Preventing Rust When Milling Wet Material

A discussion of lubricants and cleaners for preventing rust on machinery. August 14, 2007

We are looking for a used six head moulder. Which type of moulder is suitable for moulding dense, moist wood?

Forum Responses
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
When you run wood that is moist, green, or very wet, I have had the best results with through-feed moulders. Since most of the through-feed moulders are of the same basic design, most any of them will do the job. The use of the proper feed roller makes as much difference in the ability to feed the material, as does the type of machine. The machine needs to be aligned correctly and the beds need to be lubricated with a fast drying lubricant. I would avoid any bed lubrication that cans wax when running wet lumber as it can gum up fairly quickly and then reduces the ability of the material to be fed through the machine.

Be aware that wet lumber will cause the machine to rust and this can cause a long list of problems. Clean the machine regularly and use lightweight oil (I use Thrust) to keep the rust down. Do not use WD-40 as this will not prevent the rust from occurring.

From contributor R:
Popular Woodworking Jan. 2007 issue of table saws has an article about keeping a cast iron table rust free. Article is titled, "Stop Rust Now" pg.102. Seven coatings were used in their "unscientific" test. They were Camellia oil, Slipit, TopCoat, WD-40, FluidFilm, Boesheild T-9, Gun Blue, and untreated. Best of show, with photos of them all, was Fluid Film. Very close second place went to WD-40.

From contributor T:
Regarding the history of WD-40, the WD stands for Water Displacement.


From Dave Rankin, forum technical advisor:
I am aware of the WD-40 meaning Water Displacement formula 40. I have used many different sprays and lubricants while rebuilding machinery for over 20 years as well as lubricants on rifles and shotguns. I have found that the WD-40 does a very good job of breaking loose parts and displaces the water and other lubricants that may have been on the part. The residual that is left with the WD-40 has not prevented rust when it is used on moving machinery parts or on my guns.

Over the years, I have been involved with rebuilding several machines that were in fires. The machines were sprayed down with WD-40. The result was a much more involved repair and higher costs to bring the machines back into condition. It should be noted that the machines were only wet from the putting out of the fire.

If you will also notice, the sprays that I recommend were not tested by the magazine article. These sprays are ones that have been located while doing different rebuilds and service calls. The customers that introduced me to these different sprays had rust problems with other sprays including WD-40.

It is my desire to only make people aware of what I have seen and used in an attempt to avoid some of the potential problems that may be experienced. I do enjoy a good discussion and would be very open to the research and evidence that offers alternative answers and solutions to the lubrication and rust discussion.

From contributor R:
Thank you for your explanation of rust prevention and lubrication. What I enjoy about WOODWEB are threads such as yours, raising my knowledge level through the working experiences of others who freely share their time and talents. Where is Thrust sold, and why do you believe WD-40 caused so many problems in your restoration projects?

From Dave Rankin, forum technical advisor:
Thrust is manufacturer by Castle Key. Many auto supply stores and hardware stores have this in stock. Since the warehouse is local to me, I buy direct. It is available from MSI for $5 per large spray can. The cost is close to that of most other sprays.

The largest problem that I have discovered with some sprays and liquids is when a vertical adjustment is sprayed. WD-40, for example, does a good job of cleaning the adjustment and providing a very temporary film that helps to break the adjustment loose. The area is cleaned to the point that oxidation occurs.

During my first years as a machinery technician, I used WD-40 regularly. After having to re-clean machine parts a second time before I could assemble them, I asked many people what they had seen with this liquid. One of the first to begin explaining the problem was a former military Army Ranger. He had cleaned some of his personal rifles with WD-40 and put them away for a couple of weeks. When he got them back out, the barrel (inside and out), and the other blued metal parts were rusted. After watching this happen, I did a test in my shop. After that test, I no longer use WD-40 or sprays that do not provide a permanent lubrication film.

From contributor J:
I do believe Dave and would like to try this Thrust, but in WD's defense, I think it probably depends where in the world you are. I use WD (Northeast US) as one of my setting tools. It's always there. No rust. Just spindles and front stuff. But it doesn't leave a very thick film behind, so I can see where in a more humid environment, it might not stand up. However, to make it into a popular magazine as #2? I know it works in this area and will stand by it.

From Dave Rankin, forum technical advisor:
Thanks for the input from the Northeast. As with all "lubrication" sprays, humidity is a major factor in how they work. The other factor that applies is the type of surface being sprayed. A surface that has been waxed with Johnson Paste Wax, for example, uses most sprays as a bearing surface. What I mean by this is the liquid beads up on the wax and provides an improved slide action for the material. Plastic or nylon tables work well with many sprays for the same reason. However, plastic tables can also melt when used with certain sprays and chemicals.

Horizontal surfaces seem to hold the residue better than vertical surfaces. If you have problems with most sprays, you can follow them with a light coat of 10wt oil. I use Thrust in place of 10wt and seem to get good results in the US and Canada. Thanks for the input and make it a great day.