What is overcut for threadmills?

[Sbarner]

Hi All,

 

I've been exploring the use of overcut in the threadmilling. What is it? The help thing says "Increases the ID on an internal thread or decreases the diameter on an external thread"...(or something like that. But what is the purpose? Why not just use wear comp? What does the value that I enter in the overcut field actually represent? Thanks.

[jeff]

if you are cutting a 1/2-13 id thread (for example) you can put something like .004" in the overcut to make the thread size .504" diameter

 

Why not wear? some controls don't like cutter comp on a helical move.

[Sbarner]

Interesting. I just made a quick threadmill toolpath. The comp move is a straight line move before the helix begins. This is a Haas post. My control won't allow comp to begin on an arc...this is something I know by heart. Perhaps we're talking about uber-old controls, then?

[Cad-Camr]

Ideally your entry arc is at 180 deg from start point with a 1/2 pitch move in Z. If you check perp entry you should be able to use comp.

I have used overcut in certain cases to adjust for any radius present on the insert.

[Rocketmachinist]

Yea, with the Haas you have to have a strait line move greater than the radius to turn on cutter comp. The nice part about cutter comp wear is you leave the diameters in the machine zeroed. So if you need to comp out .004 then the machine will at least only have to do a .002 move to get comp working. It beats the hell out of the regular cutter comp because it's really easy to do small holes.

[Scott Lundin Shopware Inc.]

I use overcut when thread milling an OD thread where I chain the nominal diameter instead of the minor diameter. I put the thread height (radial depth) in that field.

[[email protected]]

I always use Points for threadmilling geo, that way it opens another field for you to type in a diameter. I got used to doin that in earlier versions before the "Overcut" option then you didn't have to manually change your circle geo, you could just type in a different dia in the threadmill parameters page. Overcut option does away with that, but its just habit for me to pick points now......guess its burned in my little brain

[Jayson Kramer]

Now how is this for a thought like cut tapes have GH series for overcut for plating. is another way to look at it.