Not very practical that’s all. Though, better than burning and blistering nice paint.
Bearing temps frustration.
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Dry ice isn't bad to work with. Do have to be careful or you can get frostbite.
I used to work with liquid nitrogen too, ~ -195 oC. You could put a banana in it for a while, then hit it with a hammer and it would shatter like glass. We had some jokers in the lab and one time one of them put a fish in the liquid nitrogen........
I used to work with liquid nitrogen too, ~ -195 oC. You could put a banana in it for a while, then hit it with a hammer and it would shatter like glass. We had some jokers in the lab and one time one of them put a fish in the liquid nitrogen........
Ok, at -6 degrees celsius which was what the bearing temp measured using a digital temp probe on my mm when it came out I got 27.98mm
it started at 19c
so correct me if I’m wrong with the following maths
Temp difference is 25c
Diameter change is 0.02mm
0.02 divided by 25 is 0.0008
Essentially for each degree dropped in the freezer is 0.0008mm diameter smaller.
For this bearing to fit in the pocket, it needs to be less than the pocket dia which is 27.96mm so let’s just say 27.95. which is measured at room temp at
so I then heated the mag case, this only took 120c (remember me saying about older saws and much sweeter fit)
so
To get a clearance of 0.05mm I needed a change of 103c
103 divided by 0.05 is 0.00049 (0.0005 rounded) so every degree c extra is 0.0005mm extra in dia clearance.
So in summary
if I rely on freezing alone I’ll need a temp of -75c theoritically
if I rely on heat alone I need 103c
if I freeze the bearing as cold as I can get it I’ll need a clearance of 0.03 still which means I’ll then need a temp of 60c
I’m sure the maths isn’t perfect here for sure, I’m not sure expansion is this linear.
Anyway, now I’m going to re freeze the bearing and see tomorrow if it will drop in a 60c case will report back. If it does work and I really can reduce the temp that much I’ll eat my words and apologise admitting I’m wrong. Watch this space.
it started at 19c
so correct me if I’m wrong with the following maths
Temp difference is 25c
Diameter change is 0.02mm
0.02 divided by 25 is 0.0008
Essentially for each degree dropped in the freezer is 0.0008mm diameter smaller.
For this bearing to fit in the pocket, it needs to be less than the pocket dia which is 27.96mm so let’s just say 27.95. which is measured at room temp at
so I then heated the mag case, this only took 120c (remember me saying about older saws and much sweeter fit)
so
To get a clearance of 0.05mm I needed a change of 103c
103 divided by 0.05 is 0.00049 (0.0005 rounded) so every degree c extra is 0.0005mm extra in dia clearance.
So in summary
if I rely on freezing alone I’ll need a temp of -75c theoritically
if I rely on heat alone I need 103c
if I freeze the bearing as cold as I can get it I’ll need a clearance of 0.03 still which means I’ll then need a temp of 60c
I’m sure the maths isn’t perfect here for sure, I’m not sure expansion is this linear.
Anyway, now I’m going to re freeze the bearing and see tomorrow if it will drop in a 60c case
will report back. If it does work and I really can reduce the temp that much I’ll eat my words and apologise admitting I’m wrong. Watch this space.Tom I can see you running an Australian version of Project Farm..
i have the obsessiveness, but I don’t have the money
Joking aside, It’s a horrible thing being so obsessive - it’s a mindset and way of being I should really try and get out of. For all intents and purposes it’s a total waste of energy, time and money 99% of the time. I envy people who are happily satisfied with “that’ll do” which is true, it really would the overwhelming majority of the time.. hmm. Tangent there sorry.
I guess this whole thread is case in point… who gives a rats ass about exact temps. Heat the thing up and put the bearing in, if it gets stuck, slap it a few times wjth a hammer on the outer race and seat it. Maybe you’ll damage the mag slightly, but you’ll have to change bearings multiple times like that to do any noticeable damage to function..
The key is knowing the point of diminishing reruns, what you can get away with and when. That’s where the beauty in anything lies I guess..
Right, back to work. Catch you guys in the morning.
No worries. I think the trick to it is to get a bunch of viewers donating money..i have the obsessiveness, but I don’t have the money
Joking aside, It’s a horrible thing being so obsessive - it’s a mindset and way of being I should really try and get out of. For all intents and purposes it’s a total waste of energy, time and money 99% of the time. I envy people who are happily satisfied with “that’ll do” which is true, it really would the overwhelming majority of the time.. hmm. Tangent there sorry.
I'm more of "it'll do" but it does end up with things being a mess and Hodge podge all the time..
Canyon Angler
Addicted to ArboristSite
Sounds like your freezers over there in Oz ain't very cold. Here in Virginia, in the middle of summer, our kitchen (front-loading) freezer stores food at about -10°F = -23°C
Maybe you're not hustling fast enough after you pull the bearing from the freezer.
Submerging the bearing (inside a Ziploc bag) in an ice-brine bath should help keep it cold until you drop it into your hotsaw.
Maybe you're not hustling fast enough after you pull the bearing from the freezer.
Submerging the bearing (inside a Ziploc bag) in an ice-brine bath should help keep it cold until you drop it into your hotsaw.
Very good point about temperature…
I just took a temp reading inside the freezer with the IRT all around with an average of about -15c…
I’d have thought the multimeter thermometer would be more accurate than IR as it’s actually contacting it. I guess not.
therefore let’s say the bearing at -15c dropped 0.02mm
0.02 divided by 35 = 0.0006mm (shrinkage per degree loss in temp)
I have just tried the bearing, but warmed the case to 70c rather than 60 just to make up for any slight errors in rounding. The bearing has been freezing for about 13 hours, I’d have thought that’s long enough to freeze fully. It got stuck right away when putting it in the case
it’s back in the freezer and I’ll try 100 degrees c… then 110 which it surly should slip in. If not it’s quite conclusive freezing really doesn’t do much..
Don't your dare put that bearing in a salt brine bath! Literally this is the method I use at home. I have no idea how cold the bearing gets, but it lives in the deep freeze for a day or so. If the case half is small enough it goes in the toaster oven at 350*f for half an hour. (I drag this down to the basement, only when my wife isn't home. Don't tell er she would kill me!) Half hour later out of the oven, go grab the bearing. Flop it in the hole and smile. Give it a second and it gets a sharp rap with a plastic dead blow to make sure it seated and its done. If it gets stuck a bit the hammer gets it down and in. I have a bunch of "driver plates" made up out of old bearing races. Steel round bar and what not to use as drivers. I seldomly need to use them if I'm doing my part. If the wife is home I use my map gas torch and heat up the case till the temp gun hit around 375*f in the pocket area. (Same thing I do if I can't fit it in the toaster oven.) Then in goes the bearing, wash rinse repeat. I can admire a bit of OCD, but it is just a bearing, that most mfg would just press in, or sell tools to press/pull in.
No offense meant Tom.
I heat the cases up with a propane torch for a minute or two after the oil in the cases starts smoking. Never hurt any paint on the outside and I don’t **** around with having to freeze the bearings. It’s just a saw
No electronics in good old mercury or alcohol thermometers to go haywire. I keep a few scientific/lab alcohol ones handy.
Cleaning up mercury sucks, powdered sulfur makes an amalgam, that can be swept/sucked up.
Cleaning up mercury sucks, powdered sulfur makes an amalgam, that can be swept/sucked up.
Canyon Angler
Addicted to ArboristSite
Yeah, and you definitely don't want mercury anywhere near aluminum.
Can you say, "Magnesium rot on acid"?
Canyon Angler
Addicted to ArboristSite
I'm not sure what you expect to "prove."
Regardless of what you do with the case, regardless of what temperature you heat it to, lowering the temperature of the bearing will make it smaller. That's not debatable.
Making the bearing smaller will make it easier to fit into the hole. That's not debatable, either.
And making it easier to fit into the hole isn't "useless."
Regardless of what you do with the case, regardless of what temperature you heat it to, lowering the temperature of the bearing will make it smaller. That's not debatable.
Making the bearing smaller will make it easier to fit into the hole. That's not debatable, either.
And making it easier to fit into the hole isn't "useless."
But what if you are trying to pull an old used bearing into a dirty old pocket? Which formula works best then?
I think if the action taken doesn't make a noticeable difference in the process, then why do it? If freezing the bearing doesn't make it shrink enough to make a difference, why do it? There's plenty of advice out there that comes from people just doing what they've always done and not testing it to see if it is actually worthwhile.
You’ve hit the nail on the head Adam.
but heating or cooling a "ring" will have more effect on the dia than heating a casing
a ring shaped metal is very free to expand, whereas a casing usually has ribs and gussets that are pushing against that expansion
a ring shaped metal is very free to expand, whereas a casing usually has ribs and gussets that are pushing against that expansion
It's a pretty basic idea, that's been proven to work. Im not understanding how you think it's an unproven method? Bearings and sleeves are installed via this method every day in the machining industry. Especially if there are high press fit requirements. Normally your not using a freezer, your using dry ice or liquid nitrogen so your freeze action will be much greater, and I will guarantee most go for much hotter then what tom is aiming for. By the his math the bearing should fall right in, but clearly he loosing too much heat or the bearing is warming up too fast, or both.
You’re going off topic Sean, I agree at liquid nitrogen or dry ice temperatures which are between -80 to -200c of course there will be a useful advantage for even chainsaw bearing instal. No one is questioning that. In fact I’m very aware that even the warmth of your hand holding a piece of metal, that has been machined to fit at room temp (so a change by what, maybe 15c) no longer will fit if you hold it a few minutes.
I’m testing if your home freezer has the ability to make any practical difference in installing bearings into chainsaw pockets (which so many teach and recommend as gospel).
Precision machine / milled / lathed fits where the mating surfaces are perfectly round within microns, any temp change makes a big difference to the fitment, that’s a precision fitment. A 40 year old cast chainsaw bearing pocket is far from precision.
People can do whatever they like and whatever makes them happy though, it was more to clarify it for myself and if others wanted to come along for the journey then all the better. Enjoy the video,
