I'm at an early stage of constructing my chassis, and not making any progress.
I've cut it up and started over again..twice now.

There's some measurements in the plans that just don't add up. Am I right to assume that my frame should measure correctly...to the millimetre ?

The two measurements causing me most trouble are pieces C and Q. Both supposed to be 823mm (book and mcsorley the same)

I cannot get these pieces to fit, unless I cut the to 830mm. All the external measurements of my frame are correct..

Has anyone had the same trouble as me?
Am I trying to be too precise ?
If I sound depressed....that's because I am!


[Edited on 26/7/03 by burgessj]

don't be depress'd............

cut them to 830mm n weld em in......

use the book as a guide, not gospel, once youv'e got as far have you have with the chassis all the tubes need measuring as to whats req'd rather than what the "book" says it should be..........

Just been out and checked mine, C & Q are both 830mm at the rear, hadn't noticed the discrepancy before as once I had laid out the outer rails I just made the rest to fit. As you'll realise as you go on there are several mistakes in the book, I suggest you have a good read through the chassis and running gear sections of this forum where these problems have been covered in the past.

Mick

when you see all of the built car's
mine included, you will see all of the "discrepancies"

every car is a work of art and completley
different to the next one

something I was told after I built my car was "measure twice, cut once"

very wise words. that would have saved
hacksaw blades, tears. blood and arms

I would make the part fit the hole, and dismiss the book measurements
as there are several errors

Thanks all...
I'll have those top rails on in no time..

I suppose it's most important to make sure that the frame is true, so I don't get handling problems.

Appreciate your help

I make my living out of designing welded structures. If I was to hand out a drawing of something that was over 2m long, 1m wide and 0,5m high, made out of 60 segments of pipe, welded together and ask it to be right within 1mm....actualy it is a little hard imagining what might happen but it is not a good career move. A professional welder would probably say it is impossible, a amateur don't know that, so he do it any way.
A production car is within 10mm, if it's good. I think you can do better than that without much effort. It is your car, you can do what ever you feel is right and/or convenient.

Leto,
I agree with you 100% (again) but would add that the most important thing in my view when it comes to accuracy is to try to measure everything from a common datum point or line. DON'T measure things incrementaly as each error will most likely add to the overall discrepancy.

Establish your base lines (usually a centreline and a front or back line) and work every key measurement from these. Don't add the difference between sections together or you will tot up a good few mm of error over the full length of the chassis for sure.

This is why the building board with accurate centreline is vital and you should take some time to mark this out with some of the more important dimensions before even lifting a hacksaw. Get the longest steel ruler you can (see my website for details - I got mine at Focus Do It All and it is 40" long) and use this ruler to mark your centreline after marking some dots using a taught piece of fine nylon string stretched down the centre of the board. Also use the biggest set square you can find (again Focus - 24" x 18" roofing square) and use it to mark all the critical lateral lines before starting. I'd recommend using varnish to seal these key lines in before you get the board dirty as I had to remark my board half way through my build and I was worried about not getting the same accuracy 2nd time around.

Once you have marked all your base rail lines then check that the appropriate diagonals are equal and thus the drawing is square. You may wish to also draw in some of the upper rail positions so that you can use a plumb line later to position them. If you do then just make sure the base is 100% level as a plumb line only measures plumb to the earth not necessarily plumb to your base board...

As for practical accuracy, I have got my longest diagonal (LC to O) within 1 or 2 mm. It was slightly better before fully welding it but I am pleased with 1-2mm to be honest and it is certainly "good enough"

HTH,
Craig.

Small addition to Craig's post.
Don't trust your roller to be straight or your square to be square, check them!
Also check that all your measuring tools agree.

Quite right!
Actually when I got my roofing square from Focus Do-It-All it was slightly bent and I got it for 1/2 price. I then took it home and straightened it and it was good as new. The bend was only minor anyway and didn't leave any residual damage once I had straightened it.

I did have a problem with my small set square which had a 1mm offset in the measuring scale on the inside of the square. It was really annoying until I realised where all my errors were coming from. Luckily the errors meant that I cut things too long and just had to file them back farther but it was annoying none the less and illustrates your point well. I now measure everything with my trusty 40" stainless steel rule and just use the set square's for checking angles are square.

I'd also recommend that everyone should buy a digital vernier caliper and a simple low cost micrometer. The vernier in particular is indespensible when checking all sorts of diameters and depths. I bought mine from screwfix and although it is only plastic, as long as you don't damage the jaws it is perfectly good and the fact that it is digital and reads in millimeters and inches is a boon! I often use it to convert dimensions too! It only cost me £19 (screwfix.com Part number 10216) and the micrometer was about another £12 (part number 10963)

HTH,
Craig.

Thanks again for your help. At least now I won't waste so much time checking and re-checking. Particularly annoying were the top rails J1 and J2, which are 1476mm in the book. They just wouldn't fit, an I checked all my work over and over again, until I found that the mcsorley plans show them as 1467mm, which matched up with mine!

I'm working to within the kind of tolerances youre all talking about so hopefully I'll be OK. I want to fit a ready made roll cage at some point, so I need to be as close as possible. Although I'm sure I will have some scope to get it to fit.

John. as you are at very early stage.. you need to make a decision now on your front suspension. the book is wrong, it shows the brackets approx 25mm to far forward for correct castor. There are 3 solutions
1. Go ahead with book dimensions and gusset brackets onto LA/LB,
2. Make J1 and J2 25mm shorter than book to give good contact for brackets, or
3. Make different shapped wishbones from standard.

The choice is yours.... at least you are aware now.....

Hornet..
Thanks for that. I think I'll modify the frame to accomodate the wishbones rather than the other way around.
Presumably shortening J1 and J2 means
that Assembly LA,B,C,D has to be re-made to keep the overall height at 13" because it will be canted backward a bit further.

At least I know now...thanks

Hornet/
Addition to your list:
4. Leave it as it is.
Quite a few are driving around with the wrong (2.7°) castor, but it don't seem to cause much trouble (any firsthand experiance reports will be much appreciated). Point of zero castor is reach with the rear wheels off the ground.

5. Move the top brackets 5mm to the rear. Will give 4° castor. No sweat, good enough for r&b.

Moving 25 mm will give a castor of 9.4° or is my trigonometry failing me?

Happy building!
Leif

John,

Further to the comments above about castor, if you are using Cortina uprights, the above comments will need to be taken into consideration.

However, if you are using Sierra uprights, you will need an upright adaptor, usually a turned ally insert with a hole reamed for the upper balljoint.

These inserts are available with the hole offset allowing quite a wide range of castor/camber angle adjustment.

See pic in my photo archive.

ATB

Simon

Leto...

Your No4 is the same as my No1.
and no your Trig is not wrong, it is not the brackets you move 25mm back... it is j1 and j2 to allow the correct castor with the brackets being placed centrally on LA and LB. I assume you have seen brackets hanging off LA and LB with the addition of gussets on the standard chassis?

Burgessj... yes when manufacturing the front end, you keep the same height, but increase the lean back of LA and LB

In the end.... you do what you like..... its your own build

quote:

---

Originally posted by Hornet
Leto...

Your No4 is the same as my No1.

---

quote:

---

and no your Trig is not wrong, it is not the brackets you move 25mm back... it is j1 and j2 to allow the correct castor with the brackets being placed centrally on LA and LB.

---

quote:

---

I assume you have seen brackets hanging off LA and LB with the addition of gussets on the standard chassis?

---

quote:

---

In the end.... you do what you like..... its your own build

---

Thanks for that..

I think I'll leave the front end tack welded until I've sorted the suspension out!

Anyone got any recommendations about wishbones ie.make your own, buy from MK or Luego

making my own wishbones took 4 full days, including making the jigs, making the plate sections, bending the steel, welding up and preparing for paint - how valuable is your time?

The cost for the wishbones was about £10 all in disregarding time taken

Up to you, I did it because I wanted to keep my brackets central so my upper wishbones had to be bespoke to give the castor angle. I am really pleased with the result

I got some wishbones off of eBay... It just so happened that they were attached to metalistic bushings, spindles, some disc brakes, and one 5-lug x100mm hub each....
Oh yeah, and they were from a wrecked Yamaha ATV and sold for $150 (75 pounds?). They're not the exact same length or width or thickness as ones from Ron's book, but they are meant to accomodate coilovers and are made of aluminum.
Through the power of math, I was able to determine that the maximum shock force that they would be subjected to on the road wouldn't come close to the maximum shock force that the average ATV would see in everyday use (besides, the coilovers take most of the force anyway).
I figure that I can make between $400 and $500 at work (something like 200-250 pounds) for four days, and the frustration of troubleshooting suspension parts is time that could be spent doing other things, like driving...
I will still need to modify these parts a little, but for $150 I've got myself a good jump at a front suspension.

::IMPORTANT NOTE::
I've designed my own frame rather than going with the guide, which gives me the freedom to do this - unless you get some very specific descriptions from sellers, you would be hard pressed to find components that will fit precisely.

IMO, the price of pre-fabbed pieces is worth the savings in time and effort. Also, if you don't trust your trig, don't take the risk.
-MR

BTW - what is the conversion rate of dollars to pounds?

mranlet:

quote:

---

Through the power of math, I was able to determine that the maximum shock force that they would be subjected to on the road wouldn't come close to the maximum shock force that the average ATV would see in everyday use (besides, the coilovers take most of the force anyway).

---

1. Your figures seem to be back to front. The wishbones will see far greater loads mounted to the car than on the ATV.
   
2. The coilovers don't take "most of the force", the bottom outer ball joint does, and if it's only an ATV item, it'll probably fail.
   

1. There's quite a bit on my web site about setting out, which applies to any type of vehicle, on or off-road.
   
2. To avoid large amounts of distortion, tack the entire assembly together first to prevent the dreaded warping. There's no reason why you can't obtain less than 1mm of misalignment.
   
   Ultimately though, the car's handling will only be as accurate as the points the suspension is attached to (asuming the wishbones, at least, are accurate!).
   You could build a asymmetrical chassis, but as long as the car's footprint is symetrical, all should be well.

   ---

   Hornet - 29/7/03 at 07:18 AM

   Nice 1 Leto..
   
   I have some pics and a rough sketch on this subject from earlier posts with Mark Allanson.
   You can check them out in photo section.
   Hope we are not confusing you Burjess?
   As you can see , there are many ways to end up with the same/similar result.
   
   I chose a modified chassis with standard wishbones so that at any time i need a replacement then they are staight from the shelf. In addition I did not feel a gusseted bracket was ideal.
   Have fun...
   

   ---

   davef - 29/7/03 at 12:01 PM

   Hi all just to clear things up once again more so for burgessj you do NOT move the suspension brackets back at all, you lean the front frame la & lb further back to facillitate a better weld position for the front top bracket, just take an inch out of the top rails and thats it sorted. cheers davef.

   ---

   davef - 29/7/03 at 12:19 PM

   Hi all forgot to mention car finished check photo in archive, ps burgessj check photo 7140806 re top brkts. cheers davef.

   ---

   James - 29/7/03 at 12:40 PM

   quote:

   ---

   Originally posted by davef
   Hi all forgot to mention car finished check photo in archive, ps burgessj check photo 7140806 re top brkts. cheers davef.

   ---

   
   
   Looks really good- nice one!
   
   James

   ---

   burgessj - 29/7/03 at 12:44 PM

   Yeah thanks Dave..
   I've only tacked it together so far. Should be easy enough to adjust the L assembly when I come to fit the wishbones...
   Sounds like I'm going to find these little 'anomalies' at various stages of the chassis build.

   ---

   mranlet - 29/7/03 at 03:00 PM

   Rorty-
   I'm going to have to find the notes sheet where I have the arethmetic written. I wasn't able to figure it out myself - I sought the help of my Calculus professor (who happens to be the Engineering professor). The comparison was made with the ATV weighing an estimated 500lbs with rider and being subject to falls of 3ft from the ground (not unlikely, especially with those residing in the northeast US). The Car was estimated to weigh 1500lbs with driver when completed and have 4" Jounce and 4" rebound built into the suspension.
   The final calculations put the car's force at somewhere around 80% of the ATV's force. I wish I could remember specifics but this was at least 5 months ago, and I'm on working vacation so much of my plans are not with me.
   
   Of course, this is going on theory without practice, but I do trust this Professor in his conclusions. If the ATV arms really won't work, it will be important to know that - would I still be able to use the spindles/uprights and brake mounts though?
   
   I am learning a lot about suspension forces and setup, but by no means am I an expert. One of the prime reasons that I come here is to learn more about things which I know little...
   
   Thanks for the input
   -MR

   ---

   GO - 29/7/03 at 03:37 PM

   Davef,
   
   Looking good!! Well done mate.
   
   Is that an anti-rollbar you've got on the front there?
   
   Cheers,
   
   Graham

   ---

   splitrivet - 29/7/03 at 03:57 PM

   Davef,
   Real nice looking job ,a credit to you
   Bob

   ---

   leto - 29/7/03 at 08:51 PM

   quote:

   ---

   Originally posted by Rorty
   <snip> There's no reason why you can't obtain less than 1mm of misalignment.
   
   Ultimately though, the car's handling will only be as accurate as the points the suspension is attached to (asuming the wishbones, at least, are accurate!).
   You could build a asymmetrical chassis, but as long as the car's footprint is symetrical, all should be well.

   ---

   
   
   First: "Accurate" is a expression that belong in mathematics. In "the real world", a workshop for example, it can't be used if it isn't followed by a "within".
   This is a very important key to understanding engineering and misuse makes me a little upset. Sorry for the outburst.
   
   I agree that you can, but I don't see any reason why you should obtain less than 1mm of misalignment. Except of course for the fact that you can. That is: it makes you feel good and I respect that reason.
   We were discussing the frame here. A car standing on grid waiting for for the race to start is another story. And as you say the thing that really matters then is "the points the suspension is attached to". To be of any real value these points have to be measured on a fully loaded chassis suspended on its springs, accurate within a mm or two and in a way that can be repeated with the same accuracy. This is a tricky operation that very few locost builders have the resources to carry out. Actually it is tricky to carry out on the frame alone, as the "point" turns out to be two holes with a gap between them and somehow, the centrelines from the drawing are not there
   Most builders have to rely on using jigs and do their best. Luckily this seem to be good enough.
   
   I fully agree to what you say, except the "accurate" wishbone. Do you have any suggestions on how to apply any of this on a lococt chassis?
   
   Cheers Leif.
   
   [Edited on 29/7/03 by leto]

   ---

   Stu16v - 29/7/03 at 09:45 PM

   Striving for the perfect chassis suspension accuracy is extremely important and cannot be stressed enough.
   But TBH, I have raced cars with bent chassis before now, and have still been competitive, and anybody that has watched any disipline of motorsport have have all seen examples of this to a greater or lesser degree before now.
   What I am trying to gabble is this. If a racecar being driven on the limit can be relatively unaffected by obviously serious misalignment of suspension pickups, should the ideal of building to within 1mm be important, or just a goal to merely strive for? I personally feel it's the latter. As already mentioned, production cars, especially up until a few years ago, were generally built to be within 5mm, sometimes a lot more. Look how much adjustment is usually given on door catches? Wouldnt be necessary if they they were put together properly....
   Throw the 0.5 mm buckle in each wheel, a bit of play in the wheel bearings, the slight discrepancy in the hub flanges, the twist of the wishbones, flex of the suspension bushes, the flex in the steering rack bushes, and the twist in the chassis and it's a wonder the car even goes in a straight line!
   But the more you can knock off (or at least lessen) in the above list, the better the car will handle. Accuracy is very important, but not at the expense of never getting the car finished! After all, most of the builders here will not be driving the car at 10/10ths in race conditions, they just want a decent handling sports car. With such low weight and centre of gravity, it would be hard not to improve on your average tintop.....

   ---

   burgessj - 29/7/03 at 10:28 PM

   I know I will not be able to achieve a tolerance of less than 1mm. TBH, I'm dead chuffed that I have managed to get the bottom section true and the overall length measures exactly right. I'm not going to get any better with the basic tools that I've got. The only thing that concerned me was when I cut pieces to the lengths given in the book and they didn't fit. Thanks to the advice given in these posts I now know there are mistakes in the book and I'm a lot more comfortable with it. I'm doing diagonal checks all along the way to make sure it's square and I'm making sure the outside dimensions are right. So I'm pretty confident of ending up with a decent frame for my first attempt.
   
   I'm crap at maths anyway!

   ---

   Rorty - 30/7/03 at 01:47 AM

   Davef, well done, you're on the right track!
   
   
   mranlet, theory can be a dangerous commodity.
   

   quote:

   ---

   
   would I still be able to use the spindles/uprights and brake mounts though?
   

   ---

   yes, if you can attach better ball joints, and are certain the brake mounts will accept larger calipers.
   
   
   
   Leto:

   quote:

   ---

   
   First: "Accurate" is a expression that belong in mathematics. In "the real world", a workshop for example, it can't be used if it isn't followed by a "within".
   

   ---

   Semantics! Why not encourage people to strive for perfection. If you have the attitude that "it's only out by a few mm....just like the big production companies", then all the discrepancies add up, and compound, to a botched job.
   Mr SVA is also going to be more impressed with a car that looks as if some care and attention has gone into it.
   
   
   

   quote:

   ---

   
   Actually it is tricky to carry out on the frame alone, as the "point" turns out to be two holes with a gap between them and somehow, the centrelines from the drawing are not there
   

   ---

   Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not to be accurate.
   
   
   

   quote:

   ---

   
   Do you have any suggestions on how to apply any of this on a lococt chassis?
   

   ---

   Yes! Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at home.
   

   ---

   davef - 30/7/03 at 06:30 AM

   Hi all thanks for the positive complements, and yes GO that is an anti-rollbar up front 14mm dia also Spax adjustable shocks. cheers davef.

   ---

   leto - 30/7/03 at 08:00 AM

   Rorty/
   Don't have time to answer you right now, sorry Going to visit a friend for a cupel of days
   
   See you all, later
   
   Leif.

   ---

   Viper - 30/7/03 at 12:16 PM

   quote:

   ---

   Originally posted by leto
   I make my living out of designing welded structures. If I was to hand out a drawing of something that was over 2m long, 1m wide and 0,5m high, made out of 60 segments of pipe, welded together and ask it to be right within 1mm....actualy it is a little hard imagining what might happen but it is not a good career move. A professional welder would probably say it is impossible,
   
   I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in who can do the job.

   ---

   Mark Allanson - 30/7/03 at 12:47 PM

   I agreement with Viper there, perhaps that is why Volvo's are so big?

   ---

   leto - 3/8/03 at 08:55 AM

   Rorty:
   Think we have entered the "Ways to look at the world"-department, where you find politics, religion, sport-fan-ship and such.
   

   quote:

   ---

   Semantics!

   ---

   
   Yes and..? We are, to a very high extent, dependent on the language to express our thoughts, intentions, views and ideas. Sloppy use of language, especially technical language, will just cause unnecessary confusion.
   I don't want to discourage people from expressing themselves just because they don't know "all the right words". If you don't use the words you have you will never find out what the right words are. Use your tools as good as your ability allow you.
   
   If "accurate" is used without any "within" in a technical context i will read it as "accurate within zero" and that will turn your statements into nonsense. You will never know if something is accurate within zero because there is no way to measure it without errors.
   I would really like to know how accurate your "accurate wishbone" actually is.
   
   

   quote:

   ---

   Why not encourage people to strive for perfection.

   ---

   "The perfect is the ultimate and the ultimate is death" [C.N.Parkinson, my translation from Swedish, as I don't have a original.]
   Perfection as a goal, is a dead end and will hamper creativity and curiosity. You start with a fix image of what you want to achieve and have no need to explore anything new. There is only one small point of success and it is very hard to get there, so you most probably end up with a failure. If you achieve your goal of perfection the result is useless as every thing you do will spoil it.
   I want to encourage people to strive to do better, to improve things, to find new ways, to see different solutions. I want people to allow themselves to end up with something that is better than they imagined possible.
   

   quote:

   ---

   If you have the attitude that "it's only out by a few mm....just like the big production companies", then all the discrepancies add up, and compound, to a botched job.
   Mr SVA is also going to be more impressed with a car that looks as if some care and attention has gone into it

   ---

   I fully agree. Do your best. But there is no point in over doing it, except to make you feel good.

   quote:

   ---

   quote:

   ---

   
   Actually it is tricky to carry out on the frame alone, as the "point" turns out to be two holes with a gap between them and somehow, the centrelines from the drawing are not there
   

   ---

   Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not to be accurate.
   

   ---

   Here we go again. How accurate is "accurate"? Zero, 1/100, 1/10, 1/2, 1, 2, 3, mm, inch? As accurate as your tools? How accurate are they, then and how accurate is your method of measuring?
   

   quote:

   ---

   Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at home.

   ---

   ---

   Hear, hear! Well maybe not "accurate jigs" more like, really good and innovative jigs.
   
   Happy building!
   Leif
   
   [Edited on 3/8/03 by leto]

   ---

   leto - 3/8/03 at 09:28 AM

   quote:

   ---

   Originally posted by Viper
   I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in who can do the job.

   ---

   
   And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".

   ---

   burgessj - 3/8/03 at 11:41 AM

   I have made much more progress with my build these last few days now that I know about the naff measurements given in the book, but it still doesnt stop me checking and re-checking all my dimensions every time I come across another error. I've found the best way for me to make progress is to make sure that the external measurements of the frame are correct, and then cut the cross members to fit, making sure that they are in squarely and that the spacing between them is correct (logditudenally). I had further problems with J1 and J2 though, because I had already tacked them to the front assembly only to find that they werent parallel to the the botton rails (D).
   
   Anyway the rear is coming on nicely. I managed to rig up a big set square and clamp it to the frame so that I could get the rail exactly 21" from the surface.
   
   I just hope it doesn't all move when I do the final weld!
   
   Still not sure what to do about wishbones..Luego have them reasonably priced. I'm a bit worried about having to adjust the front to fit someones wishbones in case some other bits don't fit (nose cone /bonnet etc).

   ---

   Viper - 3/8/03 at 04:04 PM

   quote:

   ---

   Originally posted by leto
   

   quote:

   ---

   Originally posted by Viper
   I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in who can do the job.

   ---

   
   And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".

   ---

   
   
   WHAT? What are you on about?

   ---

   Mark Allanson - 3/8/03 at 09:17 PM

   Leto,
   
   I think we must have misunderstood what you mean, Viper and I are both qualified professional welder, and welding a structure to 1mm accuracy is a mundane day to day task.
   
   Without proper tools and measuring equipment, it may be more difficult, but in a production environment , its just what you get paid for - I am sure that this is the same in Sweden, they (you) have a good reputation for welding, having one of the best welder manufacturers in the world - ESAB.

   ---

   jcduroc - 3/8/03 at 10:40 PM

   quote:

   ---

   Originally posted by Rorty
   Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not to be accurate.
   
   Do you have any suggestions on how to apply any of this on a lococt chassis?
   
   Yes! Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at home.
   

   ---

   
   
   This may seem redundant in this discussion but I think (I've already written that) that a Locost build should start by putting the wheels assemblies in the correct position in a jig and build the wishbones/chassis/etc from there on.
   
   At least that's the way I'm planning to do.
   
   Joćo Matoso

   ---

   leto - 4/8/03 at 09:51 AM

   quote:

   ---

   Originally posted by Viper
   

   quote:

   ---

   Originally posted by leto
   

   quote:

   ---

   Originally posted by Viper
   I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in who can do the job.

   ---

   
   And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".

   ---

   
   
   WHAT? What are you on about?

   ---

   
   
   
   Sorry to have upset you, Viper. As Mark Allanson suspected, I totally misunderstood you. Absolutely no offence intended. Thanks for setting me right Mark!
   
   My experience comes from a world were 10mm plate is refereed to as thin and something the size of a locst frame is tiny. Here, 1mm accuracy only exist in some designers dreams.
   Stupid of me to interpret this directly to "your world".
   
   Leif

   ---