help with fits specification

[soundssupreme]

Hi,
I am new to the forum.
I am trying to find informaiton on fit tolarances of hole and shafts and have read a couple on the net but they are difficult to undertand. Does anyone have a url for a web site that show this information in easy to understand form ?
My question for the moment is that I have a ring with a hole in it that is 12.03mm diameter. I want to make a shaft that is a press fit (i.e. will be difficult to remove (and will not move once pressed in),but can be press fitted in to the hole with an engineers vice, (if I am carefull !!)into this hole. The shaft and ring are both made of aluminium. Can anyone please tell me what size I should make the shaft and if they think this is possible only using a lathe for the finishing of this shaft, as I do not have a cylindtical grinder.
Thank you very much for reading this.

 

[Heckler]

In the Machinery's Handbook the section on Allowances and Tolerances for fits will answer most if not all of your questions.

http://www.engineersedge.com/calculators/machine-design/press-fit/press-fit-calculator.htm

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
o
_`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

 

[KENAT]

I think a previous thread on a similar subject gave a link to an online calculator based on the standards, take a look if you can find it.

KENAT, probably the least qualified checker you'll ever meet...

 

[desertfox]

Hi soundssupreme

try looking at this site:-

http://www.roymech.co.uk/Useful_Tables/ISO_Tolerances/ISO_LIMITS.htm

regards

desertfox

 

[soundssupreme]

Thank you all for writing back !!

I will try these all out.

What a great site and helpful people.

Thank you all once again.

Sincerely,

Soundssupreme

 

[soundssupreme]

Hi,
Tried the links given, but it all looks like gobbledegook to me. Maybe I'm on the wrong site. I am not a professional engineer, just trying to make the odd item. Is there a site where you can type in the size and it tells you the right diameter for the shaft ?
Or does anyone know what I should make the shaft to for for a 12.03mm hole to make a medium tight press fit (sorry if my terminology isn't correct).
Thanks.
Soundssupreme.

 

[desertfox]

Hi soundssupreme

Your fit needs to be decided based on the forces the shaft
and hole will see in service, so no one here will give you
figures without understanding what your application is.


regards

desertfox

 

[soundssupreme]

Hi Desertfox,
Thanks for writing back.

The item in question is not taking any stress so to speak, it is part of a hi-fi tonearm and only has a tonearm clip and a small light component (the arm cueing mechanism) to be fitted to it. The shaft is to be about 70mm long and 14mm wide along it's length and solid.The end of the shaft to fit into the hole will be machined along 7mm of it's length. The reason I want to use a fit as described is because the design precludes the use of fixing screws so I just want to make it a tight fit so it will hold it's own weight and not come out and not require any adhesive to hold it in. The dimensions cannot be changed for the design as this is a part that is a modificaiton to an existing design so I am fixed to the physical size I have given which precludes the use of fixing screws.
Can you help please ?
Thanks,
Soundssupreme.

 

[desertfox]

Hi soundssupreme

You could try a k5 tolerence shaft so the diameter would
be:- 12.039,12.031.
You might wish rather than press fit together to expand the ring by using heat or cool the shaft prior to assembly.
Without any other information I wish you to understand if it doesn't work I take no responsiblity whatsoever.

regards

desertfox

 

[soundssupreme]

Hi Desertfox,

Thank you very much for helping me. I fully understand your disclaimer and totally agree with it.
Sincerely,
Soundssupreme.

 

[desertfox]

Hi soundssupreme

Your welcome

desertfox

 

[soundssupreme]

Hi again,

I have machined it to the size you gave me (I used the larger tolerance), and it seems fine but I haven't fitted it yet. I like your idea of heating the item with the hole in it and I have a standard blow torch that might work but will the aluminium be dis-coloured if I do this as I would be polishing it when completely finished. If it does, do you think the dis-colouration will be removed by the polishing.
Hope you don't mind my asking.
Sincerely,
Soundssupreme.

 

[hydtools]

Make sure the edges of the hole are not sharp. Buff them to a radius or lead-in angle, if possible. Aluminum on aluminum picks up easily and the result is not pretty.

Ted

 

[soundssupreme]

Hi Ted,
Are you talking about if I press fit it or heat it ?

Thanks.
Soundssupreme

 

[GregLocock]

Both, or either. A stuck shrink fit assembly is a very hard thing to sort out.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[soundssupreme]

Thanks Greg,

Any idea about my previous question with heating aluminium ?
Do you know if it will dis-colour, and if so, can it be polished off ?

Thanks,
Soundssupreme.

 

[desertfox]

Hi Soundssupreme

I don't know how thick the wall surrounding your bore is but
according to my calculation on heating the bore you need at least 32 degree's centigrade rise over your ambient temperature to get the bore to expand by 0.009mm.
so if your ambient is say 20C then at 52C the bore should
increase by 0.009mm.
I was wondering if you could use boiling water to increase
the bore and avoid the possibility of discolouring the aluminium.

regards

desertfox

 

[soundssupreme]

Thanks Desertfox,

I'll try the boiling water method tomorrow, and if that doesn't work, I'll try a scrap piece of aluminium with the blow torch first before using it on my work.
I'll let you all know how I get on so it might help others.

This is all really helping me a lot so thanks to all that have replied.

Sincerely,
Soundssupreme.

 

[hydtools]

An 80C rise in temperature with boiling water should increase the bore about .02mm. It should go on easily.

Ted

 

[soundssupreme]

Thanks Ted.

Sincerely,
Soundssupreme.