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Harold Hall

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The basics

With so little experience to work on I needed to establish the basics before going on to design a machine, and started by browsing the Internet for information. Having found a few Photographs of industrial machines there was one that included a collection of files, these though were quite large and appeared to have a round end rather than the pointed tang , obviously making it easy to provide a secure mounting for them. The files therefore seemed the next to investigate.

 

My very large industrial tool supply catalogue seemed the logical place, but none were listed, with a similar result when searching the web. This, apart from just one American company that had files specifically named as being for use on a filing machine. Their dimensions though appeared to be no more than needle files, there may though be an answer to that, more later.

 

I did subsequently find one other file manufacturer, again in America, who listed filing machine files but no details were given as to their cost or where they could be purchased. I anticipate that due to limited demand they would be quit expensive.

 

I also found a forum where the subject was being discussed and the approach being taken by some was to modify standard files.

 

Most of the filling machines that I found illustrated the file supported solely on its lower end, making it possible to thread the workpiece over it. This then enabling it it to be easily removed for inspection as the work progressed. As I considered this to be a very worthwhile feature I decided that the machine must make this possible.

Metalworking

Workshop Projects

Even so, this may limit the rate at which material can be removed as the file may flex. Being able to be mounted on one, or at both, ends, therefore seemed an essential feature to aim for.

 

It also occurred to me that using the tang as a single ended method it would be cutting on the up stroke that contrary to normal practice, as, band saws and jig saws, etc. all pull the work towards the worktable. It did though make me wonder if the files mentioned earlier were in fact needle files but with their cut reversed. I decided therefore that I would have to use standard files but to remove the tang and  mount them so that they cut on the down stroke, choosing 100mm long files for the purpose.

 

With what appeared would be a relatively crude method of mounting the file I was concerned that the file face may not be parallel with the file's movement. Also the sides if a parallel sided file. This would mean that the workpiece would have to move backwards and forwards, albeit minutely, to keep in contact with the file at each stroke, a situation that would be far from ideal. Some adjustment would therefore have to be provided so that the file's face, and edges, were parallel with its movement.

 

Speed in terms of strokes per minute (SPM) would have to be decided and as I could not find any data regarding this. I had therefore to come up with what I considered to be a logical starting value. For this I chose 200 to 300 SPM being a little faster than I would file manually. However, file linier speed would also depend on length of stroke. I decided therefore that to provide the facility to change both SPM and stroke length would be worthwhile, aiming at mean values of 250 SPM and 25mm stroke length. I did though eventually find the design I had produced worked well at speeds considerably in advance of this value, more about that later.

Design Considerations.

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