INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

hole size for press fit steel pin into aluminum

hole size for press fit steel pin into aluminum

(OP)
Can someone provide a reference for the diametrical interference for a press fit steel pin into aluminum?  I need to press a .125" diameter pin into an aluminum extrusion roughly 1/4".  All references have an interference of no more than .001 between the hole & pin, but I believe that those values are for materials such as steel into steel.  

I want to use standard drill sizes if possible, but the range between sizes is not that small.  I was able to press this pin into a hole with .005" interference.   

RE: hole size for press fit steel pin into aluminum

Hi timsch

You need to use an interference that suits your application based on what loads and temperatures your fit might see in service.
You can't just say 0.005" or 0.002" interference without knowing something about the application.

desertfox

RE: hole size for press fit steel pin into aluminum

Please red flag one of your duplicate posts.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: hole size for press fit steel pin into aluminum

If you are permitted by design, use a spring pin and a drilled hole.

Ted

RE: hole size for press fit steel pin into aluminum

(OP)
desertfox, what I am looking for is a reference to provide some design guidelines specifically for steel going into aluminum, if one exists.  I realize that I cannot say .002 or .005, just like I cannot say that .001 will be sufficient, which is typically what I am seeing when looking at Machinery Handbook or ISO 286.  I have yet to see any mention of the materials being joined, which seems to me to be a variable.  I may be wrong here.  Please bear with me, as I am still learning.

My application:  These pins are pivots on which lightweight indicators are mounted.  The pins are under no load.  Temperature range is -100F to 1000F

RE: hole size for press fit steel pin into aluminum

Hi timsch

Well I don't know any standard references for steel pins in aluminium, like I stated the first time, you design them around the service conditions, take for example the temperature range you have quoted for your pins, 100F to 1000F now thats 38 degrees to 538 degrees centigrade, now expansion of steel is about 12*10^-6 and aluminium about 23*10^-6 so a 3.175mm pin of steel would have a free expansion of:-

                   12*10^-6*3.175*(538-38)= 0.01905mm

but the alumium     23*10^-6*3.175*(538-38)= 0.0365125mm

so for your pin not to fall out at 538 degrees centrigrade or a 1000F, I calculate the hole in the aluminium would have to be machined to a diameter of 1.656mm at the point of manufacture and then shrink fit the steel pin of 3.175mm diameter into it. Sadly it doesn't look like its going to work.
What happened to the pins you pressed in with 0.005" interference?

desertfox

 

RE: hole size for press fit steel pin into aluminum

(OP)
I see what you are saying now.  I do not see how you calculate 1.656mm for the aluminum hole, though.  

The difference in free expansion between the two metals is ~.018mm (.0007") at maximum temp.  If I wanted an interference of at least .001" at all temperatures, why would I not drill the aluminum at least .0017" smaller than the minimum pin diameter of .124" ?

.124-.0017" = .1223" (3.106mm)

 

RE: hole size for press fit steel pin into aluminum

Now I'm curious about what aluminum alloy is going to behave elastically at 1000F.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: hole size for press fit steel pin into aluminum

Hi timsch

Yes sorry my big mistake, had a senior moment then, I got into equal changes in diameter for a given temperature rise, but my point was you need to design your interference for your needs and that temperature rise shows my point.

RE: hole size for press fit steel pin into aluminum

(OP)
Mike, you are right to be curious - I have not given sufficient details.  This aluminum will be attached to a steel pipe that may see maximum 1000F in rare instances.  Heat transfer between the pipe and the aluminum channel will not be sufficient to heat the aluminum fully to that temperature. Other than where the aluminum channel contacts the pipe, it will be exposed to the atmosphere at ambient temperature.

RE: hole size for press fit steel pin into aluminum

The annealing temperature of aluminum is around 650F to 800F, depending on alloy.  That will relax stresses.  If, as was stated, the pins are under no load they should not fall out.  They will still have light contact.

Ted

RE: hole size for press fit steel pin into aluminum

The CTE will not be linear for steel over that temperature range.     

RE: hole size for press fit steel pin into aluminum

Given the correct press and installation driver, a 0.005 pre-install press fit on a .125 pin is probably going to swage material, thereby not giving you a true .005 interference fit.  Personal experience, all engineering formulae set aside.  You may see better results with .001 undersize hole.  And by the way, if this is a solid pin, you cannot simply drill the hole, you will need a reaming operation to maintain an acceptable hole geometry.   

RE: hole size for press fit steel pin into aluminum

Can you replace your steel pin with a shoulder bolt?  Or how about a spring pin

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close