cambered chipbreaker

[bridger berdel]

Thanks to Warren Mickley, I went to the trouble of cambering a chipbreaker to match an iron for my #4. It works nicely for the current project of a dining table with a deliberately not-totally-flat but very smooth finish.

I started with a cambered iron and filed the chipbreaker to follow the curve. This results in a chipbreaker that gaps at the corners. I tapped those down a bit then followed with files and eventually small stones, chasing points of contact. As differences of tension will open gaps either at the center or corners of the breaker it is necessary to do all of the checking with the chipbreaker screwed tight.

All in all maybe 20 minutes of careful fiddling about.

[Jason Martin Winnipeg]

Do you find it helps a lot with tear out compared to a camber iron with a normal chip breaker?

[Derek Cohen]

Bridger, I don't get this.

For most work, a smoother needs the chipbreaker around 0.4mm from the edge of the blade.

Now the average smoother shaving is around 0.05mm thick. The camber at the side is not much more than this. Therefore the reduced curve at the corners of a blade are around 0.1mm. This is not going to have any effect on the edge of the shaving. I do not see a need to camber a chipbreaker.

Regards from Perth

Derek

[Jim Koepke]

I do not see a need to camber a chipbreaker.

Need is seldom a limiting factor in the search for adventure.

jtk

[david charlesworth]

Camber may not be necessary, but it is good fun.

If C/B camber matches blade, it is possible to set 4 thou from edge without C/B going over the edge at the sides of the blade.

I have been cambering C/B for many years.

David Charlesworth

[Mark Rainey]

Wow! Sounds like quite a smoother! Bridger, can you be more descriptive of your technique for us slow learners? What do you mean by a chipbreaker that gaps at the corner? Tapping & chasing points of contact? Whatever more you can add would be helpful.

[Warren Mickley]

Wow! Sounds like quite a smoother! Bridger, can you be more descriptive of your technique for us slow learners? What do you mean by a chipbreaker that gaps at the corner? Tapping & chasing points of contact? Whatever more you can add would be helpful.

Because the cap iron rises up from the plane iron at an angle, when we round the leading edge the parts at the sides become higher and no longer meet the plane iron. In addition we undercut the cap iron somewhat so that it meets the plane iron at the front edge only. Because of the curve and this undercutting, we cannot true the true on a flat stone. It is hard to visualize, but this is why Bridger used trial and error to effect the mating, "chasing down points of contact" or carefully lowering the high spots until all was well.

I have used the double iron for tear out since 1973 and have rounded the cap iron since 1976. The rounding makes for easier use. After 30 years I noticed that Peter Nicholson also had the cap iron echo the plane iron camber. Nicholson apprenticed around 1776.

[Mark Rainey]

Thank you Warren.

[Stewie Simpson]

There is another option available that doesn't require the leading edge of the cap iron to be set within the distance of a bees scrotum. By adding a micro back bevel to the back of the irons cutting edge the effective pitch can be raised above that being governed by the planes bed. As an example, if your starting point is a 45 degree bed, by adding a 5 degree back bevel that will raise the effective pitch to york pitch (50 degrees) 10 degrees =middle pitch (55 degrees) 15 degrees =cabinet pitch (60 degrees).

On the following wooden jointer plane, the leading edge of the cap iron has a clearance gap of 1/16" (1.5mm). It has a 45 degree bed with an additional 10 degree back bevel to raise the effective pitch from common pitch to middle pitch. If tear-out was still occurring, I can opt to increase the back bevel by a further 5 degrees to cabinet pitch.

Stewie;

[steven c newman]

IIRC....usual area for a cambered jack plane to be used, is across the grain...either as a Traverse, or at the diagonals.....taking fairly thick shavings ( Shilling thickness?) taking down rough sawn stock to prep it for the longer, less cambered Try Planes....tear-out being the least of the worries. More like getting some 4/4 stock down close to the 3/4 stock most need. Traverse, and then the diagonals..paper thin shavings would be a waste of time and effort....save those type of shavings for the finish planes....

Most of the worries would along the lines of getting the shaving to fly up out of the planes, without clogging the plane up....they wouldn't be long thing ribbons, either....it being a bit hard when going across the board's grain, to get anything more than "chips"....like someone had dumped a can of Pringles on the board...

[Warren Mickley]

IIRC....usual area for a cambered jack plane to be used, is across the grain...either as a Traverse, or at the diagonals.....taking fairly thick shavings ( Shilling thickness?) taking down rough sawn stock to prep it for the longer, less cambered Try Planes....tear-out being the least of the worries. More like getting some 4/4 stock down close to the 3/4 stock most need. Traverse, and then the diagonals..paper thin shavings would be a waste of time and effort....save those type of shavings for the finish planes....

Most of the worries would along the lines of getting the shaving to fly up out of the planes, without clogging the plane up....they wouldn't be long thing ribbons, either....it being a bit hard when going across the board's grain, to get anything more than "chips"....like someone had dumped a can of Pringles on the board...

If you read the original Moxon text (1677, 1703) or Nicholson (1812), they both suggest that almost all planing with the jack plane is with the grain. Moxon says that if the board is badly cupped, you can turn the board crosswise on the bench (still loose, planing against the stop). Clogging is not a problem with a wooden plane that is nicely set up. And if you look at old work that is rough planed, you see stuff planed with the grain or occasionally at a very slight angle.

And speaking of old work, it is extremely rare to see stuff in the 3/4 thickness. The common thickness for casework or drawer fronts is 7/8, a little more or a little less. Nobody who is planing by hand wants to waste time (and energy!) planing an extra 1/8 inch of stuff when it is not needed.

[Charles Guest]

"Old work" is an awfully broad statement.

Drawer sides, backs, bottoms, door panels, etc.: this book is full of furniture with 3/4" (and thinner) components, both main and secondary:

https://www.amazon.com/Georgian-Peri.../dp/129547428X

[Brian Holcombe]

"Old work" is an awfully broad statement.

Drawer sides, backs, bottoms, door panels, etc.: this book is full of furniture with 3/4" (and thinner) components, both main and secondary:

https://www.amazon.com/Georgian-Peri.../dp/129547428X

I believe Warren is applying that to things that would have used 4/4 stock.

[Charles Guest]

I believe Warren is applying that to things that would have used 4/4 stock.

I think it's an exaggeration to assert that stock was always resawn for thinner pieces, or that pit sawyers regularly sawed stock thinner than 4/4 at all places and all times. Then, as now, a lot of stock ended up on the floor as chips and shavings when thinner parts were needed. That's why we read about jack planes and heavy cambers, and scrub planes in the Scandinavian and Germanic traditions. If you're only removing a fat eighth at the most (a 1/16"+ from each side), you need neither.

This is also why one of the first woodworking machines to be produced during the Industrial Revolution was the planer, and of course the Shakers had invented one as well. Again, not needed if all you're removing is an eighth or so.

[Warren Mickley]

Charles, I looked at the William Ware book you referenced, but the Part 2 volume in the link appears to have only architectural drawings. Maybe you are thinking of another volume that has furniture. At any rate I was talking about looking at 18th century furniture, not 19th century books.

Of course we see thinner pieces for drawer parts and backs, just not usually 3/4 stuff.

Faced with the prospect of planing away a half inch or more of material, I usually resaw instead. And you get two pieces for your labor, and the cost of your lumber, not just one.