Motorised Chisel back flattening - taking the grunt work out of it

**rsser** · 20th March 2016, 10:30 AM

This is my take-out from mechanical lapping, having used WS discs mounted on an arbour on the lathe and the Sorby ProEdge. I've done chisels and plane blades up to 2 1/4".

The first one is that reeeely flat doesn't happen. No matter what I did it was always the case that one part of the face got exposed to more abrasive, or more effective abrasion, than another. But near enough to flat meant correction with finer abrasives going down to polishing grades was possible. And in passing I'd emphasise that polishing, not just flattening, is the desirable end point.

The easier you make the process the more you use it and so a supply of quality replacement abrasives down to fine grits should be identified up front.

WS is good in this respect. You can get coarse ceramic abrasives (PSA discs) that are if anything a mite too aggressive. They leave deep scratch marks. And right down to leather for honing. Somewhere I found 3rd party discs that were much cheaper than OEMs - maybe the SandPaperMan. You can always buy PSA sheets and roll your own.

The Sorby. I much prefer this to the WS. The bump at the join isn't always a problem and I don't have a good grip on why. But you could experiment taking the high point down - maybe a light touch with an angle grinder? I note that Diablo Zirc belts for portable belt sanders from Bunnings have that point relieved, so it's possible.

I have played with a belt sander in a cradle. Control isn't easy, it goes too damn fast, grades beyond #400 aren't available, the higher grits in Flexovit belts have the bump (and they're AlOx). Diablo only go up to #120. And I have doubts about how flat the graphite pad is.

It seems to me there's huge potential in FF's invention - but I'd be looking at a lengthwise stroke cos of the dubbing.

**FenceFurniture** · 20th March 2016, 10:53 AM

Originally Posted by rsser

I'd be looking at a lengthwise stroke cos of the dubbing.

It is a lengthwise stroke (down the chisel blade longitudinal axis) which I will clarify with a pic later.

I've sorted out holding the front of the plate down, and now working on holding down the moving sheet of UHMW whilst leaving room to reciprocate freely.

**fletty** · 20th March 2016, 11:09 AM

I had only just come across Gameco while searching to answer FF's question about the grade of the ProEdge diamond belt. I also saw him/them demonstrating at the TTTG sale a few weeks ago!
In spite of searching via Google, I can't find the grit of the diamond belt but the advice i CAN find is that the grit is "carefully graded" .......

Both Gameco and the Sandpaper Man appear to be cheaper than Carbatec

but I haven't yet compared the belt size of the Noob vs the ProEdge.
more work to be done.....

fletty

PS, ProEdge belts are 50 x 785 and, Sandpaper Man's belts are not only cheaper but also have "tape" joins or "Nortape" joins which should eliminate/minimise the 'bump'?

**justonething** · 20th March 2016, 11:36 AM

Originally Posted by DaveTTC

Thats the sort of thing i meant with the orbital sander. Ising rhe sander to osilate a chisel over a flat bed with paper on it

Looking good

Dave TTC
Turning Wood Into Art

I was thinking about mounting the orbital sander upside down on a vice and then lower the chisel onto it.
What do you mean by oscillating a chisel with paper on it?

**woodPixel** · 20th March 2016, 11:39 AM

NOOB belts are 1220mm. Others are available.

Catalogue here: http://gameco.com.au/files/62.pdf

Buy from here: Home - Artisan Supplies

**DaveTTC** · 20th March 2016, 11:45 AM

Originally Posted by justonething

I was thinking about mounting the orbital sander upside down on a vice and then lower the chisel onto it.
What do you mean by oscillating a chisel with paper on it?

Oslilating the chisel over flat bed with abrassive on te flat bed

Dave TTC
Turning Wood Into Art

**FenceFurniture** · 20th March 2016, 02:13 PM

Hmmm. Hit a bit of a snag now. I've replaced the timber sides that keep it running straight with UHMW strips, and then I added an overlapping strip on top of the side strips to stop it from moving up.

The joint where the main UHMW tray slides got hot and melted together (I wondered why I had to keep turning the drill power up.....

).

I might have to run it without the top strips to let that joint breathe.

**DaveTTC** · 20th March 2016, 02:16 PM

Originally Posted by FenceFurniture

Hmmm. Hit a bit of a snag now. I've replaced the timber sides that keep it running straight with UHMW strips, and then I added an overlapping strip on top of the side strips to stop it from moving up.

The joint where the main UHMW tray slides got hot and melted together (I wondered why I had to keep turning the drill power up.....

).

I might have run it without the top strips to let that joint breathe.

The kids cant really hear me laughing as i read this.

No samny didnt ask me "what is it?"

Dave TTC
Turning Wood Into Art

**crowie** · 20th March 2016, 02:32 PM

Just coming onboard for this journey

**Pat** · 20th March 2016, 02:46 PM

How about using the side of a wet stone wheel . . . Fletty, your jet does the job and if I really, really have to flatten the back of a bench chisel, I have my old stone for the Torment . . . no heat issues . . .

**woodPixel** · 20th March 2016, 02:54 PM

what about a couple of ball bearings instead of UHMW?

**Christos** · 20th March 2016, 02:55 PM

I just caught up with this and by what I was looking at I was thinking that the speed is too high. By what FenceFurniture just mention it seems that was thinking correctly.

Is there a way to slow down the speed of the drill or by adding a wheels between the drill and plate?

**FenceFurniture** · 20th March 2016, 03:15 PM

All good now - pic coming.

**Heavansabove** · 20th March 2016, 03:21 PM

Don't know if people have tried this, but works for me...

Most backs are convex, rounded over in the vicinity of the tip. I only worry about the last 2-3 inches.

I use a Dremel (because I do not have a Die Grinder) to grind the middle of the back - after I grind the edge square and get rid of nicks and large wear bevels (using bench grinder). You know where to apply the Dremel by quickly running the chisel back over a stone or plate, and then grinding off the shiny areas away from the edges - repeat steps as necessary.

As a result the chisel back resembles a sort of Japanese shape. Therefore I only need to flatten the edges, and usually takes no time at all.

Cheers
Peter
ps machines hate me, so I avoid them as much as possible (remember paranoia is defined as a healthy state of awareness) - except my vintage GMF 8" grinder. I was going to move it, but I can hardly lift these days.

**FenceFurniture** · 20th March 2016, 03:56 PM

Modifications:

and with a chisel in place:

I think that's pretty much it now - the mdf needs to be replaced with UHMW - it's got swollen spots now.

I don't think there is any increased dubbing over yesterday. It took a little while to get used to it, and I'm pretty sure that not having the front of the plate secured own exacerbated the dubbing.

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