Setting up Shop Questions - from an NZ learner

[rodw]

I used 35 x 35 for the legs because it married up with the 35 x 65 RHS. 3mm thick RHS is heaps. I think I used 2.6mm wall thickness.
My bottom rails are off the ground a bit which when the adjustable feet were added, gave me plenty of room to get the toe of my boot under so I could stand hard against the lathe.

Maybe I'm paranoid about stability given this was the driving force for me to make a lathe stand

I'd keep the bottom rail attached to the front legs rather than recessed in like you have.

The reality is that at 280kg, the lathe is only adding 70kg load per leg which is nothing in the scheme of things.

If you have your heart set on mounting the lathe to laterals, why not use two 65 x 35mm RHS rails on each side of the lathe (eg. below the mounting holes) that are joined together with a few spacers of the same material like a ladder.

I'm not convinced the so called "torsion bar" design adds any value v's a well designed and constructed conventional stand. For starters, it is using the RHS beam with incorrect orientation. (eg. Long edge should always be vertical to attain maximum bean stiffness).

If you sketch out where the forces are, they will be downwards at the lathe mounting points with equal opposing forces upwards at each leg regardless of how its mounted. So then you end up with bending moments between the stand legs and the lathe mounting points.

 

[joco-nz]

Rod,

From my understanding of the designs intent the benefit is that the single supporting beam acts as a floating member. By this I mean that it doesn't twist or deform based on any movement in the surrounding frame e.g. uneven floor. This of course presumes there is sufficient flex in the frame. So you mount the lathe to this floating beam and in theory (got to love theory) if the beam is flat you just bolt lathe to beam and no need to explicitly adjust the lathe level through levelling bolts.

In my case I have designed for 2 square beams welded together. to get the width for the lathe's "feet". There are therefore 4 vertical walls of 100mm to provide support and spread the weight over.

HOWEVER as I play with this design more and consider the fabrication costs unless I can find either a single big beam or something close to the 100x100mm beams at a scrap merchant, buying that steel is going to be expensive compared to just doing the whole thing in a design like yours using similar sizes.
EasySteel doesn't seem to do the 35mm but Steel & Tube seems to. The thicknesses are either 2.5mm or 3mm. I think for the sake of 0.5mm I'll just stick with the 3mm. Nice and solid and I think I have weld settings that seem to be tuned nicely for it.

Been looking at the "screw jack" adjustment on the legs some more and as you pointed out conclude that with those plus a little bit of raising the lower support beams up (say 35 to 70mm) there should be plenty of clearance for the front of feet. It also means I can get a full depth shelf at the bottom which I am quite keen on. That shelf will end up holding a lot of the smaller sized/length metal stock in various boxes as well as items of <1.2m length. I might need to add some cross bracing to support said shelf, don't want it sagging in the middle.

In all I'm having fun thinking through this.

Cheers,
James.

 

[bazmak]

Don't forget you need lateral bracing either gusset or diaphram

 

[joco-nz]

Don't forget you need lateral bracing either gusset or diaphram

Assuming I go with the gusset approach how "big" should they be so as to be effective?

Given the gusset is essentially a triangle should the two sides making the 90 angle be 100mm? 150mm? 200mm? More?

And how thick a material to be effective? 3mm? 5mm? More?

Very new to this so still coming to grips with how much steel is enough steel.

Cheers,
James.

 

[rodw]

Been looking at the "screw jack" adjustment on the legs some more and as you pointed out conclude that with those plus a little bit of raising the lower support beams up (say 35 to 70mm) there should be plenty of clearance for the front of feet.

I used approx 75mm long set screws (threaded full length) I think I probably used a drilled and tapped end cap made out of some 32mm x 8mm flat bar had on hand at the bottom of the leg. These matched nicely to the 35mm shs. Either that or I welded a nut to the inside before welding on the end cap.

And remember if you add coolant, you'll need to level the lathe anyway.

With lower braces around the legs, I doubt you'd need to bother about gussets. I did use 100mm triangular gussets on my welding table as there are no lower braces. For the welding table, I copied some industrial mobile benches I had made in my last job in the printing industry which were in turrn copied from a design a friend used in his university printing centre. In fact, I got them made by the same fabricator....

 

[rodw]

One more thought. You could get your beam laser cut and folded in a 2 piece design. Fold up a c section the right width and then have a matching flat piece that gets stitch welded on the bottom side. That way you could get the dimensions perfect, have them cut the holes for mounting bolts in perfect position. It might be worth getting quoted up. Use 6mm or 8mm steel maybe. Be aware the beam could be distorted from welding....

 

[joco-nz]

I used approx 75mm long set screws (threaded full length) I think I probably used a drilled and tapped end cap made out of some 32mm x 8mm flat bar had on hand at the bottom of the leg. These matched nicely to the 35mm shs. Either that or I welded a nut to the inside before welding on the end cap.

And remember if you add coolant, you'll need to level the lathe anyway.

With lower braces around the legs, I doubt you'd need to bother about gussets. I did use 100mm triangular gussets on my welding table as there are no lower braces. For the welding table, I copied some industrial mobile benches I had made in my last job in the printing industry which were in turrn copied from a design a friend used in his university printing centre. In fact, I got them made by the same fabricator....

On the coolant front, to get the drop to the drain point did you pull that drip tray down at all? Or raise the other end up by using some flat bar as a thick "shim"?

Looking at the drip tray I'm guessing something was done as it looks pretty flat otherwie.

Cheers,
J.

 

[rodw]

I just adjusted the stand to put a little bit of slope back into a corner where I put the drain. I will say that coolant goes everywhere so its not much fun using it in winter.

 

[bazmak]

For gussets for application then even small triangles ad to the stiffness of the joints.For the loads involved deflection of the RHS is not really an issue for you
Personally if its suitable for you then a full 1.mm thk back is the way I would go
and full ends if they don't interfere,these can be riveted or bolted on

 

[joco-nz]

Some more work on the model per Rod's design with gussets to add some strength in key directions.

Now to try and figure out how I deal with draws. I just can't seem to find anything deeper than about 320mm. :-/

 

[rodw]

That will be so much easier to build. The front and rear rails hold the weight so I made them go the full length (so the leg sits under them). I cut them 6mm shorter than they needed to be and capped them with a piece of 3mm thick flat bar to make it look neat when completed.

This may show how I did it..

 

[joco-nz]

That will be so much easier to build. The front and rear rails hold the weight so I made them go the full length (so the leg sits under them). I cut them 6mm shorter than they needed to be and capped them with a piece of 3mm thick flat bar to make it look neat when completed.

Snap! Made exactly that change while sitting on the train this morning. :thumbup:

 

[Cogsy]

I used approx 75mm long set screws (threaded full length) I think I probably used a drilled and tapped end cap made out of some 32mm x 8mm flat bar had on hand at the bottom of the leg. These matched nicely to the 35mm shs. Either that or I welded a nut to the inside before welding on the end cap.

On the CNC plasma table I made I used upside down tow-balls with the nut welded to a plate on the bottom of each leg. Probably a bit heavier than needed here but an easy option to keep in mind for future projects.

 

[rodw]

On the CNC plasma table I made I used upside down tow-balls with the nut welded to a plate on the bottom of each leg. Probably a bit heavier than needed here but an easy option to keep in mind for future projects.

Thats massive! Rated for 3500 kg per leg! I was looking at legs for a plasma table. A full sheet of 32 mm plate steel only weighs 750 kg and commercial levelling feet that handle 1500 kg were only M12 threads. Still a great idea Cogsy that I've filed away. Did you put the towball on a floor plate with a cup in it?

 

[joco-nz]

On the CNC plasma table I made I used upside down tow-balls with the nut welded to a plate on the bottom of each leg. Probably a bit heavier than needed here but an easy option to keep in mind for future projects.

Nice idea. Never thought of that. Only about 18NZD a pop as well.

 

[Cogsy]

No need for a floor plate, the table was very heavy and never moved even under the highest acceleration we could run. The biggest advantage was the cost of them - had a mate that collected cars for scrap metal so they were essentially free, then a run through the sandblast cabinet and they were like new. Very much overkill, as you say, but they make great levelling feet.

Edit to add: with only point contact from the 6 legs of the table, it did make it possible for 2 guys to shove the table around when necessary (on concrete floor obviously), which I don't think would have been possible with standard flat feet. Wasn't a design consideration though.

 

[joco-nz]

I'll run with bolts I think somewhere between M12 and M16. They should be plenty strong enough. I figure once the stand has everything on it, lathe, scrap metal, some form of drawers, tools, back panel they should only need to be dealing with circa 100-130kg per leg.

 

[bazmak]

The weight of the table,total load proportional to feet area in contact
Not saying you would have a problem but,
I remember sheetmetal racks being made to hold steel plts
Great thought was put into the the strength of sections for the rack
When it was fully loaded the feet punched thru the concrete floor
No thought had been given to spreader plates
In your case the contact of the ball foot is in theory a point load
Just saying

 

[joco-nz]

Yeah, bit like stiletto shoes. Look at the damage they do to wooden floors.

Had been starting to ponder some kind of wider metal foot under the bolts. Say something like a 40x40mm square.

 

[rodw]

Yeah, bit like stiletto shoes. Look at the damage they do to wooden floors.

Had been starting to ponder some kind of wider metal foot under the bolts. Say something like a 40x40mm square.

I did do that initially for the factory stand but I did not use them as it was too unstable. You really won't have a problem as you are only talking about 100 kg per foot.

If you got socket head cap screws (eg. Allen key type), you could part off a piece of round stock in your lathe and bore a hole the same diameter as the bolt head. A couple of spot welds and it would be nice and neat.