Need to tap into the Hive knowledge base

[Thumper68]

I was doing a job on the Sheldon lathe the other day and noticed that even though it is mounted on a 2 1/2 inch thick butcher block style bench (Thats how it came) that there was a bit of flex when cutting, I was not taking a real heavy cut at all about .010 and then noticed it again drilling a Z sized hole in brass.

So here is my plan, bit of a pain since the motor and gearbox are mounted under the table.

The existing base is 34"x65" approx it has a drawer unit under the tail end and the motor and gear box at the head.

I will have a 18"x96" drop of 1" plate left over from a project in a few weeks.

What do you all think of making a base out of 2x2x1/8" tube with a built in chest (I have a 5 drawer CM box that is the perfect size) then use 65" of the 1" as the top then adding a back splash and lip to form a chip tray,

Okay guys punch holes in the plan so I can fix it before any sparks are made.

 

[larry_g]

Can you post a picture or two of what you have now?

lg
no neat sig line

 

[racingtadpole]

How far away from the chuck were you cutting/drilling?

 

[Thumper68]

Can you post a picture or two of what you have now?

lg
no neat sig line

Yes I will go take a few right now, just need to put pants on.

How far away from the chuck were you cutting/drilling?

About 1/2 to 3/4 of an inch, the part I was facing and drilling was only 1 1/2" long and 3/4" hex.

 

[bczygan]

Table bolted to the floor?

 

[Thumper68]

Table bolted to the floor?

No it's not, I would have to modify it alot to bolt it down, in that case a new bench would be easier.

Here are the pics.
View media item 71402View media item 71403View media item 71404View media item 71406

 

[laser3kw]

Yes I will go take a few right now, just need to put pants on

well... why? unless the path takes you through the neighbors living room....

 

[koditten]

Man card, revoked!

Sorry, but I can totally relate and it's funny as Hell to me.

 

[EdT]

Before you rush off and make a new bench it would be worth trying to figure out if the existing bench is actually the source of the perceived flexing. The size part you were working on would not be trying to flex things very much. There are a lot of ways to get tool deflection (if that's what you mean by flexing) that have nothing to do with the bench the machine is mounted on. It would be a shame to spend all the time on a new bench only to find that the problem is elsewhere. Don't pass up the left over piece of 1" stock at work. It'll be good for something if not a lathe bench.

 

[larry_g]

I'm not sure what to say so I'm just going to relay my experience and then maybe a suggestion or two.

When first starting out in this machine tool adventure I acquired a 10" Logan lathe on a steel bench similar to what your proposing, a bit lighter though. That lathe had a real chattering problem. After owning it for a year or so another identical lathe came along on a heavy wooden bench, think tanker desk but wood. It had no chatter problems. So I swapped the lathes on the benches and the chatter followed the bench. I reasoned that the steel bench had a resonant frequency near the lathe and they would amplify until the whole thing was dancing across the floor. The wood bench was heavier by at least 100 lbs and no issues. No sign of a resonant frequency.

This Sheldon is 2x the lathe the Logan is and should almost not need a bench to support it. Both of my machines are on a factory stand that has a 5/16" steel top. So 1" should support yours.

How is your lathe bolted to the wood? Are the bolt heads pulling into the wood loosening things up? I would consider a bridge washer minimum under the table if not a 12" square piece of steel to spread the load. Are the leveling bolts/jack screws in the lathe still tight?


Can you identify exactly where you movement is? You said that you were facing a piece, Did you have the carriage lock set? Can you repeat the cut with and without the carriage lock. Can you afix a dial indicator base to the tailstock housing and set the indicator probe on the side of the headstock. This will tell you if the bed is twisting during the cut.
Do what you can to try and figure out what is really happening so that you confirm it is the stand. It would be disheartening to build a new stand only to find out the compound was loose.

I spent many years in maintenance and one think I learned is to find the root of the problem before designing a fix.

lg
no neat sig line

 

[Provincial]

To expand on Larry's last comment, sometimes when you change the machine/mounting to eliminate a harmonic, you just change the frequency, creating a problem frequency in another area. As Larry suggests, look for other causes before changing major mounting pieces.

As I have mentioned in other threads, I am aware of someone who mounted a couple of Craftsman (Atlas) 12" lathes (1950-vintage) by casting pyramids of reinforced concrete that filled the mounting feet and the interior voids of the ends of the lathe beds with concrete. These pyramids were about three feet wide at the base. Because of this massive mounting, the owner was able to take massive cuts for the size/strength of the lathe. A stock Craftsman/Atlas is as rigid as a wet noodle, so this was an amazing accomplishment.

You should not have to do much to keep the Sheldon from chattering. Often just changing the speed, feed, depth of cut, or geometry of the tool will eliminate the problem. Sometimes it takes changing more than one factor.

 

[Thumper68]

All good points Larry and I will try and take better look tomorrow and see if I can isolate the issue.

IIRC when I was drilling that it seemed that the ways were flexing and that may be because the bolts are loose like you mentioned.

In the end after going out and taking the pictures, no matter what I will be building the new bench for the lathe for 1 main reason and a 2nd one that just fits well.

The first and main reason is to make the bench narrower, right now it is about 34 inches deep, if I can have as good or better of a stand that is a foot narrower it will fit in the shop much better.

The 2nd is storage, the 3 drawers that are in the existing stand are just about useless the 5 drawer CM box will hold a lot more tooling and accessories in a smaller foot print.

And now thinking about it, the wood is a PITA to clean up the oil and chips stick to the wood, smooth steel will be a better solution I think.

One thing that I got from your post above is that heavier is better and that would match my knowledge as well, so when I am designing the new stand I will think heavy and stiff.

 

[Thumper68]

To expand on Larry's last comment, sometimes when you change the machine/mounting to eliminate a harmonic, you just change the frequency, creating a problem frequency in another area. As Larry suggests, look for other causes before changing major mounting pieces.

As I have mentioned in other threads, I am aware of someone who mounted a couple of Craftsman (Atlas) 12" lathes (1950-vintage) by casting pyramids of reinforced concrete that filled the mounting feet and the interior voids of the ends of the lathe beds with concrete. These pyramids were about three feet wide at the base. Because of this massive mounting, the owner was able to take massive cuts for the size/strength of the lathe. A stock Craftsman/Atlas is as rigid as a wet noodle, so this was an amazing accomplishment.

You should not have to do much to keep the Sheldon from chattering. Often just changing the speed, feed, depth of cut, or geometry of the tool will eliminate the problem. Sometimes it takes changing more than one factor.

It wasn't a chatter, I saw the ways flex or twist so it could be the mounting, loose bolts etc, those I will look for tomorrow.

 

[Thumper68]

Before you rush off and make a new bench it would be worth trying to figure out if the existing bench is actually the source of the perceived flexing. The size part you were working on would not be trying to flex things very much. There are a lot of ways to get tool deflection (if that's what you mean by flexing) that have nothing to do with the bench the machine is mounted on. It would be a shame to spend all the time on a new bench only to find that the problem is elsewhere. Don't pass up the left over piece of 1" stock at work. It'll be good for something if not a lathe bench.

I actually was at my metals supplier and he has quite a few 4x8x1" plates that he got as a buy back from a 1 times use, they used them to protect the concrete in a factory while installing new equipment and he has offered them to me at $0.40 a pound or $525 a piece, just so happens that I am building a heavy work table for a client and since the 1" is only a bit more than 1/2" we decided to go with the 1"

I may just pick up 1 or 2 more for future projects at that price.

 

[larry_g]

I saw the ways flex or twist so it could be the mounting, loose bolts etc, those I will look for tomorrow.

Here is where it is a bit confusing to me and what you have to determine. Is the lathe, that being the headstock, bed, tailstock, and carriage, moving in relationship to each other OR is the lathe moving in relationship to the table.

lg
no neat sig line

 

[Thumper68]

Here is where it is a bit confusing to me and what you have to determine. Is the lathe, that being the headstock, bed, tailstock, and carriage, moving in relationship to each other OR is the lathe moving in relationship to the table.

lg
no neat sig line

It's been several days but IIRC and it was only for a few moments due to the small project but it seems that the ways were flexing or twisting as the bit started cutting.
That would leave me to believe that the lathe was not firmly affixed to the bench, either due to loose bolts or wear in the wood.

Tomorrow I have some free time to mess around and I will get out a few indicators and see if I can recreate and isolate the issue.

I will report back once I find what the issue is.

This is the first time I have noticed it and the only thing that is different is that I switched from running off the VFD with a soft start to a phase converter where the lathe spools up much quicker and during the testing I ran it at high speed for a while, It also spools down faster so I might have caused some excess vibration that loosened something up.

 

[cvairwerks]

Ahh, if you are flexing the ways while drilling brass, something is major wrong and it's not the bench. I would suspect that the headstock might be loose and you are seeing it raise up slightly. Time to chuck up and make a quick test bar first. That Sheldon should be stiff enough to drill brass with no flexing, even if it was sitting on a table and not bolted down.

 

[Thumper68]

I spent a good hour trying to recreate the issue, and now I am thinking that I must have been seeing things, I even went back and watched the video I took and did not see anything.

Man it ***** getting old and your mind starts playing tricks on you.

Any how since I will only have to purchase 3 sticks of 2x2 tube I am still going ahead and making a new stand for the lathe and will include the CM bottom for more convenient storage, that will allow me to reclaim some floor space and make things fit better in the shop.