Help! > Machines, Tools and Fixtures

How would You Do it?

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PaulR:
I need to cut a recess in my simple flywheel like the attached. I've done this before using either pointy left and right hand tools, simply digging in a bit somewhere in the middle of the area to be removed and working up to the inner and outer shoulders but I wonder what the effect of (gently!) using a parting tool (say 2mm wide) would be to make a better defined starting point? I guess there would be uneven load on the left and right edges but would it be significantly bad? 

Is there some other 'proper' way to do this operation on a lathe with simple HSS tools?

pgp001:
A parting tool will not work as there is no side clearance, so it will just rub.
I normally do it the way you have described.

Phil P

crueby:
I agree with Phil, I do it like you describe. Or, on the mill with a rotary table and end mills to plunge cut and rotate the part around. Lathe is usually quicker, unless the diameter is too small to easily do it on the lathe. There is what they call a trepanning tool, I think its like a parting tool but with the side ground back so it doesnt rub, but I have no experience with that.

ShopShoe:
I have done it as described, using HSS tools I grind myself.

That said, I just did a quick search for "trepanning tool" and found many, many different ones for sale by most of the vendors we use, both HSS ground tools and insert type systems. Faced with several parts to make with this feature I might make an investment to try something I can buy.....

I also seem to remember that the late sage "bogstandard" once posted a video that demonstrated an indexable insert for trepanning cuts, perhaps sold by ISCAR. That was many years ago, so I don't know if it is out there somewhere to find, and I don't know what the original title of the video might have been. Does anyone remember that?

Meanwhile, I never did find it hard to make a part as described above, just another challenge to reason out a solution to a problem.

ShopShoe

Zephyrin:
the tool is very easy to grind, with sufficient clearance on the left-hand side depending on the diameter so as not to rub, then just move the tool and with the lathe turning in reverse to finish the part near the hub.
making a clearance on each side risks weakening the tool with chattering if the metal is very hard and the cavity is deep.

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