Interference fit problem

For discussions about bikes and equipment.
elduderino
Posts: 16
Joined: 2 Jun 2016, 6:25pm

Interference fit problem

Postby elduderino » 2 Jun 2016, 6:59pm

Hi

i am renovating a much loved 16yr old kettler touring bike(German). i am having the frame stripped, & sprayed.
I need to remove two Bolts(threaded hollow ends. Solid centres)that are at either end of a Suspa suspension strut on my touring bike. Lefthand one is 100mm length, right hand one is 35mm length. Both bolts are 4.5mm inside dia(threaded hollow ends). both bolts are 8mm outside dia.

Kettler have told me that they were interference fitted. & if i can find away to freeze the bolts they will push out, & of course back in.
Thats easier said than done, unless somebody here can think of another way to remove them without damage(Kettler say to old for spares).

IMG_0586.JPG




Here is a pic with retaining bolts(Allen) removed, & the threaded hollow ends showing.




IMG_0580.JPG




Thanks in anticipation.

Vorpal
Moderator
Posts: 18468
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: Interference fit problem

Postby Vorpal » 2 Jun 2016, 8:16pm

You can ask at local manufacturing and job shops? Or places with industrial freezers? If they can't do it, they might know someone who can.

You can also try liquid nitrogen; your local industrial gas supplier might be able to help you out. It won't take much; they might be able to use what is left in a returned tank or something. Obviously, you need to be very careful using it; follow all safety precautions, etc. Or get help from someone accustomed to handling it.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
NATURAL ANKLING
Posts: 12350
Joined: 24 Oct 2012, 10:43pm
Location: English Riviera

Re: Interference fit problem

Postby NATURAL ANKLING » 2 Jun 2016, 8:28pm

Hi,
Have you tried screwing in a M6 bolt into the open end till it stops then a sharp tap with a hammer on the bolt head.
If you can get both bolts out of either end of hollow part then use a piece of studding into the hollow bush a large nut or a socket and a thick penny washer and a nut and try and pull it out.

They normally come out quite easy with a bolt threaded in and a hammer.

Unless I am not getting your drift................
NA Thinks Just End 2 End Return + Bivvy
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.

Brucey
Posts: 41384
Joined: 4 Jan 2012, 6:25pm

Re: Interference fit problem

Postby Brucey » 2 Jun 2016, 8:29pm

Kettler may have fitted these bolts by freezing them in the first place but I'm not so sure that they will come out the same way.

The reason for this is that during assembly the bolt can be a different temperature to the housing, but during disassembly both parts are likely to be pretty much the same temperature.

The aluminium housings will have a CTE that is at least as great as any flavour of steel that might be used for the bolt, so attempting to cool the assembly will result in the bolt becoming a tighter fit, not a looser one, unless some kind of differential heating/cooling can be employed (= 'problematic' IMHO).

if it were mine, I'd make up a drift of some kind and give the parts a sneaky tap with a hammer, having immediately prior doused the housings in boiling water or something.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Vorpal
Moderator
Posts: 18468
Joined: 19 Jan 2009, 3:34pm
Location: Not there ;)

Re: Interference fit problem

Postby Vorpal » 2 Jun 2016, 9:52pm

Brucey wrote:Kettler may have fitted these bolts by freezing them in the first place but I'm not so sure that they will come out the same way.

The reason for this is that during assembly the bolt can be a different temperature to the housing, but during disassembly both parts are likely to be pretty much the same temperature.


That's a good point, though liquid nitrogen could be applied to the bolt, & in theory at least, a quick application of torque could get the bolt off as it was shrinking, but before the housing shrunk. I have removed interference fit parts using this method some years ago when I worked in a tool room & sometimes had to repair stuff that was assembled using liquid nitrogen.

I suppose that it should also be possible to heat the housing fairly quickly (perhaps with boiling water) and use the same approach. A less extreme temperature difference (like boiling water) may not be enough, but I expect it's worth a go.

elduderino: do you know what it is in the housing? It's not completely clear from the pictures. Is anything likely to be damaged by heating?
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

User avatar
NATURAL ANKLING
Posts: 12350
Joined: 24 Oct 2012, 10:43pm
Location: English Riviera

Re: Interference fit problem

Postby NATURAL ANKLING » 2 Jun 2016, 10:59pm

Hi,
Right side plastic / rubber washers...................
NA Thinks Just End 2 End Return + Bivvy
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.

elduderino
Posts: 16
Joined: 2 Jun 2016, 6:25pm

Re: Interference fit problem

Postby elduderino » 3 Jun 2016, 8:37am

Hi

Thanks very much for the replies, & information. I am glad i found this cycling forum. :D

I have sorted the removal of the suspension strut. It was just a case of taking the bull by the horns, inserting a drill bit (smooth end, so not to damage the threads )in the hollow ends , an giving it a whack with the brummie screwdriver, an out it popped, & can put it back in as well. :D