Straight edge accuracy?

[Froggy]

I recently decided to flatten the soles of my planes has they’d never been done since I bought them. I put a piece of float glass on top of a ¾” Formica covered board and then glued the sandpaper and spent 3 days (on and off) trying to flatten the sole. I had marked the sole with a marker pen to check my progress and found what appeared to be a dip in the centre of the sole, which was untouched by the sandpaper. I then took a 750mm straight edge which I bought from Axminster and put it to the sole. To my amazement the SE sat on the centre of the sole with gaps at either end!! I concluded that the float glass must not be thick enough, so I bought some marble (about ¾” thick) and put the SE to that only to find that the marble wasn’t flat!! Next I put 4 layers of float glass together (totalling more than 1” thick) and tried again. I ‘flattened’ the soles of three planes and then checked them all with the SE. None of them were flat and in fact one of them appeared to be wavy!! At this point I started to think about the SE and so decided to move the SE along the length of the soles and see if the gaps appeared the same. They didn’t, has I moved the SE along the sole one gap would close up whilst another appeared!! I can only conclude that the straight edge isn’t accurate but I’m not 100% certain about that. Is the any way I can check the accuracy of the SE?

 

[custard]

Is the any way I can check the accuracy of the SE?

1. Against another (and proven) straight edge, try in a suppliers

2. Lay it on the float glass and test with feeler guages

3. The blades of two large (and proven) squares, with their stocks set on the straight edge, will meet perfectly with no gaps

 

[Jacob]

Pick up the straight edge and look along it. If it looks straight then it is straight enough for all woodworking processes.
To be more accurate you could draw a straight line with it onto a bit of mfc etc, then see if the edge fits the line from the other side.
Did you check your plane soles before embarking on this flattening marathon? I bet they were better then than they are now! I'd stop doing it if I were you, you'll only make them worse.

 

[custard]

Incidentally, I understand the British standard for a plane's sole is +/- 3 thou, and Lie Nielsen claim they manufacture to +/- 1.5 thou. I've yet to meet the LN plane that doesn't deliver perfectly respectable shavings straight from the box, although by investing hours of gruelling effort I've managed to convince myself/kid myself I'm getting a small performance improvement!

Actually, assuming no gross negatives, the one thing that really does deliver a clear performance advantage is polishing the sole with Autosol. It then glides across the wood so smoothly I'm sure there's a net effort advantage, a polished surface is that bit more rust resistant, and there's no longer any need to wipe the sole with a candle every few minutes.

 

[bugbear]

Did you check your plane soles before embarking on this flattening marathon? I bet they were better then than they are now! I'd stop doing it if I were you, you'll only make them worse.

Agreed - flattening a plane requires a certain degree of knowledge, care, and decent (flat/straight) references.

These are obtainable, of course.

Many planes are already "flat enough" to do what's asked of them, but the perfectionist may want to "finish them off", at least to the best of his/her ability, knowledge and equipment.

BugBear

 

[Froggy]

I'd stop doing it if I were you, you'll only make them worse.

This is getting quite frustrating. I'm not getting the accuracy in my woodwork and want to improve. So when I read someone like David Charlesworth telling me to flatten the soles of my planes for greater accuracy, and I follow his methods, and then get other forum members (who's opinions I value) telling me to stop doing it because I am probably making them worse...ah!!! Where do I go from there?

 

[Froggy]

OK So I've just been out to the workshop and checked the SE against my planner outfed table and couldn't even slip a .0015" feeler guage underneath! So firstly apologies to Axminster as the SE probably is flat.
Secondly Jacob asked if I checked the soles for flatness first. I did but not with the SE. I used a method I saw the woodwhisper use where he marked lines with a marker pen on the sole and then ran it along sandpaper glued to float glass. I did this and found that all of planes appeared to need work. This didn't suprise me as David Charlesworth says he has never bought a plane that didn't need some work to the sole, not even a LN.
So, if I have made them worse, how could that happen on over 1" of float glass? I even changed the position of my hands whilst working the planes so as not ot exert too much pressure in one spot of the plane. What have I done wrong and how do I correct it?

 

[Froggy]

Hi again,

Having done some more 'scientific' analyse of this this problem I have discovered to my embarassement that I don't really have a promblem(other than impulsiveness probably!). My earlier 'tests' were done by putting the SE on the plane sole and then holding it up to the light. I could see gaps everywhere. Having gone back and checked the gaps with feeler guages I have found that my worst plane has a gap of .003" and the other 2 I couldn't even get my smallest feeler guage (.0015") through the gaps. So I apologise for my rants and for wasting your time. Sorry!

 

[doctor Bob]

and spent 3 days (on and off) trying to flatten the sole.

Not our time....... your time..... I'm with Jacob and the others, this obsession with flatness is OTT, the guys who seem to be considered gurus are also the guys who run expensive courses teaching how to sharpen over 3 days or more.......

 

[powertools]

You can drive yourself mad trying to find out what is flat or square.
The joy of woodworking is that a few thou is not a problem

 

[Froggy]

and spent 3 days (on and off) trying to flatten the sole.

Not our time....... your time..... I'm with Jacob and the others, this obsession with flatness is OTT, the guys who seem to be considered gurus are also the guys who run expensive courses teaching how to sharpen over 3 days or more.......

This is why I value the independent opinion of you guys so much :lol:

 

[matthewwh]

I don't think you have been wasting anyone's time.

You have learned a lot about the importance of measurable flatness (feeler gauges) versus observable flatness (light penetration), and very valuably shared your experience with countless others via the forum.

You have three planes which you know to be within standard - which was what you set out to achieve in the first place.

You can trust your straight edge and feeler gauges and understand how to use them correctly.

You understand that absolute flatness doesn't exist (along with absolute squareness, roundness etc) but all get exponentially more expensive and difficult to achieve the closer you get to them - viz the difference in cost between a grade A and grade B strightedge or square.

You now have plenty of acceptably flat surfaces in your workshop (which are always useful).

All of which are directly transferrable to improving your woodworking.

We get quite a few people who are determined to spend hours on end flattening and polishing things to within an inch of their lives, most of which is completely unnecessary.

Please don't underestimate the service you have done to the community here with this thread, I for one am very grateful to you.

 

[Benchwayze]

My LN bevel up jack didn't look to be in need of flattening. It performs better than any plane I own; as it should. All of my regular Stanleys and Records have been flattened, but it does take some time with a number 7!

I never get too desperate about this TBH. If the toe, the mouth and the tail are flat and level, slight dips in between dont make much, if any, difference.

HTH

John

PS... Matthew... I am still having problems with my knees, so as yet I haven't put the Quansheng through its paces!
I look forward to having some fine shavings!
J

 

[twothumbs]

This has been a very interesting exchange for me. It has given me a lot of food for thought and I have learnt much from it like many other trails. There used to be an expression.....if it looks right it is right....not always true but possibly more useful for building than woodwork. In all the discussions on gluing paper down on flat surfaces like plate glass I was wondering if the thin paper is accurate enough and I have used this myself often before. Will it never end? Thanks.

 

[bugbear]

..gluing paper down on flat surfaces like plate glass I was wondering if the thin paper is accurate enough...

I'd worry far more about the glass being rigid enough.

BugBear

 

[Jacob]

..gluing paper down on flat surfaces like plate glass I was wondering if the thin paper is accurate enough...

I'd worry far more about the glass being rigid enough.

BugBear

And lumpy glue. Good idea to force it through a fine mesh before use and consider how it can be applied evenly. There's probably a gadget to help here.

 

[Froggy]

Thanks guys, some nice comments there. I'm glad others have found the thread useful. It's been a frustrating experience the last few days, but has Matthew pointed out, I've learnt a lot from it, and now have some dependable references for the future.
I'm not obsessed with accuracy, I just want to keep improving my standard of woodworking, and the effectiveness and efficency of my tools seems to be a major factor in that. If I felt I was at a point where working on improving my tools further wouldn't improve my results, then I wouldn't waste the time.

 

[bugbear]

And lumpy glue. Good idea to force it through a fine mesh before use and consider how it can be applied evenly. There's probably a gadget to help here.

BugBear