Aluminium build up strength

[Screwdriver]

I need to repair this aluminium part, probably by cutting off the distorted threaded spigot.

Clearly the item has failed in service, I guess by being over stressed. I assume the remaining part will be compromised so plan to chop it off and build up in weld.

Question is, since this part has already failed, is an aluminium build up going to be strong enough? Pretty sure I have regular 4041 rods and am confident I can build up successfully, tying into the part before machining down to size. I really don't want to have to make this part from scratch.

Is it better to cut the bent/fatigued part off or will it regain its structure if I were to weld onto it? I probably will have to at least cut half the thread away so that I can get right down into the bottom of the threaded hole. But I assume it will be much easier to build up from the remaining half than welding onto thin air.

Will such a repair be strong enough and how else might I effect a repair, rather than make new?

S.

 

[Chris Stevens]

Make a new part.........its going to take longer trying to repair that than making new. If you do decide to repair, then vee out the crack, and weld using 5356 (stronger than 4000 series).

 

[Screwdriver]

Make a new part.........its going to take longer trying to repair that than making new. If you do decide to repair, then vee out the crack, and weld using 5356 (stronger than 4000 series).

How long it takes is less of a concern. I am not overly confident I can easily cut an internal acme thread so it would be much easier to repair this one.

I'll order up some 5356 I guess. Would I be right in thinking 4043 is going to be too soft?

S.

 

[Chris Stevens]

Silicone rod such as 4043 is easier to use (dirty material is less of a problem) but doesnt machine as nicely and isnt as strong as 5356.............

Saying that though I repaired a Honda side case yesterday, which had been soaked in oil for more than 30 years, and it welded lovely with 5356, which I always use for those jobs..............

Yes acme thread might be a hassle, and is a good reason to go for a repair.............

 

[Pete.]

Such a small part, I'd be concerned that the amce thread will distort welding that up.

 

[Chris Stevens]

Put the acme thread part in when welding might work.

 

[Freddy0309]

How long it takes is less of a concern. I am not overly confident I can easily cut an internal acme thread so it would be much easier to repair this one.

I'll order up some 5356 I guess. Would I be right in thinking 4043 is going to be too soft?

S.

If your passing Swindon any time soon I can give you a few rods

 

[Chris Stevens]

How long it takes is less of a concern. I am not overly confident I can easily cut an internal acme thread so it would be much easier to repair this one.

I'll order up some 5356 I guess. Would I be right in thinking 4043 is going to be too soft?

S.

PM me your address and I will send enough 5356 for that job.

 

[ronan]

Is that aluminium part, part of a machine vice ?

 

[Screwdriver]

Is that aluminium part, part of a machine vice ?

Yes. A lovely little Eclipse 4 inch machine vice. Nabbed off eBay as spares/repairs. Looks like it would make a good shaper vice or suitable for my mini-milling machine which I now have to sell.

S.

 

[Richard.]

Looking at it the thread doesn't look much good at least in the top part and I think pete is right when he says welding is only going to make it worse. I think your going to be very lucky if you don't have to put a new thread in there which from my POV (novice) an acme thread does look difficult to cut.
Id probably attempt a new part. If it is a weld up job
5*** series is what I would go with as it is stronger and designed to weld higher strength flavours like 7*** series
No matter what flavour you use you will always create a HAZ which is the weakest part of the joint but a number of passes providing you watch your temp can refine things regarding weld metal deposit but can also increase the size of the HAZ. It's catch 22 I would say but given the part is now knackered I think you should have a go. Produce a drawing first incase it fails and then there is the chance of turning a new one. You've done quite a few difficult repairs ive seen so I'm confident you'll crack it. Good luck SD.

 

[Screwdriver]

Thanks. I'd probably weld it up with the screw thread in-situ to help dissipate heat. and you're right, there's nothing to lose by giving it a go so long as I measure up first. Option 2 might be to make up a steel part and form the internal thread by heating/clamping some Delron around the thread.

 

[Kent]

I don't see a repair working out but if you don't value the time and effort fair enough

I should certainly expect to make or have made the replacement so get measuring before you make start on repairing the old one

A take on. It is - "it failed as original factory bit" how is a repair going to fair better?

Does it need to be ali even?

 

[Pete.]

Does it need to be ali even?

Nope, and I bet the original was bronze or cast iron.

 

[Screwdriver]

Well the tricky bit for me is forming the internal acme thread. I need a form tool and I haven't gotten around to teaching myself screwcutting. Probably discover it's relatively easy especially if its an imperial thread.

I suspect it failed because the sliding jaw retaining blocks allowed the jaw to lift. It's not a dovetail, just plain squared ways held in place with a small sliding block iyswim. Or maybe it just slowly bent over time until the retaining screw cross threaded. It must have been designed as a weak link so I don't think a steel version would necessarily be better.

It is a candidate for a de-rusting job though. Be nice to keep the original paint so I may try Ketchup!

S.

 

[Screwdriver]

Nope, and I bet the original was bronze or cast iron.

Hmm. Just had another look at the nut. I think you may well be right. How does a half inch threaded tube of aluminium resist the sort of clamping forces that vice can generate. Answer, it doesn't. I have enough odd bits of bronze from various job lots so will have a crack at making one. Meantime I will attempt the repair on this, just because...

S.

 

[Kent]

Get someone to make you a threaded blank then sort the outside dimensions yourself if this is your issue

They will likely want the screw to size the thread well

 

[Richard.]

Don't use steel SD. You want a material quite a bit softer than the lead screw.
Brass, bronze, etc would be my choice.
I'm also learning the art of screw cutting but I ain't to that stage yet

 

[Screwdriver]

Get someone to make you a threaded blank then sort the outside dimensions yourself if this is your issue

They will likely want the screw to size the thread well

No. I should easily be able to do it. Just a question of time and mental capacity. Got a bit too much on at the moment. My workbench earlier:

S.

 

[Richard.]

As the original intention was a soft metal like aluminium.
Would it not be worth sizing one of these.
I know that means you'll have to buy one it's there for when your next screw is due. Takes out the fuss with trying to make a boring bar to size.