Heat up bearings to fit them?

[screene]

I just called a local machine shop, because I don't have a suitable tool to drive new bearings onto the steering stem of my 91 Trident. To my surprise, the guy said they could fit them but would do it by heating the bearing up.

It made me think that I could probably do this myself. Does anyone know how hot I could get the bearings before damage would occur? I am thinking of maybe where the steel just starts to turn red - is this right?

Also, would there be any advantage in putting the steering stem in the freezer overnight first?

[dphex]

heat and bearings just sounds bad, i use a piece of 2ft long all thread,,aka really long threaded steal rod, with a steal plate on each end ,with a hole for it to go on to the rod, then put a nut on each end,and tighten till they are seated,works just like a press, cost is only a few bucks,

[screene]

Threaded rod was what I was planning to use for the new races, as you suggest.

My question was about fitting the bottom taper bearing onto the steering stem - I can do this with any kind of threaded device, the only way to do it would be a piece of tube wide enough to go over the stem, but narrow enough to bear only on the inside of the bearing. Impossible to find without access to a lathe, because the OD need to be <37mm (ie smaller than a piece of inch-and-a-half mild steel tube) and the ID need to be >32mm.

[andrewb]

Heat as in "hot plate", not torch.....

USE NO OPEN FLAME

If you warm/heat the grease packed bearing to between 200~300 degrees F it will slide onto the (cleaned) stem. (takes 30 minutes)

Alternatively, you can put the stem in the freezer for a few hours and try putting it together.

I prefer the heat method.

Andrew

[Poacher886]

Surely heating the bearing will cause the metal to expand in all free directions, causing the hole to shrink.!

[Roden]

Originally Posted by Poacher886

Surely heating the bearing will cause the metal to expand in all free directions, causing the hole to shrink.!

Heating the bearing will expand the bore and it will slip easily onto the shaft.

Don't go near it with a flame. A way we used to do it years ago was in an oil bath. Heat the oil up with the bearing in it, nice uniform expansion. Popping it in the oven will work too. Remember though, when its time to fit the bearing, don't muck around, as soon as the warm bearing touches the cold spindle, it will lose heat rapidly and shrink, you don't want to get stuck half way. Also make sure your spindle is nicely polished up (with fine emery) and have a drift on hand to tap the bearing home. Only tap the inner race, if you hit the outer, its buggered straight away.

Cheers,

Roden

[KitNYC]

Here's one I picked up from the fork-swap thread over on the Sprint forum:

Take the old bottom race you removed from the stem. Cut through it on one side. You can now use it between your new race and your steel tube.

Cheers, HTH,
-Kit

[screene]

Originally Posted by KitNYC

Take the old bottom race you removed from the stem. Cut through it on one side. You can now use it between your new race and your steel tube.

Do you mean cut a slot in the side with an angle grinder so I can open it out a bit? I did wonder about that. Only problem is, I don't have a steel tube.

I think it's going to have to be heat all the way. Thanks for all the advice gentlemen, I was going to do it with a blow torch, but I'll put it in the oven instead.

(This is the kind of situation which gives a man an excuse to buy a lathe )

[screene]

Well, tried to heat the bearings in the oven for an hour, and also put the stem in the freezer. The bearings got jammed onto the stem way before the bottom - they didn't seem to go much further down than before I'd heated them. They'd also turned blue, so were (I guess) plenty hot enough.

Anyway, the stem's now with a dealer - they're getting new bearings and fitting them to the stem. The engineer said they don't use heat, they drive them on with a drift as per the Triumph manual (and Haynes).

A word of warning. I bought cheap bearings off ebay (£20 for both). Turns out they're missing a seal that should be fitted to the bottom, so wouldn't have lasted long anyway.

I'm going with OEM this time.

[andrewb]

A word of warning. I bought cheap bearings off ebay (£20 for both). Turns out they're missing a seal that should be fitted to the bottom, so wouldn't have lasted long anyway.

Sounds like a blessing in disguise. Two things not to buy off Ebay, cheap Bearings and no-name Brake Pads.

Glad that it'll get worked out though.