7mm Switch Blades - forming your own
- Thread starter Dog Star
- Start date
Susie
Western Thunderer
Hi All,
I have been playing about machining switch blades (does that sound right?) in preparation for some track building.
The trial one is a B switch in 7mm scale. I have not tried to do the proper undercut of the initial planing, but have taken the back off flat.
On the front only the bull head is machined off, as per Sclub7's diagram, at the correct angle of 20 degrees:
The top (running surface) is taken down by just under 3/4" scale as a lead in to the switch, which is why it isn't a knife edge.
Susie
I have been playing about machining switch blades (does that sound right?) in preparation for some track building.
The trial one is a B switch in 7mm scale. I have not tried to do the proper undercut of the initial planing, but have taken the back off flat.
On the front only the bull head is machined off, as per Sclub7's diagram, at the correct angle of 20 degrees:
The top (running surface) is taken down by just under 3/4" scale as a lead in to the switch, which is why it isn't a knife edge.
Susie
3 LINK
Western Thunderer
Susie,
Please excuse my asking... given that C&L offers milled switch blades in sets (A, B, C) in steel and in nickel, then what is the advantage in milling your own blades?
Apart from - because I can
.
thanks, Graham
Surely the cost is a factor, as well as because he can
.Regards,
Martyn.
Susie
Western Thunderer
Hi Graham,
The initial reason was because Richard said that he was going to mill some more for Croscombe, and I said that I would like to have a go. After seeing your post above the cost would be a big factor too: £14 from C & L for the switches, or 77p for the rail plus a bit of time. Also I can do them how I want.
Susie
The initial reason was because Richard said that he was going to mill some more for Croscombe, and I said that I would like to have a go. After seeing your post above the cost would be a big factor too: £14 from C & L for the switches, or 77p for the rail plus a bit of time. Also I can do them how I want.
Susie
Susie
Western Thunderer
Martyn,
Here are some details of the procedure:
I measured the bit of rail that I was given, and drew it out at a scale of 1mm to 1 thou: the height of the rail was .125" so that becomes 125mm on the drawing.
From this I measured how much needed to be milled off each side, bearing in mind that the top is cut away at 22 deg. For a B switch, the length of the planing scales out at just under 52mm.
The rail was to be clamped to a length of angle steel, fixed at the correct taper angle, to the mill bed. From memory it was about 25thou over the 52mm. This is set up using a dial gauge:
The angle in the photo is the one needed for milling the second side, which is the full rail width of 64 thou over 52mm.
The rail was then clamped to the steel angle, using a parallel spacer and a couple of tool-makers clamps, and the back milled off flat.
The angle was then reset (as above) and using a cutter ground to 22 deg, the top of the bull head milled off to a knife edge at the blade tip. The angle of the cutter approximately matches the angle of the wheel flange.
The top of the blade was then filed to give the top taper, which runs from zero at the start of the planing to 16 thou off at the tip. This is why the tip look thicker than a knife edge: it is! but the tip is lower than the full rail height. If I end up doing several blades, I will mill this off. Likewise, if doing several then the same bit of milling will be done for the whole batch. The other 'hand' can have the back milled off with this set-up, but the top will have to be done clamped to the back of the angle, working the other way.
Hope this helps,
Susie
Here are some details of the procedure:
I measured the bit of rail that I was given, and drew it out at a scale of 1mm to 1 thou: the height of the rail was .125" so that becomes 125mm on the drawing.
From this I measured how much needed to be milled off each side, bearing in mind that the top is cut away at 22 deg. For a B switch, the length of the planing scales out at just under 52mm.
The rail was to be clamped to a length of angle steel, fixed at the correct taper angle, to the mill bed. From memory it was about 25thou over the 52mm. This is set up using a dial gauge:
The angle in the photo is the one needed for milling the second side, which is the full rail width of 64 thou over 52mm.
The rail was then clamped to the steel angle, using a parallel spacer and a couple of tool-makers clamps, and the back milled off flat.
The angle was then reset (as above) and using a cutter ground to 22 deg, the top of the bull head milled off to a knife edge at the blade tip. The angle of the cutter approximately matches the angle of the wheel flange.
The top of the blade was then filed to give the top taper, which runs from zero at the start of the planing to 16 thou off at the tip. This is why the tip look thicker than a knife edge: it is! but the tip is lower than the full rail height. If I end up doing several blades, I will mill this off. Likewise, if doing several then the same bit of milling will be done for the whole batch. The other 'hand' can have the back milled off with this set-up, but the top will have to be done clamped to the back of the angle, working the other way.
Hope this helps,
Susie
, but as long as I make a few passes I think my mini milling machine might be up to the job.