Increasing swing on older cast iron lathes. How much is too much?

Of course, that there were some cheaply made older lathes in the past before the woodturning revolution with it's multiple facets and wide popularity. However when labor & materials were cheaper, the major manufacturers at the time seemed to over build their better quality smaller swing lathes. These lathes were essentially for turning spindles (not much large face work being done then), but they were made of fine grained quality cast iron with rugged bearings, castings and decent machining, yet often limited to a 6" throw and less than that at the tool rest.
There are a lot of these fine old timers around and reasonably priced at that. I suppose they could be easily and safely converted to a much larger swing and many have been, either outboard or inboard with raising blocks. I realize that how much larger the swing allowed depends on the lathe and its supports, the timber, the balance of the blank, the turner's ablility, the grimness of his facial expression and the decibels of his grunting and swearing.
What can you do to improve on the old machine's specs. for larger face turning? Are there any rules of thumb or warning signs and symptoms that you use to predict a particular face turning you can safely swing or for that matter that you've gone too far? (ie. before the catastrophe) :)
Turn to Safety, Arch Fortiter
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Hello Arch,
Welcome back to the group. I don't have any actual specifications on riser blocks, but I think that most of the time they are limited to 2" to 4", which increased the swing by 4 or 8 inches. It is not very practical to place a riser block under the tool rest banjo, so part of the limiting factor would be the strength of the tool post; i.e., I think on the smaller swing lathes, they generally had smaller tool rest posts, like 5/8" or maybe 3/4" at the most. Boosting an 8" swing lathe to 16" with the 5/8" tool post might bring on disaster is turning a 16" bowl blank at the furtherest edge of the tool rest. It will be interesting to see what other say.
Fred Holder
Reply to
Fred Holder
Most of the old ones allowed outboard turning of bowls. That would be 36" or 1 Meter more or less.
Some older ones were only heads - they were bowl machines. Some older ones were only spindle machines. So it depends. Some old ones weigh in the range of 1000 pounds. Most can use weight in the bases.
I can do 16" plates or 10" spindles / bowls. Plates can be 5" deep.
Martin (Owns a 1947 (birth date ) wood lathe my Dad bought.)
Reply to
Martin H. Eastburn
On Mar 27, 7:39 pm, "Martin H. Eastburn" wrote:
Here is a Powermatic 90 that has factory original riser blocks front and rear and a kit to extend the reeves drive system the additional 4" including the belt cover.
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I have discussed the performance of this lathe prior to trying to modify my own PM 90 and the owner reports there is no problem in any way with running this model modified to 20" swing (it is close to 600 lbs as is). I did locate a kit of all the factory parts required but it was almost 5 times what I paid for my lathe or a bit over $1,000 so I will have fabricate the modification myself.
Here is a DYI example to increade swing and length:
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In message , GDStutts writes
In my own case , I went for a simple design in oak, with extenders for the headstock and tailstock bolts.
Just cut a block to make a channel for head/tailstocks, do the reverse on opposite side, so you fit the lathe bed. Drill a decent size hole in centre.
Use an extender to increase bolt length, inside thread one end to match existing bolt, outside thread other end to match existing. Ideally drill a hole through the bolt and extender to allow for a split pin to ensure no unforeseen unscrewing.
Works quite well, all I need to do is find time to get to the lathe and play again, its been a year now, and withdrawal symptoms are setting in. I have enough wood for an item a day for the next ten year and I want to get started :)
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