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> Helical Thread Milling, Cannot adjust thread depth
EspressoE
post Aug 19 2014, 05:34 AM
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I am trying to use a single profile thread mill to mill an M5x0.8 internal thread. I have a D 4.2mm hole and would like to have a major diameter of 5.2mm. I have configured the thread depth to be 5.2 - 4.2 = 1.0 mm.

The thread mill has the following parameters:
D: 3.429
Ds: 1.778
P: 1

The D4.2mm hole is at X(15) Y(6.225) and a snippet of the default generated code shows the following:

Thread Type: ID
Thread depth: 0.8mm
NC Code Format: Long Hand
Thread Mill Path: Continuous

N104 G00 X15. Y6.225 Z10.
N105 Z1.
N106 M8
N107 G01 G94 Z-9.5 F32
N108 X15.273 Y6.498 F128
N109 G03 X15. Y6.611 Z-9.4 I-0.273 J-0.273 F64
N110 X15. Y6.611 Z-8.6 I0. J-0.386
N111 X15. Y6.61 Z-7.8 I0. J-0.386

. . .

If I understand the G-Code correctly, the center of the thread mill is at Y: 6.611 - (-0.386) - 6.225 = 0.772 from the center of the hole. The major diameter is the 2 * (Yc + Dtool/2) = 2 * (0.772 + 3.429/2) = 4.973. That works out to be a thread depth of 4.973 - 4.2 = 0.773mm which is a bit under the 0.8mm that was defined.


So at this point, I went ahead and bumped up the "Thread depth" to 1.0mm and surprisingly, I got the exact same output with a thread depth of 0.773mm.

Default thread depth 1.0mm
NC Code Format: Long Hand
Thread Mill Path: Continuous

N104 G00 X15. Y6.225 Z10.
N105 Z1.
N106 M8
N107 G01 G94 Z-9.5 F32
N108 X15.273 Y6.498 F128
N109 G03 X15. Y6.611 Z-9.4 I-0.273 J-0.273 F64
N110 X15. Y6.611 Z-8.6 I0. J-0.386
N111 X15. Y6.61 Z-7.8 I0. J-0.386



Software version: SprutCAM 9 (build 0.2 rev 74790 x64 RL 30/07/2014)

Any ideas if I'm doing something wrong or if there is a real issue here?

Thanks,
Eric
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Sprut_UK
post Aug 20 2014, 01:33 PM
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Hi EspressoE, welcome to the SprutCAM users forum.

I haven't done much in the way of thread milling with SprutCAM, but according to the help files:
QUOTE
spiral diameter is chosen according to the hole and the tool dimensions


which suggests that it is the tool or hole size which affects the machined size.

I hope this helps.

Dave
Attached File(s)
Attached File  20_08_2014_14_47_09.jpg ( 122.68K ) Number of downloads: 14
 


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EspressoE
post Aug 21 2014, 03:35 AM
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QUOTE (Sprut_UK @ Aug 20 2014, 07:33 AM) *
Hi EspressoE, welcome to the SprutCAM users forum.

I haven't done much in the way of thread milling with SprutCAM, but according to the help files:

which suggests that it is the tool or hole size which affects the machined size.


Hi Dave,

Thank you for the welcome and the reply. Once you select ID or OD, the diameter should be based on the hole diameter, tool diameter, and the thread depth. Here's the detailed section further down on the page that covers this.

Attached File  2014_08_20_threadmilling_W5DThreadMill.png ( 38.46K ) Number of downloads: 11


I'm thinking there's a bug (or an input configuration issue on my part) in the W5DThreadMill operation and it's ignoring the thread depth and going with a default thread depth. I'm new to SprutCAM, but I would be surprised if people tolerated this with SprutCAM 8, so I wonder if the failure is unique to SprutCAM 9 at this point.

-Eric
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