Internal radius cutter

I'm making a bit of a curved floor standing lamp for someone so thought it would be good to make a ring roller. The lamp will be made of tubing so i need to make three rollers with curved grooves to match.

In the last couple of weeks i've seen a tool somewhere (can't remember where) that will do this. So last weekend i bodged one up and today i had a go with it.

Here are a few pics of how far it's got.


The main bit is 20mm mild steel with 2 holes for some BMS turned down from 25mm to 16mm. This is cross drilled to take 8mm of tool steel for the cutter. The tip of the cutter sticks out 3mm to give a 22mm diameter cut.






This pic shows the cutter in position against the round bar (The bar was an old pin that held a 6 tonne wear plate in a crusher so may well be something like EN8)





Here it is in position with some 5" round that is being used and the long handle to turn it.





The three grooves cut for three dies.






Chopping it into 3 on a clarke 4 1/2" saw.




The first one ready to go back in the lathe to be faced and bored out.





To do the lamp i will probably just fix them up temporary to do the job and then carry on and make a tidy ring roller.

Thats a great little tool top job

Cheers Dave J, here are the finished'ish dies ready to fix to a plate and use.
The finish is a bit rough on the curved bits but i'll see how they go.

Nice wyn. Im not into machining, is that how a radius would be done like that normally?
I suppose you can change the radius, depending on the length of the tool extended out.

great minds think alike - http://www.16vminiclub.com/forums/viewtopic.php?t=15042&highlight= about 15 posts down is my design, although still not properly used it yet

I'm not too sure how they are usually done, Hitch, probably cnc. Yeah just push the tool out for a bigger radius.

Nice one chrisg, i'm sure i originaly saw something like it in a model engineering magazine. It was realy easy to make.

nice, I love simple bits of tooling like that, can save hours of work....

Hitch usual way of turning a taper/rad is on the compound slide, something like that id rough out then grind up a rad on a tool for finishing, though thats certainly not the only way offset tail stock or copier plate are a couple of other methods.....


not brave enouth to part them off wyn?

snowcat said:

not brave enouth to part them off wyn?

Click to expand...

No way

Never realy got on with parting off, would have saved seting them back up in the chuck with the DTI though.

im with you on that one wyn, i hate parting off. although i get better results with the tool upside down on the backside of the workpiece. i find it stops the workpiece trying to climb over the tool.

snowcat said:

nice, I love simple bits of tooling like that, can save hours of work....

Hitch usual way of turning a taper/rad is on the compound slide, something like that id rough out then grind up a rad on a tool for finishing, though thats certainly not the only way offset tail stock or copier plate are a couple of other methods.....


not brave enouth to part them off wyn?

Click to expand...

Thats what i'd always envisaged.

Turning isnt my forte, rough bits and bobs is fine, never really had much chance or need to do it myself. Especially anything accurate.

How have you secured the cutting bit in the 8mm cross-drilled hole?

I am unacquainted with the acronyms "BMS"and "EN8".

Thank you

The round bar has a threaded hole from the bottom right up to where the bit is. And it just has a bolt threaded up to hold the bit. I don't think any of the pics showed this.

BMS is bright mild steel
EN8 is a grade of carbon steel in the uk.

BMS, is 'Bright Mild Steel'
EN8, as a number i think is an European thing, medium carbon steel, probabaly just has an alloy number in the Us...for its composition have a look here