Drill Blanks

[mechanix]

I've been trying for over a month to find a drill rod or something similar that is just under 12mm (around 11.95m) so I can fit the 12mm bearings on it that I got from VXB.com. I've bought three separate 3' lengths of rod and none of them have worked. The last one I got from Fastenal and I measured it while I was there with their calipers and it said 11.91mm, but when I got home it was 12.01mm . This is the last step that I'm waiting for and has keeping me from finishing my two-month-long project.

I need about 3 feet of it, if anyone knows a source I would be forever indebted!

Joel

 

[johnrobholmes]

Are you getting cold rolled, or actual drill blanks?

 

[recumpence]

This is common.

I would buy precision rod for this. However, what you can do is spin the shaft at high speed in a drill press and hold sand paper to it and run the paper up and down the shaft while it spins. This will take a while, but you will be able to size it down to your needs.

I have done this MANY times myself.

Matt

 

[Jeremy Harris]

I've done the same. Over here what I think you call drill rod is sold as silver steel - ground round bar tool steel with an accurate diameter. Sometimes you can press fit a bearing straight on, but more often than not a thou or so needs to be taken off to get a reasonably good sliding fit.

Doing as Matt suggests works OK, although I'd caveat it by saying that you really need to polish the shaft up after sanding it, just to smooth the scratches out, as the scratches can themselves make the bearing a tight fit and mislead you into thinking that the shaft is still over size.

Jeremy

 

[olaf-lampe]

Just put the rod in the deep freezer and measure again...
and heat the bearings up, as much as they are allowed to.
If it's still too big, I agree with Jeremy. A good polish is better than sanding it down too much. (necessary to overcome the bad surface)
Be quick, you've only one chance...
-Olaf

 

[vanilla ice]

$13.01 Mcmaster #2900A412 is what they are calling 11.90mm but its only 5 3/4" in length.

 

[recumpence]

Just put the rod in the deep freezer and measure again...
and heat the bearings up, as much as they are allowed to.
If it's still too big, I agree with Jeremy. A good polish is better than sanding it down too much. (necessary to overcome the bad surface)
Be quick, you've only one chance...
-Olaf

The problem with that is you cannot get the darn thing off again.

Jeremy,

Yes, you are correct. I always shine it up with red Scotch Brite pad afterward.

Matt

 

[etard]

Hey Joel,
If you wanna send me a bearing along with those drill rods, I can get that machined to fit your bearings for you. Also, have you tried to freeze the drill rod and heating up your bearings? I would think this will get you a pretty close fit, if not the recumpence approach should work, I've done this myself too. Do you really need 3 feet? What are you making??!!

 

[mechanix]

Thanks for all the replies! Earlier today I went to a local machinist and he ordered some precision ground steel that is 12mm +.000 -.004 If it's still too big I'll give the sandpaper/scotchbrite a try.

etard,

Thanks for the offer, but I think round three is gonna work (hopefully). The reason I need three feet is because I need about six inches for each one of my hxt 80 100b motors, and the swingarm axle also happens to be 12mm in diameter. It comes out to around 22" total, but these items tend to come in larger segments and it's also usually cheaper to buy one large one then cut off the pieces you need.

Joel

 

[mdd0127]

I ordered a 3' section from speedymetals online and the bearings will press onto it without much effort. The shaft is 12.0mm. The VXB 2RS bearings are 11.95-11.96 id. I was worried about expanding the race but it didn't seem to affect anything. You can't get them on by hand but with light pressure in a vise and they slide right on. You can get them back off again with an automotive style puller but it is very possible that this could damage the races. I have been lucky so far.

I like Matt's idea though. If you clamp a piece of wood to your drill press table and drill a 12mm hole in it, you could use it to hold the end of the shaft during the operation.