesn't?

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Jerry Steiger Aug 29, 2014 5:56 PM

Andrew,

Jerry S.

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Andrew Pierce @ Jerry Steiger on Sep 2, 2014 9:35 AM

Jerry,

Thank you for your feedback. I have encountered the same errors you have mentioned with some of the more complex geometries I have been working with. I suppose I will just have to tinker with the fillet a bit in these situations.

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Kelvin Lamport Aug 28, 2014 8:37 PM
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Can you post the part, or at least some images, to show what you are describing?
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- Andrew Pierce @ Kelvin Lamport on Aug 29, 2014 9:45 AM
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  Ok I am posting some screen captures of what I am encountering. The first shows the error that occurs when attempting to use a single fillet (Fillet1) for both edges of the thread on the TOP end of the part. The second and third show no error when using two seperat fillet features, one for each edge on the TOP end. The fourth shows no error when re-using Fillet1 for the corresponding edge on the BOTTOM end of the part. Finally, the last shows the error that occurs when re-using Fillet2 for the corresponding edge on the BOTTOM end. I have also attached a screen capture of a part containing the female version of the same thread geometry, both edges are rounded using a single fillet feature.
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  - Jamil Snead @ Andrew Pierce on Aug 29, 2014 11:24 AM
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    Try unchecking tangent propagation and see if that helps.
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    - Andrew Pierce @ Jamil Snead on Aug 29, 2014 2:37 PM
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      Thanks for the suggestion, however turning off tangent propgation caused all the fillet features to fail with the previously mentioned error.
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Lenny Bucholz Aug 29, 2014 11:37 AM
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Add the fillet to the sketch of the V shape, but it needs to be less than half of the crest at the major dia., but it may be because of the tapered thread?

1 question, why the fillet?

You will never get one if this is turned on a lathe or if you use a die, plus it add alot of detail that slows SW down.

you can call it out on the drawing with a note.

but if you are growing it then yes you would need it modeled.
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- Andrew Pierce @ Lenny Bucholz on Aug 29, 2014 2:41 PM
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  The rounding of these edges is part of the API standard. I could simply not include the rounds in the model becuase these parts are being manufactured from a much older drawing currently. I am simply modeling parts to update a product catalog with three dimensional models. That being said, I would still like to know what the issue is here. It is strange that it works sometimes and not others.
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  - Lenny Bucholz @ Andrew Pierce on Aug 29, 2014 2:54 PM
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    So have you tried to modify the ones that work to the currents size that doesn't?
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Jerry Steiger Aug 29, 2014 5:56 PM
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Andrew,

It could have something to do with the way the fillet ends on one end or the other. Or it may just be that fillets are a bit touchy. I haven't noticed it in a while, but back in the good old days I had lots of trouble with fillets that wouldn't pattern, fillets that wouldn't mirror, fillets that worked if you started them on one end but not the other, fillets that worked if you selected some of the edges without tangent propagation and then made another fillet of the same value for the rest of the edges, fillets where a variable radius with all the same value worked when a constant radius wouldn't...

Jerry S.
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- Andrew Pierce @ Jerry Steiger on Sep 2, 2014 9:35 AM
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  Jerry,
  
  Thank you for your feedback. I have encountered the same errors you have mentioned with some of the more complex geometries I have been working with. I suppose I will just have to tinker with the fillet a bit in these situations.
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I am encountering an intermittent error with fillet on screw threads. Any thoughts?

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