Planing iroko

[Saintsman]

I'm making a couple of garden planters in Iroko: having run them through the thicknesser to just over size (using enough masks, filters and extractors to make Axminster's profit for the year) , I want to smooth them by hand.
OK so far, so reach for the LV BU jointer.

Question: a higher angle is recommended for difficult woods, yet on the John Boddy Timber website they suggest reducing the cutting angle to 15 degrees for a smooth finish due to the interlocked grain.

This could confuse a stupid person: I'm confused........

Should I try a higher or lower angle than normal, or sit on the fence and just use it as standard ?

Paul[/u]

 

[promhandicam]

Hi Paul,

here are my thoughts.

1. Are you sure that your p/t is set up right as normally it should give a good enough finish for a planter.

2. Assuming that your BUJ is correctly honed - i.e. it is sharp enough to shave hairs with - then set it to take a fine shaving and give it a try. If you get a lot of tear out then you would need to increase the bevel angle. If you only get it in a couple of places why not use a cabinet scraper to get it smooth.

I personally wouldn't recommend changing the bevel angle dramatically on your plane - you'll spend more time grinding / honing than you will planing! I have the LV Low Angle Smoother and bought 2 extra irons with it so I have one each at 25° 38° 50° giving cutting angles of 37° 50° and 62°. I'd recommend at least getting a second iron, honed at 38° as you don't want to keep changing the bevel angle each time you want to plane a different piece of wood. The advantage I think with the BUJ is that it uses the same size iron as the BU smoother and the BU Jointer and so a spare iron will work in any of them.

Hope this helps,

Steve

 

[Saintsman]

Steve,

Thanks for the quick reply.

The finish straight off the P/T is actually pretty good: I'm just being (probably unnecessarily) fussy.

I've actually got a spare 38 degree iron for my BUJ, so I'll probably try that first. I was just curious about the advice from Boddy's.

Cheers,

Paul

 

[Paul Kierstead]

Question: a higher angle is recommended for difficult woods, yet on the John Boddy Timber website they suggest reducing the cutting angle to 15 degrees for a smooth finish due to the interlocked grain.

Ah, the gap is between "better finish" and "tear out". Higher angles reduce tearout, but can leave a slightly duller finish. Compare a planed surface with a scraped one. However, the slightly better finish isn't so helpful if there is tearout; very nice smooth finish between ripped out bits of wood ain't so pretty. So we tend to see people strong advocate higher angles, since tear-out is such a PITA. Of course, different timbers react differently as well; I was unaware that interlocked grain was a particular factor. Might be something interesting for someone to experiment with someday.

 

[bugbear]

Question: a higher angle is recommended for difficult woods, yet on the John Boddy Timber website they suggest reducing the cutting angle to 15 degrees for a smooth finish due to the interlocked grain.

What on earth are they talking about? 15 degrees is astonishingly low for a cutting bevel, and certainly unachievable as an effective pitch (EP) for a plane.

BugBear

 

[Saintsman]

Hi Bugbear,

Yup, that's what I thought. Glad it wasn't just me !

I'll stick with the higher angle on the BUJ.

Mind you, it's a good excuse to treat myself to the LV Scraper Plane.

What slope ?............

Paul

 

[ByronBlack]

So, just to confirm, when planing ratty grain, it's better to increase the bevel angle of the iron?

 

[pam niedermayer]

In dealing with a truly ratty grain (I haven't a clue about Iroko), often one has to resort to scrapers and/or sandpaper, as much as I hate to admit it.

Pam

 

[David C]

Paul,

Increased effective pitch works for me.

Iroko can be particularly nasty and interlocked on quartered surfaces whereas a plain sawn surface may plane well.

Your 38 deg blade would give you an EP of 50deg if you honed it at 38 deg. I doubt this is steep enough to avoid tearout on quartered surfaces.

I would sugest very fine shavings and a very narrow honing bevel of at least 50 degrees. The honing bevel does not need to be wider than 0.2mm. This gives EP of 62 degrees.

If this does not work increase honong angle to 58 degrees giving EP of 70 degrees. I think this is certain to work if shavings kept fine.

David

 

[Scrit]

Question: a higher angle is recommended for difficult woods, yet on the John Boddy Timber website they suggest reducing the cutting angle to 15 degrees for a smooth finish due to the interlocked grain.

Do they perhaps mean adding a 15 degree face bevel to machine planer knives which would give the effect of something like a 55 to 60 degree pitch to the cutter? Just a thought as this is one way of machine planing very rowed timber

Scrit

 

[ByronBlack]

If you were planing cranky grain using a bevel down plane, is adding a back bevel the only way of increasing the pitch? I dont mean to hijack the thread but it got me thinking as i'm having a tough time planing a beech worktop where the grain is going in different directions and is the side grain as the top is made up of laminated staves turned on their side.

Or as Pam says, in situations like these is scraping/sanding the only solution. Again, forgive me if i'm hijacking the thread, just thought it would be interesting to add bevel down angles to the discussion.

 

[Paul Chapman]

Byron, there was a very good article on all this by David Charlesworth in the May 2007 issue of Furniture & Cabinet Making. If you don't have a copy I could copy it and send it to you if that would help.

Cheers :wink:

Paul

 

[katellwood]

I've made lots of things out of Iroko and never really had a problem, I use a calvert stevens smoother with a Clico Iron and an extremely fine mouth on the plane, if i get any tearout I then revert to either a stanley cabinet scraper or alternatively a LN 112 scraper plane, always works a treat

 

[David C]

Byron,

Yes in bevel down regular bench planes a tiny back bevel does the job.

As usual shavings must be kept fine.

I use 25deg for very cranky stuff.

For beech I would think 15 or 20 degrees might be enough.

Paul,
Thank you!

As Scrit says, a 15 degree back bevel on planer thicknesser knives is very effective at reducing machine tearout. All skilled old machinists used this trick.

David

 

[bugbear]

In dealing with a truly ratty grain (I haven't a clue about Iroko), often one has to resort to scrapers and/or sandpaper, as much as I hate to admit it.

Pam

Have you tried higher EP?

BugBear

 

[Steve Elliott]

The 15-degree angle recommended on the John Boddy site is based on the conventions used for power equipment, which measure cutting angle relative to the perpendicular rather than to the surface of the wood.

The equivalent angle for a hand plane would be 75 degrees.

 

[Scrit]

...a 15 degree back bevel on planer thicknesser knives is very effective at reducing machine tearout. All skilled old machinists used this trick.

The other thing worth bearing in mind is that a modern limiter-type spindle moulder block, such as a Whitehill:

has an effective cutter angle of 15 or 16 degrees (the equivalent of a scraper/hand plane at 75 or 74 degrees). Boddy's is primarily a trade supplier so you'd expect the information supplied to be wood machining orientated, I'd say

Scrit

 

[Saintsman]

Steve,

Yes, that makes sense.

Thanks for the useful replies, everyone.

Paul

 

[Scrit]

This should illustrate the point about how angles are measured on machine cutterblocks:

Scrit

 

[bugbear]

The 15-degree angle recommended on the John Boddy site is based on the conventions used for power equipment, which measure cutting angle relative to the perpendicular rather than to the surface of the wood.

The equivalent angle for a hand plane would be 75 degrees.

Thank you - most helpful.

BugBear (ignorant of hand held and stationary power tools)