MetalworkingFun Forum

Fast forward almost 5 years.

I gave away the mill that started this thread to a colleague at work. I never did get the X axis lead screw nuts installed. I handed off all of the parts to him but he doesn't have the skills to complete the repair so I will be doing it for him. Of course I'll need a lathe and mill so I'll be getting a lathe in the fall and a mill sometime after that. In the mean time I practised using FreeCAD to model up the three major parts.

I have a question about boring out the large hole in the housing. It'll start out as a rectangular block of steel and I'm wondering if it's best to bore out the hole before the final shaping of the housing or after? I'm concerned about stresses being released and distorting the hole?  

Ed

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Thats a lot of material being removed, its going to distort. I'd rough drill the center, then machine the outside, then do the final bore.

(06-03-2020, 08:22 PM)f350ca Wrote: [ -> ]Thats a lot of material being removed, its going to distort. I'd rough drill the center, then machine the outside, then do the final bore.

Thanks Greg.
Would cast iron be less likely to distort?

Ed

Not sure Ed, haven't worked with large pieces enough to say.

Agree with f350ca. Rough bore, outside, finish bore.

As to distortion, much of that will be due to heat. Keep your chips small, and your cuts reasonable, and stress will be minimized. Use oil to reduce heat. Unless your chips are coming off blue and smoking, you will be fine.

Cast will be less susceptible to distortion, but if stresses get to high, it won't warp, it will crack. You can always recut threads if distortion is an issue, but a cracked part is scrap.

Gray iron tends to be more stable than steel, but it's expensive and creates one hell of a mess when machined. Not sure you could handle that Ed.

I would stick with steel for that part and follow the excellent advice already provided.

Tom

Yea, after checking the cost of a chunk of cast iron I'd need, I abandoned that thought. Already have the steel so may as well use it.
Thanks for the advise.

Ed