Radius Tool

What kind of tool or method would be best to make a radius on something like this please?

Thanks

Edited By Dave Cee on 26/01/2017 15:02:06

Aren't you already creating a radius on the plate with the grinding wheel dia.? If I've got the wrong end of your question then you could use a boring head set up on the mill with the cutter set to the required radius, or even a fly cutter, also maybe a rota broach if you can borrow one of the correct diameter.

​George.

a) mark it out accurately and saw / grind/ file to the middle of the marked line. To mark out, pointed dividers set to radius with a vernier or digital caliper will be quite accurate. locate one point of dividers in a centre punch divot and scribe your line. To help see the line better, colour your plate with permanent marker or marking out fluid or engineers' blue prior to scribing. Also, when approaching the line in final filing, use 10X optical magnifier of some kind.

b) send a DXF file for it to your local wire edm house, arrange money transfer, and wait for the postman

Good luck JD

Whoops sorry people.

I meant the brake wheel on the end of the grinder.

I don't have a mill as yet. Have a good lathe though.

You could try a form tool but sounds hard work.

I have tackled this sort of job by creating a spreadsheet of feeds to form a semi-circular arc from the circle equation and used the handwheels and a lashed up DRO using a digital caliper for the longitudinal axis. That works fine - gives you a stepped approximation to the curve that you file to a smooth shape afterwards.  I can give you some further information on doing this if you want.

Nowadays I'd just give the problem to my CNC...

Edited By John Haine on 26/01/2017 16:00:06

If the radius matches a standard woodworking TCT router ball bearing bit you could do both sides then finish with files..

10mins in here :

As John H says work out a few co ordinates at regular intervals which will give you the basic shape then blend further by eye and finish with a file.

This shape

use these co-ordinates

As a complete beginner I think I'm out of my depth on this one for now

Thanks for the replies guys will do some more research.

Dave.

It really isn't that difficult. I cut a profile that method on one of my first projects..(and I still don't know what I'm doing most of the time). No cad software so I drew it out on a scabby bit of graph paper and worked out the depth and length of cuts from that. Yeah, a lot easier with a DRO t keep track of the numbers but more than doable without. You can see i crossed each out as i got to it:

Have a look at this **LINK**

its for a ball end but looks like it could be modified to make the radius on the handle.

You say you dont have a mill but if you have a drill press you might be able to drill a tapered hole or hold the taper bit in the chuck/collet on the lathe and clamp the workpiece to the toolpost.

Edited By Dennis D on 26/01/2017 18:06:02

Instead of calculating co-ordinates just use a fixed template (use your tailstock to mount it, it can be a drawing on card!) and a wire bent pointer from the tool-holder,

- Nick

One of the difficulties with questions like this is depends on working out what is meant. In this case, even when we are directed to the part referred to as 'this' we find a part with a radius all round the outside, and radii inside the outer edge and outside the inner one. So which radius needs to be created? This lack of precision can be baffling, especially to any beginners, non-english speakers, etc.

My advice is to stand back from your question before you post it, and think how it might be interpreted. Add a few ounces* of clarity and you might just get several hundredweight* more sense in the responses.

*And for beginners and non-English speakers these are old measures of weight - you might think 'spoonfuls and buckets'.

Cheers, Tim

This is part of an email that Gary from eccentric engineering kindly sent me.

The brake wheel is just a large diameter aluminium disc cut from a piece of bar, I rounded the circumference on it with a radius form tool.

The rest of making it etc I am comfortable with doing.

I googled radius form tool but lots of different things came up.

Cheers

Dave.

As the actual radius is largely cosmetic, I'd form the curves by hand with a graver and my GHT hand turning rest.

Cheers,

Rod

I've never seen a brake wheel before . What is it for ?

It allows you to brake the grinding wheel, and break your wrist, all at the same time?

Andrew

Not if you put your hand underneath so it was trailing surely ?

Dave,

Although many of them are spoked [and therefore, potentially, even more risky], you might consider salvaging a hand-wheel from a sewing machine.

MichaelG.

Easiest way for a beginner to get the job done with limited machinery might be to set the aluminium disc up in the lathe, probably mounted on a rough mandrel made from a bolt and nut, then by setting the top slide to progressively different angles, go around and machine a series of small flats on the OD approximating the shape you want. Start by setting the topslide to 45 degrees and make a large chamfer across half the OD surface, then move the top slide around to 30 degrees and make another smaller chamfer, then 15 degrees and repeat. Then move the topslide around to the the other side of the job and repeat teh process. Once you have a nice series of flats approximating the radius you want, you can finish the job off with a file while the job is spinning. It will help to make a rough radius gauge by drawing up and cutting out a piece of cardboard or plastic ice cream container etc etc just to make a reference to work to.

Going slightly off on a tangent, why would you want a brake wheel on a grinder, what's wrong with letting it run down when not under power?

Tony