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Wondering about Lathe spec's, "swing over bed" and "swing over gap". What is swing over gap mean?
Buck
Buck
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Meaning Of "swing"
- Thread starter GarageWrench
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Bill Gruby
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Some lathes have what is commonly known as a "Gap Bed". There is a section of the bed just in front of the head stock that can be removed at will to accommodate larger diameter material. The section is removed and a "Gap" is left. The "Swing over the Bed" refers to the largest diameter material that the lathe can hold. Hope this helps?
"Billy G"
"Billy G"
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Never seen "the gap bed" before, thanks Bill
Buck
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Bill Gruby
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That is good advice. The swing over the Gap is very limited in length. The swing over the bed is the second dimension in lathe sizing. It is the total length the bed will allow. This is a Gap Bed Lathe.
"Billy G"
http://www.sterlingmachinery.com/9770/Leblond+24"+Gap+Sliding+Bed/
"Billy G"
http://www.sterlingmachinery.com/9770/Leblond+24"+Gap+Sliding+Bed/
Old gap bed lathe.
also be sure to check the manufacturers specs for total swing. on old lathes they are usually bigger than than designated (a 12" L&S would swing 14 1/4"!). newer ones will sometimes swing less, or just barely. I had a clausing that was a 12" lathe, but only just. Some older English lathes use the radius a (the distance from center line to the ways). so be mindfull of that.
also be sure to check the manufacturers specs for total swing. on old lathes they are usually bigger than than designated (a 12" L&S would swing 14 1/4"!). newer ones will sometimes swing less, or just barely. I had a clausing that was a 12" lathe, but only just. Some older English lathes use the radius a (the distance from center line to the ways). so be mindfull of that.
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....and another figure of merit is the "swing over carriage" or "swing over cross slide" that really limits the diameter that you can turn between centres.
The "gap" only helps for face-plate turning, on some a chuck is too wide for the gap......
-brino
The "gap" only helps for face-plate turning, on some a chuck is too wide for the gap......
-brino
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Many Asian lathes have a removable gap. My 16" Grizzly will swing 24" diameter x 4" deep in the gap if I'm mounting the thing on the face plate.
It is true that there is a gamble about the gap piece fitting EXACTLY into the bed after you remove it. Be sure everything is VERY clean before trying to refit the gap piece. Fortunately,mine went back in perfectly,but we had an identical lathe at work which the gap did not go perfectly back into. There was a bump in the bed after we had to remove the gap for a large diameter job. The only cure would have been a tricky job of machining a little off the bottom of the gap piece,while trying to ensure that the gap piece would still be parallel with the rest of the bed afterward. We got a better lathe soon after the gap problem,though.
I suppose that when the bed is ground,and possibly induction hardened with the gap piece at the factory(got those 2 processes in reversed order!),there are stresses introduced into the gap piece that are released when it is unbolted.
It will not do to just leave the gap out of the lathe,as the carriage will run out of rack gear before it gets close enough to the headstock to do short work. The English have always been big on gaps,and that is probably why they put the carriage handwheel on the right side of the carriage. They will not run off the rack gear.Myford lathes have a permanently open gap with no gap filler block. So do many other English lathes,especially the hobby size ones,so you can turn the larger model locomotive wheels on them,or larger flywheels for model engines.
It is true that there is a gamble about the gap piece fitting EXACTLY into the bed after you remove it. Be sure everything is VERY clean before trying to refit the gap piece. Fortunately,mine went back in perfectly,but we had an identical lathe at work which the gap did not go perfectly back into. There was a bump in the bed after we had to remove the gap for a large diameter job. The only cure would have been a tricky job of machining a little off the bottom of the gap piece,while trying to ensure that the gap piece would still be parallel with the rest of the bed afterward. We got a better lathe soon after the gap problem,though.
I suppose that when the bed is ground,and possibly induction hardened with the gap piece at the factory(got those 2 processes in reversed order!),there are stresses introduced into the gap piece that are released when it is unbolted.
It will not do to just leave the gap out of the lathe,as the carriage will run out of rack gear before it gets close enough to the headstock to do short work. The English have always been big on gaps,and that is probably why they put the carriage handwheel on the right side of the carriage. They will not run off the rack gear.Myford lathes have a permanently open gap with no gap filler block. So do many other English lathes,especially the hobby size ones,so you can turn the larger model locomotive wheels on them,or larger flywheels for model engines.
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On my Enco 13x40 lathe (with it's Grizzly manual), once the gap is removed, it is recommended that it is never replaced. The manual says that it is not likely that it will fit the same way as before it was removed. Seems to me that the feature is much less useful if you should never remove it... but what do I know?
GG
GG
