Slant vs. Flat Bed Lathe

[vmatos]

What are the advantages/disadvantages of these two types of lathes?

[Fred the thread]

Sometime during the last century, engineering workshops were expanding - yes! it really did happen - and they were reaching the limit of how many lathes that could be crammed into a restricted space.
The machine tool industry them came up with the bright(??) idea of reducing the footprint of lathes, by slanting the X axis. To make it possible to offer the biggest number of tool stations and allow access to the turret in order to mount and change toolholders, they invented the disc turret and mounted it on that side of the centreline of the spindle which is away from the operator.
However, because they didn't think it through considering all the functions required by a lathe, they positioned the turret in the wrong place! Mounting the turret to the rear of the bedway, means that when the spindle rotates forwards (top coming) M03 in CNC code, it forces the operator to mount right-hand (the industry standard) toolholders upside-down, so that the tangential cutting force is trying to lift the toolholder and the turret away from the bed. This causes an even bigger headache when thread turning, as vibrations offer occur when using right-hand toolholders, threading towards the chuck, to make right-hand threads. To use a holder the correct way up (cutting edge facing towards the sky) it means that a left-hand toolholder has to be used and the cutting direction then must be away from the chuck to make a right-hand thread.
Flat bed CNC lathes are far more stable as the toolholders are mounted the correct way up. That ensures the tangential cutting force is pushing the turret down onto the bed, where the biggest surface area of contact lies.
It is quite rare to suffer vibrations on machines of the flat bed type when thread turning whereas slant bed types almost guarantee problems when thread turning.
So, machine tool industry, open your eyes and switch your brains on - engineering is shrinking - so please let us go back to common sense and bring back the flat bed style lathes! It doesn't matter that they need an extra square foot of floor area, because there is plenty of spare room, and there will more than likely be more spare room before this recession os over.
Fred the thread

[vishnu]

You are absolutely right regarding the threading problems and also wear and tear from the downforce on the Z axis is minimised on a flat bed. The only problem would be cleaning the Swarf & chips on a flat belt else the flat bed is better, rigid and economical that the slant bed.

Vishnu