Best angle for sharpening plough plane irons

[Doug N]

Hi all,
This is my first post so hopefully I get it right!
I need to make some 10mm wide x 5mm deep grooves in some pieces of oak (just under 1 metre long) for which I will use my Stanley combination plane, but before I start I need to sharpen the irons. What would you recommend as the best angle to sharpen the irons at for this please? Looking on line some people say sharpen the whole bevel at 30 degrees, whilst other suggest a 25 degree bevel with a 30 degree secondary bevel so I'd be interested in your thoughts.

Regards

Doug

 

[spb]

As long as the bevel angle is less than 45 degrees, it won't make the slightest difference to how it actually cuts - the blade is mounted with the bevel down, so the cutting angle is set by the bed of the plane and not the bevel.

The difference is in the distribution of effort for repeated sharpening - if you grind a primary 25 degree bevel and then hone at 30 degrees, you have to do less work each time you re-sharpen it, until you have to spend ages regrinding the primary again. If you hone the whole thing at one angle, each sharpening session takes a little bit longer but you don't have the hassle of having to eventually re-grind the primary bevel.

Honestly, just get it sharp and don't worry about the angles.

 

[AndyT]

Yes, on a narrow iron like that it really doesn't matter much. Record recommended a single 30 degree bevel for those fiddly little combination plane irons and that's what I do. It's really only on bigger bench plane irons that there's any saving of effort from a double bevel, but whatever works is ok.

 

[thetyreman]

I have found with really tough woods such as beech and oak I prefer 35 degrees, most of the time though 30 works just fine.

 

[Argus]

I mostly work in Oak and Ash and I usually keep mine at a nominal 25 degrees, but I don't think that it's crucial within reasonable limits. I think that its best done by hand, jigs on these narrow blades can unintentionally introduce all sorts of skews. Secondary bevels are not an essential part of my blades, but some folk like 'em.

The steel in these smaller blades is not usually hard in comparison to, say, a chisel and for the narrower blades I find that if I have the correct angle sitting on the stone or plate, drawing it backwards on each stroke rather than push/pull tends to prevent introducing an unwanted skew. Whatever angles you go for, make sure that you have an equal protrusion on each side of the blade when it's mounted in the combination plane, or it'll stop cutting after a few strokes. You only need to hone enough to develop a fine wire on the blade, then take it to a strop and you're ready to go.

It may sound odd, but when you have sharpened the bevel, don't forget to do the back and both edges. Do it once and thereafter give them a stroke or two to keep them well defined. The direction of cut with a bevel-down blade means that you will need to flatten the back and get the last 1/2 inch or so nice and shiny.
On a plough plane blade it is essential that both the corners are pin-sharp. Hence sharpening a clean aris and corner on each side. If not, a rounded corner will prevent the blade cutting down more than a couple of strokes before it bottoms out and stops cutting.

Additionally, if it is an old blade in an old plough plane, it is more than likely that the blade will be trapezoid in section - only the front and back faces were parallel. The sides were usually slanted very slightly from the back..... only a degree or two and you'll need a small square and good light to see it, but most old combination plane blades were like that.
This was intentional so that, as the blade got lower in the cut, the sides did not bind and a clean aris on each side burnished the sides.

Hope that this helps..... good luck.

 

[D_W]

shallower grind (like 25) and then 30-35 secondary. halfway between there is where chipping stops, but the cut width is fairly small and the depth usually not so much, so like a mortise chisel, absolute perfection at the edge isn't as important - you just need enough clearance to not fight it. separate secondary and primary makes it a lot easier to touch the irons up quickly.

 

[Woody2Shoes]

I don't bother with a secondary bevel (because) - my technique is:
1) Ensure back is flat and shiny, as mentioned above.
2) Place tip of index finger on back and use this to keep the (primary/only) bevel absolutely flat on the sharpening medium (diamond stones for me!) while using the other hand to move the finger+blade assembly backwards and forwards on the stone. My Record irons still have the original labels on them with the bevel angle marked (30 deg from memory).
3) Stropping.

 

[Doug N]

Thanks everyone for your advice - much appreciated.

Regards

Doug

 

[billw]

Yup 30 degrees and no need for a secondary in my book.