Thread: Using Imperial Dimensioned Drawings

I convert everything to metric. The only thing that irritates me is router bits.

Imperial is obscene. It needs to be strangled to death.

Hi Chris

I don't work from the drawings of others. I do essential measurements when I make my own. They would likely look nuts to most woodworkers - or drive them nuts - as they are in a mixture of imperial and metric. Many of my handtools (e.g. plough plane blades) are in imperial, while my jointer/thicknesser is metric. I grew up with imperial and in my teens switched metric. I have used both for many years, and switch reasonably effortlessly - whatever seems best at the time. For example, I am about to build a kitchen full of frame-and-panel doors, and plan to use a Domino 500 for the mortice-and-tenon joints. The frames are roughly 3/4" thick, so my jointer will end at 19.5mm (and I will remove the remainder with a smoother). Now I have an accessory for the Domino that centres on 3/4". One router is a 1/2" running a 1/4" slot cutter, and the other router is a 1/4" running a 6mm upcut.

I guess what I am saying is convert what you want and round off if you need. Or do as I do, and in this case switch to imperial. I doubt the metric machines will know the difference.

Regards from Perth

Derek

I spent a day converting 4-pages of the most hyper-detailed imperial plans for a job a few weeks ago. This particular unit was getting AV gear installed in it that we didn't have access to, so we just went with their instructions of "do exactly what the plans say and it'll all fit".

I had to go metric anyway because of the CNC, but it did mean that I was converting every dimension exactly so 5 7/8" became 149 and not 150

I don't work from other peoples plans. But if I did, the first thing I would do regardless of metric or imperial, would be to fix the plans so I am not cutting wide boards down into strips or sending epic amounts of material straight up the dust chute. so 12" wide timbers become 290mm wide boards, 4" boards become 90mm wide boards, 3" legs become 65x65 etc etc. I do float between metric and imperial, often within the same sentence which drives my clients nuts because most of them operate with centimeters. what the hell is a centimeter!!!!!!!!

Originally Posted by Kuffy

I don't work from other peoples plans. But if I did, the first thing I would do regardless of metric or imperial, would be to fix the plans so I am not cutting wide boards down into strips or sending epic amounts of material straight up the dust chute. so 12" wide timbers become 290mm wide boards, 4" boards become 90mm wide boards, 3" legs become 65x65 etc etc. I do float between metric and imperial, often within the same sentence which drives my clients nuts because most of them operate with centimeters. what the hell is a centimeter!!!!!!!!

Love it!

Regards from Perth

Derek

I too was educated in imperial and converted to metric in my late twenties when the drawings for my workshop were done in metric and I had no choice and I would never go back to imperial willingly. I am forced to work from others drawings as I cannot draw in 3D/isometric due to some short circuit in my brain. I know a lot here would find that hard to believe but it a fact that some people cannot draw anything except a straight line with a ruler. I have just seen a plan for a small table I like but it is in imperial so I will convert it to metric and see what the dimensions come out like.

I was converting every dimension exactly so 5 7/8" became 149 and not 150

Why not just convert to a round figure, say 150mm. I do not understand the need to be exact, and make the measurements so much more difficult and fiddly.

Regards from Perth

Derek

Originally Posted by derekcohen

Why not just convert to a round figure, say 150mm. I do not understand the need to be exact, and make the measurements so much more difficult and fiddly.

Regards from Perth

Derek

'Cos this desk is getting AV gear installed interstate/overseas, so for the inconvenience of being exact now I can save myself trouble later. If things don't fit I don't want there to be any arguments about not following the plans.

Originally Posted by Chris Parks

How do others do this? Do you convert each individual component or abandon metric and just work off the imperial drawing? The problem then would be that our machines are metric, maybe there are other approaches I have not thought of?

Unless the dimensions are critical you can use the 24mm inch, a quarter inch is 6mm, half an inch 12mm and so on. That's about 5% smaller than the designer intended.Edit: I've found that the plans in woodwork magazines and such have errors, some major, more often than not. So it's worth checking them carefully.

Originally Posted by Chris Parks

How do others do this? Do you convert each individual component or abandon metric and just work off the imperial drawing? The problem then would be that our machines are metric, maybe there are other approaches I have not thought of?

I never "abandon" any measurement system, I just use the rule appropriate to the dimensions on the plan. But for me, a component's length, width and thickness are arbitrary. 50 mm (or even 49 mm) is close enough to 2" (= 50.8 mm) as makes no practical difference.

Except for my Japanese chisels and 3 or 4 blades for the plough plane all my hand tools are imperial.
But all that really matters is that tenons fit into their mortices and that reveals are uniform.

For me, the only machine with a frequently used gauge is the table saw, but for critical cuts I don't rely on the scale, so I always measure from the outer edge of a tooth to the fence or stop.


and, unlike Kuffy, I don't down size 3" components to 65 mm, etc without checking with a scale or full sized drawing that I'm happy with the change in proportions.

Originally Posted by elanjacobs

I spent a day converting 4-pages of the most hyper-detailed imperial plans for a job a few weeks ago. This particular unit was getting AV gear installed in it that we didn't have access to, so we just went with their instructions of "do exactly what the plans say and it'll all fit".

I had to go metric anyway because of the CNC, but it did mean that I was converting every dimension exactly so 5 7/8" became 149 and not 150

I'm rather surprised that your CNC controller doesn't accept imperial dimensions

BTW, I get 5-7/8" = 149.2 mm

Use metric, it's a dozen times easier.

I avoid imperial at all costs. Try converting imperial sectional properties (for steel ub sections for example) to metric. It's ok when you are only dealing with a distance or weight or volume but when you are combining units and have mm^4 converting to and from unit systems is a serious drain on productivity.

The Americans always justify imperial by saying that imperial units are easier to use for everyday things and are friendlier. That's all well and good but it's an absolute disaster for technical design, manufacturering, research etc

Chris I to grew up with Imperial during tech years it began to change one thing that came up during that time is USA imperial rulers & tapes are different standard (teacher had one to show) USA 1" is longer than Imperial UK 1". I've since seen the same thing.

During my latter years working off my apprenticeship we were working in both, then as vehicle maintenance man for a number of companies who had vehicles built long before metric buying imperial tube and other fittings etc became a nigh mare.

Give me back Imperial any day just because European's can't count past 10 why should the rest of the world suffer. After all there are 12 months to a year, 360 degree's which equates to 1hr 60 sec's , 24 hours, 12 loaves 13 if you get bakers doz LOL. 12", 1ft, 36"

In industry I still hear terms used by people who were born well after metric came in which are imperial.

Chris somewhere on this forum many moons ago this topic raised its head and proof was made Imperial IS far more accurate than metric.


Hey Kuffy I always work on 3" being 75mm so your are short changing there or trying to save timber