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### Author Topic: Inscribed circle, what am I missing?  (Read 28816 times)

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#### RICH

• 7,412
##### Re: Inscribed circle, what am I missing?
« Reply #10 on: December 02, 2010, 08:48:50 PM »
Jim,
Art never got back to me on my question......

Let me now try and explain something on where the / my confusion on the definition exists.
Looking at figure 5.13.2, the figure is dimensionaly correct. Now if you were find and use the "inside" inscribed circle along with the tip radius,
then LT should provide an "image" such that the long length would be 0.758". So let me test that and confirm what you originally posted.

Now, for talking purposes ONLY, should you use the inside circle as given by "some" manufactures with a given radius, and say there is a total tolerence of ( .002")  to the cutting edge,
then LT would not give you a true cut of the profile. This is a different issue.......

Now if you define the tool as using the tip center along with a defined tip radius, and it is by definition a 35 deg insert then all will be fine with the exception  of a too large flank cut depth ( by formula
that would be restricted ). So practicaly speaking even if the tool "looks" too big all may be just fine in the path generation.

RICH

#### Kingjamez

• 13
##### Re: Inscribed circle, what am I missing?
« Reply #11 on: December 02, 2010, 09:58:36 PM »
Yep, I agree completely. The tolerance should absolutely be accounted for. In my case I'm using a diamond profile insert so, yep, as long as the angle, and tip radius is correct I should be good to go.

Square cutters at 0 degrees (and perhaps trigon) would need to be accurately defined.

Let me know what you find. When I use 0.379 on a 35 degree diamond as the inscribed circle as per one of the figures in the manual, the tool generated by LT is well over 2" long.

-Jim

#### Dan13

• 1,208
##### Re: Inscribed circle, what am I missing?
« Reply #12 on: December 03, 2010, 01:46:33 AM »
Hi Rich,

I don't think I understand your point about insert tolerances. Define it whatever you define in LT, in the end it all comes down to touching off the bar and measuring the diameter. Furthermore, for discussion purpose, the insert tolerances are much better than what you mentioned. It is in the range of 0.01mm (0.0004") for the critical dimensions.

Dan

#### RICH

• 7,412
##### Re: Inscribed circle, what am I missing?
« Reply #13 on: December 03, 2010, 06:28:38 AM »
Dan,
True if you use the tip radius, the range on tolerances vary depending on the tolerance class, insert shape and size.
Let not your heart be troubled as the manual will get fixed. Practically speaking, I am thinking all this will boil down to LT's displayed image size of the insert.
RICH

#### RICH

• 7,412
##### Re: Inscribed circle, what am I missing?
« Reply #14 on: December 03, 2010, 07:39:53 PM »
Dan,
Here is what I found.......thanks for bringing attention to the problem.

http://www.machsupport.com/forum/index.php/topic,5767.msg113278.html#msg113278

RICH

#### Dan13

• 1,208
##### Re: Inscribed circle, what am I missing?
« Reply #15 on: December 04, 2010, 01:02:44 AM »
Hi Rich,

Thanks for finding this. Can't take the credit for this, as Jim is the one who found this

As to the tool inserts, the world standard to define the dimensions of inserts is by using the inscribed circle, (except for parallelogram shaped inserts). It is coded in the number of eights of an inch. It is usually a sequence of three numbers along with insert thickness and tip radius. In metric system the insert is defined by the cutting length in mm along with thickness and tip radius. Machinery's Handbook has a good description of the American standard.

Dan

#### RICH

• 7,412
##### Re: Inscribed circle, what am I missing?
« Reply #16 on: December 04, 2010, 06:26:29 AM »
Thanks for the info Dan. Only Art can say what is actually used by LT.
RICH

#### ART

• 1,700
• Tough as soggy paper.
##### Re: Inscribed circle, what am I missing?
« Reply #17 on: December 15, 2010, 06:46:14 PM »
Hi Guys:

Srry, havent checked this forum in a bit. "Inscribed Circle" is the circle inside the tool tangent to its edges.. as per standard..

Basically it is used only to specify the tool size, but once the tool is created, only the tool itself is used in calculations, LTurn
is really a complex collision calculator.. All of its paths are the collision responces from the created tool to the part..

Back to my bevels..

Art

#### RICH

• 7,412
##### Re: Inscribed circle, what am I missing?
« Reply #18 on: December 15, 2010, 07:56:47 PM »
Thanks for the clarification Art,
So noted in my manual ........page 16

RICH

#### Kingjamez

• 13
##### Re: Inscribed circle, what am I missing?
« Reply #19 on: December 15, 2010, 08:19:07 PM »
Thanks for the clarification Art,
So noted in my manual ........page 16

RICH

As I have been saying for this ENTIRE thread, rev 8 of the manual DOES NOT say that!!!!! The manual says over and over the EXACT OPPOSITE of the definition given by Art above. I don't know how I can say that any more clearly so that you'll get it.

-Jim