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How Not to Produce a Simple Wood Pattern

C

carrdo

Well-Known Member
Hi All,

Well, it started off very badly.

As I had the right (odd size commercial hardwood dowel of approx.1-3/32" dia) I said right, I will use that for the two cylinder pieces. So, I got to the stage shown in photo 30 when I started to measure things more closely and I discovered that this "round" dowel was really egg shaped and by a lot!
And, as well, after further calculations on how deep the two cylinder cutouts in the base block needed to be, the base block turned out to be too thin so scrap everything shown and start over again.

So, square up a new thicker base block and then carefully layout where the two cylinders needed to be (1-3/16" centre to centre with a 9/32" deep cutout). And, in addition, since everything needed to be centered lengthwise, this took a while.

To rough out the two cylinder cutouts, I had a 1" dia. ball end mill and end mill holder. This was spotted on each cylinder centre line in turn as shown in photos 33, 34. Because the base block wood was just some unknown (a no, no) scrap wood which I had, I had to proceed very slowly and cautiously so as not to break the edges of the wood when the end mill entered and exited the piece. Some very minor splintering did occur but nothing which could not be fixed.

The only casualty; a lot of lost time doing everything the hard way again.

to be continued.
 

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  • 31 Re-turning the Two Cylinder Pieces.jpeg
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  • 32 Base Block and Cylinder Components.jpeg
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  • 33 Locating a Cylinder Recess in the Base Block.jpeg
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  • 34 After Ball End Mill Milling.jpeg
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Hi All,

To finish the cutouts in the base block, I switched to a boring head tool as seen in photo 35. To ensure everything remained square in both planes, I used the setup shown in photo 36. Afterwards, I checked the accuracy of the work and to my surprise the vernier height gauge shows both cylinder heights dead equal and the spacing was that way also.

Again, the only casualty was the amount of time taken and the fancy machining involved.

to be continued.
 

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  • 36 The Setup Used to Maintain Square.jpeg
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  • 37 Checking Cylinder Height after Machining the Base Block.jpeg
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  • 38 After Machining.jpeg
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Hi David,

This will be the new double steam or air brake cylinder pattern for my 3/4" scale Hoffman NYC Hudson live steam locomotive. I now have the design for this and Carl Hoffman never had the casting for it. The original Hoffman brake cylinder drawing shows a single cylinder only which is based on a UK (appears to be from a Don Young) design.

The Hoffman brake cylinder drawing, as originally supplied, leaves much to be desired and is not prototype for either the NYC Hudson or for North American practice.

I will have to make a new model print to suit what I am producing as well.
 
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