Aluminum saw guides: to remachine or not to remachine?
POST DATE Jul 08, 2020
Every once in a while, I get a call from a customer with a version of the following question: “We have thicker aluminum saw guides in our filing room that we want taken down to a smaller size. Can you remachine it?”
There’s a very simple answer to this question but before we get to it, let’s examine what we’d have to do in order to remachine a saw guide.
Stripping the saw guide.
First of all, if the saw guide has the proper engineering hard coat anodizing applied to it, that needs to be stripped. To do this, you have to put the saw guide in acid.
There’s a challenge though: only roughly 50% of the anodizing sits on top of the aluminum. The rest of it lies below the surface. To remove all of it means you have to remove aluminum from the body of the saw guide.
This leads to two issues. First, you lose material on the saw guide. Second—and more importantly—acid doesn’t remove the anodizing evenly so you also lose all true surfaces.
Trueing the surface.
In order to true the surface after the acid bath, you need material, which is why it’s an issue that you’re losing thickness in the acid. By “trueing,” I mean getting the surfaces flat and parallel. This is not simple and many times impossible because of the machining tolerance a saw guide is required to maintain. And if you can’t true your saw guide, you’re going to have accuracy issues.
This means that a remachined saw guide will never be as accurate as saw guide that’s machined from scratch.
The consequences are huge. Accuracy of a saw guide is one of the most important elements in achieving accurate and consistent lumber from an edger! Poor saw guide accuracy causes downtime, poor lumber and bad recovery.
Reanodizing the saw guide.
Once you’ve stripped off the existing engineering hard coat and remachined the guide to your desired specifications, the next step of the process is to reanodize your new saw guide.
First, we have to remove all metal inserts. We then apply the proper engineering hard coat at freezing temperatures by putting a 660 volt/200 amp current through the saw guide. That’s how you build your anodizing layer.
If any foreign metal particles are in the saw guide, the aluminum will erode off, making it look like the material melted away. I’ve seen and heard of this happening more often when the aluminum is in poor condition (like after they’ve been soaked in acid…).
These melted saw guides are useless and need to be thrown away.
The verdict on remachining saw guides.
To answer the original question: “Can we remachine saw guides?” the answer is “Absolutely” if:
- You’re willing to lose your saw guide due to melting.
- You’re willing to have a less accurate saw guide, resulting in more downtime, poor lumber and worse recovery in your sawmill.
So yes, we can remachine it. Should you? In most cases, no!
Why are you remachining saw guides to begin with? It’s probably to save money. But the reality is you’ll be paying a lot more in the long run because you’re using an inferior product. Your effectiveness and quality will decrease and you’ll just end up having to replace your remachined saw guide.
That’s cost-cutting at work for you.
Want to really save yourself some money and trouble? Better to choose new and accurate saw guides to start. They’re worth the investment every time.