Bearing fit problem

[Drei]

Another question,

I have a situation where i want to fit a needle roller bearing in a crankcase. The bearing diameter is 8mm but as you know this has to be a press fit hole say like a diameter of 7.98 or so. But the problem is that the hole is located in the crankcase at about 40mm deep from the edge. i tought of boring the hole but the is only about 3 mm clarance from the crankcase wall. i was going to bore it in the milling but at that small diameter and long distance i think i wouldnt achieve the dimensions i want.
i already have already tried reaming the whole on a piece of scrap with the same setup; but the hole came to big and the bearing wasnt a press fit!
What set up i van use and do you have more iedas....??

Thanks

 

[gbritnell]

Hi Drei,
There's no reason that the reamer should make a hole bigger than the nominal size of the reamer unless the holder isn't holding the tool concentric to the spindle. In that case it acts like a boring bore as it rotates off center.
gbritnell

 

[Drei]

I have tought about that and i held the reamer in the collet chuck rather then in the chuck to achieve more centricity. The hole will come bigger by 0.01 to 0.03 which will be the clearnce of the spindle beraings and the collet chuck and without mentioning the ecessive lenght which the reamer is protruted because the depth. This will be enough for the bearing to go in without a good fit.
If theres no resonable solution i toghut of loctite the bering in place after i assemble the shaft and it will harden in place.
Please comment and give me feedback

Thanks

 

[Drei]

Sorry for my to much questionsbut i have some free time and i want to gater as much info as possible....
What will be the ideal clearance on a 8, 10 and 12mm diameter shaft to be a good push or press fit in a ball bearing?? i was hoping for 0.02 to 0.04 less than the proper shaft diameter.

Thanks

 

[jonesie]

drei, when you put the reamer in the collet chuck set up an indicator on the table and set it up on the reamer and rotate the reamer by hand and check to see how the flutes are running, and see how far it is running out, you can take a small piece of brass and tap on it and getting it to run true, if it is not way off, you can also loosen it and turn in collet and then reindicate. i would only have about.01 or .0005in undersize for the press fit. good luck jonerie