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I have to englarge a hole in s sprocket to fit a hub. The size of the hub is 14.5 mm. The hole in the sproket is 14.1 mm. The plate is about 3-4 mm thick ( I am just eyeballing the thickness since I didn't measure it).
What ideas do you folks have for enlarging this? It has to be centered and I don't have a lathe, which would make this a no-brainer
Ideas appreciated?
Shotgun.
lathe is the right answer, but if you have a steady hand a die grinder might do the trick.
Well, my father would have used something called a "tapered reamer" and from the verb part of the name, that thing would give you nightmares. It looked like a big sidemill tool head except it, well, tapered from maybe 20mm down to almost zero, and it had a T-handle on the big end. The sidemill edges were sharp.
Unfortunately it disappeared when he died and we closed his shop, but something like that may still be available.
Maybe some sort of tapered grinding head mounted in a drill press? Since it is so thin if you can get it close while keeping it centered you can square out he taper pretty easy.
Good ideas Shotgun... not too precise
Some form of tapered thing in the drill press would be the ticket
A cylinder hone might work.
Duke wrote:Well, my father would have used something called a "tapered reamer"
Quite possibly one of the most useful tools I own.
Do you have a drill press?
14.5 - 14.1 = 0.4mm or .0157 inches. You're only removing sixteen thousanths of an inch. With the plate bolted down to a dril press table and the chuck centered over the hole, you can easil sneak up on it with a series of drills.
14.5mm divided by 25.4 = .5708 inches
36/64 = .562 37/64 = .578
Or....
There's a head that can be put into a drill press that holds a lathe type cutting tool. Ease the tool out a few thousanths and bore down the hole. Ease it out a few more, take another pass. It's at .571 before you know it.
Plan B:
Rat tail file, it's only fifteen thousanths. 
Dan
big Unibit?
4cylndrfury wrote:big Unibit?
That's what I was thinking... they work incredibly well at making a hole slightly larger... they only issue is how close to 14.5mm it has to be.
If the accuracy of the hole (center and diameter) is critical, then I would probably just take it to a machine shop. Doubt they would charge you much since I can't imagine it taking more than an hour with the proper tools.
Grind hub ;)
What speed does the sprocket run?
How is the sprocket attached to the shaft, by a nut'n'washer?
Does it have a keyway?
You said sprocket, so I assume a chain.
Does it transmit power, or is it a tension/idler?
What material?
Either a 14.5 mm reamer or tapered reamer would do the trick. Hand held may get the holesize right, but getting it true (so that the sprocket does not wobble) is hard. A drill press will should yield a hole that's fairly true, but a lathe is best.
But a reamer will cost some bux (check McMast-Carr) , cheaper to just pay a machine shop.
As 914Driver suggested, if precision fit is not required, a rat-tail or small half round file. But if it's soft material, carefully carve it with a sharp tool (like deburring the edge, but on the inside surface).
Carter
Looks like this would do the trick, except it's too small. Maybe they make a bigger one?
http://cgi.ebay.com/ebaymotors/Taper-Reamer-1-8-to-1-2-Diameter-KD-2043_W0QQcmdZVi...
Carter
milling machine and a rotory table.
44
You're only taking off .016".
Put a 1/2" diameter sanding drum w/ an 80 grit band in your Dremel and keep it moving with light pressure. I recommend advancing it so it's cutting downhill, ie. same direction as rotation.
Take off a little material, say 10 seconds, try for fit.
Repeat.
A 1/2 round file and vise will work fine too.
Or-
Spin hub, apply flat file to shoulder that sprocket seats on. Should take no more than a minute.
how big is 14.5? what about just using a stepped drill bit in a drill press? you can get them pretty big.
As mentioned earlier, a T-reamer is designed for this job. Readily available, I think mine came from Home Despot.
But a tapered reamer gives a tapered hole. He needs a straight hole.
Then take the reamer in from both sides (hee hee). With 0.016" removed, that minuscule taper shouldn't matter.
alex wrote:Then take the reamer in from both sides (hee hee).
PIITB??OUCHEEEEEEE
Especially if the plate is only 3-4mm thick.
Depending on the material, a hone (the sort you'd use on a master cylinder) may do the job as well.
if its only sixteen thousands of an inch, have you considered freezing the center section and heating up the sprocket and tapping it on?
Spin hub. Apply wet sandpaper. Test fit. Repeat.
andrave wrote:if its only sixteen thousands of an inch, have you considered freezing the center section and heating up the sprocket and tapping it on?
Not .016". A few tenths up to.0008 maybe; possibly .0012 if it had the expansion coeffecient of aluminum. Something would crack upon warm up then he's be back with harder questions.
