Choosing and buying a milling machine

You will know how much space is available in your workshop for the overall dimensions of the machine you can accommodate but don't forget to allow for the table to be at its extremities of movement in both directions. Milling machines can be deceptively heavy and can be top heavy and therefore difficult, and dangerous, to move. Make sure your workshop floor will take the weight. Don't buy a three phase machine unless you have the supply to suit. There are many differing styles of milling machine and ability to do heavy work is the one factor which might influence your choice. If much of your work is in softer materials like plastics aluminium or wood then one of the drill/mill hybrid machines may well be sufficient – they are cheap, light and versatile but they loose a lot of accuracy from lack of rigidity. The mill/drill hybrid often has a cylindrical column which does not allow you to move the head up and down without it turning and loosing your settings. Under heavy loads the column can move when you don't want it to and that can be a disaster! Smaller machines can be very rigid with dovetail vertical columns but will inevitably the lack power to drive big cutters. If your work pieces and cutters are small then one of these could prove ideal. If you are going to do heavier work and want accuracy and finish the a heavy milling machine is the only answer. Turret mills like the Bridgeport have a very heavy column and bed with a versatile turret head with variable speeds and the ability to swivel in two planes on some of them. A vertical milling machine is one of the most popular and versatile and they often come with useful changeable heads to carry out such operations as slotting. A horizontal milling machine is unlikely to be of great use in the home workshop as they are heavy and somewhat restricted in what they will do. Cutters for horizontal machines can be expensive and take a lot of sharpening. Many horizontal machines come with a vertical head which gives the best of both worlds but do not be confused – the universal milling machine is not one of these but has a swivelling bed to facilitate screw milling. One facet of the horizontal machine is its ability to be used as a horizontal borer with cutters mounted directly in the spindle, if this is something you want to do keep an eye out for a boring head – expensive but indispensable for these operations. Look for accessories which can be expensive if you have to buy them later. Collet chucks for end mills and slot drills are essential. Keep an eye out for the ability to fit a morse taper in to the quill – there may be an adapter with the machine to enable this. A machine vice in good condition is a must, look for one that is big enough for the machine bed and for your expected workpieces. A dividing head and/or rotary table can be very useful, dont forget the matching tailstock for the dividing head. Look for sets of work clamps and tee slot nuts. A box of milling cutters may look insignificant but could save you a fortune. If possible run the machine to check for excessive noise and to be sure all of the feeds and speeds work well. Also, if it is fitted be sure to check the operation of the rapid traverse drives especially the vertical travel which is the heaviest loaded – the clutches can often be wanting. Make sure the table is in good order with not too many gouges where the operator has run the cutter in to it. Check the table slideways for wear by putting a dial gauge against the side, near the end and manually heave it back and forth – do this at both extremities of travel and in the middle where most of the work takes place. Often one finds the wear has been taken up by tightening the gibs and this will be evident when you find tightness in the travel at the extremities. Try lifting the end of the table up and down to check for play in the column. A dial gauge can be used to check for wear in the head stock spindle and don't forget the overarm support bearings on horizontal machines. Be sure to get all the appropriate operating handles for speeds, feeds, rapid travel and bed locks.

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