Re: on bed design.

Gregg Eshelman

On 1/5/2016 1:17 AM, john kling [SOUTHBENDLATHE] wrote:

Looking at pictures of Hardinge lathes that have what looks somewhat
like a wide flat bed, I see that they have angles on both the front and
back side. In a sense this like having a single inverted V - with
several inches of metal where the peak would otherwise be. So I will
take the Hardinge off of the precision flat bed lathes. I have seen
pictures of 1900 Drummond lathes with a tube type bed. The pictures do
not reveal a slot in the "tube" - which I assume must be there to make
any sense as a design.
Before Hardinge went to the dovetail bed they used a flat bed with outward sloping sides and a slot down the middle. Commonly called a split bed. The exact same profile was used on at least two other makes of lathe so accessories are interchangeable.

The split and dovetail bed lathes mostly do not have any kind of a conventional saddle/carriage or any type of leadscrew or power feed. Accessories like cross slides or compound slides are movable along the bed but get locked in place while in use.

The lathes are intended to work on small areas of the workpiece. When they do threading, it's with an attachment that does thread chasing with a follower on a master thread mandrel, usually mounted on the left end of the spindle. Thus they cannot do things like cut long tapers or very long threads. Nor can they easily make full length turning cuts for doing things like rounding rough stock. Usually they're fitted with collets in the spindle for starting with smooth stock.

Some of the Hardinge lathes with dovetail bed have power feed, and the most desirable HLV-H model can also do threading without a chaser attachment. Their earliest dovetail bed lathes were essentially the same as the split beds with a different profile on top. Same accessories but also altered for the dovetail. Some accessories for the split bed had removable alignment blocks that could be swapped for ones to fit the dovetail.

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