Axial Constant Grinding: Is It Worth It?

A discussion on the costs and benefits of switching to an axial constant system on moulder and shaper knives. August 18, 2009

Just wondering what your opinions are on axial constant? We have a new machinist at my work who wants to bring it in! I don't see the point, as we don't have a problem with setting our moulders or grinding our tools. We also have hundreds of profiles which we would need to make new templates and knives for and also a lot of our profiles have 90 degree angles, for instance dowels and rebates. I know it cuts down setup time, but is it really worth it?

Forum Responses
(Solid Wood Machining Forum)
From contributor R:
In short, the answer is yes. Let's say 5 spindle moulder setup... Every spindle has 2 movements, 1 axial, 1 radial. If you're constant on the axial you have saved 50% of your setup time. Add up all the setups you do in a month, year, etc., and the savings can be whether or not you get a pay raise. Think of all the set up pieces of wood that are wasted trying to get the profile correct. Look at the walls in your shop and see all the wasted wood. Be smart and use what the people are trying to teach you - a year down the road you will be very thankful.

From David Rankin, forum technical advisor:
I agree with contributor R. Using axial constant, I can set my moulder up in less than 10 minutes. I also have some tools that were not axial constant. It is very simple; oversized tools get the side ground off, while undersized tools get shifted in the head with a depth gauge.

From contributor K:
I don't have a moulder. I run all my own millwork on a 7 1/2 hp, 1 1/4" shaper. First explain the difference between axial and radial constant. I get that you are keeping certain points of a tool the same all the time, even after sharpening, but I just don't know which is which. Then, running on a shaper, should these methods apply to me also?

From contributor O:
A better solution would be an optical measuring stand, as this allows you to measure your axial reference as well as your tool radius. It also has other time saving benefits. Axial constant requires a number of assumptions, but is better than what you are doing now. Whether you go with the optical stand or axial constant, there will be a cost to you, however as contributor R pointed out, you are already paying on the installment plan every time you set up a machine and get nothing in return - not a very good deal in my opinion.

The axial movement of a shaper is the height adjustment. If the point on the knife that corresponds to the start of the profile (that which aligns vertically to the plane of the table) is constant from one tool to another, then you will not have to make a knife adjustment from tool to tool. A good solution for a shaper is to add a Siko counter to the height adjustment if possible or a digital scale to the spindle. This will help you if you are ground constant. It will also save time if not constant, as once set the first time for a given tool, the measurement from the counter can be recorded and dialed back in for future setups.

From contributor K:
Thank you - makes sense now.

From contributor J:
I would start using it moving forward, meaning on new jobs that come in. Over time you can phase out the old (non AC) knives, as they get too worn to use, and replace them with AC knives. If everything is set up properly, you should never have to adjust the moulder more than a few thousandths, throw the heads on and go. I am oversimplifying some of the headaches you will find when you start to switch. My guess is your new guy is used to just throwing the heads on and running. The troubleshooting involved with manual setups may take him a little while to grasp.

From the original questioner:
We already have an Opti-control to measure axial and radius of heads. We have no problems setting our moulders! It just seems unpractical for us and a lot of time and money making new tooling.

From contributor R:
It appears to me you have answered your own question. You asked for this forum's opinions, but you obviously do not want axial constant implemented in your company.
So I would say, keep things the way you have them, if all is working the way you want them to.

From contributor V:
Axial tooling is the way to go. I have lots of tooling that was not ground all to the same axial setting. I keep a log of the axial settings on these knives - this makes setup much easier, by simply dialing in the numbers. Now that I do my own grinding I grind all my knives to the same axial setting.

From contributor N:
I like it. But that is what I started out with. But it isn't always constant - sometimes it's off a few thou. But I have to agree with contributor R and the beginning of Dave's post. If you have something that works well, don't shy away from progress, but ask "is it worth it?" If you have a sample with the setting written down or a log of it to dial that setting in every time for that setup, you probably don't need it. But it might be something to consider if you're looking into positive change for the future. I'm sure that's where your new machinist is trying to go here.

From contributor J:
I think the cost to switch will answer your question. You said you have hundreds of sets of knives, so pick a number to get 1) new templates, 2) new steel, and 3) pay your grinder to make a new set. Just for laughs, let's say $100 total per set. For 200 sets of knives, that's $20,000!

That's why I said "make the change moving forward" - you get the benefits of axial constant on all future profiles and can slowly hand pick which to change of what you already have.

If you save 10 minutes on every setup, that is 10 minutes more work you get out of your operator, and 10 less minutes your operators help will spend looking for something to do. It will add up quick.

From contributor M:
What you are looking for is repeatability. What is the quickest way to get from point A to point B? Grinding axial constant is definitely quick, but not 100 percent - there is always a slight adjustment. We use a method of using index cards to record the setup on a particular profile, along with any adjustments made and when the last time it was run. After a head is sharpened, the card goes with it to the moulder so the info can be updated by the operator. Point being, axial constant or repeatability doesn't mean using only 20mm or 1/4", but whatever the numbers are, record it and you will still save huge amounts of time on setup by going right back to the recorded dimensions at the grinder and moulder.

From contributor N:
"...10 less minutes your operator's help will spend looking for something to do. It will add up quick."

That statement can open a whole can of worms and is very true! Especially if you're trying to improve the shop flow. What does the helper do while you're doing setups? Teach him what you're doing. I'm bringing mine to Shelton, CT for Stiles free class to get his foot in the door.

From the original questioner:
What contributor J wrote is what I was thinking! I know axial constant works, but won't the axial change if you grind something that has a 90 degree angle like a rebate cutter? If all we produced was arches, I would not have a problem changing.

From contributor C:
I don't know if I could function as a moulder/grinder operator anymore without my optical measuring stand. It makes life at both stations so much easier. It uses a system that one of the Weinig techs called "axial identifiable," which is preferable to me and covers any axial size, and so a greater range of tooling types. How this would apply to a moulder without Siko counters is a different matter, though.

From contributor J:
It is pretty much impossible to re-grind a head with 90 degree angles regardless of whether it is axial or not, without changing the profile a little bit. 90 degree angles will, in many cases, cause some part of the knife to shrink when re-ground.

That is why it is important to figure in 2 degree angles anywhere possible to replace 90 degrees, unless it is a 1 time job. The axial position will also change any time you regrind the head because you are removing material from the knife (maybe your grinderman pushes a little harder on the grinder this time than he did last time), and it will also change because you have removed the knives from the head and can not guarantee they go back in exactly the same way.

Axial constant is great, and it can be perfect every time, but it takes tremendous discipline. I am sure that is why Weinig created Opticontrol measuring stands - it takes a lot of the issues away (again, only if used properly!).

From contributor E:
If you have an Optistand, you wouldn't gain a thing by changing to axial constant. Almost all of our knives that we made years ago were not ground axial constant. With the Optistand you can find the axial on any knife, and the seconds that it takes to dial in the moulder is not worth replacing all of your knives.

Do you grind your knives? If so, did you ever look into ordering them out? We found that we couldn't afford to keep making our own knives for what we could order them for. By the time you buy the knife stock, and spend hours making a template by hand, and another few hours grinding the knife at $15-20 an hour, it's not worth it. We use Hot Knives, and they are great. Besides them, there are numerous other places to choose from, and all the new knives you get would all be axial.