We mill a lot of maple mouldings and our knives are Weinig M3+ Steel or M2. It is not uncommon for us to get sizeable nicks in the knives after only a few boards go through the moulder. There are sometimes little black marks in the maple and those black marks are very hard and can nick the knives. This can be very frustrating, obviously, as we have to hone the knives after just a few boards.
Honing is a last ditch effort to finish a run; it should not have to be done to a pair of knives that have just been sharpened on a profile grinder. Would we have better success if we were using Weinig's Supre 18 grade steel? It is a harder steel, I believe.
(Architectural Woodworking Forum)
From contributor L:
Yes, same problem. The mineral streaks also occur in walnut. Whenever possible we use red maple instead of hard maple. Since we always do a light grind on the profile grinder before starting a run rather than honing, we will go back to the grinder and take a very light cut, measure and reset the readouts for the diameter loss. For flat or S4S we run the double back system using carbides. Lots of moldings have a large percentage of their area just flat, so we will run the carbide in the other two slots and the profile in the opposite slots. We rarely get long runs to do, so having custom carbide profile knives made doesn't pay. We have a Weinig 950 grinder so we can only do the straight carbide knives on it, not profiled.
My suggestion would be to buy a bar of each and see what works best for your application. Others might have something even better.
Contributor L, how do you like the red maple? Do you find it has similar appearance to the hard maple? How do you like the double back carbide knives?
Contributor R, glad to hear this problem exists elsewhere. It can be very frustrating. We do not grind in-house; we outsource. So, once I get a set of knives back (and spend sometimes up to $50.00 for a pair to be sharpened) and then have a nick occur with just a few boards through the moulder... Ahhh! You know what I mean? Then, by honing them, I am in essence ruining the edge by removing the nick. I can hone pretty good but not as good as a profile grinder. I will check out the steel you recommend.
The tooling company I use for sharpening and knife production is willing to grind other steel; if I purchase a bar they will make them into knives for us. Do you find it is much more difficult to grind Supre or the Endurance Steel vs. M2 or M3+? Does it take much longer? Do you need a different type of grinding wheel?
A fair amount of the knife steels mentioned in this discussion are radial ground materials. Other things to consider are hook angles, especially in hard maple. Hard maple (heavier mineral content in general) harvested in Western NC (where I'm located) machines much differently than hard maple harvested from Michigan (lower mineral content), for instance. We have used 10 degrees and even as low as zero degree hook angles on occasion.
WKW offers a diamond back coated steel that we've used on mineral streak issues. More often, carbide ends up being used on rock maple.
I've also found that Weinig heads are more accurately ground than the DML heads we have. For the first bottom spindle we run a segmented insert head. The inserts run a long time. But if one breaks it will usually wipe out all the inserts that follow it. It also runs a lot quieter than the straight knife heads. Have you considered buying a profile grinder? We have a Weinig 950 that is okay (for a small shop) but lacks the adjustability to grind profiles with a diamond wheel. We do grind the double back carbides using a straight diamond wheel on it. If you look for a used grinder, donít buy a Weinig 925 - thatís what we had first. Profile grinders require a take-apart and good cleaning periodically.
We outsource our grinding and I am happy with the excellent service this company provides. At some point I may be interested in a grinder but for the time being I feel that outsourcing is our best solution; there are not enough hours in the day as it is. The company we use has excellent customer service and they always do what they say they'll do. If they say you'll have the knives for this Thursday, you'll have the knives for this Thursday. The company is Galt Wood Tool from Cambridge Ontario; I have been using their services from day one (about 14 years now).