How To Chamfer A Hole That Enters A Bore?

[great white]

That probably sound confusing so let me expand on that.

I've got a motorcycle master cylinder. It's a typical Chinese bit of execution. Which basically means it's all there, but needs some cleaning up and adjusting.

The bore has a piston with seals on it and it runs back and forth to build pressure in the braking system.

In that bore is a drilled hole to allow fluid from the reservoir to enter the bore.

The problem is the hole was simply drilled and left at that. There is a burr (which is obviously bad for the seals and piston) and i would like to put a light chamfer on the hole edge to make life a little better for the seals.

Now the bore is only 19mm ID, so no real room to get anything in there. The drilled hole is even smaller, perhaps 1/8" of so.

I've seen rather expensive (what I would call) internal chamfering tools, but i can't justify a high dollar tool for a one time use and having it cost a couple times more than the master cylinder itself.

Can anyone think of a way I could do this without resorting to some expensive piece of tooling?

 

[JimDawson]

Two ideas come to mind: A quick pass with a brake cylinder hone might do the job. Or...Reach in with a carbide burr and deburr the hole that way.

 

[great white]

Two ideas come to mind: A quick pass with a brake cylinder hone might do the job. Or...Reach in with a carbide burr and deburr the hole that way.

good suggestions, but I don't think they will work the way I need.

the bore is anodized and I'd rather not run a hone through it.

The bore is also so small that I can barely get more than my finger tip in it so I don't think I'd be able to maneuver anything in there.

 

[JimDawson]

OK, reach down through the 1/8 hole with a bent paperclip in an electric drill and burnish the burred edge.

 

[Tony Wells]

Well, short of dragging out all of the camera gear, I rigged up a magnifier and used my phone. If you want, later I'll get some better pics. This is ground from a 1/8" center drill. I made it to deburr the backside of some 0.1245 holes. Made a decent chamfer.

 

[great white]

OK, reach down through the 1/8 hole with a bent paperclip in an electric drill and burnish the burred edge.

That's quick and simple, I like it. I'll give it a try.

Well, short of dragging out all of the camera gear, I rigged up a magnifier and used my phone. If you want, later I'll get some better pics. This is ground from a 1/8" center drill. I made it to deburr the backside of some 0.1245 holes. Made a decent chamfer.
View attachment 134108 View attachment 134110

Neat. Kind of like the ones you can buy but on a smaller scale. I'll see if I have enough room to try that if the paper clip idea doesn't pan out...

 

[Tony Wells]

I forgot to put in that I simply put it in a pin chuck (pin vise, whatever you prefer to call it), or a spare 0-1/4" drill chuck. This is all hand work mind you. Don't get the idea to put it in the mill, or use it in a Dremel. Stick it through the hole, push it sideways and pull it back as you turn it. Be sure and clean out the little chips. You said the port was about 1/8", so something like this should be workable. It was just a broken, long center drill. The reduced area behind the cutting edge on it is about 0.09 dia, so I had no trouble putting a 0.010-0.015 edge break on the back edge. This tool lasted years, and still works as intended. I don't think my eyes would let me grind one these days as good as that one. Hands aren't as nimble as then either.

 

[kd4gij]

It is aluminum I would use a small rat tail file and clean the burr up. through the bore. Or a small round grinding stone in a dremel tool.

 

[Cobra]

I forgot to put in that I simply put it in a pin chuck (pin vise, whatever you prefer to call it), or a spare 0-1/4" drill chuck. This is all hand work mind you. Don't get the idea to put it in the mill, or use it in a Dremel. Stick it through the hole, push it sideways and pull it back as you turn it. Be sure and clean out the little chips. You said the port was about 1/8", so something like this should be workable. It was just a broken, long center drill. The reduced area behind the cutting edge on it is about 0.09 dia, so I had no trouble putting a 0.010-0.015 edge break on the back edge. This tool lasted years, and still works as intended. I don't think my eyes would let me grind one these days as good as that one. Hands aren't as nimble as then either.

I think one of the key points here was that this is hand work not suited to a mill, drill, or dremel tool. Working with aluminum at that scale will only take grams of force to take the edge off the hole.

 

[tq60]

You also can get a ball shaped burr and by hand through the cylinder push up against hole and turn by hand.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk