Tool accuracy

[Rhossydd]

When I first did woodwork at school we used wooden rulers and worked to 1/16". When I first started making furniture at home I had a metal ruler that measured to half a millimetre. Coming back to do more work in the 21st century and I have digital depth gauges and callipers that measures to two decimal places of a millimetre.
Now we have such cheap and accurate measuring tools available, what sort of tolerances are people expecting their tools to work to ?

As some examples;
How flat do you expect a thicknesser to deliver across 150mm ? within 0.1mm ? 0.2 ?
What would be acceptable accuracy for parallelism of a mitre slot to a blade in a table saw ? +/- 0.1mm ? 0.2mm ?

I realise that a lot depends on the work, but I'm curious to know what people expect from their machinery.

TIA

Paul

 

[bugbear]

Early practise revolved around folding 2 foot rules, which were only marked in 1/8". However there was an extensive jargon of working "in the gaps", so a given size might be scant, bare, or full, which sort of means you're really working in 1/24".

BugBear

 

[Spindle]

1/32nds surely

 

[bugbear]

1/32nds surely

Each 1/8" has three options.

BugBear

 

[Spindle]

Hi Bugbear

How does that work then?

Surely its:

zero scant bare full zero (the next eigth increment)

Regards Mick

 

[SuperAB]

I generally like things to be within a 0.01cm tolerance but as you said it depends in what I'm building. My new work bench was within that tolerance but I built some scenery items for a play and I wasn't so concerned about the outcome.

 

[Spindle]

Hi

In round figures 0.01mm is four tenths of a thou - I'm impressed if you're woodworking to those tolerances :wink:

Regards Mick

 

[Dangermouse]

I generally like things to be within a 0.01mm tolerance but as you said it depends in what I'm building. My new work bench was within that tolerance but I built some scenery items for a play and I wasn't so concerned about the outcome.

That's more like engineering than woodworking !!!!!!! Wood is a natural thing and what ever unit you use to measure it with, it will expand and contract over time with humidity etc.

 

[nathandavies]

As long as you don't get to bricky tolerances of being in the right field. As long as setting up to .01mm doesn't take all morning then it makes life easier down the road. also depends on whether there has been a good deal on 80 grit recently.

 

[Cheshirechappie]

Do you want machines to do the worst of the heavy preparation - ripping, surfacing, thicknessing, rebating, moulding, grooving - and subsequently refine fit and finish using hand tools and 'traditional' techniques, or do you want machined components to fit first time without adjustment?

The first seems a sensible set-up for craftsmen making one-offs and small batches, the second is well-nigh essential for volume production work. The machinery required is vastly different to satisfy the two requirements. In the first instance, flexibility and a degree of versatility is needed to accommodate a range of work over a short timescale; in the second, once set machinery must hold close tolerances for long production runs.

Horses for courses, as so often.

 

[blackrodd]

Hi

In round figures 0.01mm is four tenths of a thou - I'm impressed if you're woodworking to those tolerances :wink:

Regards Mick

In my day it was either a fag paper or a gnats bo--ock! Rodders

 

[Jacob]

I think he must mean 0.1mm, which in woodwork terms is extremely precise; probably even smaller than a gnat's nurgler.

 

[SuperAB]

I generally like things to be within a 0.01mm tolerance but as you said it depends in what I'm building. My new work bench was within that tolerance but I built some scenery items for a play and I wasn't so concerned about the outcome.

That's more like engineering than woodworking !!!!!!! Wood is a natural thing and what ever unit you use to measure it with, it will expand and contract over time with humidity etc.

Oh I completely agree the material is very natural however, I like my machines to be set exactly right to begin with. An example is my mitre saw fence was off when I bought it but a bit of tweaking and it is now exactly true.

I would like to think because I took the time to get my machines right is the reason why I was able to get my workbench angles down to such a tolerance. I fully accept that it will completely change over time and I'm happy with that.

As you say it is engineering but I quite like the feeling of getting it bang on to begin with.

Maybe I'm just a bit to fussy on that sort of thing?

 

[Spindle]

Hi

Personally I'd be interested to know how you were measuring to those tolerances.

Regards Mick

 

[SuperAB]

Hi Mick

I have quite a few different digital measuring devices which I use. Mostly Gemred stuff which I have been more than happy with.

Hope this helps

Cheers.

 

[Spindle]

Ahh - OK Thanks

Mick

 

[Jacob]

I'm sure you could measure to 0.01mm but very few machines would be adjustable to that level of precision, still less if you are looking at deviation over any length. You don't mean 0.1mm do you? 10 times bigger but at the very edge of what can be seen with the naked eye.

 

[Dangermouse]

I'd love to know what wood your getting these very small tolerances with ?

 

[SuperAB]

Sorry no I meant within 1mm! Sorry i meant to put CM! Not mm!

 

[Jacob]

Sorry no I meant within 1mm! Sorry i meant to put CM! Not mm!

Phew that's a relief! I'd say plus or minus 1mm is pretty normal, fairly relaxed in fact.