Follow-up: "A better measurement and marking system"

Following the advice I got in the thread, I ordered a 300mm Incra rule from Amazon.de, as the product isn't available on Amazon.co.uk.

I received it this morning via Parcelforce, within two days of it being despatched in Germany. Marketplace Supplier: DICTUM GmbH - Mehr als Werkzeug

Total price I paid in GB pounds, including fast delivery: £25.27

This is cheaper by roughly a fiver than buying it in the UK.

The product is:

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I've just measured and drawn some test lines on a sheet of MDF and it is absolutely fantastic!

MM

Reply to
MM
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Drawing lines is one thing. Machining or cutting timber, or timber based products, to the same degree of precision, is another. Never mind expecting it to measure exactly the same in a few days, a few weeks or a few months time. Unless of course its being stored in optimal conditions and constantly being monitored using precision temperature and humidity equipment.

michael adams

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Reply to
michael adams

Warning: tool pr0n and money drain alert!!!

Thomas Prufer

Reply to
Thomas Prufer

Wood movement is predictable and allowances easily made for it. It is not a n excuse for adopting sloppy measurement techniques. We work to 0.5mm and h ope for 1.0mm In the steel industry where I once worked they worked to 1.0 mm and hoped for 5.0 mm Back to the o.p. These Incra rules are freely available. Axminster once sol d them. I have a few of them including the protractor. They are very useful especially to those of us with older eyes.

Reply to
fred

Exactly! I have three pairs of specs for: driving, reading, working at computer. But none is quite right for measuring with my bog-standard steel rule. I was starting to use my pocket magnifier as an aid, which is a pain. But now it should be much easier, thanks to Incra. I may also get the bend rule (90° one) in due course. Many people would say it's a lot of money to pay for a stainless steel rule, but this is NOT a bog-standard steel rule!

I didn't have a 0.5mm mechanical pencil to hand when the rule was delivered this morning, but the instructions state one can use a very sharp normal pencil, which worked fine just to try it out. I shall get a 0.5mm mechanical one the next time I go shopping -- although I looked on Amazon and there are quite a number to choose from, all at different prices. Maybe Wilko will have one. My next project is to make a wooden case to protect the rule, which is quite thin.

MM

Reply to
MM

ISTR they require 0.4mm lead.

I have the bend rule bought one time when I was feeling flush but rarely us e it

Reply to
fred

## Wood movement is predictable and allowances easily made for it.

Easily ? Movement in timber boards results from a combination of species, growth pattern in individual boards, and moisture content, both prior and just after machining and during the projected actual lifetime of that particular piece. In manufactured boards movement results from the ratio of wood products particles/veneers to glue again in combination with moisture content both past and present and is expressed as tolerances the extremes of which may apply or not to any particuar board.

## It is not an excuse for adopting sloppy measurement techniques. We work to 0.5mm

We ?

Could you explain precisely what you mean by saying you "work" to 0.5mm?

Obviously if you have access to a cast iron base Wadkin dimension saw say or similar heavy equipment this will be no problem and once properly set up you can replicate this precision all day long.

The only screw adjustments I can think off on conventional DIY tools are the turret screws and precison side fence on things like old model Elu/DeWalt(spit) routers.

But how is this easily achievable otherwise with standard DIY equipment is questionable.

I would expect rather greater precision than that for steel myself. After all Henry Maudslay's bench micrometer circa 1810 was measuring down to 1/10,000 in and I'm sure the likes of Richard Roberts, and James Naysmith weren't that far behind.

Horses for courses, and all that.

michael adams

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Reply to
michael adams

Nope. It says 0.5mm on the package.

MM

I feel fairly flush, given I'm not going to live forever! (Had a CABG x 3 in March 2013. Ticker now good, but who knows....? Better spend it now, I reckon!)

MM

Reply to
MM

Is it? I've been playing with wood for over 50 years and whilst I have a fair idea of what it will do I certainly can't make accurate allowances for shrinkage in something 'live' and with a moisture content of anything between 12 and 25%,

What I can predict is that unless it's been acclimatised to the same conditions that its to be used for a fair period of time, then it will expand or shrink accordingly - other than across its length.

Now as for you measurments in the steel industry - then your accuracy wasn't all that good. I was apprenticed on maintenance work in a egineering factory where their accuracy was decreed in fractions of a thousandth an inch - and in theory, they could have drilled a hole lenthways through the centre of a thin sewing needle (or so the engineers use to say to a rather green fifteen year old then ;-) ).

Ah, but the rules may be accurate, but do they take into account the thickness of the line that is drawn - which can vary according to the grade of lead in the pencil or nib or point of a pen?

Just being a bit of a devils advocate here!

Cash

Reply to
Cash

I seem to recall a boast by Tube Investments when I was a kid: an American company sent them a sample of their thinnest tube. TI sent it back with one of theirs threaded inside.

Reply to
Tim Streater

Absolute nonsense. I can easily cut to 0.5mm accuracy with my TS55, in fact I'd be disappointed with any cut that was that far out.

Reply to
pcb1962

I don't think he was talking about the engineering industry, I guess he worked in a foundry.

Reply to
pcb1962

The first sensible comment. The steel industry is NOT the precision enginee ring industry. The steel industry I referred to was the structural steel in dustry manufacturing steel frames for buildings hundreds of metres long. An error of 5mm in 20-50 metres is acceptable in that case.

The movement of wood due to atmospheric conditions has been understood for centuries and methods of dealing with it long worked out. If I want to make a panelled door I don't fix the panel within the frame, I allow it to floa t and leave room for it to float withing the frame. If I wish to finish the end of a solid wood table top with a cross grain piece I use a breadboard end. Equally if I am fixing this table top to its frame I use slotted screw holes.

None of these preclude using accurate dimensions. No-one is suggesting wood workers work to 0.01mm but if making a chest of drawers with inset drawers an error of 1mm in the gap around the drawer front can be detected by the human eye.

Back to the Incra rules. The lead used, ISTR, is .4mm wide. They are only u sed for marking out. Allowance would be made for the width of the pencil ma rk when trimming to size. This type of accuracy is to be aimed for but in r eality will not generally be achieved in the final article unless one is go ing to fine tune each joint. What you need to remember is that with wood an d many other things the level of accuracy you achieve is dictated by the le vel you apply. The two will not be the same.

We manufacture furniture in a small way,generally with man made boards. All of our machines can be set to at least .25mm and some to .1mm. Regardless of this the design of the piece will incorporate features to hide any inacc uracies.

As a hobby I do woodworking. I have a Felder combination machine which also can easily be set to within 0.25mm and less.

I use routers with side fences settable to 0.1mm.

I have a pull over mitre saw which can be set to 0.5mm and less.

This type of accuracy is easily available with any sort of decent machine a nd if working by hand a sharp plane and a shooting board will get you to th e very edge of the 0.4mm pencil line

Reply to
fred

From all I can see all the TS55 offers that's different is an aluminium saw track. Costing a few hundred quid. When many people myself included have been been more than happy to make their own out of ply. Birch ply in my case - 4mm for the base and 9mm for the two runners at the sides.

So what specific advantages in terms of accuracy do you get for that extra 150 quid ? As from what I can see it still all boils down to first having to line up the track against a set of marks. Same as you need to do with a home made plywood track or even a sawpoard. So what exactly do you get for all this extra money ?

There doesn't even appear to be any means of keeping the track parallel to the side of the sheet. And how do you make adjustments if say your cut is 0.3 out? Just make another set of marks but

0.3 further across ? And try and line up the track all over again ? And then clamp it in some way ?

And no I won't ask you how you'd measure this 0.3 mm to make the new mark.

On something like a dimension saw like any other precision tool the rip fence can be moved using fine screw adjusters. The only limit to the precision of this adjustment is the pitch of the adjuster screw. When using a rip fence, the side of the board runs parallel to the blade by definition. Something which doesn't apply with a saw track. So that once set up you can knock out pieces of wood to exactly the same width - to a precision determined only by the pitch of the adjustment screw, till the cows come home. One after the other.

Whereas with your 300 aluminium say track you have to line it up against a set of marks, clamp it, hope it hasn't moved in the process so check again, and then hope for the best. Same as with a sawboard really. So much for all the precision.

In fact the only real precision adjustment I can see in the Festool ads is for the depth adjustment on the saw. As if being able to set the depth of the cut on a circular saw to the nearest

0.5mm has ever been a big problem except in circumstances where you don't want to cut whatever's underneath. Where you saw up all your panels on the dining table, maybe ?

michael adams

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Reply to
michael adams

michael adams

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Reply to
michael adams

Your point being ?

Reply to
fred

In the first extract you say there can be no excuse for sloppy measuring techniques, yet in the second extract you say you design pieces so as to hide any inaccuracies.

But if you successfully avoid sloppy measuring techniques how can there ever be any inaccuracies ?

michael adams

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Reply to
michael adams

The ability to take and apply precise measurements doesn't preclude errors creeping in when making something. An accumulation of small errors can leav e one with a large error if none of them are compensatory. A 1mm error can easily be spotted by the human eye on small to medium sized objects. The tr ick is to design shadow lines or similar in places where this type of erro r can be egregious. These will hide minor errors. If your manufacturing eth os allows errors of =/- 0.5mm then two non compensatory errors may amount to 1mm. You can run this up and down either end but can't get away from th e fundamentals. Errors will occur. Examine the shut lines on cars for a sim ple example.

Of course if one is hand making individual pieces then one can correct the inevitable errors as one goes but assembling something from a stack of prec ut components makes this approach unsustainable commercially.

Reply to
fred

Indeed.

Which is exactly I originally said

"Drawing lines is one thing. Machining or cutting timber, or timber based products, to the same degree of precision, is another."

Which you took great exception to, for some reason

michael adams

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Reply to
michael adams

On 18/05/14 22:44, michael adams wrote: >

And as I told you, you're wrong, very wrong. With the professional's tool of choice these days cutting timber to

0.5mm precision is a piece of cake. You carry on disputing that if you want but I'm not going to waste my time arguing with you.
Reply to
pcb1962

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