Have we lost the plot as far as tollerances are concerned?

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I think Would Not has got it right. I too am an engineer, but in the end it's mostly a matter of working methods.

Engineering works to very close tolerances (a) because it's frequently a functional requirement, and (b) as he says to enable interchangeability.

But unless you're on first fix carpentry there's not too many woodworking joints that will look or perform decently with up to 1/32 in marking and making variability on each part, especially not if (to speak engineering) the tolerances on the two mating parts add and you get a gap of 1/16in.

The reality is as somebody else has said that most joints are actually fitted to within a thou or so. The first half of the joint e.g. the mortice may well be made to quite an approximate tolerance, but the mating part will be hand fitted using a shoulder plane or whatever to match.

This probably won't deliver interchangeability, because even though the fit is very finely adjusted the dimensions will probably be different. Not to mention that the completed item will probably subsequently move all over the place with changes in humidity.

This hand fitting is in engineering/manufacturing known as craft production. (pre-Henry Ford) If on the other hand you are engaged in repetitive manufacturing - even of wooden items - then it becomes a matter of economics that parts are interchangeable. Nobody is going to be able to afford to spend loads of time on each item either hand fitting, or selectively matching parts that happen to fit.

Does it matter? Personally i'm very happy to be able to set a cut to within a thou using e.g. an Incra positioner, and then make the cut on a machine that's accurate and rigid enough that it's to dimension and square. More or less that is, because at our level of wood machines are still pretty approximate by engineering standards.

There's a huge level of skill involved in working around the vagaries of inaccurate machines - this starts at the design stage, and if you have to adjust/fit parts then sequencing is important too.

But is it necessary to do this to be credible? I don't think so because even so called accurate kit needs very careful set up and use if you are to even hope to get parts off it that are even close to simply slotting together without fitting. We're quite some way off machines that can do this without an intimate understanding of what's going on. People seem to demand ever higher standards of fit and finish anyway, and it's just another skill set...

It's not of course a 'good thing' in itself i think either - there's not much to be had from obsessing about this one aspect of making when it's possible to produce stuff that has it's own unique look and feel, and is fully functional despite much less precision. Nor is there anything that makes it great (art?) just because you spend hours slaving away over it, other wise we'd all be working with nail files!

Maybe it's just a matter of personal preference, of what you are trying to achieve (how you mix art and economics) - with the possibility of either approach (within reason) producing great work???
 
promhandicam":1c00f33b said:
....I've been making quite a number of frame and panel doors recently and if I could only get to within 0.25mm on each piece I machined I would end up spending the next month sanding all the components .....
There's always a rail which isn't quite flush with a stile however perfect your procedure; I always expect to have to bring something into alignment after it's all glued up but I'd use a hand plane. Sanding is for finishing not for thicknessing, except for things impossible to plane.
 
It is perfectly possible to work to a very fine degree of accuracy in wood - just ask Robert Inham or John Makepeace.

It's also very easy to feel something that is a few thou out with the fingertips and if it’s an illuminated gap - by eye too. It makes perfect sense to try and eliminate imperfections that are noticed.
 
would not":t6pa4zbb said:
........
As for a rule vs digital vernier....that's just progress that enables you to do the job easier, would you throw your cordless screwdriver away and always use an ordinary screwdriver?.....
I prefer a non-digital vernier caliper as it removes one link in the error chain. I can still read to 2 thou if necessary - much more precise than I need. I only use it for checking whilst machine thicknessing. And for survey measurements of course, if I'm copying something.
Have both varieties of screwdriver. 2 drawers full of ordinary ones in fact! Need them all.
 
I would add my views are the same as Woody Alan and Richard Findley, I am satisfied if I also have done the best I could do.

Regarding the Felder machines, it looks to me if I am right, don't bother to do woodwork in the winter, not only do the machines not like it but nor do I. Motors don't like the cold nor do rubber belts on machines.
 
mr grimsdale":2b4lz3oe said:
There's always a rail which isn't quite flush with a stile however perfect your procedure; I always expect to have to bring something into alignment after it's all glued up but I'd use a hand plane.

I quite agree and have had to do make minor adjustments on a couple of the doors using a hand plane. However most of the joints were spot on and did only need sanding once they were glued up.

mr grimsdale":2b4lz3oe said:
Sanding is for finishing not for thicknessing, except for things impossible to plane.

I have a medium size drum sander so for smaller items like drawer fronts I can thickness to a certain extent using this but would agree that hand sanding or using an ROS aren't suitable for thicknessing other than very small items.
 
devonwoody":3622lnr9 said:
. . .Motors don't like the cold nor do rubber belts on machines.

Do you have any basis for those sweeping statements? IMHO they are nonsense. Do you seriously think that, for example, cars in Alaska or Canada have to use an alternative to rubber for fan belts?
 
The 0.25 difference through the thicknesser could be caused by a few factors. The difference between either side of the bed could be 0.25mm The piece being planed could have been made higher by being caught under some chips. Some snipe on the ends is altering measurements etc.

I am pretty sure most of the stuff that comes of my planer will show up to 0.25mm differences. This doesnt affect any further machining as everything is usually machined from a face side so all joints will be perfect and aligned. If some thing is really crucuial thickness wise it goes through the drum sander.

Cheers

Jon
 
I'm an ex design engineer & tend to try to apply tight tolerances to my work. However if has been known to backfire on me.

My most important client (SWMBO) has commented on stuff that I've made to nearly perfection (in my eyes) by saying "well I could have bought that in a shop".
What she means is it looks machine made on a production line.
I made a oak door that was absolutely spot on & she said it looked like plastic. And to be honest I could have bought something identical from B&Q kitchen range. I now never use lacquer or varnish only wax.

I make her stuff that I'm technically unhappy with and she raves about it "because it looks handmade".

I use a digital caliper gauge because its easier to read than my rulers
 
Prom, it was a sweeping statement, but I attempted to run my P/T a few weeks ago and it would not work, I stripped of the gear covers to see what was wrong and the rubber belt was slack, moulded to the shape of the drive shafts (kind of kinked).
I removed an made enquiries on the forum about locating replacement but the next day I observed that the belt , which had been left overnight indoors had become supple again and when I refitted the P/T worked perfectly.
So perhaps the belts in Alaska are toothed or not the same as fitted to woodwork machinery, also their electric motors must also be manufactured to different standards.
Sorry if hijacking,back to posted thread?
 
We used to have all old Wadkin Bursgreen machinery in the workshop I use to work in, and never used to have any problems with any of them, even when one of the walls was replaced in the middle of winter and it was freezng inside.

The problems started when they swapped the spindle moulder for a new all digital, singing and dancing one, it was so tempremental. It would just work when it felt like. And of course, with these newer machines you cant just open them up and have a fiddle about inside. They have to send over a technician from Germany or somewhere to sort it!

There is a lot to be said for the older machinery! Not as many things to go wrong on them for sure.
 
devonwoody":3hroe3ql said:
Prom, it was a sweeping statement, but I attempted to run my P/T a few weeks ago and it would not work, I stripped of the gear covers to see what was wrong and the rubber belt was slack, moulded to the shape of the drive shafts (kind of kinked).....
Sounds like it was not tight enough to start with.
I've had no problem with any of my machines through this winter (coldest for 30 years) in an unheated workshop.
 
lurker":2vmt77o1 said:
I'm an ex design engineer & tend to try to apply tight tolerances to my work. However if has been known to backfire on me.

My most important client (SWMBO) has commented on stuff that I've made to nearly perfection (in my eyes) by saying "well I could have bought that in a shop".
What she means is it looks machine made on a production line.
I made a oak door that was absolutely spot on & she said it looked like plastic. And to be honest I could have bought something identical from B&Q kitchen range. I now never use lacquer or varnish only wax.

I make her stuff that I'm technically unhappy with and she raves about it "because it looks handmade".

I use a digital caliper gauge because its easier to read than my rulers
This whole discussion in my view, really comes down to the type of woodworker you see youself as.
Do you really want to work to tol of 0.1mm as Robert Ingham does?..or at the other end of the scale, tol judged pretty much by eye as the late JK did?.. (except important mating parts such as joints, where a snug 'push by hand' sliding fit is sufficient)
If it's the former, then you'll need to invest in the appropriate machinery and ensure it's set up correctly. If the latter, then decent, robust ordinary machinery will do the job (the emphasize here switches to hand skills)
I suspect that most of us fall somewhere between the two, within the limits a) of the material and b) our back pockets.
At the end of the jour, it's a lump of wood and will do all sorts of stupid things that we as woodies need to take into account and therein lies the skill, not in whether or not we can produce it to a tol of 0.1mm but whether it fits our purpose and more importantly...SWIMBO's (read customer :wink: ) - Rob
 
woodbloke":24w9cpel said:
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This whole discussion in my view, really comes down to the type of woodworker you see youself as.

Quite so. Accurate machining makes sense where production calls for large numbers of identical and interchangeable parts, but for most domestic furniture or joinery there is actually very little need for numerical measurements. If pieces need to be the same size you cut them together or mark with the same gauge. The absolute size is of little importance and will be adjusted to suit the materials to hand.
 
JonnyD":akh7rgxx said:
This doesnt affect any further machining as everything is usually machined from a face side so all joints will be perfect and aligned.
Cheers

Jon

My own experience has brought me to the same conclusion - pieces out of the p\t can and do vary and the only way to deal with it (for me anyway) is to reference from a face side.
 
for me it depends entirely on what I am trying to achieve. If I am making a jewellery box then I want tollerences such that I can not see or feel any gaps in joints or the mating of the lid to the base. I will spend ages getting mitres to exaclty 45.0 degrees and each piece to 0.1mm variation of thickness.

On the other hand the other night I built a stand/cabinet for the grinder and Tormek. Doing that the tollerances were as good as I could get with a 40" ruler and a reasonably sharp pencil.
 
I am both a traditionalist, using tools of over 100 year vintage...and a modernist...using gauges that have little Chinese men inside holding up digits.

I use whatever suits the purpose at the time in ease of use and accuracy.

I also tend to use analogue devices (with pointers and dials) if I want to see changes in reading and digital ones if I need spot readings.

I bought the little bevel box from Axminster as a fad buy and boy is that thing handy! MUCH easier than faffing around with angle gauges IMHO.

But extreme cold...prolonged cold and battery failure push me to think that if my life depended on a choice...I would have a good quality accurate analogue device anytime.

Jim
 
If the eye can spot it it is an issue so it is important to at least attain a high level of precision in the machining process so that the fit and finish is as spot on as it can be. Wood moves, so i doubt we need to be as critical as machinists and i don't rely on much digital goodies to achieve the high level of accuracy i strive towards. That doesn't mean that i don't take the time to align my fences and miter gauges, and other equipment though. I think i spent close to two days setting up my thicknesser. But experience tells me that the more accurately the machine is set up the less I'll be faffing about trying to true something up on a daily basis.
 
It really depends what you are doing imo - in my home workshop i generally try to get things spot on and use machines where appropriate to get the tollerances as low as possible - though that said i'm not going to worry about a few thou discrepancy.

but in the shop at work where we are largely making signs, gates, anmd benches, for outdoor use the general maxim is that "good enough" is good enough but perfect is always a pain in the @rse - the tollerances we are working to are usually a mm or so each way assessed by eye and we are of the school that if it doesnt look quite right you tap it with a mallet til it does.
 
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