Dovetails – A question

[SaxalbyParticipant @saxalby]

[SaxalbyParticipant @saxalby]

I have just noticed (after owning them for 20 years) that the dovetails on the lathe and mill are 60 Deg. My Boxford shaper however uses 45 Deg. dovetails, except the vice which has 60 Deg.

What is the perceived wisdom, if any, as to which is used on a machine.

Barry

[Keith LongParticipant @keithlong89920]

I'm glad someones asked this as I was wondering as well. The only thing I can think off that dictates it, is the geometry of the assembly – ie whether there is enough depth in the part for 60 deg slides and still allowing sufficient depth of metal over the dovetail such as in a T slotted cross slide. The other thing is that 45 deg slopes will put more load at 90 deg to the dovetail when the gib is tightened than a 60 deg will, which may be an issue in some cases.

Keith

[Sub MandrelParticipant @submandrel]

Some machine tools work perfectly well with 90 degree surfaces (e.g. mini lathe saddle which is also guided by an inverted V, a la Boxford) – it all depends on the overall design and duty. A steeper dovetail puts more force into horizontal location of than parts than vertical location, and vice versa. 45 degrees would be equal in both planes, which is unlikely to be the optimum but is probably a best guess if you don't know what forces will be applied!

Neil

[SaxalbyParticipant @saxalby]

Thanks guys, never though about the difference in the forces acting in the various planes.

Barry

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