Just to explain an apparent contradiction:
- John (DMB) says: 'Do not try to use end mills on your lathe without a proper milling chuck or the necessary drawbar to hold chuck tight to the mandrel.'
- Paul says: 'As for cutter holding, if you are careful you will be fine. When I first got the micro mill it came only with a Jacobs chuck and I couldn't afford anything else so that was used for end mills, slot drills and drills! I never had any disasters and the nay sayers will proclaim that was pure luck!'
They are both right.
One of the shortcomings of milling on a lathe slide is the strong temptation to hold the cutter in a 3-jaw chuck. They're far from ideal as tool holders, because cutters are liable to come loose due to vibration and being pulled backwards and forwards by cutting forces. And vibration is highly likely because milling slides aren't very rigid.
However, on my lathe there was no danger of a done-up tight milling cutter coming out of the 3-jaw because the slide's lack of rigidity bouncing about on the saddle made it impossible to take heavy cuts. But, on a bigger machine with a more rigid slide, there's a real risk of cutters coming loose because heavier cuts can be attempted.
Similar coming out issue with milling cutters in drill-chucks. Light milling is possible, but drill-chucks aren't designed to take sideways forces or vibration. As drill-chucks limit how much metal a real milling machine can remove, proper milling chucks with drawbars etc holding cutters as firmly as possible are the rule.
Of course shortage of cash and space often means making the best of what we have! Just stay within what the set-up can cope with. The limitations will become obvious when you try it, just don't have high expectations.
Finally, using a lathe slide requires a certain amount of skill. Common learner mistakes are taking cuts that are either too small or too big. Lack of rigidity makes it hard to strike the right balance. Too small is the worse error because the bad effect is hidden. It might seem that lightly used tools will last forever, actually the opposite is true. Rubbing the cutting edge of tools blunts them, and they have short unsatisfactory lives. Apply more force to make them cut and they last longer. Too much force is bad for other reasons. Thing is milling slides is may not be rigid enough to allow decent cuts, so the new operator ends up struggling with a wobbly set-up and blunt cutters! I recommend learning to get the best out of the lathe first – getting a feel for cutting metal – before attempting a milling slide. They do work, but mine had to be seduced.
Dave