Monday, 2 July 2018

I found something out at the weekend!

Whilst discussing the machining of the holes on the frames at the weekend with Matt, I learned something about the way the holes are being machined.  I understood that the holes were being machined with cutters and not drills in the normal sense, but hadn't quite appreciated the subtleties of the process.
The  hole is, as I have described before, centre punched which created a positive location for the tool.  This is best shown in the picture below.
The annular cutter used for machining the holes
 The point seen on the tool is on a moveable spring loaded centre, this locates in the centre punched mark and ensures a true location for the hole (so the triple checking of the hole positions pays off!). As the cutter produces the hole, a pellet is formed which is connected to the frame plate until the cutter breaks through.
The Annular cutter with some of the pellets produced
In the picture the centre punch marks can be seen on the pellets.  This maintains position as the process is carried out.
A closer view of the pellets.
The use of this type of cutter ensures the quality and verticality of the hole.  It is not unknown for a "conventional" twist drill to wander off centre or produce an oval hole, both of which would prove disastrous to the quality of the frames. When the holes have been machined, and we are ready to start the erection of the frames, the holes will be reamed to final size and the fitted bolts or rivets will be inserted.

A small group of volunteers will shortly be spending a week cleaning and applying protective paint to the cab structure, currently stored on the top of one of the containers at Sheffield Park.  This is to arrest any further deterioration and will help in the restoration at a later date.
The cab structure shortly to be worked on.
Another view of the cab showing missing rivets in the rear corner joint.
The front quarter of the cab.
The work to be carried out on the cab will be purely protective but will allow us to make important decisions when it comes to the final restoration of it.  As the work is done notes and pictures will be taken to assist matt and the team later.

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