How on earth do you mill a curve? (machinist question)
 

I've got myself a lathe/mill combo (well, to be more precise it's a Unimat SL, so it's really a 1/3rd scale lathe/mill combo, just about big enough to sharpen a pencil... but what a lovely wee toy) and I've been mucking about with it. Turning's simple enough, and I've done a few bits of reasonably succesful milling with a small end mill, but I can't get my head around how to machine out a curve.

I want to make myself some aluminium brackets with curved ends y'see. Trying to do it with the table always gives a horrible wobbly line at best, but that could be down to be being completely rubbish... CNC is obviously out of the question, though it's been done with stepper motors it doesn't make any sense given the quality of the hardware. So, how is it done? I've thought maybe move the work not the tool, but I can't see any easy way to do that. I can see some ways of making something that'd maybe work, as long as there's a hole in the middle of the piece...

Re: How on earth do you mill a curve? (machinist question)
 

Good morning.

You need a rotating milling table, these are some available that are not too expensive but you will rarely use it.
If I were you I would mark out the work & mill the curve as close as you dare, & then finish by hand using a file.

I have a 4.5 inch Boxford lathe, which although constructed to toolroom standards does show it's limitations when doing anything other than normal turning i.e. turning tapers or thread cutting.
Machines such as yours which are intended for hobby use tend to be very time consuming particularly when milling. So often one has to 'cheat' when it comes to machining a radius if extreme accuracy isn't required.

For a good range of affordable machine tools & accessories try www.rdgtools.co.uk. They will probably have anything you require.

I must warn you that machining is addictive, & it's easy to get carried away & spend a small fortune on things you will never use:D

Cheers.

Re: How on earth do you mill a curve? (machinist question)
 

Like the man says,for the cost the extra kit it would probably be cheaper several times over to get the whole job done by a local engineering firm. An alternative Andy is wait till a local firm is closing down or see if there are any auctions for engineering kit i.e ex MOD stuff is good

Re: How on earth do you mill a curve? (machinist question)
 

Rotary milling table as mentioned,(aaw such sweet memories of my apprentice years!) Another method although a bit drawn out, is to mark the metal to be cut with the desired curve profile and niblbe away at it with cutters taking off a series of "flats" gradually as the flats merge in to each other the finishing curve can be tidied up by filing or grinding.HTH.


(What's he building now?????:confused::))

Re: How on earth do you mill a curve? (machinist question)
 

In this weather?


A roof

Re: How on earth do you mill a curve? (machinist question)
 

Nah, he's replaced everything else on the SV.


The time is now to do his version of a Vyrus milled alloy frame.
I expect to see this unveiled for the Ice Cream Run! ;-)


http://www.moto-station.com/ttesimag...3_2v_st1pz.jpg

Re: How on earth do you mill a curve? (machinist question)
 

Or go to a college machinery evening, where you allow to make full use of the workshop. My college currently does this.

Re: How on earth do you mill a curve? (machinist question)
 

At first glance at the thread title i thought you were hacking down a curvy to make one of them horrible pointy jobbies :lol:

Re: How on earth do you mill a curve? (machinist question)
 

What he said. That's the way I used to do it (when I had access to a mill).

Re: How on earth do you mill a curve? (machinist question)
 

I really miss having access to workshop facilities. When I worked for Leyland I had the benefits of a whole prototype department geared up for building trucks/engines/gearboxes etc. So special tooling, gear cutting, access to metallurgist for advice on materials, and a huge source in the material stores, heat treatment and plating. Oh happy days.

Then when I started with GEC similar facilities available but simply huge. Set up for
machining turbines and generators so 40ft between centres, vertical borers that can turn 30ft diameters etc. There the welders were top class.

Now, I only have access to my garage, bench grinder and a file are the limits of my metal shaping. My local colleges offer nothing. I keep looking out for a decent lathe and milling machine but I cannot justify the space/cost. Anyone want to give me a boxford or colchester type centre lathe with metric and imperial screw cutting and a cnc milling machine.

Re: How on earth do you mill a curve? (machinist question)
 

Oi, get to the back of the queue! ;)

Not that I know how to use them, but I'd learn. Quick.

Re: How on earth do you mill a curve? (machinist question)
 

Thanks for the advice folks, much appreciated. I'd seen rotating vices, but I don't quite understand how you use those to mill a full semi circle, say to round off a metal strip. It seems like the tool would foul the jaws, unless it's possible to mount the work offcentre? Can't quite get my head around it.

The reason I went with such a totty wee machine is just space, I'm already kind of cramped in the garage so this is ideal, it's either a small one or none at all for now. Price, too, it was very cheap. It's actually surprisingly good at turning though, even in steel, better in aluminium obviously. Not very good at milling, really... But it's so cute :cool: Plus, since I'm not used to the real thing, I can forgive its weaknesses more easily, Timwilky would probably hate it. I've tried to find local courses etc, for welding too, but no luck so far.

I could get the work done professionally but there's been a load of times over the last few years when a lathe or mill would have been really handy, making wheel spacers and the like, and I end up doing stuff by hand or with an angle grinder, which isn't so great. It's not really about saving money, I don't see that happening, it's more about convenience. Also, I like DIYing stuff. Obviously! Having said that, if I'm succesful with the wheel spacers I'm about to make myself (when the ally gets here) then that'll be about 25% of the way towards paying for itself.

Plus, it's already 30 years old so it shouldn't be depreciating fast :D