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Accuracy - general hints and tips ?

8954 Views 40 Replies 17 Participants Last post by  steamingbill
Hello,

Was wondering how other people approach making accurate cuts.

If I am making some sort of 3d object and I make relatively small errors in my cuts then by the time I have either "gone round a loop or a carcass" or gone around a few 90 degree bends in different orthogonal directions then I find that bits dont quite meet up with other bits and things arent quite square.

I try to be as accurate as possible in my cuts but I can mess something up - it seems to me there are 2 issues

1. How do I organise myself top make measurements and cuts as accurately as possible ?

2. Ways of correcting or even hiding things - for example - I noticed when I was owner builder of my house that I could hide a poorly cut plaster edge with the final architraves and skirting boards - ie the very last thing done is the most visible and needs to be perfect but the stuff underneath has some "slack"

Any good general tips or threads or web sites or hints for measuring and making accurate cuts when doing normal jobs in the shed ?

ie use of story sticks instead of rulers ?

empirical measuring rather than using a tape measure or ruler - ie take the thickness directly off a piece of timber rather than measure thickness (possible error) and then mark up using ruler ( another possible error) ?

use of a marking knife or gauge rather than a pencil ? How many people do this ?

use of jigs to make all relevant pieces the same length, width, holes in the same place etc

I often think to myself things like "cut so that you can still see the edge of the pencil line"

How do the rest of you organise yourselves to be as accurate as possible ?

Regards

Bill
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Hi Bill

You touch on some interesting issues. Like you I'm aware of the ways of working in the construction industry which means that a multitude of small errors can be overcome simply because the last items in the process, such as skirtings (baseboard) which can be used to cover minor defects in the plasterwork (although to be fair I was taught that plaster should always end 1in shy of the floor in any case to reduce moisture wicking).

When making a piece of furniture or a cabinet it's a little different. All the cuts for the man carcass or frames need to be bang on and to that end you need to check and double check the accuracy of your right angle cuts. As others have said, though, don't set-out the joints until you have prepped the materials, after all the 24mm called for in the drawing might be 22mm in your material because you needed to take ot some cupping. Are your squares accurate? Do you know how to check them? Many woodworkers squares are a mile out to start with; cheapish all-steel engineers's squares of "B" grade are a fare better bet and very affordable. Is your saw (table or mitre) cutting a true 90 degree cut? Again do you know how to check it without using a square? Getting the angles and measurements right is a must and to that end you touch on a technique used by time-served joiners and cabinetmakers for centuries which does away with the inherrent human error-prone use of a measuring tape - the rod or story pole:

ie use of story sticks instead of rulers ?
If working from scale drawings it is always better to set-out everything full-size on the "rod" then transfer all dimensions directly from the "rod" to the material. Smaller dimensions are often best transferred using relatively cheap wing dividers:



(the somewhat tattier ones I carry cost £2, or $3, from a flea market) Which can also be used in conjunction with a steel ruler and a set square to divide lines into any portions you want - want to mark something so that it's 2/7ths of 15.6in (comes to more than 10 decimal places on my calculator)? No problem. By now you'll be getting the impression that I don't measure all that much and you'd be right.

Another aid in this area is to use a single tape throughout a job - not all tapes are equal. If you don't believe me pull out three 3 metre (10ft) tapes side by side and I'm almost certain that at least one of them will have some obvious variations (and that's for the better quality makes like Stanley or Lufkin). If you need to measure something absolutely then the only way is an engraved steel engineers rule and not a screen printed aluminium rule or a tape.

Knifing to a line is traditionally how cabinetmakers worked, just as they also use cutting gauges to mark out across the grain and marking gauges to mark with the grain


Above: Cheap carpenter's and joiners marking gauge - for use with the grain
Below: Cutting gauge - for use across the grain. Note that the blade is removeable for sharpening



(and a mortise marking gauge for setting out M&T joints, Jerry) and they also use a knife with the blade sharpened only on one side:



not a Stanley knife (the bevel face is used on the waste side of the cut). For joinery this is less of a need because the level of accuracy required is generally somewhat less, but it doesn't mean that you can be slapdash. On less critical softwood joinery tasks I often mark out with a pencil - generally a Staedler 2H rather than a cheap Chinese HB - the harder lead makes a finer line and you can sharpen good quality pencils more easily whilst on hardwood jobs I tend to knife the line

If you are making multiple identical components it can make sense to gang saw two or three pieces simultaneously or if cross cutting on a mitre saw or radial arm saw to set a fixed end block then cut all alike components in one run. as soon as you get the tape out your accuracy is gone.

A small, competent marking and measuring kit with a couple of squares, a steel rule, a marking knife, marking and cutting gauges doesn't cost a fortune and reaps dividends in terms of accuracy. Over here in rip off Britain I could probably put a flea market kit together for £15 ($22) - new tools would up it to £40 ($60). Other stuff like sliding bevels, mortise gauges and a good quality (engineer's) combination square can be added at a later date, or when required. Without such a kit I cannot see how I'd ever do any reasonable work

I have found that marking knives while accurate are at times difficult to see. I have a drawer full of sharpened pencils with very fine points.
Hi Mike

The reason for using a marking knife is partly that it shears the grain at the surface and makes for a cleaner cut on joints like tenons. An oblique directional light source, as opposed to the diffuse illumination of strip lighting is preferable although the cut can always be highlighted by using a pencil afterwards

other than the Lion knife (the company closed it's doors)
Hi Stick

As you are probably aware, the Lion was a generic mitre guillotine which almost every woodworking machinery seemed to make a version of from the late C.19th until into the 1950s, often in 4 or 5 different sizes. Pootatuck Corp. were the last man standing in the USA until they finished, but here in Europe the place of that type of machine was taken over by the Morso-type guillotine from the late 1950s onwards:



This type of machine is especially favoured by picture framers, although there are other, slightly different machines made by the likes of Orteguil:



although there are Chinese copies of the traditional mitre guillotine still to be had, such as this one sold by Axminster Power Tool in the UK (although there are other people selling them both here and in the USA):


Of course traditional hand woodworkers made do without such contrivances and simply made a mitre shooting board for use with their jack or jointer plane like the ones in this excellent article by Derek Cohen

Regards

Phil
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Hello Phil...

I see you have been rummaging thru my stuff...

On the miters I kept Lion Knife (bottom pic) and sold the shear years ago (third pic from the bottom)... But I still like doing them the traditional way and prefer the LA smoother...

All the hand tools you show routinely come into play here... I'm very comfortable being old time... The latest and greatest toys pull their share of the load though...

80+% of my work is cleaning up/repairing/finishing after others... Either adopting their style or blending theirs to mine for completion...
Also have a production side too and the bottom line matters... Power all the way....


just finished an apothecary having 840 drawers... Picked it up at the incomplete carcase to finish... The face frame almost had me whimpering and have had my fill of dovetails for a while... Started having dreams about them before I was finished... Why can't people think outta the red oak box???
Then there was the maple on maple on maple on maple on maple kitchen w/settee and maple wide plank flooring in old world method...
Or the walnut on walnut on walnut den...
But that's OK... the kitchen got painted several shades of blue, the floor tiled and the den became white within a week of completion... that was only the tip of the iceberg..

Sorry, had to rant.... I'll put my soap box away now...
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It seems, when machinist get old, they start woodworking.

I have all types of gages, and methods of calibration.
I can use this equipment to fine tune my woodworking machines, make fixtures to close tolerances, ect.

This is the main problem I encounter- the wood.
I have wood that is a hundred years old, been sitting in my shop for years, so, its about as normalized as it can get.

I can machine this wood to very close tolerances today, but it will not be the same the next day, and way out of tolerance next week.

I found its just not predictable, doesnt matter much what type of wood, even boards I resaw from the same beam, can behave differently- cup, twist, stretch, and shrink.

It seems the more cuts that is needed, adds to the distortion, that seems to begin even more rapidly. The worst for that is long box joints, I must get those together with in hours of making them.

I solved all my machine alignment problems, and finally bought a planer, that really is helping in getting my projects together much quicker, less time for distortion to set in.

Just from my observations, I can cut the wood accurately, but it does not stay that way very long.

Don
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I'm with you, Don. I saw that very issue when I tried to mill some oak down for my router fence. It was flat, straight, and square the day I milled it. A week later when I checked it, not so much. There was no way I ws going to use it in my fence and simply introduce error in my projects. That's why I went to MDF. I have more trust in engineered products to retain the shape and dimensions I need for jigs and fixtures. Since then I tend to under mill till I'm sure I can assemble after the final milling and hope the structure of the assembly will brace the work against the wood movement to some degree.

GCG
It seems, when machinist get old, they start woodworking.

I have all types of gages, and methods of calibration.
I can use this equipment to fine tune my woodworking machines, make fixtures to close tolerances, ect.

This is the main problem I encounter- the wood.
I have wood that is a hundred years old, been sitting in my shop for years, so, its about as normalized as it can get.

I can machine this wood to very close tolerances today, but it will not be the same the next day, and way out of tolerance next week.

I found its just not predictable, doesnt matter much what type of wood, even boards I resaw from the same beam, can behave differently- cup, twist, stretch, and shrink.

It seems the more cuts that is needed, adds to the distortion, that seems to begin even more rapidly. The worst for that is long box joints, I must get those together with in hours of making them.

I solved all my machine alignment problems, and finally bought a planer, that really is helping in getting my projects together much quicker, less time for distortion to set in.

Just from my observations, I can cut the wood accurately, but it does not stay that way very long.

Don
decide what tolerance works for you and stay there...
I like 1/64 which does a pretty good job of staying within a 1/32 parameter.... but as you noted, nothing seems to last... Achieving 1/128 on the spot is easy.. but it lasts after the fact for what, all of a minuet or less...
There is a reason why non- machinist rules and tapes are graduated in 1/16th's....
Like Dan, I use a .5 mm mechanical pencil for all my woodworking if I am using a pencil. However, the best a pencil can do is a line about 1/50". A sharp steel edge will make a line about 1/250". For mitre saws I strongly recommend blade stabilizers unless you are using absolute top-of-the-line blades. I thought I had purchased a good blade but was still getting poor cuts until I put them on the saw. For repetitive cuts use a stop or use a jig if the piece is too small to hold or too awkward to hold. Even at that you may have to custom fit the last piece. If you try to sand to fit be careful. Sanding tends to produce rounded edges. Only use a solid sanding block (e.g. mdf) with the paper glued to it.
Hi
If you are like me I use many of the Incra tools and the mechanical pencil is a must have item.

Amazon.com: incra rules: Tools & Home Improvement

========
Speaking of mechanical pencils.
I just purchased 3 of these from .5 to .9.
I use them so much, I think the modest cost is worth it.
Hard to see in the photo, the thin sleeve tip is extra long.
Amazon.com: Pentel Graphgear 500 Pencil - 0.5 mm Lead Size - Black Barrel - 1 Each: Office Products
Hi
Just a suggestion, so when I’m doing a project, no matter what i will not switch tools, say if I measure with one type of device I’ll stay with that device until project complete. I have about a hundred tape measures but the one i start with is the one that gets used throughout the whole project, same with squares, marking devices, what edge I’m marking and measuring from.

It helps me, I’ve noticed even with an old worn out tape measure that if there is an imperfection in the tape that imperfection caries through the whole project, then really is there and imperfection, of course this applies to most projects but not all.
Hi
Just a suggestion, so when I’m doing a project, no matter what i will not switch tools, say if I measure with one type of device I’ll stay with that device until project complete. I have about a hundred tape measures but the one i start with is the one that gets used throughout the whole project, same with squares, marking devices, what edge I’m marking and measuring from.

It helps me, I’ve noticed even with an old worn out tape measure that if there is an imperfection in the tape that imperfection caries through the whole project, then really is there and imperfection, of course this applies to most projects but not all.
unless you take the time to calibrate and verify measures, squares and anything else you have at your disposal... weed the non-performers, fix or get rid them or give them to somebody on your do not care fore list...

Remove or lower the possibilities for mistakes/errors...
I use story sticks, jigs, direct "measurement", set up bars, American made drill bits (imperial and metric), and a tape measure (as infrequently as possible).
Machine angle set ups are verified with Wixey or draftsman's plastic triangle.
To verify an angle on the miter gauge I use a MITERSET. Once I had the Miterset, I sold my old Lion Miter trimmer to a frame maker in town.
Mechanical pencils with .05 lead are bought at the Dollar Store. Five on a card for a buck.
I like fancy marking knives gauges because they are neat to look at and hold. I rarely use them because I always have to darken the line with a pencil, anyway.
I saw that very issue when I tried to mill some oak down for my router fence. It was flat, straight, and square the day I milled it. A week later when I checked it, not so much.
Hi Patrick

Mike (MAFoElffen) and I were discusssing this quite recently and it turns out that we have two different but equally effective approaches to the problem. We are both in areas which can experience rapid changes in relative humidity, so our respective approaches are: (Mike) machine slightly oversize at the start of the project then machine to final dimensions, etc just before assembly; (me) I tenf to machine only as much as I know I can joint and assemble in a single session or store machined timbers/partly completed work in a sealed "box" between sessions (which can be just a poly bag inside another poly bag with then ends taped shut). Both techniques aim at minimising the amount of movement in the timber. As to fence stability I've always preferred plywood over MDF, but well sealed with polyurethane lacquer to minimise the amount of moisture absorbption. I do make-up MDF router templates from time to time, and if they need to last I'll go for green (moisture resistant) MDF well lacquered if possible

If you try to sand to fit be careful. Sanding tends to produce rounded edges. Only use a solid sanding block (e.g. mdf) with the paper glued to it.
Hi Charles

I do the same for what we call sanding boards. A little wrinkle that we use is to screw a piece of planed 2 x 1in softwood down one side on the sanding board which makes it easier to true-up slightly out of square edges

I like fancy marking knives gauges because they are neat to look at and hold. I rarely use them because I always have to darken the line with a pencil, anyway.
Hi Gene

It can help to have a cheap Anglepoise (Flexo) lamp near the bench to provide obtuse lighting across the timber. They have other uses, too, such as helping to see surface defects/hollows and in picking-out finishing defects

Regards

Phil
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There is always need for judgement for when what degree accuracy is needed.
What comes to mind is a chicken shed and a show case.

Don
Hi Patrick



Hi Charles

I do the same for what we call sanding boards. A little wrinkle that we use is to screw a piece of planed 2 x 1in softwood down one side on the sanding board which makes it easier to true-up slightly out of square edges

Regards

Phil
I have one pretty much as you described. The main job I use mine for is to flatten, smooth, and straighten the build-up strip applied under a counter top for the edge strip. Another sanding aid I use is a piece of counter top laminate, usually about 50mm x 75mm (2x3 for those who don't know metric), and glue various grits of sandpaper to the backside. It's good for sanding areas like the flat of a fillet where a sanding block would be too large and awkward to handle.
If you are making cuts all the same size you must set up a jig or stops on your saw. it is very hard to measure and make precision multiple cuts the same. But if you have to keep a sharp pencil or knife. I have an electric pencil sharpener right next to my miter saw.
This reminds me , I see guys on jobs using a thick carpenter pencils for marking and cutting trim. I give them a little grief and ask them, are they going to cut on the right side of the line, the left side or in the middle and leave a line on both sides?
" I have an electric pencil sharpener right next to my miter saw"
Doesn't it damage your mechanical pencil? :)
" I have an electric pencil sharpener right next to my miter saw"
Doesn't it damage your mechanical pencil?

Dan,
I don't know I will have to try that and see what happens!!!LOL :lol:
" I have an electric pencil sharpener right next to my miter saw"
Doesn't it damage your mechanical pencil? :)
would one at the battery charging station count???

and then there is are the colored pencils....
sometimes the marks from a regular pencil become invisible...
color coding helps too...
"would one at the battery charging station count???"

Ooo,,,a digital pencil! I want one!! ;)
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