electrosteam
15th Jun 2020, 10:33 PM
The photo shows the first 'paid' job on my CNC mill.
This is a trailing wheel for a 5" gauge live steam loco, 18 mm thick and 105 mm diameter, made from 1045 bar.
The spokes are recessed 2 mm from the rim, so the spoke thickness is 14 mm.
387241
My mate made the disc on a Mori Seiki CNC lathe, my job is to mill out the pockets between the 7 spokes.
This is a prototype wheel, with 20 production wheels to follow.
The pockets are about 18 mm triangles with corners 5 mm and 3 mm radii.
I drilled through on the curve centres at 9.5 mm and 4 mm, then milled out the pocket with a 6 mm solid carbide end mill.
Cutter was 1200 RPM with feed at 100 mm/min, depth of cut 2mm, giving 8 steps.
Side step-over was specified as 0.3, giving 3 paths for the pocket.
The next job is to round off the spokes with a corner rounding HSS end mill, 1 mm radius.
Single cut at 1 mm depth with speed 1000 RPM and feed 100 mm/min.
Problems:
a) the 6 mm carbide cutter rattles as it goes into the corner holes,
b) the corner rounding cutter leaves witness marks at top and side and the rounding has a poor presentation.
Discussions:
a) I intend re-doing the design to specify the corner radius as something greater than 3 mm, say 3.1 mm.
I have also been told that a single large hole in the middle of the pocket is preferred. A 13 mm drill is practicable.
Do the speeds, feeds and cuts seem efficient ( with 20 to come ! ),
Single 13 mm drill ?
Coolant ?
b) I think I need to increase the rounding cutter radius to 2 or 3 mm, but contact with the hub and rim is a risk.
Perhaps a different cutter shape would be better.
Any suggestions on how to get a nice rounded spoke edge ?
Keep well,
John.
This is a trailing wheel for a 5" gauge live steam loco, 18 mm thick and 105 mm diameter, made from 1045 bar.
The spokes are recessed 2 mm from the rim, so the spoke thickness is 14 mm.
387241
My mate made the disc on a Mori Seiki CNC lathe, my job is to mill out the pockets between the 7 spokes.
This is a prototype wheel, with 20 production wheels to follow.
The pockets are about 18 mm triangles with corners 5 mm and 3 mm radii.
I drilled through on the curve centres at 9.5 mm and 4 mm, then milled out the pocket with a 6 mm solid carbide end mill.
Cutter was 1200 RPM with feed at 100 mm/min, depth of cut 2mm, giving 8 steps.
Side step-over was specified as 0.3, giving 3 paths for the pocket.
The next job is to round off the spokes with a corner rounding HSS end mill, 1 mm radius.
Single cut at 1 mm depth with speed 1000 RPM and feed 100 mm/min.
Problems:
a) the 6 mm carbide cutter rattles as it goes into the corner holes,
b) the corner rounding cutter leaves witness marks at top and side and the rounding has a poor presentation.
Discussions:
a) I intend re-doing the design to specify the corner radius as something greater than 3 mm, say 3.1 mm.
I have also been told that a single large hole in the middle of the pocket is preferred. A 13 mm drill is practicable.
Do the speeds, feeds and cuts seem efficient ( with 20 to come ! ),
Single 13 mm drill ?
Coolant ?
b) I think I need to increase the rounding cutter radius to 2 or 3 mm, but contact with the hub and rim is a risk.
Perhaps a different cutter shape would be better.
Any suggestions on how to get a nice rounded spoke edge ?
Keep well,
John.