Whether to Make Your Own Moulder Knives
Info on how to grind moulder knives, and thoughts on whether it's worth the time and cost to do so. December 30, 2007
Please tell me about ease of grinding your own custom moulding knives versus ordering them in. What is the least expensive way to make these and still get the best finish? How do you know how to get the right gib to fit with the knife? I am trying to figure out what type of moulder to purchase to add this service to a custom cabinet shop. I could also make a lot of my own crowns and special moulding for projects. There are numerous places that would also do more of this business with me.
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
Grinding your own knives is a skill that can be learned in a day or so. It generally takes three or four sets of knives to be able to produce good tooling.
A few secrets:
1. Quality of the template; I use a template making CNC router.
2. Good quality grinding wheel; I use the MSI magic purple ceramic wheel. Run this at the correct speed. Use a dressing stone to keep the wheel unloaded.
3. Good coolant.
4. Proper technique, generally taught by a technician.
5. Take your time and do not rush.
All in all, a few days and you can grind almost any tool. The correct grinder is the other factor. There are many good used and reconditioned machines as well as new ones. Most of the time you get what you pay for. If you can, watch someone grind knives on the machine that you are looking at buying. Another major advantage is you can remake tools and sharpen tools as needed.
From contributor J:
Most people have a grinder on site for the convenience of knife repair and replacement. If you run very few profiles, and very few jobs, then it probably wouldn't be worth it to invest in a grinder and all the steel necessary to stock your tooling cabinets.
A used grinder is a tricky thing. I have seen used grinders which produced about the same quality finish as a bad file. And they are expensive to fix.
For one time runs, I would buy the knives and hone them if they get a little dull. If you are going to buy a moulder, and run the same profile many times, then a grinder would be a good idea. Just make sure you get a quality machine, or you will wear your elbows out sanding out defects.
From contributor R:
Some very good comments made already. Most of the clients that I produce custom knives for already have a grinder. A lot of them are small shops and they feel their time is more important doing other things than standing behind a grinder making a new set of knives. They pass the cost off to their customers anyways. They like the luxury of getting the knives, loading them in a cutterhead, and away they go. This frees up their time to do more important things like making mouldings. It does have its drawbacks if they don't have a grinder themselves. I have hit stuff in the end grain of the painted ends, dirt, staples, etc., then you have to send them back, costing you time and money. If you're making a lot of mouldings, I would agree you should buy your own grinder. Remember, everything you do prior to the moulder being run is costing you money. When the moulding is running, you're making money. If customers have the time and it is slow, then they just buy the template and make the knives themselves. Keep in mind contributor J's comments on used grinders. I have seen the same. Make the person grind on the machine so you know what you're buying.
From contributor F:
I will add that there are many of us out here that grind excellent molding knives freehand with minimal equipment. I won't go into a long explanation. For a quickie molding match job, trace the outline of a molding profile onto the knife steel with a sharp #2 pencil. Grind to the line at the proper clearance angle with 1/4" or thinner wheels. For a typical 3" crown knife, it takes me two hours or so from start to ready to cut wood. I use a planer style molder and I have about $250.00 tied up in grinding and honing equipment. I met a guy the other day who has a shop with all the large molding machine equipment. He told me he grinds all his knives, as I do. He also uses a planer style molder in his shop for when he needs to run radiused work.
From contributor R:
Contributor F makes some good points. Fact is, that's how I started making knives by hand. The other fact is, I never was really any good at it. It is an art in itself and takes much more skill to keep the back clearance angles and side clearance angles correct. Contributor F is a master at this, as most of you know.
The other thing to think about is contributor F said it takes him about 2 hours to produce a 3" crown. I don't know about anybody else, but as a small business owner, I must make about $100 per hour to cover all my costs of being in business. That means those knives contributor F made cost him $200, plus the cost of the steel (two hours of his time at $100 per hour). I would have charged $180 for the two knives and the template and you would have used your two hours running your moulder making much more money than the $180.00 it cost you for the knives. 30 ft per minute x 60 minutes = 1800 lf per hour - you do the math. Look at both sides of the coin and decide for yourself which is the best for your situation.