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topic: 2802Filing the switch blades ?
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posted: 9 Dec 2015 00:14

from:

madscientist
 
 

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This one always puzzled me

I know the process in filing the side of the switch rail that touches the stock rail and the tables give the planing length etc

But on the other side of the switch blade , ( the gauge face ) there is a some thining of the rail , with the foot left lin place , but are there any dimensions for how long the taper is on this side ,

In relation to the taper on top , for the undercut ( no joggle ) does that extend over the same distance as the taper with the rail foot remaining or is it over a shorter distance

Ps , is it necessary to file the planing length on the switch blade gauge face , and bend it to bring it into a straight line running face ?

Edit: I hope Ive Made myself clear here. On the gauge face I'm referring to the small taper right at the end of the switch blade. As well as the overall taper on the gauge face

I've seen reference to the overall gauge face taper as being the same as the blade taper in general , in other commentary , I've seen mention of give it fir 20-25 mm

Or perhaps that's a good link explaining this

Dave
Last edited on 9 Dec 2015 01:01 by madscientist
posted: 9 Dec 2015 08:20

from:

Jubilee42
 
Rødovre - Denmark

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As you know I'm very new to track building. I bought in the summer the filing jigs from Scalefour. I just choose the appropriate letter according to what Templot tells me and file away. Having filed the side that will touch the stock rail I then take the rail out, file off the inevitable burrs on the top and bottom of the rail, and turn it over and file the other side. I haven't really worried about lengths of filing, the jig sorts this out for me. I end up with nice pointy switch rails which work well. I have also filed (also in the jig) the stock rails where the two rails will touch. I just file them so the face is flat, or fairly flat, so the wheels don't bump when they first meet the switch rail. It seems to work fine for me.

posted: 9 Dec 2015 11:15

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Here is some stuff which I wrote recently on the Scalefour forum, see this topic (3 pages):

 http://www.scalefour.org/forum/viewtopic.php?f=5&t=4408



If you are having trouble filing blades, here's a Templot idea for a filing aid which might help.

For "B" blades, print a straight template for a strange-size turnout having a 12ft straight switch and 1:32 crossing angle. The turnout road will then be straight. You need to print only this part of it. Make it up on some scrap copper-clad with the stock rails only (blue rails). Make sure the set bend is accurate and correctly positioned by measuring the stock gauge at 2 in the diagram. There are no curved sections:

2_090803_310000000.png2_090803_310000000.png

The yellow rail is the blade being worked on. Mark it all over with waterproof felt-tip marker, so that you can see where you are filing. Make sure you have it the right way up (thick edge at the top). File the back of it, just going down to the web at the tip, and running out in a length of 29mm (29.33mm to be precise) at the end of the planing. Don't go far into the web, otherwise the blade will be too flexible at the tip, and it will be difficult to get a clear flangeway all along behind the open blade.

Clip it to the stock rail all along the planing (bent-up paper-clips are ideal), at 1 in the diagram. Adjust the filing until it sits nicely flush against the stock rail all along the planing, and the rails diverge at the end of the planing, at 2 in the diagram. At this stage the rail at 3 will be wrong (too close to the stock rail).

Remove it and make a small bend at the end of the planing (2 in the diagram), so that when clipped back in place, the rail at 3 is correctly aligned. You can check this using track gauges from the opposite stock rail. Repeat trial and error as necessary.

When you are happy with the fit, you can start filing the front of the bade. Getting this right is not as important as the back of it. Remove the bulk of the metal first, then for the final filing you could perhaps do it in place on the above filing aid if you clamp the rail down at 3. To that end it would be good to make the filing aid on a piece of board which can be held vertically in the vice.

Use the file at an angle, with the safe edge at the bottom to leave the rail foot intact, and file until the the blade tip is a knife edge at the top of the tip, with the running edge dead straight all through the filing aid. The filed length is the same as for the back of the blade, running out to nothing at 2. Some more ink on the rail may help to see it.

Finally fettle it with abrasive paper to make a smooth top edge against the stock rail for the wheel flanges. This will cause the knife edge at the end to be reduced a little below the top of the stock rail in the prototype manner.

2_010613_550000000.png2_010613_550000000.png

That makes a left-hand point blade. Now print a right-hand version and repeat the whole process to make a right-hand blade.

For "A" blades make the template a 9ft straight switch and 1:24 crossing angle. The planing length is 22mm.

If you are careful these filing aids should be good for several blades. But cost next to nothing if you need to replace them.

More about planing lengths and the stock gauge here:

 http://templot.com/companion/real_track.php

Here is some prototype information. It is next to impossible to copy this exactly in 4mm/ft scale, the above methods produce an adequate representation:

2_041213_250000000.jpg2_041213_250000000.jpg

regards,

Martin.

posted: 9 Dec 2015 13:29

from:

madscientist
 
 

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Thanks guys

Martin , all very clear

The reason that I am looking at this in detail again, is I am trying to setup my little CNC proton milling machine to do all these for me , Im looking at what fixturing I need, for both the switch blades and the crossing vees.

With 30 turnouts to make in the new year its worth a bit of investigation


Have anyone ever tried milling them ?, nickel sliver at this dimension is not easy to hold , but the cutter can take the material away very slowly
Last edited on 9 Dec 2015 13:29 by madscientist
posted: 9 Dec 2015 14:06

from:

David R
 
Hatfield Heath - United Kingdom

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There are many ways to skin a cat.  Here's mine (no joggles required, all dimensions are full size, reduce to your modelling scale).  The red lines show the rail-shape before work starts:

100_090834_280000000.gif100_090834_280000000.gif

1. File the back of the rail until the web is just broken into. The prototype only reduces the end of the web by a sixteenth of an inch so don't go too mad! However, the web of most model rail is overscale so you may wish to reduce it's thickness to a scale eleven-sixteenths of an inch to avoid the switch looking too "chunky". It is essential to be as accurate as possible with the planing length as a few thou can make a lot of difference to the switch angle.

100_090834_570000000.gif100_090834_570000000.gif

2. Put a set (that's a bend to you and me) in the rail at the planing length so that the end of the rail is aligned where the running face was (the picture should make this clearer). This location of this set is important since this affects the switch angle.

100_090835_180000000.gif100_090835_180000000.gif

3. Plane the front of the rails at angle to suit the wheel-flanges. This planing should be to the full flange-depth and rail-thickness at the end, tapering to nothing at the planing length. It is this bevelled edge which guides the wheels away from the stock rail. Again, the picture paints better than my words.

100_090836_380000000.gif100_090836_380000000.gif

4. Top planing comprises two parts. Firstly three-eigths of an inch at the end tapering to nothing at 82% of the planing length.
Secondly another three-eigths of an inch at the end tapering to nothing over a distance of about seven inches. 

100_090835_410000000.gif100_090835_410000000.gif


5. Radius the sharp edges along the running edge of the rail. Drill holes for fishplates and stretcher bars as required.

100_090836_060000000.gif100_090836_060000000.gif

6. Remove all sharp edges and polish out any surface scratches.

posted: 9 Dec 2015 14:09

from:

madscientist
 
 

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David R flipping fantastic, just wow , those diagrams should be all over the interwebby

ps

op planing comprises two parts. Firstly three-eigths of an inch at the end tapering to nothing at 82% of the planing length.
Secondly another three-eigths of an inch at the end tapering to nothing over a distance of about seven inches.


I presume these are inches of the prototype !
Last edited on 9 Dec 2015 14:12 by madscientist
posted: 9 Dec 2015 16:22

from:

Jim Guthrie
 
United Kingdom

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madscientist wrote:
Have anyone ever tried milling them ?, nickel sliver at this dimension is not easy to hold , but the cutter can take the material away very slowly
Dave,

I am CNC milling my crossing nose rails and my switch blades in 1:32 scale using Code 180 bullhead rail and it is working very well.  I made up jigs to hold the rail for the machining operations.  I've described the process in a thread in Western Thunder...

http://www.westernthunder.co.uk/index.php?threads/a-venture-into-the-garden.4597/page-5

...and I think you have to register as a member to see the pictures in full size.   The milling processes start about a third of the way down the page.

The only machining I don't do is the angled inner top of the switch blade,  which I do by hand with a file,  along with the shaping of the nose of the blade.   It has worked very well and I'm hoping to apply the same methods in machining Code 87 rail for S scale.

Jim.

posted: 9 Dec 2015 18:28

from:

madscientist
 
 

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Thanks Jim

I'm currently toying with the fixturing on cad , I'll probably produce that in delrin. The main issue is to hold the rail vertical and square to the bed. I can then program in the different tapers as required

With code 75 , my preliminary tests show too much flexing in the rail , even with very shallow cuts. So I need backing plates behind the rails.

The current idea is to have removable backing plates so that both side tapers can be done without resetting the jig

Of course the great thing is a Cnc mill can make its own fixtures !
Last edited on 9 Dec 2015 19:19 by madscientist
posted: 9 Dec 2015 21:04

from:

Jim Guthrie
 
United Kingdom

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madscientist wrote:
Thanks Jim

I'm currently toying with the fixturing on cad , I'll probably produce that in delrin. The main issue is to hold the rail vertical and square to the bed. I can then program in the different tapers as required
Dave,

Remember that you need to put a bend in the rail when doing crossing nose rails so that there is full web support under the ends.  I dare say you could mill crossing rails with the rail straight and do a bend afterwards,  but that might get a bit complicated if you're trying to do a nice splice as well.

Jim.

posted: 10 Dec 2015 01:56

from:

madscientist
 
 

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Yes Jim , I'm aware of the issues at the crossing nose , milling isnt much of a time advantage, there . I'll do the switch blades first and then see

posted: 31 Aug 2016 14:20

from:

madscientist
 
 

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Guys , can I just confirm something , when I plane the " rear " of the switch blade , ie the area that will come in contact with the stock rail , do I make the set or bend in the switch rail towards the stock rail ( the term running face has me confused )

Then I plane the running face ( I understand that as the inside face , ie when the flange might rub on the switch blade ) , no further bending after the front or running face planing

In my turnouts ,I find the crossing much easier to get right then this area

Dave

posted: 31 Aug 2016 14:43

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Dave,

The usual practice is to do all the filing before putting a set in the rail at the end of the planing. This is a diagram of the top surface of the rail after filing (with the angle much exaggerated):

2_301147_340000000.png2_301147_340000000.png

The running edge is the gauge-face of the rail, against which the wheel flanges run. The set bend returns the running edge to a straight line.

That diagram is perhaps over simplified. Normally the rear of the blade (i.e. not the running edge) is taken down only to the rail web at the tip, preserving as much stiffness in the tip section as possible.

The running edge is then filed at an angle, so that the above diagram represents only the top of the rail head, and the rail foot remains largely intact. Again for stiffness. If the tip section is made too flexible, only that part of the blade will open and you won't achieve a full running clearance all along behind it.

The filed length (planing length) is the same on both sides. It is a good idea to mark the rail all over with a waterproof marker before you start filing. You can then easily measure the filed length from the tip, to match the marks on the template.

regards,

Martin.

posted: 31 Aug 2016 16:29

from:

madscientist
 
 

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Thanks martin , i was being dense , I reviewed your stuff on this and David R pics and I see what is meant. I think I confused myself in the past by not filing the running faces in equal proportion to filing the rear face ( leaving the for in place on the funning face etc )

thanks

Dave



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