View Full Version : Cylinder honing

02-12-2004, 12:05 AM
Does anyone out there know where I can buy a hone for 5/8" to 1" dia. cylinders? I have a break hone which will just go down to 1".

Or does anyone have any ideas for removing the boring marks from this size cylinder?


02-12-2004, 12:33 AM
Check McMaster Carr. They have something called a -ball hone- that comes in a variety of sizes. It sort of looks like a bottle brush, but at the ends of the bristles there are little balls of abrasives.

02-12-2004, 12:37 AM
They are flex hones. J&L also sells them. They are available in a surprising variety of grits.

02-12-2004, 12:39 AM
Yep, them "bottle brushes" work good. I think they go down to 1/4 inch. I've used the 7/8 and 1" on wheel cylinders. Lube, move and watch... they cut quick!

02-12-2004, 12:49 AM
sounds like a job I had on a brake master cylinder. I used a solid rod with a slit cut across one end. make the slit wide enough to accept two stips of emory cloth. wind the sandpaper around the rod untill it's a loose fit in the hole. spin the rod with a drill and use a little cutting oil or wd-40. insert the emory strips back to back. works prety good ad you can make one in ten minutes.

Jason J
02-12-2004, 01:16 AM
You can buy wheel cylinder hones that good down to about 1/2" for import applications. They will tend to straighten the bore you are honing a little more than a ball hone will.

02-12-2004, 01:37 AM
You can make a lap or a split lap easily for that small a cylinder and use lapping compound instead of honing it. I do this for model engine cylinders.

Paul Gauthier
02-12-2004, 01:01 PM
You can find flex hones here:


Paul G.

02-12-2004, 03:11 PM
Make your own lap from some lead. Just machine the lead rod to just fit the bore. Cut a slot down the length of the lap and drill and tap for a small headless screw accross the slot. Use lapping or valve grinding compound on the lap. Run the drill at about 600-1000RPM and shoot some WD-40 at the lap while its running to keep it wet. About 15min to take off 1 thousands.

02-12-2004, 06:15 PM
I don't understand the "...small headless screw across the slot". I'm trying to visualize that's somehow being used to expand the lead slot, but I'm having difficulty.

02-12-2004, 06:23 PM
"a screw accross the slot" This is a small set screw that threads in one half of the lap and presses against the other half accross the slot through the middle of the lap. The screw hole is aligned perpendicular to the lap axis. This expands the lap and keeps pressure on the bore as its being lapped. The lap should fit slightly tight in the bore, but obviously the lap needs to move.

Also, recharge the lap by rolling it through the compound every few minutes. Keep the lap moving through the bore as it turns but don't let it protrude from the bore more than a 1/16" or so. Else, the ends of the bore will be wider than the middle in kind of a hourglass shape.

02-12-2004, 06:37 PM
Is the slot cut all the way thru the rod (except on the two ends),...if so it would seem the screw will bulge the rod only in the middle.
..Or is the slot cut most of the way thru, along the full length, leaving a 'hinge' along one side? In which case I can see the screw expanding the rod uniformly (more or less) along the full rod.

02-12-2004, 08:12 PM
For the homemade lap, the slot is cut from one end of the rod, so it opens a bit more like a hinge. Of course its only going to open a few thousands during lapping job. Sometimes it is helpfull to drill a hole accross the end of the slot cut to relieve the strain.

The lap is usually only good for one job. Then you toss it and make a new one. A steel shaft can be threaded in the end so that only the lead part is the full bore diameter. Also, turn down the lead around the end of the slot so the full width part of the lap has the slot all the way through. The lap need only be a little longer than the diameter is wide.

For example: 1.000" bore x 2" long cylinder.
First make the lead rod by pouring your own. I wrapped a bit of aluminum foil around a dowel and mashed the end closed. Voila, a lead rod mold. I melted some sinkers in an old aluminum pan on the stove and poured into the mold. When cool chuck the lead rod in the 4-jaw on your lathe. Turn a lap just big enough to fit the bore of the cylinder. Test using the cylinder. Turn down the area around the end of the slot by .100 or so. Square, drill, and tap the end for a 1/2" thread. Part off at 1 1/4" Thread the end of about 8" of 1/2" rod. Screw into the lap and hold the assembly in a vise with the lap up. Saw a slot through the full width length of the lap. Next drill and tap a hole, 1/4-20, through the side of the lap to the slot. Put a set screw in and you're set.

Adjust the set screw for a tight fit in the cylinder. Roll the lap in compound. Put the lap in the bore and start the drill. Keep working the lap back and forth. Squirt some WD-40 in there to keep it wet. Recharge the lap every few minutes. Measure often. Note this gets messy so clean well before you measure.

02-12-2004, 08:30 PM
As mentioned by Jason J there are small brake hones available. There is a two stone model that easily goes to 1/2". Snap On, Mac and Matco dealers all have them avaiable as well as the the bottle brush type hones. Brush Research makes them, or used to.