The next stage was to sort out the motion plate by machining the top mounting lugs for the cross head slide bars. The hole centres on the cylinder lugs are 30mm apart so this dimension is repeated for the top slide bar positions.
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- The main components for the Opus P. main frame are assembled and checked to ensure everything is squared up.
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- The areas to be cut away are scribed in the normal way plus a bold indication of the areas to be removed are clearly marked.
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- A 2mm radius end mill provides nicely rounded internal corners which will match the rounded ends of the lugs.
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- A centre finder is used to locate the spotted postion of the lug hole. My finger nail test tells me when the centre finder is running true.
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- Using a drill bit as a fixed pivot point the lugs are neatly rounded off. Take fine conventional cuts and avoid any attempts at climb milling.
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- The main components are brought together for trial assembly checking for squareness and determining mounting position for cylinder.
We now get to the stage where there are a number of detail jobs to be completed. I confess to not having taken many photographs but if you have successfully reached this stage with your build then I don’t anticipate that you will have much problem in the finishing stages. However, should you require any guidance I am only an email away and more than happy to give you the benefit of my (limited) experience.
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- One deviation from Stan Brays notes was to machine the crosshead from a solid brass blank to avoid the traumas of silver soldering 4 or 5 small items.
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- Using a drill bit held in the vice the rounded shape was milled round the inside edge of the cross head guide. Again, take light cuts and watch those fingers !
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- Taking great care the connecting rod tapers were accomplished with the aid of supporting centre in the tailstock.