KeithB
Resident Half Fast Machinist
One of the items we recently started making is a two piece tailwheel for a pneumatic tire. The inside flange of the wheel where the bead of the tire contacts it needs to be roughed up to prevent the tire from slipping when the plane touches down and the wheel goes from 0 to 90 MPH in a split second. When we ran the first batch we used a small drill and the capabilities of our CNC mill to make 180 drill dots. While this worked OK it was time consuming and could be done better. Since we want to give our customers our best efforts I decided to make a simple tool to do a better job faster.
The tool is made from a scrap piece of 1" diameter 1018 steel. I turned the end down enough to clear the knurling wheel and drilled and reamed a .250" hole in the end. Next I used the manual mill to cut the shank down to 3/4" square to fit my lathe's quick change tool holders. I also drilled and tapped a hole for a setscrew. Then I cut a short piece of 1/4" O1 drill rod to fit into the hole for an axle.
I ordered a couple of knurling wheels from MSCdirect - one is supposed to impress a crosshatch pattern into a part, the other is designed to raise a crosshatch pattern. Normally knurling wheels come in pairs, left and right. Using them both creates the crosshatch pattern. But knurling wheels are available for single wheel knurlers that create the total pattern with one wheel. I used the wheel that raises a diamond pattern for maximum roughness. For the record it is a 40 KPI (knurls per inch, the pitch) wheel.
This tool is used to knurl a face instead of a diameter and there is a part feature in the way so there is no way to support the axle at both ends. I found out that if I mount the axle center slightly above the center of the part the wheel gets pushed back against the face of the tool and does not show any tendency to come off. In use all I did was put a few drops of way oil on the wheel and then run it up against the flange with the lathe running at 80 RPM. A few seconds later and the deal is done. I also put a little chamfer on the inside edge to prevent cutting into the tire bead.
In order to hold the part I used a piece of 4-1/4" aluminum round with a 1/2-13 hole tapped in the center. It lines up in the bearing bore and the bottom of the bore sits flush when the rim hits the face of the fixture. Tighten it down and it's concentric with full access to the supported flange to chamfer and knurl.
The first batch had a bunch of drill dots to roughen the rim.
The single wheel knurler.
A fixture holds the wheel with access to the flange for knurling and chamfering.
The resulting knurl - it's rough enough to sand your fingernails on.
The tool is made from a scrap piece of 1" diameter 1018 steel. I turned the end down enough to clear the knurling wheel and drilled and reamed a .250" hole in the end. Next I used the manual mill to cut the shank down to 3/4" square to fit my lathe's quick change tool holders. I also drilled and tapped a hole for a setscrew. Then I cut a short piece of 1/4" O1 drill rod to fit into the hole for an axle.
I ordered a couple of knurling wheels from MSCdirect - one is supposed to impress a crosshatch pattern into a part, the other is designed to raise a crosshatch pattern. Normally knurling wheels come in pairs, left and right. Using them both creates the crosshatch pattern. But knurling wheels are available for single wheel knurlers that create the total pattern with one wheel. I used the wheel that raises a diamond pattern for maximum roughness. For the record it is a 40 KPI (knurls per inch, the pitch) wheel.
This tool is used to knurl a face instead of a diameter and there is a part feature in the way so there is no way to support the axle at both ends. I found out that if I mount the axle center slightly above the center of the part the wheel gets pushed back against the face of the tool and does not show any tendency to come off. In use all I did was put a few drops of way oil on the wheel and then run it up against the flange with the lathe running at 80 RPM. A few seconds later and the deal is done. I also put a little chamfer on the inside edge to prevent cutting into the tire bead.
In order to hold the part I used a piece of 4-1/4" aluminum round with a 1/2-13 hole tapped in the center. It lines up in the bearing bore and the bottom of the bore sits flush when the rim hits the face of the fixture. Tighten it down and it's concentric with full access to the supported flange to chamfer and knurl.
The first batch had a bunch of drill dots to roughen the rim.
The single wheel knurler.
A fixture holds the wheel with access to the flange for knurling and chamfering.
The resulting knurl - it's rough enough to sand your fingernails on.
