a. Friction guide ways
b. Antifriction guide ways
c. Frictionless guide ways.
Friction of Guideways
Friction guide ways are those wherein there exists surface contacts between the guide ways and the slide. Such guide ways finds its application in conventional machine tools because of their low manufacturing cost and good damping properties. These guide ways have varying coefficient of friction and operate under condition of sliding friction. In such guide ways the co-efficient of friction varies with sliding velocity.
There are four distinct types of friction guide ways based on their cross section. They are
a) Vee guide ways
i. With apex upwards
ii. With apex down wards (Inverted vee)
b) Flat guide ways
c) Dovetail guide ways
d) Cylindrical guide ways, and combination of these.
All these have distinct merits and demerits over each other. Some time it becomes desirable to use a combination of these guide ways.

Vee Guideways
The most widely used guideway on machine tools is Vee or Inverted Vee type as shown, in fig. 4.2, particularly on lathe beds. The Vee type guideways are advantageous because of the self adjustment action due to the weight of the guided parts and therefore the possibility of any play is eliminated. With Vee guides having its apex upwards there is no chip falling or chip accumulation. But lubrication in such cases is difficult. Such guideways donot check the over turning tendency of slides or guided parts. Vee type guideways wears away rapidly due to lack of bearing surface and is difficult to manufacture.
Cylindrical Guideways
Cylindrical guideways offer restraint free guidance fig. 4.5. This fulfills the conditions of kinetic principles being fully, constrained. However high accuracy of manufacturing is essential and hence are expensive. Cylindrical guideways are very efficient for short traverse and light loads. It cannot be used for long traverse and heavy loads because the guideways may sag or bend in the centre of the span under the load.
Dovetail Guideways
Dovetail guideways are preferred when both horizontal and vertical location of the moving parts is considered essential. The guideways have large load carrying capacity and tend to check the overturning tendency under eccentric loading. Fig. 4.4.
In the case of inverted Vee type guideways there is possibility of falling and accumulation of chip, and lubrication is easier.
Flat Guideways
Flat guideways are easy to manufacture and offer a large bearing area, than other guideways and hence suitable for heavy load transmission. Although Vee type have certain advantages, it is the flat or the dovetail type that are used in CNC machine tools. However chip accumulation and lubrication problems are serious. In addition flat guide ways do not wear uniformly. Jibs are used to ensure accurate fitting of the slide on the flat surface. Fig.4.3.
Fig. 4.3 : Flat type guideways