Best engineering practice to fit parts together?

Joshua Slocum

LE
Book Reviewer
take a short length of wooden dowel thinner than the hole in the unit
cut a slot at 90 degress with a small handsaw
cut a strip of emery and feed it through folding it into a z shape
put the dowel into a small drill, and run it gently
thats from my 90 year old dad Ex REME and trained toolmaker
 

bcsack

Old-Salt
I've repaired similar domestic / commercial equipt and they're all made to assemble easily. That housing should slide over the drive shaft and then the pin secures it. No need for anything other than a sliding fit.
Are you sure they haven't updated the model or maybe different country of origin spec ??
 

slick

LE
As others have said, the shaft looks case hardened so fiddling about with that is a no no.
There`s something odd about having a locking pin when the shaft is an interference fit, but then it depends on how much of an "interference fit" it is.
I would think in an ideal situation a small block of wood on one side of the case lightly tapped by a hammer should be enough to drive it into position near enough for it to be rotated so the pin can locate. Is there possibly a burr in the hole or could it be mis-shaped ?
Only solution I can think of is one of the bits below in a dremel, and buzz it around in the hole until the shaft enters reasonably freely.
bits.jpg
 

OneTenner

LE
Book Reviewer
As others have said, the shaft looks case hardened so fiddling about with that is a no no.
There`s something odd about having a locking pin when the shaft is an interference fit, but then it depends on how much of an "interference fit" it is.
I would think in an ideal situation a small block of wood on one side of the case lightly tapped by a hammer should be enough to drive it into position near enough for it to be rotated so the pin can locate. Is there possibly a burr in the hole or could it be mis-shaped ?
Only solution I can think of is one of the bits below in a dremel, and buzz it around in the hole until the shaft enters reasonably freely.
bits.jpg
I would imagine the pin is there to prevent rotation on the shaft, the torque going through that connection will be quite high - especially if a dough hook is being used. Any slack in the joint will allow premature wear to develop not only on that joint, but also on the gears as the contact points will move. IMO, it needs to be as tight as possible.
 

slick

LE
I would imagine the pin is there to prevent rotation on the shaft, the torque going through that connection will be quite high - especially if a dough hook is being used. Any slack in the joint will allow premature wear to develop not only on that joint, but also on the gears as the contact points will move. IMO, it needs to be as tight as possible.
Indeed, but having to press it on seems overkill, a reasonable interference fit would be acceptable. As an afterthought can the other end of that shaft be supported, if not then pressing that black case on might cause undue stress to that alloy case, as it will be supporting the shaft itself.
 

OneTenner

LE
Book Reviewer
I'd be interested to see the measurements - and the smoothness of the bore in the cast piece, if it's reasonably coarse, then its clearly intended to deform as the shaft is fitted.
Fully agree about supporting the other end of the shaft, whatever level of pressure is required.
 
I'd be interested to see the measurements - and the smoothness of the bore in the cast piece, if it's reasonably coarse, then its clearly intended to deform as the shaft is fitted.
Fully agree about supporting the other end of the shaft, whatever level of pressure is required.

I'm sure it isn't the case here, but I once had great difficulty with something that needed a bush reaming before fitting. I didn't realise. It was large, heavy and in a very awkward position. Another school day - trial fit first!
 

OneTenner

LE
Book Reviewer
I'm sure it isn't the case here, but I once had great difficulty with something that needed a bush reaming before fitting. I didn't realise. It was large, heavy and in a very awkward position. Another school day - trial fit first!
One of the best things I ever invested in was a set of expandable blind hand reamers, had them for years - don't get used very often but ideal for jobs like this.
 
If this was in my workshop I would measure the shaft and hole with digital verniers to check what kind of fit they are before deciding how they need to be fitted together. The shaft will need to be within the limits that the hole in the casting can take, if not it will crack to bits. If it's pinned anyway then the fit is not going to be a taking the load or they would have used a splined end.
 

OneTenner

LE
Book Reviewer
.. If it's pinned anyway then the fit is not going to be a taking the load or they would have used a splined end.
Maybe that's why it needs replacing? Machining a spline is more expensive than a pressed interference fit - but yes, it does need measurement, especially given the different materials.
I'd imagine that the fit is to keep the gears in alignment (there's a gear missing from the photo) to ensure the drive is across the working area of the teeth equally.
 
Maybe that's why it needs replacing? Machining a spline is more expensive than a pressed interference fit - but yes, it does need measurement, especially given the different materials.
I'd imagine that the fit is to keep the gears in alignment (there's a gear missing from the photo) to ensure the drive is across the working area of the teeth equally.
Yup @Roadster280 , as @OneTenner says, your photo doesn't show us much :( .

Can you also post a more "general" photo of the components?

I don't anticipate offering a solution, I'd just like to better understand the problem, that the others are discussing !! ;) .
 

Tyk

LE
Is there any chance that there's a ridge (manufacturing defect or caused by you interference fitting) inside the cast part? It wouldn't need to be much to stop a tight interference fit.
From how you described having to get the old part off I'd guess it's more interference than fit as it were. May well have been hydraulic pressed on in the first place.
 
$729 for a new mixer, $40 for the part, so I’ll try fixing it first!

And yes, it is the correct part.
You begrudge spending $40?
Which part of Scotland are you originally from?

If your repair isn't perfect, you do realise when you turn it on you'll break some other part, thus adding to the cost of replacement parts you'll need to buy.

Also, spending $729 in the first place on a food mixer is only something a woman or someone good with colours would do.
 

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