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post #10 of (permalink) Old 06-06-2016, 06:14 AM Thread Starter
mrmicron
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Join Date: Aug 2010
Country: New Zealand
First Name: John
Posts: 5
 
Default DW625eK base plate

Hi all.
I am feeling that you all think this is a very simple problem and you are all right – it is called a fully dimensioned drawing!
To start with Everend first, you are correct in all you say including the no 2 option!
By way of an explanation, I am not a woodworker at least not in the way that you all are. I come from a precision engineering background where dimensions were always critical and I had the reputation of being the tightest of the tight when it came to tolerances (hence the nickname). Great for my previous life but not when working in wood!
I am designing a new router table and base plates to improve my abilities and options with a router. The table I am designing is a combined horizontal and inverted vertical table and so far I am still doing the cad drawings for it. My previous or current table is a simple table with only a fence and no mitre or T slots and the fence isn’t even split although this is a simple mod to improve but I have never needed it because I have always worked between the fence and the bit. My existing table and offset plates were made using the exact method described by Stick486. I then dimensioned the holes and made a template with 0.3mm holes at the hole centres for future use. Years later and recently I found a drawing on the web for the base plate giving linear dimensions for adjacent pairs of holes. For the five hole pattern there are five different dimensions and for the three hole pattern there are two dimensions. Whilst there is an assumed symmetry between the holes, drawing a line between opposing holes does not describe the arbour centre or even the same centre. Also, for the five hole pattern, if the holes were equidistant you could assume they described a circle but they are not and they do not show an obvious relationship to the arbour crs., and even so it would be an assumption. Without at least a dimension between two pairs of opposing holes or a PCD there is an infinite quantity of locations on which the holes could exist and still maintain the dimensions between the holes given on the drawing. Also there needs to be a stated relationship to the arbour centre. Therefore the drawing is as much as tits on a fish! Also given any pattern of mounting holes, be it 3, 4, 5, or even 6 there is no requirement for them to be coincident to the arbour crs. Drawing a line between any of them is simply assuming that the manufacture has centred them on the arbour.
Hopefully you all now understand my dilemma, yes I may be OCD about my PCD’s but it is for good reason. Drawing a line between opposing pairs of holes in a four hole set only describes the centre IF the holes are equidistant between each hole and also diagonally. And then it only describes the centre point of the hole pattern and not necessarily anything else.
Errmm….I don’t spose anyone has a drawing………do they?
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