handling with screw

[aleset]

Hello, I have a doubt.
I make a premise. Since I started working, I've always been told that to make movements, you have to take a trapezoidal profile screw for locking a normal screw.
in these days I am reviewing an old project (of those on glossy paper designed to tecnigraph).
and I have seen that for the handling of a plate on trolleys there is a simple threaded bar with bronze ring. from my point of view, supposing a simple movement with bronze snail. If I compare a m20 with a tr20 at the same pace I should have a lower resistance in the movement with trapeze. I also would also have a lower bending of the screw and it seems to me but I am not sure even a less wear of the profile. All points that would benefit from when I go round the flyer.
What do you think? Are those years taken of pumpkin on the basis of a false myth?

 

[MassiVonWeizen]

except that you understand little of what you wrote. punctuation is important if you make periods longer than 5 words and if you are making a slightly more articulated speech of a sms.
if it is in old design will be based on old technologies; in the 1930s the screws recirculation of spheres, so much to say, did not exist. the lathes that were already old in the mid-1990s had mother-of-peace and bronze bushing that danced and demanded a recovery of mago copperfield games

 

[aleset]

I apologize for the syntax of my post.
leaving the recirculation of spheres.
therefore a movement can be done indifferently either with a threaded bar or with a trapeze.

 

[MassiVonWeizen]

I didn't say that. sure it's a normal metric filet?

 

[aleset]

Yes. I saw the boards, as there are several adjustments are all quoted with a metric thread. In addition to this case, I would like to know the theory behind it. I've been looking for material, but I haven't found anything.

 

[MassiVonWeizen]

the catalog of the martinetti of the unimec has some formula that perhaps can be useful to you.
even trapezoidal screws accounts

 

[rinato]

Yes. I saw the boards, as there are several adjustments are all quoted with a metric thread. In addition to this case, I would like to know the theory behind it. I've been looking for material, but I haven't found anything.

could assume that they were "in economics" or "a tantum" movements, so it did not make sense (based on the experience of that designer) to employ the most expensive trapeze screws?

 

[antonio_sc]

I don't think there's any surprise. For example, today many 3d home-made printers still use that system to move the vertical axis, and it works, so why spend more to push over a limit that doesn't interest? (and only one example). .but we are talking about 3d home made printers

 

[MassiVonWeizen]

even what antonio_sc says.
So the question to do is what is this mechanism for? a designer should know that without this information any analysis, calculation or hypothesis is valid and not valid at the same time
if you have to move the office head coffee cup from one side to another of the desk then a threaded bar is more than good.
if moving a equipment with coarse precision and without axial efforts can go well.
if moving equipment that need medium/high precision probably is not good or should be analyzed with extreme care.
if you undergo continuous and/or interrupted axial efforts or require high precision surely it is not okay.

 

[bip]

I add that a standard thread allows to use standard pieces, not only cheaper, but also easier to find, with a piece of bronze, a male and a piece of threaded bar that recovers anywhere you can repair the machine.
too many designers do not think of who the machines must maintain them and repair them, in some applications it is useless to have hyperperfect components that, however, cannot be repaired or the spare parts are too problematic to be found.

if you do not need something excessively accurate, keep it simple and you will see that it costs less, it will probably break less, but above all repair it will be easier and less expensive.

 

[meccanicamg]

I confirm that you can make screws of maneuver both trapeze and metric to big step. steel screws c45 and bronze, brass, nylon.
there are axes for grinding spring compression grinding machines that are made with metric screws in a large step.
Let's use the myth that can't be maneuvering lives.

 

[meccanicamg]

the trapezoid screw is softer than a metric but has radially more play.

 

[aleset]

I understand. I was convinced that the maneuvers could only be done with trapeze lives, banally, because they had always told me who does so and I never wondered why.

 

[meccanicamg]

by standard and by ancient definition, a robust screw is defined, especially etc.
metric screws have always been considered only to embluate, because they are not accurate, because they have a 60° point profile and therefore if they hit us mark etc.
However you can make register screws of wagons and axes using even fine and combined steps between left and right. you make handling boards provided adequately protected.
then if you use big screws type 40 on it is clear that you are prepared to make screws trapeze.
you can also make m 200x3 as screws of maneuver...I use nitrates made to design... .

 

[andrea1974]

the catalog of the martinetti of the unimec has some formula that perhaps can be useful to you.
even trapezoidal screws accounts

useful mooolto, especially on the accounts is explained in detail.... thank you very much