Machining N scale frames

[woodone]

For you out there who machine frames for DCC sound installs . How do you hold the frame to machine?
One I have questions about is the Kato SD 70 ACe. There are no screws that hold the two frame halves together. There is just the perimeter frame the holds the two halves together.
Not many places where you can clamp without damaging the frame.
I have my own way but was wondering about any other ideas.

Thanks in advance. 

[RBrodzinsky]

I didn't mill these sides together (have done some others).  For this, I clamped each half frame, with a small piece of MDF on each side to protect the central part of the frame. And just scratched the dimension lines on the outer parts of the frame (which were marked with the frame together).

[woodone]

Well you get a laugh at whatI do. I put the two halves together and clamp them. Then I use low temp metal (cero metal) and fill the inside cavity, this holds the two inline, now use some small filler pieces to fit the small reliefs in the frame and then use two pieces of tool steel on each side of the frame. These are all then clamped into my milling vise.
Then I mill the places that I need to.
The low temp metal keeps the frame halves from being bent when I clamp into the mill vise.
This makes mirror frame on both halves.

[peteski]

Well you get a laugh at whatI do. I put the two halves together and clamp them. Then I use low temp metal (cero metal) and fill the inside cavity, this holds the two inline, now use some small filler pieces to fit the small reliefs in the frame and then use two pieces of tool steel on each side of the frame. These are all then clamped into my milling vise.
Then I mill the places that I need to.
The low temp metal keeps the frame halves from being bent when I clamp into the mill vise.
This makes mirror frame on both halves.

Haha!

That is an excellent idea - thanks!

[jdcolombo]

I have a very small mill (the Proxxon) and what I do is simply screw the chassis halves together (without the insulating spacer) and then clamp them in my milling vise with a small piece of hardboard on each side to protect the frame halves and build up the thickness past the fuel tank, so that I'm clamping to the full frame and not just the fuel tank.  This method has worked like a charm for me, has not resulted in any bent frames, and is a lot easier to do than trying to mill each frame half separately.  Whether this would work with a larger mill (and larger milling vise), I don't know.

John C.

[peteski]

The frame woodone mentioned is screw-less.  Nothing to keep the halves aligned.

[woodone]

John, I think that the mill you and Rick use has a much higher RPM than I use. I am guessing 15,ooo to 20,000 RPM and you use small diameter mills.
I use a modified drill press. I also use larger mill diameter. My drill press is equipped with a X Y table and I have a indicator on the Z . This gives me very good control of what I am doing. The only problem is the RPM. Only about 2,000 RPM. I have to be real careful that I don’t try to climb mill. Even with very tight gibs and almost zero back lash the milling bit will grab material and spit it out of the vise unless the material is held very secure. With wood fillers I would think that would let the work piece flex or move too much. That is why I use tool steel and clamp very tight.
I have a digital read out for the z axis but don’t have it installed.
Too much work and not enough time- bet you have heard that before.
Thanks for the input!

[RBrodzinsky]

Jerry,

Yes, the Proxxon mill has a 20,000 rpm setting, which, with a two flute bit, cuts very nicely.

[woodone]

See I can't post some phots of this.  Works very well for me.

[jdcolombo]

The frame woodone mentioned is screw-less.  Nothing to keep the halves aligned.

OOPS - missed that.  SD70's are far beyond my 1957 layout. 

John C.

[AKNscale]

This is how I hold most of mine while milling:

Generally I'll have my wrist resting on a solid surface when I do this. It will work just as well for split frames too.

[peteski]

Ah, a digital method with manual feed.    Hopefully you remove the greased worms and bearing blocks before milling - metal shavings happily stick to the grease.

[AKNscale]

Maybe, depends on how lucky I feel, lol.

[woodone]

every time I use that method I end up with a cut finger or two!

[AKNscale]

Makes sense, though I've honed out the center of my fingernail once(definitely not on purpose), with the new bits I've been using I don't hurt myself when I slip.

Here's what they look like:



As angry as they look, they surprisingly don't eat skin, at least not without trying