View Full Version : A good lathe of gunsmithing
June 17, 2005, 01:14 PM
I'm looking for recommendations for a lathe for barrel work. I was looking at Grizzly and a few others, but I'm unsure and it's a big investment. I would appreciate any help. Thanks
June 17, 2005, 02:10 PM
Examine import lathes very carefully. Many have metric compound screws with inch graduation rings (one crank of the compound or cross feed is not 0.100, but is 0.127 in, or 2.54 mm/2). Others do not have quick lock rings for zeroing (though they can often be modified).
The typical import tool holders are really lousy. Wedge (‘dovetail’) tool post clamp mechanisms are still about the best going. The piston clamps are probably next, followed by whatever ‘Quadrex’ crap comes with the typical import (one of the chief failures being a lack of any vertical adjustment except by shimming the tool holder).
You can look to the used equipment market, but many parts of the country never had a large machine shop/manufacturing base. High quality used equipment is often expensive (you are bidding against the parts guys who part out equipment to keep other pieces working) and can be worn. Tooling rarely seems to stay with the machines also (follow and steady rests, etc). It is possible to perform decent work with some of the imports, but a lot of extra measuring setup and alignment is often required.
There are kits made for some imports to get to all US feed screws.
June 18, 2005, 02:30 PM
Thanks for the advice. What brands specifically would you recommend?
June 18, 2005, 03:52 PM
This all depends what expense you are willing to go to? You can buy, as I did, an Enco Chinese lathe, but get it with a DRO, so you have zeroable measuring on all but the cross-slide and spindle. I have rigged a dial indicator with 4” of travel to following these latter two parts as needed.
Having used it, my criticisms of the machine are that it has too much vibration to produce smooth finishes and that the dials, though in English, are in 1/8" per turn calibration, with the exception of the tailstock, which has 1/10" per revolution. There is no carriage travel limit switch or spindle brake, so crashes are a real worry and you can’t time a thread to just stop at a fixed position. Instead you have to cut them from behind and heading toward the tail end of the bed (using an inside threading tool) if you don’t want to reduce the shaft diameter for stop space at the shoulder of a barrel.
The lead screw is 0.1" per turn, thank God, so you can cut English threads accurately, but there is no 127:1 gear mixed into the change gear set, so you can't get true metric threads; only very near equivalents. I made a table of the change gear ratios and the exact feeds for metric equivalents. OK for a class B nut or other short thread length, but not for anything long.
The gear box on the saddle leaks oil heavily, so I can't keep the sump filled. To cut vibration, I balanced the motor and pulley and built a much more rigid base from 1/4" wall square tubing and added machine leveling feet. Together with a 12" millwright’s level, I have got it fairly well trued up and it will chamber barrels just fine.
The reason I got this particular lathe (13” x 40” gap bed) was it had a large enough hole through the spindle for a rifle barrel, and it has threads on the back of the spindle (for a collet drawbar) that I could hijack for a threaded spider to support through-spindle chambering. I then bought one of Greg Tannel’s (Gretan) lubricating tools for through-the-spindle chambering and a bronze carbonation pump and motor from MSC to move the lubricant; this results in very clean chamber finishes.
Were I buying over again, I might look at the lathe offerings at MSC and J&L as well. I would probably see if I could fork up the money for one with helical gears in the head to further reduce vibration. I would stick with the DRO, now being spoiled by it. I would also tend to favor Taiwanese rather than mainland made Chinese tools, as they tend to be a bit more precise. The Italians make really nice tools, but the cost is predictably greater.
I did look at used tools. The dealers want too much for old Southbend and Logan lathes whose ways are deeply grooved from years of running over toolpost grinder wheel grit without upkeep of the way wipers or proper way lubrication. I found it easier to buy an inexpensive new machine with intact figuring and count on having to modify it.
Another engineer and I used to hire out to do machine repair when engineering work was slow, so I had some background for fiddling with the thing. If you find the idea daunting, you might buy the late David Gingery’s series of books on how to make a machine shop from scratch ( http://www.lindsaybks.com/dgjp/djgbk/series/index.html ). He begins with a back yard foundry for the castings, and never looks back. One of the books is a lathe project. You can learn a lot from these books on how you might approach modifying machinery. Also, if you can find a copy, Connelly’s Machine Tool Reconditioning, is a gem. Written in 1955, all setups and techniques and tools needed to refigure basic machine tools are covered in this book. It was reprinted in 1989, and some copies might yet be found. I believe I got mine through Lindsay Publications, but I don’t see it on the website.
June 18, 2005, 09:49 PM
I like Grizzly. I've got a 12x36 that the 3 jaw chuck only runs out .001TIR! It was $2000.00 and very well spent; aslignment is next to perfect.
June 20, 2005, 01:23 PM
I was looking at their high-precision 13"x40" tool room lathe. It's a little spendy, but I think it will do everything I would want it to. I would rather spend a little more money initially and get a lathe that I won't grow out of.
June 21, 2005, 01:00 PM
I bought a Smithy BZ239g recently. It is a 12x36 lathe. it unlike the others that I looked at is set up to cut both english and metric threads. You have to change out the gears to thread a metric thread. They also have a LZ1340 which is heavier and has 40" btw centers. I looked at Grizzly and enco and liked the Smithy more. I was told by a lot of folks to buy a second hand South Bend or Lablonde and I could save a lot of money. The only problem with that is you can get a piece that is wore out as far as accuracy is concerned and spend more money in the long run. The folks at Smithy give you a 2 year warranty and will take the machine back if your not satisfied with it. Plus they have technicians on hand to help with any problems you find or if you have machining questions. There's not too many folks at auctions that will give a refund if you buy a lemon of a machine.
I am not saying that you cannot find a good South Bend or Lablonde and get a heck of a deal as well as machine, but you will find the good buys few and far between. For me, I wanted a good machine that I could hit the ground running and not have the headaches of having to replace parts or find tooling to fit.
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