Tool accuracy

[Rhossydd]

I don't really see where you're going with this.

It's a pretty simple question really; What tolerances do people expect to get out of their woodworking machinery ?

Whilst your question is yours, it is only the starting point for the discussion.

Yes, it can be the starting point for further discussion, but in most other forums it's polite to make an attempt to answer the OP's question before hijacking a topic.

 

[blackrodd]

I've been here before!
I was at a friends house, one evening and his father in law remarked that he had been working on parts for British Aerospace and his work was to within extremely fine tolerances, something like 100th of a thou.
He was somewhat shocked when i told him we had been doing a cut roof and we had no tolerances to work to, our cuts had to be spot on! Regards Rodders

 

[John15]

My eyes can barely read a rule to the nearest 0.25mm. I'm not sure where that leaves me.
Cheers,
John

 

[devonwoody]

My eyes can barely read a rule to the nearest 0.25mm. I'm not sure where that leaves me.
Cheers,
John

You need an electronic calliper around a tenner when lydl have them.

 

[bugbear]

I've been here before!
I was at a friends house, one evening and his father in law remarked that he had been working on parts for British Aerospace and his work was to within extremely fine tolerances, something like 100th of a thou.
He was somewhat shocked when i told him we had been doing a cut roof and we had no tolerances to work to, our cuts had to be spot on! Regards Rodders

Yes, I've heard woodworkers claim that their squares (e.g. if they've ponied up for a Starrett) are "dead on". I've never heard a precision engineer make such a claim.

:lol: :lol: :lol:

BugBear

 

[Cheshirechappie]

I've been here before!
I was at a friends house, one evening and his father in law remarked that he had been working on parts for British Aerospace and his work was to within extremely fine tolerances, something like 100th of a thou.
He was somewhat shocked when i told him we had been doing a cut roof and we had no tolerances to work to, our cuts had to be spot on! Regards Rodders

Yes, I've heard woodworkers claim that their squares (e.g. if they've ponied up for a Starrett) are "dead on". I've never heard a precision engineer make such a claim.

:lol: :lol: :lol:

BugBear

The phrase "fit for purpose" covers most eventualities. Rodders' 'tolerances' in building the roof may not have matched his father-in-law's toolmaking, but no doubt the roof is still giving good service.

----------------

The finer the tolerances you wish to work to, the more rigid the machine needs to be, generally speaking. Hobby grade machines are too flexible to work to the same level of accuracy as an industrial machine, and trying to get them to is a waste of time. Use them to save the time and effort of heavy stock preparation, and be prepared to trim for fits later. The more rigid machines probably can hold tolerances of better than +/- 0.05mm, but expecting that of lightly-built machines is over-optimistic.

 

[deema]

Well, to quote an old cabinet maker, engineers work to a thou, I work to spot on.

 

[Rhossydd]

The finer the tolerances you wish to work to, the more rigid the machine needs to be, generally speaking. Hobby grade machines are too flexible to work to the same level of accuracy as an industrial machine, and trying to get them to is a waste of time. Use them to save the time and effort of heavy stock preparation, and be prepared to trim for fits later. The more rigid machines probably can hold tolerances of better than +/- 0.05mm, but expecting that of lightly-built machines is over-optimistic.

That's what I would expect.
I'm just surprised, and a bit disappointed, that there haven't been many(any?) people who can actually quote some real world numbers from their own machines. When digital callipers and dial gauges cost less than a couple of pints of beer, I would have expected many people to have them and take an interest in knowing what their machines are delivering.

 

[Jacob]

The finer the tolerances you wish to work to, the more rigid the machine needs to be, generally speaking. Hobby grade machines are too flexible to work to the same level of accuracy as an industrial machine, and trying to get them to is a waste of time. Use them to save the time and effort of heavy stock preparation, and be prepared to trim for fits later. The more rigid machines probably can hold tolerances of better than +/- 0.05mm, but expecting that of lightly-built machines is over-optimistic.

That's what I would expect.
I'm just surprised, and a bit disappointed, that there haven't been many(any?) people who can actually quote some real world numbers from their own machines. When digital callipers and dial gauges cost less than a couple of pints of beer, I would have expected many people to have them and take an interest in knowing what their machines are delivering.

My Minimax lab300 has a scale in mm for the thicknesser. The cursor is a sticking out bit of metal which you calibrate by bending it. To read accurately you have to crouch to avoid parallax. So it quite accurate in woodworking terms but I check (the workpiece) with a cheap Draper vernier calliper every now and then which means I can thickness to about 0.1mm (if necessary, not usually), as measured, which is very precise for woodwork. I don't bother with digital calipers (another thing to go wrong, need battery etc) and dial gauges are precise well beyond my needs.
It's important to distinguish between accuracy and precision. One doesn't necessarily entail the other. You can measure as precisely as you like but still be inaccurate due to the limitations of the machine, the material, variations in handling.

 

[Cheshirechappie]

The finer the tolerances you wish to work to, the more rigid the machine needs to be, generally speaking. Hobby grade machines are too flexible to work to the same level of accuracy as an industrial machine, and trying to get them to is a waste of time. Use them to save the time and effort of heavy stock preparation, and be prepared to trim for fits later. The more rigid machines probably can hold tolerances of better than +/- 0.05mm, but expecting that of lightly-built machines is over-optimistic.

That's what I would expect.
I'm just surprised, and a bit disappointed, that there haven't been many(any?) people who can actually quote some real world numbers from their own machines. When digital callipers and dial gauges cost less than a couple of pints of beer, I would have expected many people to have them and take an interest in knowing what their machines are delivering.

I suspect that reflects the different natures of the different crafts. Wood moves with the seasons, metal (thermal expansion excepted) generally does not. The traditional techniques of woodwork depend on trimming parts to fit each other, without much reference to their absolute measurements (who puts micrometers to tenons?). The traditional techniques of engineering tend to the more absolute - 'make to size' is more common (especially in modern times); even the more traditional engineering fitting usually calls for components to be machined within a few 'thou'.

There is some cross-over. In an earlier post, I mentioned the mass production of flat-pack furniture from man-made boards. The machining of those MUST be more precise - you wouldn't want to scrap a batch of 1000 cabinets because the left-hand sides were 1.5mm longer than the right-hand sides, and the slots for drawer dividers were 0.2mm tight on the divider itself.

In general, there's little to be gained by thinking in 'thous' in a hobby woodworking shop - the wood will swell more than that if it comes on to rain in the afternoon. Treat wood as the variable material it is, and just make things fit each other. By all means adjust a thicknesser so that it planes parallel within a smoothing plane shaving or two, but don't obsess about engineering tolerances. Wood won't respond in the same way as toolsteel.

 

[Tony Spear]

As a friend of mine, who was (still is!) a really superb folk guitarist, used to say:
twang, ping, buzz, more twang.......... "Oh well - near enough for Rock and Roll" :mrgreen:

 

[Rhossydd]

[By all means adjust a thicknesser so that it planes parallel within a smoothing plane shaving or two, but don't obsess about engineering tolerances.

It's not about expecting 'engineering tolerances', but what tolerances do people think are acceptable from their machines ?
At what point would you reject a new thicknesser because it wasn't good enough ?
At what point do you stop trying to optimise a table saw ?
Or do people simply not care what comes out of their machinery ?

 

[heimlaga]

The thicknesser part of my combination machine has no scale at all. There was one but it was not readable any more and since I replaced the post I have just not gotten around to make a new scale. I use a caliper and count turns on the crank to get the correct thickness within 0,5 mm. One turn on the crank equals 5 mm. The boards get flat across their width after I had the worn out table remachined but I have no clue what flat is. I have't tested it with my machinist's rule.

The table saw part of it is parallel enough. I quit hand scraping when everything worked all right. There was 54 years of wear that had to be set right.

I have fairly high standards for machine accuracy and can spend quite a bit of time with files and scrapers to make worn moving parts move without excessive slop but I have no numbers for the tolerances I use.

 

[adzeman]

We have been down this thread before and engineers are always making comment regarding their accuracy but, they are working with a different medium. Our medium was a living breathing plant which we make it fit. I have a neighbour who is a retired engineer who builds wonderful boats and he is the first to say when he works in wood he has a different mind set.
The engineer mind set is one of measurement while the woodworker is one of geometry and regularising. Producing a rod or full size drawing and using this to set his dimensions. In theory you don’t need a rule. The square, dividers a compass, a marking gauge, a marking knife are the only measuring tools he needs. Think about 200 years ago boxwood rules were expensive, not many woodworkers could afford them and those that could, there accuracy or similarity to others in the shop would be doubtful. Woodworkers would make their own rules or rods. If they were measuring say for a window they would measure the opening as to their rule but more than likely take a physical mark on a long length of timber and for the mullions divide this length with geometry not by measurement. The skill is making the cuts either by hand or machine as well as an ability to set out.

 

[Dangermouse]

[By all means adjust a thicknesser so that it planes parallel within a smoothing plane shaving or two, but don't obsess about engineering tolerances.

It's not about expecting 'engineering tolerances', but what tolerances do people think are acceptable from their machines ?
At what point would you reject a new thicknesser because it wasn't good enough ?
At what point do you stop trying to optimise a table saw ?
Or do people simply not care what comes out of their machinery ?

I think your asking impossible questions to answer, as every woodworker has different parameters and standards. One gets it as near perfect as you can, is the best answer I can give. But then I use my machines start on the basics and then finish off by hand, maybe a woodworker who wanted to go from machine to assembly would spend days getting a machine to turn out perfect results, which I doubt is possible.
Why do you want to know this rather esoteric information? Sometimes I do believe this is becoming for some people more about obsessive delving into pedantic obscurities i.e. this thread and the thread about Stanley plane screw threads, than about actually doing some woodworking.

 

[rdesign]

to try and answer your question ! I have a sip 01332 table saw with slider. the blade is parrallel with the blade by the noise it makes when the same tooth hits my adjustable square. the sider runs parallel with my mitre slot by clamping a piece of timber to my carriage and visually seeing if it stays to the same mark. my cuts are 90 degrees when i cant see over a hairs thickness of light between the wood and my engineers square.
i check my engineers square by drawing a line flipping it over and drawing another they should be perfectly parallel.

my planer thicknesser is a mini mas fs30 and i posted a similar question u can see my tolerances and others response here planner-thicknesser-set-up-except-able-error-t72101.html

for hand power tools and hand tools sick of having inaccurate cheap tools so will spend the money once on festool for my power tools have the ts55 and a domino, router and sander r next on my need list.

regards
Richard

 

[blackrodd]

Down here, in common with other makers, we had a "skid" drawn up on a piece of ply, full size. This would be for everything, a door, clock case or furniture, whatever was being made.
Every thing was made to fit that skid and a rod was used for length sometimes plus 3" or whatever.
The next time 10 or 20 clock cases were made they were probably slightly different in measurement. Cabinet makers skill and Craftsmanship to be seen.
You can always see quality and skill. Smacks you right in the kisser! look at some of the stuff on here, some by self taught craftsmen, Wonderful stuff!!
I personally can't see the "marriage" of engineering tolerences with woodworking, a natural moving material being very sucesful, We'd be planing off all winter and glueing see through shavings all summer!
I have a sneaking admiration for someone whom can talk and work to a measurement i cannot see. I need him to make my bearings and cutterblocks to those exacting standards. regards Rodders

 

[Rhossydd]

I think your asking impossible questions to answer,

There's nothing impossible about it at all. Just measure a bit of wood as it comes out of the planer.
It's a very simple question. I'm just incredulous that no one here seems to bother to quantify how well their machinery performs.

maybe a woodworker who wanted to go from machine to assembly would spend days getting a machine to turn out perfect results, which I doubt is possible.

As mentioned earlier; the idea is to get an idea of where to stop when setting up machinery. If you've ever had to adjust a set of planer blades it can be a time consuming process to get acceptably correct, just how much time do you spend on it ? Knowing the limits of what's possible and when you hit the point of diminishing returns is important.
Every book on table saws will have a chapter on setting them up correctly. Don't people here bother with that ?

Why do you want to know this rather esoteric information?

I don't see it as esoteric at all. It's just simple facts about machines performance.

Sometimes I do believe this is becoming for some people more about obsessive delving into pedantic obscurities i.e. this thread and the thread about Stanley plane screw threads, than about actually doing some woodworking.

But that's the whole point of the question. Once a machine has been set up optimally you can get on with doing some productive work. The more accurate the machine, the less spend you'll need to spend later on coping with any inaccuracies.
You can also keep an eye on dimensions as a form of quality assurance to keep things working for you.

 

[Rhossydd]

to try and answer your question !

Thanks, nice to know I'm not the only one that cares.

 

[Jacob]

.....
There's nothing impossible about it at all. Just measure a bit of wood as it comes out of the planer.
It's a very simple question. I'm just incredulous that no one here seems to bother to quantify how well their machinery performs.
........

I think you will find that everybody quantifies (where quantifiable) the performance of their various tools and machines, some of the time, in one way or another, to suit the job in hand. What makes you think they don't? Do you think people make things blindly without looking at them and checking as appropriate?
But we also judge performance by appearance, without quantifying anything. If something comes out looking wrong, we make adjustments until it comes out right, without necessarily measuring anything at all.

NB you don't seem to have answered your question yourself - we are all waiting, with bated breath!