Saws and Techniques For Cutting Moulder Knife Steel
Advice on choosing and using equipment for cutting off moulder and planer knife blanks. October 1, 2010
Question
I am in search of a saw that I can use to cut 1/4" and 5/16" HSS moulding knives. I am fed up with using a steel cutting chop saw - way too inconsistent. Does anyone have experience using Grizzly G0665, Slow Speed Cold Cut Saw?
Forum Responses
(Solid Wood Machining Forum)
From contributor O:
A good steel cutting chop saw with the right blade works just fine for this operation and will cost less than $200. Perhaps it is your technique. What issues are you experiencing?
From the original questioner:
Thanks. I have used Makita chop saws for the past 17 years for cutting knife steel. The problem seems to be in the cut-off wheels - they are so inconsistent. I have tried every brand out there. Some will cut straighter than others within the same brand. Some will cut off square by about 1/8" over a 2" span. Besides, I am sick of the smell and mess. Water cooled sounds great to me, but I am afraid to drop a minimum of 1K for one without knowing how it will perform.
From contributor M:
I hear you, as I have also used a Makita 10" miter saw for cutting our steel for years. I don't believe a cold saw using the typical blade for that device can cut hardened steel. Your moulder steel is as hard or harder than the blade. You are still stuck with an abrasive blade of some form, and a cold saw turns at a very slow speed.
From contributor J:
This won't help with the smell or mess, but have you tried clamping the knife stock into your saw laying flat instead of standing up? I would think as long as the fence is true to the blade, it should be square every cut. The flex in the blade shouldn't wander too much over 5/16".
From the original questioner:
Thank you. That's good to know about the cold saw; thought it might have some kind of diamond wheel or something hard. I have not thought of lying the steel flat in the cut-off saw, and will give it a try, but am concerned it could cause extra burn marks on the steel.
From contributor R:
Your thoughts about lying the steel flat are correct. It will burn the steel more. As for the cold saw, contributor M's comments are correct unless there is a special blade to cut hardened steel. I used one on an installation once and I ruined the guys saw with just one cut. Have the people who want to sell you the saw demonstrate it first.
I cut a lot of steel in a week. I use the Kalamazoo KM 14" chop saw. I have had it for 9 years and use the Makita 14" #724603-3 blades. I also have the Kalamazoo dust collector to catch all the sparks from the saw. It's American made and cuts straight as an arrow with the steel standing up. It has a three phase 5hp motor and there is no flex in the blade at all. I paid somewhere in the vicinity of $1500.00 for the saw and $1000.00 for the dust collector. It will last me a lifetime.
From contributor A:
Those Kalamazoo saws look pretty rugged. The 10" is $1000 with the stand/vise. It should give a squarer cut and save a pile of money. I realize you will get fewer cuts per blade, but it is hard to overcome the $500-$700 difference between the 10" and contributor R's 14".
From the original questioner:
If the cold saw is totally out of the question, I will seriously consider the Kalamazoo. Sounds like it would save me a lot of time in squaring and balancing out the knives. The dust collector would be nice too. I'm sick of that fine black dust everywhere!
From contributor J:
Are you selling knives to customers or using them for production? The burn on the edge does not affect the performance of the knife, but does look bad to the buyer.
From David Rankin, forum technical advisor:
I use both a Makita 14" cutoff saw and a larger cutoff saw (sorry, no name on it) that I picked up at auction for $50. I have added a couple of things to the larger unit, which can be added to the Makita, a coolant mist unit and a corrugated fence.
The misting unit allows the cut to stay cool and be lubricated. This greatly reduces the burn seen on the edge of the steel. It also allows the cutting wheel to stay cleaner and this helps with the squareness of the cut. I still square the knives on my profile grinder with a squaring fixture I built. By adding the corrugated fence, the knife steel is always held perfect so the cut is consistent.
As for cutoff wheels, I have used many different ones over the last 25+ years of doing installations and training. Most will work okay, but using the proper wheel is always best. For me that is a special wheel designed for the Rockwell (hardness) of the steel we use. The negative is that this wheel is more expensive to buy and does not last any longer than a wheel that you can buy at Lowes or Home Depot. The cut is straighter and cleaner with the correct wheel. This saves me a lot of time when it comes to squaring the knives. If your budget allows, the Kalamazoo is by far the best cutoff saw that I have found.
From contributor T:
If you're trying to get multiple knives exactly the same, further machining is needed. You don't install a length of base with a raw edge because it looks square. Cut long, then clean up on a surface grinder. If you gang grind, there is no balancing issues.
From contributor R:
I respectfully disagree with contributor T's comment about not having a balance issue if blanks are gang ground. Very rarely will you have the exact weight on knives cut due to the molecular structure of each piece of steel, regardless if they came from the same bar. Weight of knives should be balanced before and after profile grinding. This ensures the perfect balance that is critical on today's advanced moulding machines.
From the original questioner:
The knives are for my own production, but I hate the look of burn marks on the edges. I know they do not affect the performance; it's just an aesthetic thing for me. I like the ideas that Dr. Rankin has mentioned; I might make some modifications on my Makita for the time being until I make up my mind on which size Kalamazoo to purchase.
I will have to agree with contributor R about balancing knives before and after grinding. Steel density does seem to vary on every inch of a bar of steel. I have seen Weinig M3 steel cut the same length in a set and be off by several grams, and then once they are balanced, I have seen them up to 1/8" difference in length.
Thanks for all your help; you've had some great suggestions.
From contributor J:
Dave does have some good points. I welded a piece of corrugated filler stock to the fence for the same purpose he mentioned, a few years back. It works great.
When things get busy and there is no time to make them, we order them pre-hogged and I just have to finish them up. But there are no burn marks on the steel whatsoever compared to the ones I cut (standing up).
From contributor T:
In response if the structure of the steel changes, then balancing should be done after each sharpening, and I don't think someone using a 100.00 chop saw on knife stock has a 200,000 dollar molding machine.
From contributor J:
You are right. Balancing should be done after every sharpening. On an unjointed moulder, you can have the knives perfect out of the tool room. When you clamp it onto the grinding arbor, the knives are going to be off a bit and one will get sharpened a little heavier than the other. Hence the importance of balance.
From contributor I:
As someone said, your steel is harder than a coldsaw blade. Abrasive blade is the way to go. Laying the blade down will be your best bet. I prefer a thinner type abrasive cutoff wheel. Cold saws are great for stainless and regular steel. I've used them plenty and they are certainly better in most cases than an abrasive blade.
From contributor R:
Weinig has a good video of it on their website. I don't have one, so I can't answer your question, but Alliance can - they used to run the program over there. They are good people and I am sure they are taking good care of you.
From contributor O:
Woodworking miter saws and techniques do not work well for cutting high speed steel. I have seen a new 12” Dewalt burned to a crisp in a heartbeat doing this. When cutting high speed steel, unlike cutting wood, the general idea is to cut through the bar as fast as possible to minimize burning and glazing of the blade: heat = glazing = more heat = more glazing = more heat and on and on. The aggressive cutting of the steel will also cause the edge of the blade to fracture and expose sharp particles, increasing the efficiency of the saw.
Laying the bar flat is also a recipe for disaster. If you have ever cut a steel pipe with a hacksaw, breaking through the circumference is slow, and once through, cutting through the vertical walls is very fast and easy. The same concept applies to cutting a bar of high speed steel; laying it flat is like cutting through the circumference of the pipe, the large amount of steel presented to the blade will result in more friction, heat, and glazing and on and on. Stand the bar up vertically and blow through it as fast as the saw will allow without forcing it. Basically this means maintaining RPMs throughout the cut. If the saw is underpowered, plunge in and out to maintain RPMs and keep everything cool.
If you are a grinding professional or running a busy tooling department, the setup contributor R describes is certainly the gold standard. If you can’t go that route, in my experience the Makita 14” metal cutting chop saw has the right combination of blade and power to cut through a bar of high speed steel in one pass relatively square and cool. In fact, if done properly, you can pick up the steel at the fresh cut edge with your bare fingers without being burned.
It is also not necessary the ends be perfectly square. Common and fundamental cutter head setup addresses this. Surface grinding the ends would be an absolute waste of time and resources. Balancing, as others have noted, is essential regardless of how accurately the steel is cut, however with a corrugated fence and dead stop, again described by pervious posts, you will be within a few tenths of a gram and a minute within a couple of perfectly balanced knives. Digital scales now available will also speed things up a bit versus the older Ohaus mechanical scales (which still work quite well).
From contributor M:
Good input, contributor O, with one contradiction. I have used the same Makita wood miter saw for the past 15 years to cut steel, and probably a good 12 years prior for trim work. It actually cut better than the 14" metal saw we had at the time with a lot nicer fence. This model is, however, the old heavy cast iron version and, needless to say, we don't turn it off 90 degrees and probably couldn't if we wanted to. We added a DeStaco type pusher clamp and mounted it right to the table to hold the steel upright for cutting.
