Possibly a dumb question about table saw rust

[Steve Morrissey]

Hey folks,

Still fairly new to woodworking, and I have a question about imperfections appearing on the shiny new tools I got last summer.

For context, in August of 2020 I got a new Powermatic PM1000 table saw and a Powermatic 54A jointer with a shelix head. From the beginning I put paste wax on the cast iron tops of these tools, but I live in Minnesota and the shop is in a non-climate controlled garage. Humid summers, freezing winters, and large temperature swings are the normal.

I'm starting to notice marks appearing on the cast iron surfaces on these tools. They aren't huge, but they aren't scratches either -- they look like tiny rust marks perhaps? Maybe? So I went forward assuming it was rust. I used mineral spirits to get the paste wax off, used WD40 and some 400 grit sandpaper to attack the spots, but they don't really seem like they're going away.

So now I'm reaching out to you experts, with photos, to determine if I need to stress and work hard to get rid of these marks before my tools disintegrate before my eyes, or if they can be left alone because they're harmless.

460377460378460379

Thanks in advance for looking!

[Jacob Mac]

If rust is a concern, I’d look into getting a dehumidifier, and Boeshield T9. I am in he Midwest with similar swings and paste wax didn’t stop rust. A combination of all three helped me

[Carroll Courtney]

I don't blame you for wanting to keep that surface new looking for as long as you can. You will get several suggestions on what each of us use so be prepared. They all will work but its going to be required to be repeated several times through out the yr. Myself I use this product and I really like it, but I also keep my machines covered up with old bedding sheet just to help. I never consider questions as being dumb cause advances is being made all time so there may be new product out there that us WW'ers need to know about. So old questions become new again.

[Alan Lightstone]

Living in Florida, I feel your pain regarding rust prevention, albeit my shop is climate controlled.

A few of the woodworking magazines have published reviews of the effectiveness of many products for this. And all have their boosters, and neigh-sayers.

This is the link to Fine Woodworking's test: https://www.finewoodworking.com/membership/pdf/10038/011227030.pdf


Personally I use CRC Industrial 3-36, which I can get on Amazon. It was highest ranked on one of the reviews. Boeshield T-9 has lots of supporters as has Johnson's Paste Wax, but the reviews weren't that fond of the effectiveness of the wax (flaming start in 5,4,3,2,1...)

As has been said, keeping the humidity out of the shop is important, but not necessarily easily done in some climates.

Oh, and welcome to Sawmill Creek!

[Charles Coolidge]

Here in the Pacific NW rain forest where Boeing resides and Boeshield T-9 was invented and it can rain every day all day 4 weeks in a row...Boeshield T-9. When machines are not going to be used for a bit I apply petroleum based past wax then Boesheild on top of that, apply it wet with a blue paper shop towel (they sells rolls of this in auto parts stores, basically a fancy paper towel) and let it dry. When I need to use the machine I remove with low odor mineral spirits, apply paste wax and use the machine. When done I reapply the wax and Boeshield until next use.

[David Lageman]

Not that it's needed, but I'll cast another vote for Boeshield T-9 in the mix. Works well in swampy SW Florida.

[Marc Fenneuff]

Powermatic used to recommend cutting a sheet of hardboard or similar and laying that on the CI table when not in use. Stops moisture from condensing on the surface. Maybe try that in addition to the paste wax.

[Charles Coolidge]

Powermatic used to recommend cutting a sheet of hardboard or similar and laying that on the CI table when not in use. Stops moisture from condensing on the surface. Maybe try that in addition to the paste wax.

But I once drilled holes in some wood to put all my Forstner bits in, it was dry wood, they all rusted like the wood absorbed the moisture from the air.

[Charles Coolidge]

I'll also add gravity is a factor. On a flat table surface that's fine, but on a round or vertical surface where the product can basically fall off you have to watch it. Learned that lesson on my metal lathe after treating it then coming back a couple months later and seeing the rust.

[William Hodge]

Hey folks,

Still fairly new to woodworking, and I have a question about imperfections appearing on the shiny new tools I got last summer.

For context, in August of 2020 I got a new Powermatic PM1000 table saw and a Powermatic 54A jointer with a shelix head. From the beginning I put paste wax on the cast iron tops of these tools, but I live in Minnesota and the shop is in a non-climate controlled garage. Humid summers, freezing winters, and large temperature swings are the normal.

I'm starting to notice marks appearing on the cast iron surfaces on these tools. They aren't huge, but they aren't scratches either -- they look like tiny rust marks perhaps? Maybe? So I went forward assuming it was rust. I used mineral spirits to get the paste wax off, used WD40 and some 400 grit sandpaper to attack the spots, but they don't really seem like they're going away.

So now I'm reaching out to you experts, with photos, to determine if I need to stress and work hard to get rid of these marks before my tools disintegrate before my eyes, or if they can be left alone because they're harmless.

460377460378460379

Thanks in advance for looking!


It's humid in your shop.
Make it not be humid. Things won't rust.
Even if you put whatever on the top of the machines, the rest of the machine is still being exposed to humid air as long as there is humid air. Get the relative humidity below 50%.

[Thomas Wilson]

People also use magnetic sheet sign material on the surface. The way waxes and oils protect the iron is by slowing the diffusion of water and oxygen to the iron surface. The magnetic sheet should do even more.

I had tools in an uninsulated, unheated garage for a while. Rust was a problem. Cold night followed by a warm rain, I would get condensation inside the garage. I was planning to move so I did not actually work on the problem beyond wax and Boeshield, but that did not stop me from thinking about what I could do. If you are in your long term shop, you may want to work on keeping the heat in and the moisture out, and conditioning the air both with heat and dehumidification. Sealing around and insulating the garage door would be huge. Get a thermometer with a hygrometer (humidity meter) to know when you have a problem. Iron (your saw table) starts rusting about 50%, steel varies with composition but 80% is typical. You may need just a bit of heat to get the RH below that. I live on a lake in East Tennessee. It is a temperate rainforest. I have heat and dehumidification in my new shop and no problem with rust. We are death on dehumidifiers around here, but I have had good luck with HiSense dehumidifiers. They have a humidistat so they just run when needed.

Rust is a problem and it is so evident on the brand new table saw. You can find people who routinely condition the surface with fine sandpaper and pad sander to maintain that look. They clean the surface down to bare metal and then wax or oil. I do not use sandpaper unless the rust got way out of hand (someone working in your shop set a cold drink on the saw table). I want that thin layer of oxide to protect the metal. It is that black oxide that is down in the fine grooves from the surface grinder. The surface is still smooth. I let that go, not everybody does.

[Erik Loza]

My experience = Accept or reject as like: All machines rust in shops. Some more so, some less so, but all do. Having a climate controlled space really helps but it’s inevitable at some level. Focus on keeping the cast iron work surfaces waxed, to avoid serious rust, but you’ll make yourself crazy trying to 100% prevent it.

Erik

[Frank Pratt]

Relax, it's a tool. Take reasonable care of it (which you do) & just use it.

[Mel Fulks]

Take a look at the Bullfrog rust blockers. They have treated covers and other products

[Alan Lightstone]

Relax, it's a tool. Take reasonable care of it (which you do) & just use it.

+1

We have a tropical storm / hurricane heading our way (if the cone is accurate). So I just went down and sprayed all my big machines with CRC 3-36. Out of curiosity, I checked the temp and relative humidity with the meter that lives in the shop. It's rainy season here, but the readings are pretty normal. 75F and 63% relative humidity with the split AC set at 75F. Totally normal readings for this part of Florida indoors. Upstairs in the house its 72F with 57% humidity.

No way you could get humidity below 50% here in any reasonable manner. So you take care of your machines, spray them every time you think of it, and do your best. Some minor rust will occur. As Erik said, "All machines will rust".

[William Hodge]

+1

We have a tropical storm / hurricane heading our way (if the cone is accurate). So I just went down and sprayed all my big machines with CRC 3-36. Out of curiosity, I checked the temp and relative humidity with the meter that lives in the shop. It's rainy season here, but the readings are pretty normal. 75F and 63% relative humidity with the split AC set at 75F. Totally normal readings for this part of Florida indoors. Upstairs in the house its 72F with 57% humidity.

No way you could get humidity below 50% here in any reasonable manner. So you take care of your machines, spray them every time you think of it, and do your best. Some minor rust will occur. As Erik said, "All machines will rust".

Do you guys in the south air seal and insulate?

In Massachusetts we air seal the attic, and anywhere else air flows through the building envelope. After that, we do a blower door test to see how tight the building is. If it's tight, we insulate with cellulose to R 40 in the attic, and whatever we can in the walls. Air sealing makes all the difference for keeping the houses humid in the winter, and dry in the summer. There is no chimney effect from holes in the ceilings.

So, getting to 45% or 50% RH in my shop is not a problem, even when the humidity outside is 90% during the day. We just had a heat wave, and the trunks of trees were condensing water, because the ground cools the trunks. All the rocks in the woods were sweating.

[Mel Fulks]

Not all of the Bullfrog stuff has to be applied. It is drawn to steel.

[Bruce Mack]

Another Minnesotan here. My shop is in the basement and has similar non-controlled humidity. I was upset at initial discolorations and acquired scratches. I found that rust erasers and ultra-fine silicon carbide paper created a different kind of blemish. The cast iron surfaces remained smooth whatever I did or did not. Like you said, they are harmless.

[Alan Lightstone]

Do you guys in the south air seal and insulate?

In Massachusetts we air seal the attic, and anywhere else air flows through the building envelope. After that, we do a blower door test to see how tight the building is. If it's tight, we insulate with cellulose to R 40 in the attic, and whatever we can in the walls. Air sealing makes all the difference for keeping the houses humid in the winter, and dry in the summer. There is no chimney effect from holes in the ceilings.

So, getting to 45% or 50% RH in my shop is not a problem, even when the humidity outside is 90% during the day. We just had a heat wave, and the trunks of trees were condensing water, because the ground cools the trunks. All the rocks in the woods were sweating.

Actually, very tight shop, and the wall to the garage is extremely well insulated (double 5/8" drywall, Green Glue in between, then R30 Rockwool, followed by double 5/8" drywall with Green Glue in between. Not sure many people have that much insulation in a wall, FWIW), but the largest wall area is cinderblock with stucco on the outside. Unfortunately, not insulated, but it is what it is. It's quite the luxury to have a shop this large down here in a house. Never seen one, actually.

I can dial in any temperature I want in the workshop. To freezing cold. But it's still a large shop and extremely humid down here.

Just checked my house RH. It's up to 72%. Ah, the storms coming....

[Steve Morrissey]

Thanks for the replies folks. Lots of good takeaways for me!

1. It seems these imperfections are a fact of life, and that the marks I highlighted in the picture aren’t anything to stress over and are alright if I don’t sand them out. Correct me if I’m wrong, but that was my read on these replies :)

2. Thanks for the pointers on various things used on the surfaces. I hadn’t heard of Boeshield before, looks interesting. I ordered some up.

3. I also like the suggestion to cover the tool tops with plywood or magnetic surface. I saw a video of a guy who does the magnetic cover on his bandsaw and it looks pretty straight forward, will be giving that a whirl because….:

4. While I like the suggestion of removing humidity from my garage, I’m not totally sure of the practicality. I have a dehumidifier, so I’ll be trying to run it in my 3rd garage stall that contains my shop, but I’m not yet certain it’ll be effective in the 3 car garage. Especially since I like to work with the garage door open, and with kids, the garage door is open a lot from their comings and going’s. At any rate, I’m down to try it, and can see it helping especially over night.

So yeah, thanks folks, this was super informative. It was a bit disheartening to sand and sand and sand and not see some of the tiny rust dots go away, but it seems that stems more from my lack of understanding on how pristine/rust free tool surfaces need to remain at all times.

Cheers!

Steve

[lowell holmes]

I coat my table saw with Johnson floor wax and it does not rust. I live in a moist climate. Sand the rust of with 120 sand paper and then coat the top with wax.