How would You Do it?

[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.

[Jo]

Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges.  If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate  You now have a nice tool for cutting the flat face.


I regrind old centre drills to make these 


Jo

[PaulR]

Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges.  If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate  You now have a nice tool for cutting the flat face.
Jo

Sorry, being thick, as per.... you mean a regular D-bit with a vertical notch on the semi-circular end?

[PaulR]

Didn't know that was called trepanning (thought that was boring holes in skulls!). Just found this, which is what I was hinting at with a parting tool.

EDIT: Although I was thinking of moving it left and right as well

<a href="https://www.youtube.com/watch?v=6PcEBaset1I" target="_blank">http://www.youtube.com/watch?v=6PcEBaset1I</a>

[Jasonb]

I usually do it much as you describe except I don't swap between left and right hand tools. I work out towards the hrimwith the lathe running in the usual direction and in towards the hub with the lathe running in reverse. Saves time and you feed in to the same handwheel depth to get a flat bottom. Careful if you have a screw on chuck when runing backwards.

If the topslide is angles a few degrees you can also mimic the draft angle of the cast looking flywheel you are trying to make.

A mill and rotary table or a CNC are other options if you have them.

[Jo]

Make yourself a D bit with a square end out of a bit of silver steel or HSS, then cut a slight Vee shape into the centre of the square end leaving an inner and outer cutting edges.  If you want to be really posh you can slightly relieve the sides of the steel dowel and then you can cut the inner and outer rims as well. Heat treat as appropriate  You now have a nice tool for cutting the flat face.
Jo

Sorry, being thick, as per.... you mean a regular D-bit with a vertical notch on the semi-circular end?

See attached.

On a D bit there is only one cutting edge, on these there are two. It is worth radiusing the cutting corners.

Jo

[PaulR]

Thanks all for the replies, seems like what I planned to do (again) is as good a way as any.

Jo: Ah, I see that's a wider notch than I was visualising, so effectively it's a double headed tool. Problem is I'd need to make a holder for it as well but I like the idea!

Jason: Yes, that's what I've done in the past although with a bit more point to the tool - I don't recall running the lathe in reverse to do it though.

[Art K]

Paul,
I just happened to catch this post. I did something similar to what Jason did, I will put a link to my build post.
https://www.modelenginemaker.com/index.php/topic,3653.msg66100.html#msg66100
I was turning the flywheel for Val I have a lathe tool that is HHS and a fairly sharp tip. Used it like a boring tool on the outside of the lip running the lath in reverse. Then put the lathe in forward and turned the hub. I think I just happened to have that tool ground that way. It also helps that I have an indicator that clamps onto the ways to have the two halves match up.
Art
PS the setup is post #41

[PaulR]

Paul,
I just happened to catch this post. I did something similar to what Jason did, I will put a link to my build post.
https://www.modelenginemaker.com/index.php/topic,3653.msg66100.html#msg66100
I was turning the flywheel for Val I have a lathe tool that is HHS and a fairly sharp tip. Used it like a boring tool on the outside of the lip running the lath in reverse. Then put the lathe in forward and turned the hub. I think I just happened to have that tool ground that way. It also helps that I have an indicator that clamps onto the ways to have the two halves match up.
Art
PS the setup is post #41

Thank you Art. When running in reverse I take it you're working on the 'far side' of the rim so the same tool can be used (to cut on top as normal)? I don't think my cross slide will reach that far without swinging the toolpost round which then puts the tool at the wrong angle.

[john mills]

I would grind a tool out of either HSS  brazed on carbide (i have lots of plain grade) worn tips from when i did a lot of work on milling machines
shape to turn both in side and outer radius  i like a bigger radius in the corners with the lathe running forward only.

[PaulR]

I would grind a tool out of either HSS  brazed on carbide (i have lots of plain grade) worn tips from when i did a lot of work on milling machines
shape to turn both in side and outer radius  i like a bigger radius in the corners with the lathe running forward only.

Would this be a long thin tool shape like the one in Jason's photo that you angle depending upon which corner you're working on?