Need tips in selecting lathes

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Mike Walsh
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Need tips in selecting lathes

Post by Mike Walsh » Sat Aug 09, 2008 4:00 pm

Sirs,

My club, the WFPRR, is looking for a lathe that can handle a maximum of 20" diameter drivers... If we are on the hunt for a lathe of this size, what would we be looking for in the product description? I've read around, and seen dimensions such as __" x __" with ___" bed.

Input would be appreciated!

Thanks,

Mike Walsh
www.WFPRR.com

Harold_V
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Post by Harold_V » Sat Aug 09, 2008 4:46 pm

Assuming you aren't concerned with a long machine, one that is suited for doing shaft work, seek a machine that has a center/center distance of something in the area of 30" or slightly greater. That will keep the OAL of the machine to a minimum, although as swing increases, so to does bed length. It is generally assumed that large diameter parts are generally long as well. Large parts often demand great center distances to allow for long boring bars and drills that are used from the tailstock. Said another way, you're unlikely to find a machine that will swing 20" that has a very short center distance. An example of a machine that might be suited could read 22" x 48". Bed length isn't a concern, but is an indicator of the overall length of a given machine. The shorter the second figure, the shorter, overall, will be the machine.

That being said, there are machines made that have a natural gap, so that a reasonably small machine can swing fairly large diameters, assuming they are short in length (like a driver). My Sag 12 (12" swing) Graziano is such a machine. The tailstock ways stop 12-5/8" short of the headstock, and the carriage ways are mounted well below the top of the bed, covered, so they do not interfere with swing. The 12" rated machine can swing 17½". Certainly not suited to your needs, but it is an example of the concept.

Graziano made larger models, including a 15" swing, made in the fashion. Such a machine would likely serve your needs, although it isn't likely to be found for a reasonable price, unlike larger machines.

There are large swing machines on the market that can be acquired for a relatively low price. They have been rendered obsolete by CNC machines, and are often too large for consideration by home shop types, so there isn't a strong market.

There are problems associated with larger machines, one of which is power. If you have three phase at your disposal, that won't be an issue. If not, you'll have to consider a rotary phase converter. A static converter is not a good choice for a lathe, due to the ever changing load characteristics. You are often limited to motor choices as well, in that large single phase motors are not common, and are expensive to acquire. They also may not be suited to the particular application.

Large lathes tend to be quite heavy, so you should have an adequate base on which the machine can reside. Handling can be troublesome, both in transporting and in installation.

It is often a good idea to buy a machine that is slightly larger than your maximum demand, to insure that you won't have problems with parts that may start life slightly larger in diameter than the finished product. Best to check any machine you find that you feel will serve your needs to insure that you can start with a raw casting and still have room for clearance.

Hope some of this helps----

Harold

kvom
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Post by kvom » Sat Aug 09, 2008 5:49 pm

You might need 11" over the carriage, depending on what type of machining you are doing on the drivers.

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MikeC
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Post by MikeC » Sat Aug 09, 2008 7:15 pm

Clearing 20" over the ways and being able to work 20" is actually two different things. If you can locate a 24-30" lathe, I think it would serve your needs. As Harold says, you don't need a long bed to do this kind of work, but your choices may be limited to what is nearby.

Good news is that big manual machines like this are usually dirt cheap when you find one.
18x72 L&S, Fosdick 3ft radial, Van Norman 2G bridgemill, Van Norman #12, K. O. Lee T&C grinder, Steptoe-Western 12X universal HS shaper, 16spd benchtop DP, Grob band filer, South Bend 10L

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boaterri
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Post by boaterri » Sun Aug 10, 2008 6:51 am

IF you can find a "ships lathe" (originally found on Navy ships) they frequently have a large swing and a short bed it might work welll for you.

Good luck,

Rick

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ALCOSTEAM
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Post by ALCOSTEAM » Sun Aug 10, 2008 11:16 am

Mike, as I have offered in the past, if and when the rare need arrises that you guys need something that large machined you need to do nothing more than ask. I also would be seriously concerned about where the WF&P would put such a beast, especially considering the current shop would not support the weight and anywhere ground level is going to give problems due to flooding. Moving a 10K + lbs machine to higher ground is not a spur of the moment thing.

I have a 20" lathe at home and a friend has machines up to about 30" swing. Moving a 19,000 lb machine nearly 100 miles was a feat in itself, but it was a deal that couldn't be passed up.

tim

Herm Williams
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Post by Herm Williams » Mon Aug 11, 2008 11:06 am

Another large consideration is spindle bore size, imho a very important point. Most of the large lathes I have seen have less that two inch bores while a four inch of the same or similiar spec's would cost about much more but be worth the extra purchase price.
re
Herm

Jose Rivera
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Here is what you need

Post by Jose Rivera » Mon Aug 11, 2008 11:23 am

You need something like this.

Best machine ever!

http://sfbay.craigslist.org/search/tls? ... uery=lathe
There are no problems, only solutions.
--------------
Retired journeyman machinist and 3D CAD mechanical designer - hobbyist - grandpa

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Richard_W
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Post by Richard_W » Mon Aug 11, 2008 12:28 pm

You would want at least a 24" swing lathe with 54" centers.


Richard W.

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