Drill bearing holes on center?

go mike

go mike

Joined
Dec 5, 2008
Messages
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I am working on my 2x72" belt grinder, and I need to get two contact wheels. I found these at this link: http://www.accesscasters.com/8axs82-8-x-2-non-marking-wheel.aspx and they are about durometer 70 in shore a (what Tracy at USAKnifemaker says is the right hardness for grinders), and the only problem I have with them is that they are 3/4" roller bearings with a 1/2" sleeve inside, and they aren't meant for high speeds, so I want to drill a larger bearing hole in the plastic, but I don't know of a good way to do both centering a drill into a 1/2" hole, or what kind of drill to use for drilling the bearings.

Any advice on doing it myself, or is it only reasonable to go to a machine shop and have them drill it bigger? (Really trying for the cheapest route)
 
go mike said:
and they aren't meant for high speeds
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I think that would about sum it up for me. I'm not sure that I would trust that plastic wheel to hold together under speed and grinding load. Maybe someone else could chime in.

--nathan
 
you wouldnt want to drill it out. something like that needs to be bored. the outside of thoes wheels look like they have rounded corners which need to be squared off. i would take it to a machine shop and have them do the work. is there a machine shop in your area? i can do the work for you but i might not be able to get to it for a little while.
 
Nathan, I meant the roller bearings aren't meant for the high speeds; I'm not sure about the rubber/plastic bond.

Richard, I do have a few shops near me, I was just hoping that they could work without more costs. (I haven't bought them yet, I'm still trying to figure out what's best)

Ron, those look like they are more for a drive wheel, on a keyed shaft.
 
When you bore something like this for bearing the size of the bore is only 1/2 of the work. The other half is depth of the bore. If the bearing is say 3/8 through you need the depth of the bore to be that or .375" (actually just under to get a press fit)so that it has a shoulder to keep it from going all the way through. So you have to chuck and center it twice once on each side. I have done this on Grizzly wheels both 8 and 10" also you need a spacer in the center when you install the bearings and bolt the wheel to an arm it does not press the centers of the bearing together. I used a piece of schedual 40 1/2" pipe that I machined to length

That being said. What you need to do is get one of the wheels, pull out the bearing and get a high speed bearing with the same OD and depth as the original with a 1/2 ID. Install those in the original seats and add the spacer in the center which you could make carefully with a grinder out of 1/2 pipe.
 
My small wheels on my flat platen are 1" dia white derlin. It is a wear resistant, capable to work above 200F and very easy to machine plastic. I'm using those wheels about 2-3 years and never showed any deformation. For this application you have to be sure of the plastic type. If not right type your grinder may be out of order in the middle of an important grinding job, and this will be very frustrating...
 
go mike said:
Ron, those look like they are more for a drive wheel, on a keyed shaft.
Click to expand...

Indeed they are. but a machined hole on something rated at 300# plus dynamic load is good to go for your grinder.

It would depend upon your bearing as to whether it works or not. (the size of the bearing)
 
Mike, do you have a lathe at school? I am going to make my idler wheel in September (I graduated but I will come in and bum it off of the school for a day hehe) Gladly we also have a dial indicator, 4 jaw chuck and boring bar there.

On second thought, you could just make it square to the lathe and do the boring and the surfacing in one setup pretty easily. (I think that machining rubber would be a PITA though) It might be hard to chuck it like that, though on third thought.
 
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Keith, there is a lathe or two at my school. Maybe I'll talk to the shop teacher (I am in his class next semester) and see if he could help me out.
 
In case anyone was deeply concerned about this thread: I just ordered wheels with precision ball bearings in them, so thanks for the help, I just didn't need it.
(they ended up being much cheaper too! :thumbup:)
 
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