New Lathe Bench

[Ray C]

Ryan,

What kind of lathe are you building that bench for? Also, I hope you saw the thread about "how level does a lathe need to be" -or something like that... I had a tall bench very similar to yours but the legs were heavy-wall 2" black pipe. It was pretty solid indeed because I'm a fiend when I got a welding torch in my hand... When all was said and done, I still had to brace the daylights out of it and add about 400lbs of ballast (in the form of tools etc). If it's an Atlas-type with the idler pulley and/or suspended motor, you might need to brace-up the short sides too. Criss-crosses of heavier angle iron did the trick. Light angle iron did little to help.

I took for granted the 1+ ton LeBlond I learned-on and grew up with. When I got back into machining, I got an Atlas -and consequently learned a lot more than I cared to about rebuilding lathes and getting the vibration ghosts out. Anyhow, the upshot was that the machine's weaknesses had to be addressed so the motor, belts and sheaves etc. needed fine-tuning and chucks had to be balanced. After that, the rest gets fixed with brute-force strength and mass. And much to my surprise, much of the table vibrations were coming from the short-sides (back and forth, not side-to-side in the long direction).

Anyhow, your bench looks good -and I bet folks are happy that it's out of the kitchen now...

Ray

 

[Smudgemo]

Ryan,

What kind of lathe are you building that bench for?
And much to my surprise, much of the table vibrations were coming from the short-sides (back and forth, not side-to-side in the long direction).

Ray

Disconcerting, for sure. But I'm almost done, so I'm going to see what happens. I'm not sure which lathe type you are describing, but mine is a 12x36 all mounted on top of the bench. It would seem that mimicking the factory stand or bettering it (maybe) would be a safe bet, but that's a trap we all fall into eventually, I suppose. I should find out next weekend when I move it over and get things leveled out. I've got a three-day weekend and couple of fancy Starrett levels on loan from a friend, so at least that part won't be a question mark.

-Ryan

 

[tripletap3]

Once you get it done I bet that bench is going to make that lathe come alive. It will make a huge difference in accuracy. My pet peeve with the Atlas/Craftsman lathes is that they need a VERY solid place to sit. I think the Atlas lathes were designed with a lighter weight bed and were intended to be mounted on something heavy enough to be part of the lathe bed and give it mass and strength. I love these old machines and I personal don't think they were designed to be light weight to be cheap, it just made it easier to ship from a catalog and more available to the average Joe.

 

[Ray C]

Ryan,

Please realize I was not trying to be critical -not intended that way at all. I'm really trying to spare you from days/weeks/months of figuring-out how to make an Atlas (or any lathe but especially the Atlas) cut well. I was spoiled on a monster machine and had to learn a lot to get the Atlas (TH-42, smaller version of yours) to work well.

First, your bench looks great! And, it's a solid base to work with. If you feel it needs tweaking after trying it out, I would suggest putting heavy duty criss-crosses on each end that extend from the top to about 2/3 to the bottom. Also, an additional 1x2 spanning from left to right in the front and back about 8-10" from the table surface.

On the plus side here, these mods can be done afterward and since you used square tubing, you can make brackets or bolt them into place. -No big toll on the paint job. I on the other hand had round pipe which is a pain to weld and difficult to make brackets for. I went with ruining the paint and re-welding it.

Believe it or not, there are very strategic reasons for those struts in those places -and being the nut-job I am, I actually put some analytic thought into it.

As it turns-out, I'm making a new bench for my lathe. I just returned home with 500lbs of 1/2" wall, 3x4 angle iron and about 250lbs of it is for the bench. Last, as an engineer, I hate grossly overbuilding things but when it comes to lathes, you have 2 choices... A) Buy a 25 kilo-buck machine in which every gear is balanced and the (balanced) chucks cost a grand each or, B) be like the rest of us and buy decent/affordable machines that need brute force to kill the remaining vibrations that exist after the machine has been tweaked as much as possible...

Again, sorry, I did not mean to be rude with the original post...

Ray

 

[Smudgemo]

Hey Ray, no worries! I place great value on "good, old-fashioned crusty old-guy" advice (not that you are any of those, of course), and I appreciate the input. I didn't mention it, but I do think it will be helpful to have some sort of roadmap as to why I might ultimately experience problems. Gotta be more sturdy than the desk it's currently on, but we'll find out soon.


Best,
Ryan

 

[wa5cab]

Ryan,

There is one thing I would suggest after you get the lathe set up on the new bench as you want it. Assuming that the switch on the side of the top cover with the yellow cord coming from it is the main switch, I would relocate it to just under the drip pan and bench about even with the right face of the headstock. That's where I put mine 30+ years ago and I've never wished that I had put it anywhere else. I have the lever pointing to the left with ON-FWD being up. When you are standing in front of the machine, maybe with your right hand on the feed or the cross feed lever, you left hand will mostly be dangling right by the switch. Not only is it more convenient. It's also much safer (you aren't reaching across the chuck to operate the switch)/

Robert D.

 

[Ray C]

Well, I have my theories -and here they are...

Most if not all lathes have some vibration. It comes from out of balance motor rotors and all the gears and chucks. -And worse yet, the workpiece and lathe dog. If you have drive belts, they're often less than perfect and they impart vibration too. On lighter machines (say, under 5-600lbs) you're often better served by taking lighter cuts because the machine is not heavy enough to take deep cuts. Therefore, you're usually always taking lighter cuts. I'm of the belief that lighter cuts are more prone to flaws due to vibration because the bit is not engaged deeply into the material. ie. if you're taking a 50 thou cut (which I do all the time) the bit is so jammed into the material, you could probably intentionally shake the table and not see too much disturbance in the workpiece. I feel that heavier machines will show less flaws in the workpiece than a lighter machine assuming they had the same amount of vibration. So that's my theory -and thinking back on the differences between using a 3,000lb lathe vs a 1200lb unit vs a 300lb lathe, I feel it's a reasonable theory. And by the way, I'm talking about natural vibrations -not the kind caused by bit chatter. -That's a different matter.

If you subscribe to this then, vibration needs to be addressed more carefully in a light machine than heavy one -and in the next breath, I'll also say it's very important in all size machines. -But it shows-up more in smaller machines.

The table... Your table has long legs and long spans and unless you got very lucky and have a lathe that runs smooth as a sewing machine, it's going to shake the table -probably a fair amount. Take a solid wooden stool, place it next to the leg of the bench, hold a dial indicator on the stool and indicate near the top 5-6 inches of the bench. It will be jiggling constantly 5-15 thou and it will come and go with a periodicity you can observe. The constant 3-5 thou jiggling is due to mechanical action and are called primary or 1st order vibrations. The "swaying" of larger values are due to the 2nd order vibrations which are the sums of various harmonics that resonate through the long spans. They have no place to go so they resonate and try to find nodal areas. Go ahead and get a solid camera tripod, mount a DI and indicate off the toolpost. Let me guess... 5, 10, 15 thou worth of vibration. -I'll bet you a cup of coffee on it. Now, if you're taking a 2 thou deep cut and the toolpost is giggling 10 thou -well, you tell me the outcome. Sure, you'll get a 2 thou cut but it will show artifacts of vibration.

So, first you fix as many vibration problems as possible. Gears are pretty flat and static balancing them is very effective. Chucks most often benefit from static balancing but often need dynamic balancing. -Belts and sheaves? -They just suck no matter what. The motor rotor (often a big source of vibration) -buy a very expensive motor to avoid that problem. And BTW, the pulsing of cheap single phase motors causes plenty of issues.

There will always be some degree of remaining vibration -if anything, from the workpiece or lathe dog so, you kill it with tough love (translated: Mass and reinforcement).

I've been through all this -more than once on more than one kind of machine... And not only that, it makes perfect sense from the pure perspective of physics (which I happen to know a little bit about).

So there's my theory and folks can shoot it at and we'll have have fun learning in the process -and I always look forward to learning...

Ray

Hey Ray, no worries! I place great value on "good, old-fashioned crusty old-guy" advice (not that you are any of those, of course), and I appreciate the input. I didn't mention it, but I do think it will be helpful to have some sort of roadmap as to why I might ultimately experience problems. Gotta be more sturdy than the desk it's currently on, but we'll find out soon.


Best,
Ryan

 

[Ray C]

BTW, here's a picture of vibration evidence. It's just 1018 HR cut at a few different depths and speeds. See the smeary lines on the left side. That was only taking off a few thou at a speed which I know my chuck develops a noticable dynamic balance vibration -about 840 RPM. The real shiny part was a 20 thou cut with same chuck around 1200 RPM where the balance issue magically goes away. -A little different... Same carbide bit, same lubricant, same feed rate. This is what vibration does. That's not chatter vibration BTW, it's from the loosely engaged bit losing it's grip on the cut. Push the bit in and the problem goes away.



Ray

 

[Smudgemo]

Ryan,

There is one thing I would suggest after you get the lathe set up on the new bench as you want it. Assuming that the switch on the side of the top cover with the yellow cord coming from it is the main switch, I would relocate it to just under the drip pan and bench about even with the right face of the headstock. That's where I put mine 30+ years ago and I've never wished that I had put it anywhere else. I have the lever pointing to the left with ON-FWD being up. When you are standing in front of the machine, maybe with your right hand on the feed or the cross feed lever, you left hand will mostly be dangling right by the switch. Not only is it more convenient. It's also much safer (you aren't reaching across the chuck to operate the switch)/

Robert D.

It's actually the switch added to reverse the motor. The main switch is still located on top, however, that does make me think of using it as the main, and that does sound like a great location

 

[wa5cab]

Oops. I missed the little toggle switch. Looks safe enough if you operate it with your left hand. The only bench model Commercials I've had or been around had been modified for transformer winding with variable speed compound wound DC motors and their controllers were probably mounted to the front of the bench (they were loose when I got the machines).

Robert D.