Some observations and a question or two

**rsser** · 8th August 2007, 05:08 PM

The generous posts of forum members in this sub-forum and in Handtools and machinery have been terrific aids in my coming to terms with chisels, plane blades and soles and the like. Thanks all.

One thing that's emerged is that between a good diamond stone and two lengths of float glass the lapping results can vary ... a puzzle cos they're all supposed to be flat.

Mostly now for flatening and lapping I use a bit of 10mm thick float glass and stuck-on fabric backed paper sitting on 19mm thick MDF. I've learned that unless the paper is absolutely flat you do of course take more off the corners which defeats the whole point (except perhaps for a jack plane iron). Apart from that I wonder whether such paper has some give and that might cause the same problem as well. Any comments on this?

Just recently I added some 3M micro-abrasive sheets to the kit: 15, 5, and 0.5 micron. The glazier reckoned 6mm float glass on a flat surface should do. I pulled out a couple of lengths of 19mm MDF that had done light service as shelves, checked them with a straight edge and they're not flat. Makes me wonder now whether or not all MDF out of Bunnies is flat too. Reason I checked was I recalled Derek posting that he mounted his glass on three layers of MDF. (... but laminating might or might not cancel out bows in the MDF).

So now of course the question is how flat is flat? (btw, I keep all this away from machined cast iron surfaces since I don't want water or grit around them, and unless destressed before machining they're not going to be flat either

).

With spray-on adhesive I've found that if you're heavy handed on glass to take fine papers you get build-up and that doesn't help either

To end, the 3M micro-abrasives 'feel' different from everything else. Sorry to be so vague. Why do folk speak so well of them? Why can't we buy the stuff here in Oz? They've done a fine job of producing a mirror like polish but are they all that much better than going down to 2500 grit W&D?

It's all a bit obsessive when a plane iron edge might only last 10 minutes but there is a certain amusement to be had trying to count your nose hairs in the reflection of a lapped cutting tool (copyright ScarySharp).

Appreciate hearing about your experience.
.

**joe greiner** · 8th August 2007, 10:56 PM

Hi, Ern.

I can't claim to have much finesse with sharpening, and never tried to count my nose hairs. I generally omit the adhesive to avoid possible uneven-ness, and lay the paper directly on the glass. The paper tends to curl, but time to replace by then anyway. I don't go that fine, either, so maybe not as scary sharp as it could be.

Joe

**mic-d** · 9th August 2007, 07:27 AM

Perhaps you should try paper-backed wet and dry and break the back of it before sticking it down with water only. As I understand it, the fabric backed stuff is spongy enough to roll up slightly in front of the edge .

Cheers
Michael

**rsser** · 9th August 2007, 04:16 PM

Thanks guys ... food for thought.

**BAZMick** · 9th August 2007, 08:46 PM

G'day Ern!

I work a bit with MDF and find on hot or dry days the upper face will start to curl up, no matter what the size or thickness.

No way of getting it back successfully either, we have tried turning the panel over as soon as we see it. Best way we found was to seal both sides with a spray on lacquer or paint (mineral based of course!!)

Like Joe Greiner, and you know as well that I'm no expert. I have been told that float glass is by far the most reliably flattest surface you can get aside from a machined surface, but that would be prohibitively expensive exercise. Just don't stand your glass upright, as over time it will get thicker at the bottom than the top because it's still technically a liquid; that I have actually seen for myself pulling out some 100 year old windows on a renovation once, the panes were a full 2-3mm thicker at the bottom

. Belive it or not!!

As to sticking down the W&D as flat as possible I couldn't comment other than maybe to suggest to use a light machine oil like air tool oil as it won't evaporate like water and maybe won't curl the ends up when the water drys out of the paper.

Cheers to all and Ern, I love that waterstone.

Bazzy

**hansp77** · 9th August 2007, 09:14 PM

if you are dealing with any of the spray adhesives I have used (for screenprinting- not scary sharp), then just give the glass a wipe over with a turps soaked rag.
It should melt the adhesive residue off in a flash.

**rsser** · 9th August 2007, 09:47 PM

Thanks Bazzy ... glad to hear the stone's found a good home ;-}

Good point about MDF ... the new strip had in fact been sealed on one side but not the other. Might well account for the bow.

And glass a liquid eh? So if I don't get the port down fast enough it'll end in my lap ;-}

Thanks Hans .. a good tip to recover from overspray.

**BAZMick** · 9th August 2007, 10:12 PM

Ern if you've got port that old I'll be on the next flight down and knockin on your door offering some of my N'Qld Silky Oak.

I'm a young man and will find some more good timber, but port like that doesn't grow on trees!!

Bazzy

**Cliff Rogers** · 9th August 2007, 10:36 PM

Originally Posted by BAZMick

Ern if you've got port that old I'll be on the next flight down and knockin on your door ......

Study this picture.

**Cliff Rogers** · 9th August 2007, 10:39 PM

Did you see it?

He has plactic cups just in case glasses leak.

**BAZMick** · 9th August 2007, 10:50 PM

Cliff, my hat is off and I'll be scrapin' the boots on the mat so man the peephole, but just gotta stop by a mates place in Cape Tribulation after and borrow his chainsaw.

http://www.leuracellars.com.au/list.asp?id=27&start=50

Got the cups!

**Cliff Rogers** · 9th August 2007, 11:40 PM

Ern is a fine host & easily plied with timber.

**Chris Parks** · 28th August 2007, 08:32 AM

To raise this thread from the dead. Someone mentioned machined surfaces being flat, I have some very thick marble slab and use it, the point being it is surface ground. You should be able to get some at the stone masons who do headstones etc, just look for the nearest cemetary.

**kman-oz** · 7th September 2007, 03:35 PM

A note on warping MDF also; I've experienced the warping router table top problem and it also seems to be a result of not sealing both sides. Over winter it expanded on the underside, but in the recent warmer weather it's straightened out again. I only sealed the bottom last week when I was satisfied it was flat again.

You may also note that most production router table tops made from chipboard/MDF are laminated on both sides, presumably for this very reason.

I'm still yet to decide how to keep my new glass/MDF lapping plate flat.... any suggestions?

**rsser** · 7th September 2007, 03:47 PM

LOL, buy your gravestone early, and lay the MDF/float glass flat on it. From time to time ponder the inscription you might want on the headstone ... eg. 'Now at last he got it really flat'

Thread: Some observations and a question or two

Thread Tools

Search Thread

Some observations and a question or two

Similar Threads

Sorry, Another sharpening question

LV Mk II Honing Guide: Skew blades and further observations.

Observations

Tags for this Thread

Posting Permissions