Precision Tools in Woodworking

[Chris Griggs]

A dial or digital caliper is actually something that I don't own that I would like to get (you can get basic ones so cheap don't know why I haven't). I don't bother to evenly thickness my wood unless I have too for the piece's particular use, but there are times when it really matters and it would be convenient just to check with a caliper. Its not a requirement.... just check with my marking gauge or a stop rule and feeling if it is even around the board is good enough, but a digital caliper, while not necessary, would be handy in some cases. A lot of the tools we talk about on this forum aren't required, but that doesn't mean they aren't nice to have. Would also be nice for say, checking auger widths against dowel stock maybe....I could even see if being used for checking fits of joinery in some case - not to dial an exact numeric fit, but maybe just to get an idea of how far off things are. Another place it might be useful...sliding dovetail...ever been fitting a sliding dovetail and trying to figure out exactly where its off. Its not always and issue of being just to fat, sometime the angle is a tad off and by measuring both the widest and narrowest part of both the male and female parts of the joint you could very quickly tell if and where things are off (of course dividers will do this for you as well). Anyway, would I actually use a dial or digital caliper this way in my shop? Maybe, maybe not....don't know. Just kinda reflecting on ways in which one might be handy. For me it probably wouldn't be used to check all me tolerannces within .0001", but I can see it being pretty handy as a point to point comparison tool. For me the question as to whether or not to use such tool comes down to whether they will make certain things quicker and easier and if the advantages they offer are worth he expenditure....if I think they'll lead to lots of fussing I'm not interested...if the have the potential to help with a few things here and there, but are really expensive and not required, I'm probably not interested....but if they can make some tasks more convenient and aren't a huge investment its a worthwhile consideration.

I too really like the matched straight edge Kees and Stan describe. Since match plane my winding sticks in this way I use them as straight edges all the time. When its time to true them up, I clamp them together in the vise, plane a slight hollow, and then plane until I think that hollow is gone. If when I hold them edge to edge up to the light I see no light or just a small amount thats good enough, as the amount of hollow I might still be seeing is actually twice what each individual stick has in it.

Good stuff. Interesting thread.

[Chris Griggs]

That must be some rarified field. Looking it up gave me no clue as to what it is. Attachment 254228

jtk

Just saw this post. LOL!!! Yeah its a select somewhat esoteric major, only offered by a handful of universities, and only students who are absolutely certain about their career path tend to pursue it.

[george wilson]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

[Charlie Stanford]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

Yup:

http://home.comcast.net/~jaswensen/m...ight_edge.html

[Stanley Covington]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

I see your point. But do you think it is likely the bumps and hollows of the two pieces of an awasejogi lightly planed or scraped while joined together will align so perfectly when the edges are placed against each other? Seems counterintuitive. What do you think?

Stan

[Zach Dillinger]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

That's true. I keep one that I don't use and just make a new pair when I need them, relying on the unused third. I don't need three for my work, but two can be helpful.

[george wilson]

Mitutoyo is a good brand. Never heard of Mitsutoyo.

The making of 3 straight edges or 3 master flats was brought into standard practice in the early 19th.C.. Beginning machinists were required to make their own master flats starting with 3 castings .

[ian maybury]

It seems like there's been plenty of psychology in play/on display in this thread anyway....

The interesting bit is that there clearly are techniques on the more traditional side of the house that translate to machine based measurement driven woodworking, and vice versa.

It's been mentioned before, but the role of skill is a big deal in my mind. Machine based and production oriented methods by definition have their roots in an approach that sought to de-skill most operations - but (especially with woodworking machinery which isn't always as precise as it could be) there's another skill set that becomes important there too.

Craft methods on the other hand tend to rely heavily on manual and individual woodworker skills - the video of that Scottish woodworker somebody posted recently doing tenons with a few strokes of a chisel and bit of paring was a great example of this. Or the guy turning beautiful chess pieces in a Moroccan market using a small bow lathe, a single cutter and his foot. Neither technique is likely to be remotely useful to anybody not prepared to put in the hours needed to build either skill - but both are cost effective and fast compared to beating the same task to death with technology. e.g. router and fixtures and maybe a router plane for the tenons.

Neither is right or wrong per se, and as hobby woodworkers largely free of output targets we each have the freedom to choose our preferred approach. Whether that be a productivity minded and machine based, or a gloriously self indulgent insistence on the use of hand tools for its own sake, or one of the many many points between these extremes on the continuum.

What I do feel is that it'd be a pity if we were to get bogged down in an ideological insistence on one approach or the other. We're each in different situations, from the point of view of budget, time availability, workshop facilities, skill set/level and everything else, and what's more are not necessarily chasing the same objectives. As in one guy may be trying to get his house fitted out ASAP at reasonable cost in the his spare time, another may be in the realm of pure art.

As before it'd be nice to see the methods that people use shared and explained. The design, and subsequently the methods used to make the parts for and to assemble e.g. a simple shelved cabinet presume an approach to the control of dimensions and fits right from the first step - but you don't see the methods discussed in any more than peripheral way in the mags....

Here's an offering from the engineering side of the house for what it's worth. I recently got fed up with the inconsistencies and inaccuracies in tape measures, and bought a 600mm/24in vernier calliper from these guys in India: http://www.ebay.com/itm/600mm-24-HAR...b602ac&vxp=mtr It's not digital, and it doesn't have a dial (it's the older vernier scale type i was brought up on) - but it's very well made and actually of very comparable quality in hardened stainless steel as say an old Mitutoyo. It wasn't perfect, in that the length of the set screws locating the gigs/bronze bearing strips needed a little fine tuning with a file to solve a glitchiness in the movement - but it's 100% now and all for about $100. For a tool of which type cost many many hundreds back in the day.

Is it the sort of thing you use for every measurement? No - it's often easier to make a part and then transfer measurements from that. Or set a machine stop once, and use that. It doesn't even have to be done that way, in that it seems likely that with a story stick and a carefully thought through approach to the sequence of work you could get there without every needing the know any dimension exactly. But it's very useful at times when e.g. you want to get an accurate measurement and use it to make a part to fit a gap precisely to be able to determine dimension to within a pretty close tolerance (maybe 0.1mm or so)...

ian

[Charlie Stanford]

Mitutoyo is a good brand. Never heard of Mitsutoyo.

The making of 3 straight edges or 3 master flats was brought into standard practice in the early 19th.C.. Beginning machinists were required to make their own master flats starting with 3 castings .

Yup, again (U.S site, in English):

http://www.mitutoyo.com/

We all could probably use one of these since it measures without making any contact with the thing being measured:

http://www.mitutoyo.com/wp-content/u...serScanMic.pdf

[Kees Heiden]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

You could argue that the plane is the 3rd straight edge.

In fact it is easy to make one concave and then on fitting you automatically make the other convex. But when you turn him around, the error would show up (probably). I guess it's best to use the match planing technique.

[Chris Griggs]

Actually,to make a straight edge or a master flat,you need to make 3 that fit together interchangeably,not 2.

Interesting. That's the first I've ever seen that. I don't fully understand why though. I'll have to read though the link Charlie posted when I have some time this evening. Great info guys, thanks

[george wilson]

Ian,there is no substitute for personal skill,that is for sure. And,of course,without TASTE ( a judgement that may or may not be in the craftsman's head),it all comes to naught,anyway.

Not sure that you could argue that the plane is the 3rd. straight edge. What if the plane is not perfect? Besides,the plane does not rest entirely flat upon the wood,does it? It rests on the throat,just before the blade,and upon the heel of the sole in operation.

This discussion is verging on how many angels can dance on the head of a pin. Are ANY of you going to implement anything discussed here in your wood working? It would be better to be perfecting your skills than niggling about things like this. But,I suppose that's the nature of these fora.

[Chris Vandiver]

Interesting. That's the first I've ever seen that. I don't fully understand why though. I'll have to read though the link Charlie posted when I have some time this evening. Great info guys, thanks

Three surfaces are required(if none are a known flat) to keep from creating mirror image surfaces.

[Mike Cogswell]

Digital calipers, actually, but everyone calls them micrometers so I try to do that too.

John,

Since you apparently know the difference between a micrometer and a caliper (dial or digital) I respectfully suggest you refer to them by their correct name. In your earlier posts, where you made many references to using a micrometer I foolishly assumed you meant you were using a micrometer and not a caliper. While I suppose some people may call a caliper a micrometer, you are the first I have actually encountered. I suspect the vast majority of people reading this also know the difference and use the correct name. I try to also use dial or digital caliper, at least the first time, to make it clear I'm not referring to an inside or outside caliper.

I enjoy your posts and very much appreciate the very different aspect of woodworking you bring to the table. Please don't confuse me. I need no additional help in that area.

[Kees Heiden]

Here is a description how you make two straightedges. Indeed matchplaning them together and then folding them open and look for a lightgap in between.:

http://investigationsblog.wordpress....-straightedge/