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Member postings for Keith Wilkinson 1

Here is a list of all the postings Keith Wilkinson 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Using Micrometer/Hi-Spot blue
05/07/2011 17:21:36
We ashape and ground smooth then hardened and we ground them to a shallowV looking in profile.We lways had old files drawn out to a broad "Y"The drawn out edge was a slight radius and was sharpened on a Carborundum wheel not a grind stone.If there was a lot of material to remove a square profile carbon tipped scraper was used with an oblique edge,the same tool was always used for scraping steel.
Rough scraping is done using long curls like a letter c and each area is scraped from various directions when the final bed is starting to appear the long curls can be reduce to proper curling in small areas before finish curling ot mottling whichever is chosen.
Imagine a planing machine with 40 foot bed and a table in two pieces joined together.The bed has to be levelled and jointed before any scraping can begin and then the table jointed and scraped to the bed.The sheers (slides) were about 15 inches wide and there were 4 of them.It was a long tedious job but when completed gave much satisfaction.
 
11/06/2011 12:42:56
Of course we are only touching the surface of the use of scrapin g ,we set up the basic machined bed casting with headstock base using a precision level ,we then scraped the (shears ) horizontal but of course our machines could not always be accommodated full length because of available space,we therefore scraped both ends of each piece of bed flat and square also the level of the jointing keys which wer levelled using a dial guage (It was a long time ago).We must not forget that on machines with uprights such as a vertical boring mill,or planer the uprights had to be vertical to the bed and to do this to the fine limits required they were scraped,and had to be scraped unevenly so as to counterany vertical misalignment.This was achieved by scraping one area more than others long before bed and surface finish were thought about .It was very skillfull as it was not econimical to keep lifting the uprights to the base to test if they were vertical, This was known to us as" throwing" the upright to vertical.Scrapinng of course was used in the alignment of the loose head stock also.
10/06/2011 16:46:41
I return to this subject again .The machine tools i worked on were large precision lathes 6 to 8 foot centre lathes up to a 100 feet or more in length each section of bed had 4 or more slideways so had to be accurate across the bed as well as along it.The surface plates we used were lifted and moved by overhead crane the surface finish acceptable was 10 to 12 spots of blue per sq inch as accepted by the inspectors.The surface retention of oil and the finiished no of Spots per Sq In in the final assessment were achieved by Mottling or curling with the scraper
03/06/2011 20:03:45
Hi
I am a retired engineer I served my apprenticfship on machine tools where scraping was the bedrock of accuracy ,The blue can be applied to the master surface and the mating component rubbed well ,the hardest wearing blue sections where the colour has gone almost black are the areas to scrape first and to the greatest extent then less so the paler hades where contact has been made.Wipe of the very light coloured bits of blue and re rub .Carry on doing this until the required surface bed is achieved.Then mottle or curl the surface using the scraper.Scrape in a different direction after each rub.
The flat scraper can be made by extruding the end of an old file then grinding to a good Keith Wilkinsonpolish to about 1/16 thick at its tip then grind at a ( v) and hone.
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