Reconditioning a linear slide rail?

[hotponyshoes]

Probably better asking this on here than a catering forum!

I've obtained a cutter thing for making chips.
It's hand powered so not exactly a high speed or precision tool


Basically you pull the handle and the top bit moves up and down the 2 shafts in the picture.

Now these have worn quite badly and, although it's not a precision tool there is enough slop that the spud pusher die catches on the blades if you don't hold the handle in just the right position which makes it slow to use which defeats the whole point of having it.

The 2 shafts are some sort of magnetic steel. Inside the alloy housing are bushes (I'm guessing bronze) that are probably pressed into place.

The shafts themselves are not so much of an issue as I don't think they have worn much. They is a bit of corrosion but I reckon I could polish them both up ok.

Then maybe just press the bushes out and replace them with new ones?

But, the O/D of the shafts is about 15.4mm.
The O/D of the bushes is maybe 18mm
The I/D of the bushes is about 15.8mm depending where you read it.
Length of the bushes is about 60mm.

Is it likely that a 60mm x 18mm/15.5mm bush would be a standard stock part?
And if it was, would 0.1mm be a suitable clearance for this sort of thing?
Or are they more likely to be imperial sized?
(It's a modern European machine though)

I'm fairly optimistic that I can get the old bushes out. I can heat the whole alloy block if required or cut them etc and should be able to press the new ones in if I can find them.

The other thing I though of doing is trying to ream the bushes out to 16mm (or whatever size reamer I can find) then get some new bar (maybe stainless) but the bars have a step and a thread and I need 2 of them so there will be a bit of machining involved plus the bushes have worn oval and I'm not convinced they won't pick up and start spinning if I try reaming them?

 

[eLuSiVeMiTe]

Machining the shafts down a little and making new bushes to suit would probably be the best course?

 

[Screwdriver]

The bushes are currently disposable so I'd start with them. If you can ream them out, nice easy job, just replace the shafts with larger items to suit.

If the bushes start to spin then they should pop out easy enough and you can decide if replacing them is easier than finish reaming or replacing with new to suit the old shafts.

 

[Agroshield]

Look for bushes in the correct or nearest size and then make the shaft to suit them.

Presumably, they need to be somewhat food safe, so standard oilite might not be OK. I do not know if oilite do an edible version. Maybe Igus bushes would do.

It is a lot easier to turn down the outside of of a bush than to ream it. If you need to spend money on a reamer, get one to ream the housing so the new bushes fit nicely. Cut through the old ones from the inside with a hacksaw and they will drop out.

Nearest standard sizes would be 16mm or 5/8" for the shaft/bush ID. You could keep the reduced diameter, threaded lower section of the old upright, turn a plain shoulder on it and loctite on a plain stainless extension. Then the only machining you do to the stainless is to drill a hole in it. I would start with 19mm or 3/4" for bush ODs.

 

[pressbrake1]

Imperial dimensions?

 

[mike os]

Check the shaft is reasonably round and parallel first.

If they are then just replace the bush.. no need to make it overly complicated

If you still have play then replace the shafts with something turned to fit the new bushes

 

[500e]

Split Bearing Bushes from Bearing Boys

Bearingboys has a range of glacier style bearing bushes, split bearing bushes, flanged split bearing bushes, DU split bearings & DX split bushes. Buy online today for great prices and fast delivery.

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[bricol]

Need to measure a bit more accurately - then

Bearing Selector | Bearing Calculator | Bowman

www.bowman.co.uk

 

[hotponyshoes]

I had a quick look last night and couldn't find any bushes/bearings the right size.

I have found some 18mm od x 16mm Id but only 25mm long but I reckon for this application i could press one in at each end and leave a gap in the middle and it would be fine.

I've also got some 16mm stainless bar here.
My concern is if there will be enough clearance on this?
Is a 16mm bronze bush designed to slide along a 16mm shaft?
If I'm going to need to ream the new bushes out (or turn the shaft down) then I may as well just make something from scratch to start with.

The bronze bushes are only a couple of quid each but the postage is a tenner so I may as well order all of them at once so then I'm up to 20quid of stuff that might not work!

I'll have a look at the reamers today as I might have something suitable. With the existing bushing being worn oval I'm not sure how well it will work and I'm not sure if the alignment will be correct if I do manage to make them round again but I reckon I can 3d print a couple of pegs to check that easily enough.

And, like screwdriver said, if they do pick up and start spinning they can come out for replacement

 

[hotponyshoes]

If they are food-grade oilites there are likely two bearings, not a single one.

This might well be the case.
I noticed when looking for new ones that 60mm was far longer than any that diameter were available.
I'll clean the existing ones up tonight and have another look at them..

 

[tom2207]

turn some ptfe ones , its only potato chips ,,,, its not a space chip your working with here

 

[mike os]

if you want accuracy you really want centreless ground/linear shaft.... which will be 16.00mm +- a knats ball hair

however i foresee issues with concentricity and pin alignment unless you can turn very accurately

 

[Agroshield]

I have found some 18mm od x 16mm Id but only 25mm long

I've also got some 16mm stainless bar here.
My concern is if there will be enough clearance on this?

A bush top and bottom will be fine. The 10mm gap in the middle will grow a good colony of e-coli.

You will not need to turn down the shaft. At worst, you will need to polish it down a bit. Install the bushes and try the shaft in the hole. Do not test fit until the bushes are installed as they can close up a tiny bit when you push them into the housing.

however I foresee issues with concentricity and pin alignment

If you connect the new to the old with a loctite joint, you can run the outer up and down the shafts to self-align before the loctite sets.

 

[Chippie]

When/if you install new bushes, use a piece of steel bar of the appropriate size, will aid setting the bushes into the housing and help prevent them closing up/aid alignment....try lubing with some Vaseline..