How do i cut a concave in a square block?

[NeoTech]

Hi everyone,

I have a little problem, i have a small BF20L mill, this is a Morsekone2 mill, and not the most practical to run a big multitooth carbide cutter in.
Here is the thing i'm trying to build a Pipe bender.. For this i have made a rolling die, with a radius cutter not much unlike the small ball cutter you find on this forum.

Now the problem, i need to cut a straight concave surface in a piece of  square stock. This will make up the "shoe" in my pipe bender. I have been pondering this problem for a while
but cant really figure it out. Anyone here know how i can cut a concave straight channel in my mill?

[jgroom]

If you have enough clearance the easiest way would be to stand the block on end and mill the groove with a boring head or small flycutter.

Cheers

Jeff

[sbwhart]

You can use a boring head like this.



Stew

[Anzaniste]

Clamp two pieces together and drill down the split line. OK you will get two components but a spare never goes to waste.

[NeoTech]

Thanks all of you!, it was using a boring head like that i was a bit.. well afraid of first, i have limited experience so i didnt know if it was a good way to go. =)

And clamping to pieces together is not a bad idea either, probably less stress on the tools that way. I have some experimenting to do.. Thanks! =)

You can use a boring head like this.



Stew

[PeterE]

There is also a third-ish way to do it, but it incorporates setting the milling machine head at an angle. This could be useful for large concave cuts. In this case the workpiece is clamped flat onto the table using suitable means, the mill head angled and using a suitable size tool passing over the surface.

The downside is that to get back to "normal" state, the mill head needs a careful tramming again to be properly vertical.

Just as an idea, of course.

BR

/Peter

[BillTodd]

I made mine using the lathe:

I don't have pictures of the process but the set-up was similar to this: using a long boring bar with the block mounted to the vertical slide:

[NeoTech]

There is also a third-ish way to do it, but it incorporates setting the milling machine head at an angle. This could be useful for large concave cuts. In this case the workpiece is clamped flat onto the table using suitable means, the mill head angled and using a suitable size tool passing over the surface.

The downside is that to get back to "normal" state, the mill head needs a careful tramming again to be properly vertical.

Just as an idea, of course.

BR

/Peter

I have actually considered this approach but as you say you will have a tramming hell in front of you afterwards, and last time i trammed the machine it took med a good 2 hours to get it within a couple of thousands...

[NeoTech]

I made mine using the lathe:

I don't have pictures of the process but the set-up was similar to this: using a long boring bar with the block mounted to the vertical slide:

Thats exactly the type of bender i'm trying to build. =)
That long boring bar setup i havent seen anyone do that before. did you make the boring bar? How is the toolbit setup in the bar? With an angle to the workpiece or a 90 degree?!

[BillTodd]

The boring bar is just a length of steel bar (1" 316 stainless I think). The cutting tool is ground from a broken  6mm (carbide) end mill. It's fitted in a cross drilled hole (90° but it probably could be anything) and held in place by a couple of grub screws.

The cutting radius was set my measuring how much stuck out of the bar. (getting the bearing fit required in the illustrated set-up was tricky ;))

That long boring bar setup i havent seen anyone do that before.

No originality here, that's a very old, standard lathe set-up

[wildman692]

The easiest way is to use a bullnosed end mill of the correct size. Nice bender by the way.