Keeping concentricity using tube on axle question

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jon price
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Keeping concentricity using tube on axle question

Postby jon price » Sat Feb 04, 2023 2:12 pm

Hi

I want to bush a 1/8" axle to 4mm.(I need to do the whole axle) I can obtain brass tube which is OD 4mm, and either 3mm or 3.5 mm ID. !/8" is by my calculation 3.175mm.

Is there a way to use the 3.5mm ID tube whilst maintaining concentricity? If not would it be possible to bore out the 3mm tube to 3.175mm without a lathe, maybe using a 1/8" drill bit?

Jon Price
Connah's Quay Workshop threads: viewforum.php?f=125

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Winander
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Re: Keeping concentricity using tube on axle question

Postby Winander » Sat Feb 04, 2023 3:59 pm

jon price wrote:Is there a way to use the 3.5mm ID tube whilst maintaining concentricity?

Without machine tools, very unlikely,
jon price wrote:If not would it be possible to bore out the 3mm tube to 3.175mm without a lathe, maybe using a 1/8" drill bit?

A hand reamer would be better but I don't see why a drill wouldn't work. It depends on the accuracy of the drill dimension - cheap drills are often smaller than advertised in my experience. You can buy 3.1mm drills and it may be better to open up the tube in stages. You will need to think about holding the tube without distorting it e.g. in a second chuck.

The question that will be asked is, exactly how concentric does it have to be and how many times do you have to do it?
Richard Hodgson
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davebradwell
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Re: Keeping concentricity using tube on axle question

Postby davebradwell » Sat Feb 04, 2023 4:30 pm

I suppose you might look for 5/32" X 1/8" tube although it would be a thou' undersize if it matters.

DaveB

Stephan.wintner
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Re: Keeping concentricity using tube on axle question

Postby Stephan.wintner » Sat Feb 04, 2023 5:04 pm

I've not tried it, but Ian Rice claimed loctite works, in part, by expanding. So using it should help minimize eccentricity.

But I would the 0 3 mm is too big a gap, better to ream out a 3mm ID Tube. Or use 1/8 ID as Dave suggested. Drills can wander, I'd ream it.

Stephan

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Tim V
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Re: Keeping concentricity using tube on axle question

Postby Tim V » Sat Feb 04, 2023 5:16 pm

If you are doing the whole axle, why not use a piece of 4mm material and forget the bush?

Alternatively you can use heat to expand materials, and pop the axle in the freezer to shrink it - maybe an idea?
Tim V
(Not all railways in Somerset went to Dorset)

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Will L
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Re: Keeping concentricity using tube on axle question

Postby Will L » Sat Feb 04, 2023 7:52 pm

Stephan.wintner wrote:I've not tried it, but Ian Rice claimed loctite works, in part, by expanding. So using it should help minimize eccentricity.

I've always understood Locite retaing fluids are supposed to centre concentric shafts/ gaers. Their documerntaion suggest that a .25mm gap is the uperlimit.
See LOCTITE 638 High Strength Retaining Compound

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jon price
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Re: Keeping concentricity using tube on axle question

Postby jon price » Sat Feb 04, 2023 9:33 pm

Thank you everyone for the helpfull comments. I can't start with 4mm rod, because I'm looking at Romford axles to upgrade an HO loco. As far as carefully reaming this might be quite frustrating for me with my skillset. I wondered about the centering abilities of Loctite. In the end however, as a result of my query I have a kind offer from someone clearly better equipped than me to ream out the tubes which I am going to take up.

Sorry to have put in a request which turns out not to be P4, but the expertise in S4 soc is applicable across all scales. I am also still building P4 stuff (in fits and starts) honest!

So thanks again

jon Price
Connah's Quay Workshop threads: viewforum.php?f=125

Terry Bendall
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Re: Keeping concentricity using tube on axle question

Postby Terry Bendall » Sun Feb 05, 2023 9:17 am

jon price wrote: In the end however, as a result of my query I have a kind offer from someone clearly better equipped than me to ream out the tubes which I am going to take up.


Which is where the advantages of an area group or local club help and this is probably the best solution to the problem.

Winander wrote:You will need to think about holding the tube without distorting it e.g. in a second chuck.


This is always a probem when holding thin tube. A pin chuck is useful, if it will open enough to hold the tube. I quite often use the tailstick chuch from the lathe. Another way is to use the chuck of a hand drill, either a traditional hand operated wheel brace or even a power drill. (Not under power of course)

Terry Bendall


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