Need threadmill info

[Thoob]

I have a part that is 7" ID and I need to put a thread inside. This will be done on a VMC. The thread is a ball shape as in I need to use a 1/2"R tool to get the thread form. Hope that makes sense. The problem is I have a tool that is 5/16R and I wanted to know if i can do such a thread with that smaller cutter. Kind of like surfacing? I might be out on a limb here but I would think I could program that somehow?

[cunder]

The 1/2" radius almost implies You thread ia 1 per inch? This sounds like not enough info.

[Goldorak]

may be swept 3d will work

[Thoob]

TPI shouldn't matter to what I'm asking. The thread shape is not like your normal thread. Its a round bottom. 1/2 Rad, 1/2 thread depth on dia and 7" ID. I thought aboout using surface contour but not sure if that would work.

[hugh jars]

I'm assuming your cutter is something like a rounded off T-slot cutter with R=5/16 and that the cutter major diameter is over 1inch greater than the shank diameter so that you can cut 1/2inch deep.

 

Sketch up your thread profile on cad and position your cutter profile against it in as many positions as you think you may need to get the cusp height down to what is acceptable - probably an odd number - about 9 positions should be enough. Jot down the cutter centre positions. Thread mill using these figures for radius & depth with radius compensation off.

 

You will get a distorted thread form. If the cutter dia is small compared to the bore then the distortion is small but it's beyond me to quantify it.

[GoetzInd]

Keep in mind you will not be getting a true form if your using a t slot cutter since it is ramping.

 

Mike

[Metalmuncher]

If I understand right, I did something similar using 5-axis multi-surface and output in 3-axis. This might work for you.

[Thoob]

Ok I'll try that. thanks fellas.