base tolerances for rubber rollers

[alex83]

Hello everyone,

according to you with what tolerance should I mount the bearings on the rubberized roller you see in the attachment? ?
Could a h6 fit for the seats on the roller and m7 in the supports?
I can't do a stuck couple on both for mounting needs.
or would it be better to pack the bearings on both sides?

Tell me yours! !

Thank you.
alex

 

[meccanicamg]

a rigor of logic you must follow the indications of the skf for assembly. at practical level often you do also h7 and h6. often they leave themselves free from both sides and keep everything wrapped up by the side shoulders.

 

[alex83]

Wow!

But according to you, with a h6 tolerance, is there no risk that the roller rotates within the inner ring of the bearing?
someone also suggested using loctite to make sure that this does not occur.

 

[meccanicamg]

In fact, if the rollers are not of extreme importance and are not mounted on a perfectly worked structure, as in most cases, if the application is coarse (transport of packages, sheets, cartons etc.) it does not need precision, then the loctite for coaxial blocking is fine. often the bearings are oversized for their application and therefore you can also allow the possible rolling of the inner ring even little preloaded.

 

[MBT]

Many times, according to the philosophy of the "block that does not turn" you commit apocalyptic disasters!
If the shaft heats up and dilates, if the crates "work", if there are deformations in general, the bearings begin to work badly and destroy. If you leave them free... They last less, but they last!

 

[cacciatorino]

If you leave them free... They last less, but they last!

The problem is that it doesn't last the tree.... the technical director of a company for which I worked always kept a damaged tree in the meeting room, to show how a (apparently banal) neglect had provided the stop of the plant, and the urgent transfer of a maintainer in a foreign country....

a well-designed mounting with the bearings locked on one side and free on the other is always to be preferred. the rotating ring with respect to the load must also be blocked, or by interference, or with a braking as remembered, or with a traction compass.

 

[cacciatorino]

Hello everyone,

according to you with what tolerance should I mount the bearings on the rubberized roller you see in the attachment? ?
Could a h6 fit for the seats on the roller and m7 in the supports?
I can't do a stuck couple on both for mounting needs.

the assembly you indicated is not good because it does not allow the axial expansions of the tree. You should keep them locked on one side (maybe the transmission one) and let them free to slide on the outer ring on the other. the tolerances you indicate are not good, you have to do m or k on the pin and h on the seat, the value it depends a little from the diameter, here being small you can use quietly a 6 or 7.

 

[MBT]

The problem is, it doesn't last the tree. .

Yeah!
and false!
depends on the boundary conditions
How much do you rotate? with what load? how frequently?
I have in the workshop a 120 tree making a round and a half every 45 minutes
It's all locked up, because "the mounting is done like this"... but in those conditions it would have changed so much to leave it lasco?

 

[meccanicamg]

the assembly you indicated is not good because it does not allow the axial expansions of the tree. You should keep them locked on one side (maybe the transmission one) and let them free to slide on the outer ring on the other. the tolerances you indicate are not good, you have to do m or k on the pin and h on the seat, the value it depends a little from the diameter, here being small you can use quietly a 6 or 7.

if it is as I often see around in the various companies, there are tolerances (not even indicated by drawing) of length between shaft and shoulders of the hub where the bearings go with at least 1 mm of difference from the nominal (and this already on lengths of 100 mm of roller board.

Surely that if you need to make a dynamically balanced roller, diameters above 200 mm and high lengths and have to turn at large peripheral speed (5 m/min up) it is good to use tricks like creating the two bearing constraints as an isostatic beam: a zipper and a cart.

It is necessary to take account of the thermal expansion of the roller shaft and to carry out a lower length with a safety margin.

for other occasions, however, if the shaft or roller is very rigid and there is no problem of thermal expansion, you can realize the hyperstatic system with barrel-oriented bearings or two roller crowns obtaining greater precision at rolling.

 

[cacciatorino]

Yeah!
and false!
depends on the boundary conditions

eh, our user has specified: 200 rpm. we do a little stick, with a bearing d=20.00 and a tree d=19.95 at each turn the bearing remains back (20.00-19.95)*3.1416= 0.16 mm approximately. in a minute will be 32 mm and in an 8 hours turn come about 15 mt.

It's not so much, but I'd rather do things orthodox, so much so we're talking about a d20 mm pin that you're crying at the press without any big problems.

 

[cacciatorino]

Surely that if you need to make a dynamically balanced roller, diameters above 200 mm and high lengths and have to turn at large peripheral speed (5 m/min up) it is good to use tricks like creating the two bearing constraints as an isostatic beam: a zipper and a cart.

I don't know, my designs always do them as you say (scratch and cart). The fact that there are different schemes does not mean that they are the correct ones to follow. Clearly if we're drawing a tensile galoppino we can also settle to mount the bearings with axial play between the shoulders of a mm, no one will ever tell us anything. But in the case of the discussion, given the length between the supports and the angle velocity not small, some care would put it.

 

[alex83]

I thank you for all the answers you have given me; meanwhile I did some research and manuals confirm your theses as I thought.

Unfortunately, given the strict corporate rules where I work, I am forced to use already codified and logical pieces that I sometimes do not share.

Whereas this is a rubberized roll for sheeting, therefore, considering that there is no need for rolling accuracy, whereas the thermal expansion for a 1200mm long ø50 roller is negligible, and also considering the assembly and disassembly requirements,
I will proceed to the progress of the project as I have submitted it, with the bearings planted in their seats (m7) and free on the roller (h6). the internal rings I will block them with type 641 loctite for bearings.

would you know how to say that, then, a bearing held by the loctite fell down? ?
I heard about hot air guns. Are you okay? ?

thank you for everything, really great this forum
alex

 

[meccanicamg]

the bearings glued with the loctite should be heated with cannello and/or hot air to make dry and lose the elastic properties of the glue...poi mazzuolo or press to extract

 

[stevie]

I thank you for all the answers you have given me; meanwhile I did some research and manuals confirm your theses as I thought.

Unfortunately, given the strict corporate rules where I work, I am forced to use already codified and logical pieces that I sometimes do not share.

Whereas this is a rubberized roll for sheeting, therefore, considering that there is no need for rolling accuracy, whereas the thermal expansion for a 1200mm long ø50 roller is negligible, and also considering the assembly and disassembly requirements,
I will proceed to the progress of the project as I have submitted it, with the bearings planted in their seats (m7) and free on the roller (h6). the internal rings I will block them with type 641 loctite for bearings.

would you know how to say that, then, a bearing held by the loctite fell down? ?
I heard about hot air guns. Are you okay? ?

thank you for everything, really great this forum
alex

so do the opposite of what the sacred manual skf provides, i.e. you have to lock the rotating ring against the load. I recommend a k6 on the roller and a h7 in the seats.
then there is also to consider the type of bearing you want to mount, because on a 1200 mm long roller 2 rigid bearings are not recommended. considers that in this type of application it is good to use a swivellable bearing on the one hand to compensate for the misalignment between the 2 seats that at the long time from problems of duration to the rigid bearings and the shaft.

 

[alex83]

I have another very questionable example.

Take a look.

but you think it is correct that to drag the inner ring of the bearings is the friction of the wreath on the bearing itself since the tolerance in the bearings is g6? ?

 

[Focus]

personalmante I think both fittings are wrong, they go against all the assembly recommendations of bearing manufacturers.

Hi.

 

[cacciatorino]

personalmante I think both fittings are wrong, they go against all the assembly recommendations of bearing manufacturers.

Hi.

I agree, I don't understand why you don't want to mount two very common adjustable supports...

 

[PierArg]

so do the opposite of what the sacred manual skf provides, i.e. you have to lock the rotating ring against the load. I recommend a k6 on the roller and a h7 in the seats.
then there is also to consider the type of bearing you want to mount, because on a 1200 mm long roller 2 rigid bearings are not recommended. considers that in this type of application it is good to use a swivellable bearing on the one hand to compensate for the misalignment between the 2 seats that at the long time from problems of duration to the rigid bearings and the shaft.

Hi stevie, I'll tell you what!:finger:

I would have said the same thing, too.

 

[alex83]

Good evening to all,

In the case of the last example, I just wanted to know what you thought,
These are already done (not by the undersigned) and are assembled in the company where I work.

I was interested in knowing from you whether it is correct that it is the friction of the wreath on the inner ring of the bearing , to drag the latter since the tolerance of the roller at the bearings is g6.

Thanks anyway for the answer you gave me.

 

[paulpaul]

Hi.
if the roller is slender and you do not have particular precision requirements I would go with the following solution:

1. adjustable rollers of "wine" transmission side, mounted to interference on the hub (or with traction compass) and external ring blocked axially (spalling + plug lock);

2. cart from "carb" opposite side, same assembly of the previous (the carb has sliding rings axially) or an adjustable as the previous always mounted to interference on the hub but with the outer ring free.

Although I have no strong thermal expansions, if the installation allows me, I prefer the isostatic "canonical" solution. then it happened to mount also bearings with loctite eh...so as well as preloaded bearings axially because I needed precision... or other cases again.

surely in your case there will be other reasons behind this choice.. .