Machining a radius

[peterhodParticipant @peterhod]

Hi

I have a wheeling machine (English wheel). The wheels are 8″ top 2″ bottom.

I want to radius the edges of the wheels to soften the edge so the edges don’t leave lines.

I can’t use a ball turning attachment as the wheels are to big. I could grind a form tool out of H.s.s but that won’t work on the upper wheel as it is ground and hardened and anyway I want a nice radius!

I can’t seem to find any carbide tools with suitable inserts. I did find one tool but £212+vat is a bit outside my budget!

 

I would ideally like to buy something off the shelf. Any advice?

 

Thanks

 

Peter

[JasonBModerator @jasonb]

Grind the form tool from carbide not HSS

May work holding a TCT router bit in the toolpost and use that as your form tool, Though I have only done that on unhardened steel.

Work out a set of co-ordinates to machine the curve in a series of steps with a carbide insert and then use abrasive to blend the resulting stepped surface smooth

[Martin ConnellyParticipant @martinconnelly55370]

Anyone local to you with a CNC lathe that can help?

Martin C

[Martin KyteParticipant @martinkyte99762]

Hand turn them

[duncan webster 1Participant @duncanwebster1]

What Jason said, but I’d take off the steps with a file. Just make sure you have a good handle on it. Single cut file for preference.

[JasonB]

On JasonB Said:

Grind the form tool from carbide not HSS

May work holding a TCT router bit in the toolpost and use that as your form tool, Though I have only done that on unhardened steel.

Work out a set of co-ordinates to machine the curve in a series of steps with a carbide insert and then use abrasive to blend the resulting stepped surface smooth

A combination of several of these might do the trick. I think my DRO does stepped curves. Also liking the router bit idea. Using a file on the lathe is a no no for me. I used to do it but was careless one day and picked up some bruising and cuts on my hands. Luckily nothing more. I keep the guard down nowadays.

 

One way might be to mill the edges on a rotary table. with a suitable cutter. I’ll look what cutters might be available.

 

Thanks to all

 

Pete

[bernard towersParticipant @bernardtowers37738]

If you fix a radius point to the bed of the lathe  and have a pivot against the crosslide you will get a radius equal to the length of the pivot rod as you feed the tool across the workpiece

[old martParticipant @oldmart]

Unless you have a large DSG lathe, it would be extremely difficult to turn the rads on a hardened wheel. I would use one of my 10″ diamond files and a low speed in the lathe, say under 100rpm and gently form a small radius. Then the surface would need finishing with progressively finer wet and dry paper, with the lathe suitably covered to keep any abrasive dust off it. A machine shop with a cylindrical grinder would be able to do it for you if there is one handy. The large wheel should be plenty wide enough when used with the smaller rounded profile wheels to not allow the work to come near the corners.

[bernard towersParticipant @bernardtowers37738]

Sorry Old Mart thats a right faff and would not be a measurable rad just do it properly it doesn’t take that long and the tools are there for the next time

[Author]

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