Interference Fit - Bearings and Axle

[JRMN]

I'm working on a project and I am having an axle turned down to 1". I purchased these bearings. The machinist asked me if he could turn down the axle just under 1", that way I can just slide the bearings up to where they need to go rather than having to press them all the way.

I'm new to all this and I'm wondering if someone could explain how it works for go karts. If you have a 1" axle and bearings, how do you press the bearings the length of the axle?

 

[mckutzy]

A few tho under is fine, just so it slips on or your going to need to get a puller ever time to move the tire off.

 

[JRMN]

Thanks mckutzy. Is there a standard tolerance to go by? If I were to buy an 1" axle and bearings an online shop, would I need to have it turned down or would it already be taken into account? Just wondering what you guys are doing as far as getting your bearings on your axles. Oh and are you talking about a bearing puller, wouldn't that be too short for something like a go kart axle? Most bearing pullers I've seen are about about 6" long.

 

[Scout]

buy the parts and see how they fit. What bearings are you buying? have a link?

 

[Axx3d]

post #1 had a link to these..

http://www.bmikarts.com/High-Speed-Wheel-Bearing-1-x-2_p_2523.html

 

[JRMN]

Yup, those are the bearings.

 

[firemanjim]

The axle should be 1.00 and the bearing id should be like 1.005"......

 

[mckutzy]

I'd just first take the bearing and fit it to the shaft you plan to use. If it slides alright no need to do anything, if not, one probably needs to just polish the shaft and mostlikely wil help.
Machine it if it really needs to.

I should have asked earlier, is this for your tires or is this for a live axle setup?

 

[Doc Sprocket]

As a general statement- when one buys a "shaft" (NOT rod or bar stock), it is dimensionally perfect- which is to say that it has been ground to a very close tolerance. Bearings, hubs, and other accessories sold to go on said shafts, are also finished to a close tolerance- but slightly oversize. As long as the shaft (and bore of the accessory) is rust and burr-free, it is a slight clearance fit, not an interference fit.

However- that's replacement market stuff. Quite often when servicing and engine or gearbox, these parts are indeed often an interference fit. Assembly sometimes requires a press, and can even require freezing the inner part, and/or heating the outer part.

 

[Poboy kartman]

Now. ...I've ran into this....a 1" axle may be a 7/8"......but a 7/8" bearing doesn't fit.....WAIT........That wasn't me.......that was a nut anyway......

 

[mckutzy]

Doc- Ahh yes that is true."true" shaft is ground, I meant keyed shafting, which isnt always ground, its usually a milled cold finish steel rod, typically have good dimensionally straight bar stock.


OP- Pics????

 

[firemanjim]

Doc- Ahh yes that is true."true" shaft is ground, I meant keyed shafting, which isnt always ground, its usually a milled cold finish steel rod, typically have good dimensionally straight bar stock.


OP- Pics????

If its bought from a kart supply house, it's going to be finish ground to 1.000 +- .0005 (count the zeros) ..... If it is an axle someone made from 1" round bar stock, well then that 1" could be anything........
Bearings are made in metric and what us Yankees use, inches... (you get the idea ). If you are buying a bearing for a 1" (25.4mm) shaft, it is made to slide on to that shaft, and with minimal force/no force . (the type we use for kart axles) there is an industry standard tolerance, so that this bearing will slide on, and is considered slip fit.
Remember when you got them new bearings and you had to sand down the axle to get the rust and dirt off? Just that fine layer of crud, is more than enough to keep the bearing from going on or off.......

 

[Scout]

those bearings I would think are more for front wheels/dead wheels. What do you use to hold the OD? Something like this http://www.bmikarts.com/1-Bearing-Kit-3-hole-_p_486.html is what I would use, the ID has set screws to lock the bearing onto the shaft.

 

[JRMN]

@mckutzy, bearings are for my live axle setup (Honda ATC70 axle turned down to 1"). Are they the wrong bearings?

@Doc Sprocket, I am having a Honda ATC70 axle turned downed to 1". I'm also having some bearing carriers made as well. Should I tell the machinist that I want a straight fit instead of a interference fit?

@Scout, I'm using those bearings on a live axle setup. Are they the wrong bearings? I am having some custom bearing carriers made.

 

[OzFab]

Put simply, with those particular bearings, you'll need locking collars as well, if you use something like this, it has a collar built in...

 

[JRMN]

I am using this swinarm and bearings carrier. I started with the swingarm. Bearings carrier, axle, and sprocket and rotor hub will be all custom.

 

[OzFab]

Ah, I remember this one; Yeah, you're gonna definitely need some collars &, maybe, spacers between everything...

When using spacers, it doesn't matter where the lock collars sit, they could be in the centre, as long as they hold the axle centred...

Having said that, you're probably best to have them outside the bearings...

If you're having all the hubs, etc custom made, have them made so they're wide enough to hold everything in place between the bearings, just make sure your math is absolutely spot on...

 

[JRMN]

Only the outer portions of the axle will be turned down to 1" for the bearings and bearings carrier. Axle end has splines, so I'm good there. The middle portion of the axle will be 1.25" to keep the bearings in place. Still not sure what to do about the sprocket and brake hub. My plans was to buy 1" aluminum hubs and have the machinist turn and key them to fit the 1.25" middle section of the axle. Or have the machinist make a custom one piece that acts as a spacer, sprocket, and brake hub.

My biggest issue what to do about the axle and whether I should turn it down slightly less than 1" or not. Still not sure what to do about that.

 

[firemanjim]

Machine it to exactly 1"+/- .0005.....
(I am a machinist first class, 20 years in the business. Manual and cnc lathes and bridgeport type 3axis mills, among other machines..... )

 

[JRMN]

Thanks firemanjim. The entire length of the axle machined -.0005 1" or just a portion?