Boring out a tractor axle

[brewdexta]

Thanks Wyn

Seeing as I'm bored on the train, I thought I would work out theoretically how much the bearing would shrink and the axle expand.

Coefficient of expansion of standard oilite is 12 x10 -6 per degree Fahrenheit which is about 22 x 10 -6 in centigrade/Celsius
Steel is about 13 x 10 -6 per degree centigrade

Assuming a hole/bush size of 52mm
ambient temp of 15c in the workshop
freezer temp of -22
assume I can warm up the big lump of an axle to say 100c with a blow lamp inn the area that matters

equation - linear expansion = coefficient of expansion x initial length x (final temp - initial temp)

results

bush will shrink 42 x 10 -6m and the axle (or the bit around the hole) will expand 57 x10 -6m so in total the difference will be about 0.0001m or 0.1mm which sounds about right.

I should be able to get the axle hotter than that so may get a bit more.

Anyone agree/disagree? Not sure its that scientific as the bush is not solid, may have to work out the circumference of the bush and apply the equation to that an work out how that affects the diameter?

A teabreak conundrum.

Cheers
Andy

 

[AndyStobbs]

The bit which always puzzles me is relative thermal capacity of the parts - for want of a better term. Ie. How can a small part remain at a slightly cooler temp than ambient for long enough to be fitted, when you have such a large part (axle in your case) at considerably higher than ambient temp pouring heat into it the moment they touch.

 

[gordon stephenson]

I don't think I would bother with the freezing bit. Just heat the casing a little.Go for around 0.05mm to 0.075mm interferance (0,002" to 0.003") Get the bush started square and either press in or draw it in using a decent sized bolt and support washers etc. I used to fit 5" diameter. crosshead pins during big Linde compressor overhauls using dry ice, you could hear the metal squealing as it shrunk.

 

[brewdexta]

Thanks guys
I guess it works if your very quick

One thought, it was suggested that I use loctite, not sure that will work on oilite ....

Kids are away with the grandparents this weekend so I should have time to do this.

I was just thinking, the chip shop deep fat fryer would easily fit the axle with room for chips

 

[Bill Edwards]

Well putting things together with heat does work very well - as long as you can get it all the way while the parts are at the right temperature.
It's when you get the thing half way and it all stops that you start to panic.

 

[brewdexta]

So I have got bang it in the hole while it's still hot and hope I don't damage the bush and if I fail I will have to give it a good tug to get it out.

How many double entendres is that

 

[brightspark]

[just make it a slip fit and use loctite 603 job done no fannying about and it wont come loose without great heathttp://www.henkelna.com/product-search-1554.htm?nodeid=8797923082241

 

[Woody.v8]

[just make it a slip fit and use loctite 603 job done no fannying about and it wont come loose without great heathttp://www.henkelna.com/product-search-1554.htm?nodeid=8797923082241

Loctite on oillite though Bs ? Im not sure there's owt to stick to.

 

[brightspark]

Loctite on oillite though Bs ? Im not sure there's owt to stick to.

read on last paRAGRAPH + the locktite gets in to the pores of the oilite bush and set solid

 

[brewdexta]

Loctite on oillite though Bs ? Im not sure there's owt to stick to.

I was wondering that so looking on the practical machinist there are a few that say it does and as BS says, use 603.

And here was me looking forward to banging it in up to the makers name as quick as possible, instead I'm going to take it steady and slide it in nicely

 

[brewdexta]

Thanks guys, sorted, 603 bought

 

[Woody.v8]

read on last paRAGRAPH + the locktite gets in to the pores of the oilite bush and set solid

Every days a school day,If you haven't learned something you haven't listened

 

[brewdexta]

The loctite 603 arrived however I'm having the axle sand blasted before I fit the bush, hopefully I'm dropping off a load of tractor bit tomorrow to be blasted.

In the mean time I moved on to the pin, I drilled the lump of EN24T with a 11/32 drill to a depth of 95mm, then tapped it out to fit a NPT grease nipple. I used this thread as it needed the biggest drill size I had to hand and I had a tap to match.

I turned it down to fit the bush, I tried both indexed tools and HSS and with power feed but didn't get a nice "professional" finish however it was a big lump of 2" steel and I would rather slow it down a bit than have a missile wondering around the workshop. The finish was good enough and I got a nice tight fit in the bush. I drilled through to meet the hole I tapped with the nipple so it would be directly under the middle of the bush.

Here's the dry run to ascertain where to cut the slot for the keeper. Its much easier without the axle.

Just preparing to cut a slot for the keeper and job done.

Cheers
Andy

 

[octo0072000]

Andy remember you will need some groves in the bush or the pin so the grease can get round the axle no good without them

 

[brewdexta]

Hi Octo

I was planning on cutting a couple of grooves on the pin with a ball end cutter.

Cheers
Andy

 

[octo0072000]

all the bushes ive seen over the years seem to have had like X on both sides joining for the grease to flow
but on your use any grease is better than none and will still be ok long after you and me and a lot of others have left this earth

 

[brewdexta]

I was toying with the idea of doing something fancy and use my dividing head to make a spiral groove but I thought the same as you, it will outlast me, and I would probably screw it up in the process

 

[octo0072000]

I was toying with the idea of doing something fancy and use my dividing head to make a spiral groove but I thought the same as you, it will outlast me, and I would probably screw it up in the process

like it samr thoughs all the best Andy

has the toylander been fixed now ?

 

[brewdexta]

I have moved the toylander back into the workshop to fit "Pennine" class brakes, fix the bumper, touch up the paintwork, fit the windscreen and generally finish off the wiring. I also need to make a secure cage or garage for it so it can sit in the barn without doing a Herbie and going off on its own

 

[octo0072000]

can't you use the original scooter brakes or are you thinking push bike discs