Why Cast Iron?

[Peter Aeschliman]

So here's a potentially stupid but potentially interesting question. :)

Why do most high quality woodworking machines come with exposed cast iron tables and surfaces?

I'm completely sick of cleaning and waxing my cast iron surfaces. I understand that cast iron is heavy and stable, and that the machining process that makes them flat leaves exposed cast iron behind.

I guess my question could be asked a different way: Why aren't cast iron surfaces treated with something to keep them pristine, smooth, flat, and rust-free? There has to be some chemical out there that could do this... like paint.

Talk amongst yourselves. ;)

[Rich Engelhardt]

There has to be some chemical out there that could do this... like paint.

There are several HPAC coatings that will work.
How many hundreds of dollars extra would you care to spend?

[Callan Campbell]

I'm sure the cost of painting or coating them factors into the equation somewhere when you're dealing with the lower end of the market. Higher end tools and machines often have more money attached to the finishing side. From what I've seen of older machines, paint was applied to many more sufaces than it is now. That means slower output from a factory while you're waiting for the paint to dry enough to move the machines around or out the door.
Although I could take a brush to all the sides or bottoms of my cast iron tables on all my machines, I don't, probably like everyone else. I just wax or apply a coating of Boeshield once in awhile. And that's just to the top and any bare sides.
Maybe you're the guy Steel City was aiming for with their Granite tables on their tools. Or the coated ones that were out before the Granite.
As for the actual worksurface, I think plain cast iron is the way to go, no coating to rub off or transfer to your work. I like the patina that the cast takes on with age as well.

[Joe Jensen]

One of the few benefits of living in AZ, no rust :)

[David DeCristoforo]

You asked...

"Why do most high quality woodworking machines come with exposed cast iron tables and surfaces?"

You then said...

"...I understand that cast iron is heavy and stable, and that the machining process that makes them flat leaves exposed cast iron behind."

It might be suggested that you answered your own question...

[Michael Dunn]

Must be nice!!! Before I learned how to care for my cast iron surfaces, they would literally have rust over night!

Hey, at least I can get a decent pizza. Sweet home Chicago!!!!

If I have my way (and I usually do!!!) I'll be joining you in AZ sometime, someday.

shotgunn


One of the few benefits of living in AZ, no rust :)

[Frank Drew]

I don't pretend to understand the chemistry involved, but the cast iron surfaces in my shop, both old and newer machines, were more or less rust free in situations -- prolonged periods without heat or air movement, essentially -- that left the steel surfaces completely covered in rust.

[Peter Aeschliman]

You asked...

"Why do most high quality woodworking machines come with exposed cast iron tables and surfaces?"

You then said...

"...I understand that cast iron is heavy and stable, and that the machining process that makes them flat leaves exposed cast iron behind."

It might be suggested that you answered your own question...

Not exactly. I understand the benefits of cast iron, but I want to know why nobody has addressed the major drawback (rust). I like the cast iron, I just don't like the rust.

I just bought a Sawstop, so no granite tops for me... at least not for a long time.

I'm no chemist, but we can put men on the moon. There must be some kind of permanent clear coating that manufacturers can put on the cast iron to solve the problem...

[Brendan Plavis]

There is.... but do you want to see the price of tools double? I certainly dont... Ill rather stick with my money, and just use floor wax and deal with the rust, than to part with more of my money, and have the benifit of no rust.....

[Chip Lindley]

Frank, probably your CI surfaces were treated with wax, etc. to prevent rust at one point or the other. CI is porous, and residue of the treatment is left behind. I doubt your steel was ever treated? Am I wrong?

I have had two BAD episodes where all the equipment in my shop was still cold from winter temps. Suddenly, warmer foggy air moved in and condensed on every exposed surface. RUST CITY!!! No amount of wax could save me! Only covering the machines with plastic to prevent DEW forming would have helped.

Hey! Perhaps SawStop might plate their tablesaw tops in black chrome to stay Wayyyyy ahead of the competition? No doubt there are many takers out there. Hmmm...

[Michael Dunn]

I agree, plus it's nice to stand back and look at the beautiful cast iron surface that you may have restored or just maintained yourslef. I love my cast iron surfaces.

[Peter Aeschliman]

There is.... but do you want to see the price of tools double? I certainly dont... Ill rather stick with my money, and just use floor wax and deal with the rust, than to part with more of my money, and have the benifit of no rust.....

And that is the question, my friend. What is the product you have in mind, and how much does it really cost?

If it's labor that's the problem, I'm not afraid of a little elbow grease. I'd be happy to apply it myself. If it's the chemical itself that's expensive, that's another story.

This is the discussion I'm trying to foster.

[Peter Aeschliman]

I agree, plus it's nice to stand back and look at the beautiful cast iron surface that you may have restored or just maintained yourslef. I love my cast iron surfaces.

Couldn't agree more. When I unpacked my sawstop and cleaned off the grease, I was grinning ear to ear looking at that beautiful cast iron!

I cleaned and waxed the top immediately, but unfortunately within a few weeks it was already starting to show faint signs of rust.

I'm considering a dehumidifier for my shop, but I'm worried that it will cause a difference between the humidity in my shop air and the humidity of the homes where my projects end up living.

My shop has a concrete floor, so I'm also considering putting in a moisture barrier and a cheap laminate floor (ala ikea) to keep some of the moisture out of the air.

But in my mind, the best option is to have tools that don't rust over! ;)

[Dan Lee]

As far as tops didn't one mfgr offer CI top plated with titanium or something? It was kinda bronze color.

[Bruce Page]

One of the few benefits of living in AZ, no rust :)

New Mexico too.

[Bruce Page]

One surface treatment that is both highly durable and rust resistant would be hard-chrome plating. Machinery with hard-chrome plating in the wear areas is pretty common in machine shop machinery. Trouble is most people wouldn’t want to pay the extra cost…

[Rich Engelhardt]

If it's labor that's the problem, I'm not afraid of a little elbow grease. I'd be happy to apply it myself. If it's the chemical itself that's expensive, that's another story.

Labor per say isn't the issue. It's skilled labor, plus the right equipment & the correct hi performance coatings.
I can think of a few powdered metal coatings, a couple of moisture cured coatings as well as some acid etching primers that could be applied to the cast iron surface, that would be tough & durable enough to resist wear.

As a "Joe Homeowner" type,,,trust me ,,your neither equipped with the right equipment nor do you have the skills/training to mess with that type of product.

I'll go back to my original answer - how many hundreds of dollars extra are you willing to spend?

Bear in mind - the working surface is worlds more critical than the sides.
100% adherance to the tolerances must be observed.
That makes application of any type of film coating extremely difficult to do except under controlled conditions.

[Kyle Iwamoto]

Have you tried Boeshield?

I have a SS and live in the rust capital of the world. Salt air and high humidity. Works good, spray on and wipe off. I also do either Ren wax or more recently went to Johnstons paste, since I like to use the Ren wax for actual wood polishing. Either wax works, Ren wax is expensive.

Oh yeah, I do like the CI look and actually like to polish and care for the top. I may be in need of some psychiatric help.

[Peter Aeschliman]

Labor per say isn't the issue. It's skilled labor, plus the right equipment & the correct hi performance coatings.
I can think of a few powdered metal coatings, a couple of moisture cured coatings as well as some acid etching primers that could be applied to the cast iron surface, that would be tough & durable enough to resist wear.

As a "Joe Homeowner" type,,,trust me ,,your neither equipped with the right equipment nor do you have the skills/training to mess with that type of product.

I'll go back to my original answer - how many hundreds of dollars extra are you willing to spend?

Bear in mind - the working surface is worlds more critical than the sides.
100% adherance to the tolerances must be observed.
That makes application of any type of film coating extremely difficult to do except under controlled conditions.

Makes sense, I guess! Maybe I'm naive, but couldn't a guy get some kind of rattle can of "something" and use a good long sanding block to smooth it between coats? I my mind, if your sanding block is flat and your table is flat, it would be tough to screw up.

I have not used boeshield on my cast iron, no. I've used top saver, past wax, and lately "Slip-it".

All of them require weekly application to avoid any kind of rust.

[Neil Brooks]

I don't have any skin in this game.

As the brother of the Product Rep for MagSwitch, I was the idiot who bought an aluminum-topped table saw :rolleyes:

But ... what I always wonder (sincerely) is why I don't get the sense that MORE people employ DE-humidifiers in their shop -- both for the wood AND for the tools.

Heck, if you live in the steamy areas ... for pure comfort, too.

ISTR they're fairly cheap, cheap to run, fairly reliable, etc., etc.

:confused:

[Derek Noel]

If i remember my material property classes correctly one important material property of CI is its ability to dampen vibration.
Also, casting iron is much cheeper that forging or machining steel.
I suspect any coating that is not worth more than my saw would ware off, scratch, or chip.

[Michael Dunn]

I'm in Chicago, it is pretty humid all year round here (85% minimum usually) I use T9 Boeshield liberally. I let it dry overnight, then buff aggressively. Then I use Bostik TopCote. I don't know how this system would handle, say actually being rained on... But it makes my cast iron tops impervious to the humidity.

You NEED this stuff. Buy it now!!!

First this... (technically use Mineral Spirits to remove whatever may be on there now)

http://www.amazon.com/Boeshield-61974-T9-12oz-Aerosol/dp/B0011G0HT6/ref=sr_1_4?ie=UTF8&s=sporting-goods&qid=1272071449&sr=8-4

Then this...

http://www.amazon.com/Bostik-10220-Aerosol-Top-Cote/dp/B0000223UD/ref=sr_1_1?ie=UTF8&s=hi&qid=1272071478&sr=8-1-catcorr

Use this method. No rust period. Then Bob is yer uncle.

shotgunn


Couldn't agree more. When I unpacked my sawstop and cleaned off the grease, I was grinning ear to ear looking at that beautiful cast iron!

I cleaned and waxed the top immediately, but unfortunately within a few weeks it was already starting to show faint signs of rust.

I'm considering a dehumidifier for my shop, but I'm worried that it will cause a difference between the humidity in my shop air and the humidity of the homes where my projects end up living.

My shop has a concrete floor, so I'm also considering putting in a moisture barrier and a cheap laminate floor (ala ikea) to keep some of the moisture out of the air.

But in my mind, the best option is to have tools that don't rust over! ;)

[Michael Dunn]

Yup, me too. Once I learned how to care for it, I quickly started to enjoy the process.

Not to mention I LOVE the smell of T9 and TopCote.

I too, may in need of (further) phsyciatric (and immediate medical) help.


Have you tried Boeshield?

I have a SS and live in the rust capital of the world. Salt air and high humidity. Works good, spray on and wipe off. I also do either Ren wax or more recently went to Johnstons paste, since I like to use the Ren wax for actual wood polishing. Either wax works, Ren wax is expensive.

Oh yeah, I do like the CI look and actually like to polish and care for the top. I may be in need of some psychiatric help.

[Joseph Tarantino]

peter......do you cover your CI when it's not in use? i have never had a rust problem once i learned to clean it, wax it and, most importantly, when not in use, cover it. note my motiser. it's the only CI tool i neglected to cover over the winter. cleaned it and waxed it last summer, didn't cover it and it rusted. note the jointer, table saw and band saw. just like the mortiser, they were cleaned with topsaver, waxed with johnson wax and covered when not in use. and the table saw is only covered with the outfeed table, which folds onto it. no fancy cover there. i'm just north of NYC and my tools are in an unheated garage and i've covered them with wood, blankets, those gray covers that htc sells (like on the jointer), etc.

doesn't seem to matter what they are covered with, as long as they are covered. HTH.

[Paul Ryan]

I have had two BAD episodes where all the equipment in my shop was still cold from winter temps. Suddenly, warmer foggy air moved in and condensed on every exposed surface. RUST CITY!!! No amount of wax could save me! Only covering the machines with plastic to prevent DEW forming would have helped.




I deal with this senario almost every spring. My advice keep your tool surfaces coverd with something that sits right on the surface. It can be a simple as blocks of wood, a cross cut sled, or as nice as a magnetic cover. I made a cross sled that covers the cast iron on my sawstop pefectly and I also have a magnetic cover that I use to protect the surface when used for operations other than cutting. And wax the heck out of the top. A few of coats, to get you started, and then a coat about once every other month unless used heavy. T-9 works well in a pinch but I think coats of wax work just as well. But the covers are key. My shop floor sweats in the sping and the air inside is like pea soup. But with the covers and wax I have the tamed rust problem.

Granite topped saws are the nice but the company making them is kind of falling away I think.

[Myk Rian]

I have had two BAD episodes where all the equipment in my shop was still cold from winter temps. Suddenly, warmer foggy air moved in and condensed on every exposed surface. RUST CITY!!! No amount of wax could save me! Only covering the machines with plastic to prevent DEW forming would have helped.
That's why I cover my TS and jointer.
Some people see no need for it, but I'm a believer after having an episode of rust from the weather.

[Jeff Duncan]

My guess is that most shops that have traditionally bought "high quality" tools have been pro shops that don't deal with the same conditions homeowners seem to. I've got a fair amount of iron in my shop and no problems with rust. It's heated in the winter, though it gets humid as heck in the summer.
I'm guessing condensation is the culprit for most of the rust problems people are having?
JeffD

[Neil Brooks]

I'm considering a dehumidifier for my shop, but I'm worried that it will cause a difference between the humidity in my shop air and the humidity of the homes where my projects end up living.



Peter-

I missed this.

My thoughts:

- At what RH does rust form on CI?

- How much lower than that would you need to go? (Effectively ... not lower)

- Dehumidifiers (some, at least) have humidistats to control the level

- How much difference, then, would there be between your shop and the destination for the piece?

- How much difference in EMC would that really amount to, and what effect would that have on your projects, actually?

[Neil Brooks]

The first answer I found showed that 50% or less, RH, will almost certainly nail it, but that 35% RH WILL nail it.

Provided you don't eat your pork rinds OFF OF your CI top:

http://www.corrosionist.com/effect_relative_humidity_corrosion_chemistry.htm

Can you fill in my other blanks ??

[Mark Woodmark]

Cast Stainless Steel

[Neil Brooks]

I live in a DRY climate, and have a whole house (ADDS) humidifier.

Shop's in the basement. RH runs 46-50%.

I DO have CI on my band saw and on my jointer/planer.

I've never seen a spot of rust on either, and I do NOT make a hobby out of putting Johnson's Paste Wax on them, weekly.

There.

Back to you :)

[george wilson]

In case no one said it,cast iron's graphite content helps prevent wear. Years ago,some company tried making large jointers with steel tables. Running plywood over them soon grooved the steel.

[Rich Aldrich]

Cast iron is used because it remains flat, absorbs vibration, is inexpensive compared to stainless steel, and is heavy.

Cast iron normally has no residual stress that can warp a flat surface. If stress remains in a piece after it is formed and machined, temperature, loading while in operation, vibration, etc. can cause the stress to relieve which will warp a flat surface.

Cast iron has a way of absorbing vibration probably due to its porosity.

Stainless steel is expensive. Many of us couldnt afford to buy a piece of equipment made of stainless. Cast iron is one of the most affordable materials pound for pound.

Cast iron is heavy. When dealing with wood, you need the weight in the machine to counteract the forces we put on the machine while machining wood.

A lot of manufacturers do not want to add the cost of rust preventive coating to the cast iron. They also need to make sure the coating doesnt chip, will not mark the work piece, etc. I think there are coatings out there that would hold up in these applications, but they dont want to take a chance either price wise or affecting our materials.

I use Boeshield and have no problems, but I am in the north. This was developed by or for Boeing in Seattle where the humidity is a killer for bare machine surfaces.

Some of our best frames on our paper machine are cast iron. The ones that are welded steel are good as long as the weldment is stress relieved before machining.

We had a suction roll shell that was made from rolled and welded stainless steel that was supposed to be stress releived. It was in the easiest application possible for a suction roll shell, but bent the first time the shell was ground. We have to grind the shell to keep the shape with in 0.002" diameter accross the machine. After grinding, the shell bent while in the machine. It wasnt dropped or anything abnormal. It started to wabble while in the machine.

[michael osadchuk]

One more recommendation here that you deal with the temperature/relative humidity issues in your workshop........

... I have a basement workshop north of Toronto, Canada; the shop is well insulated and never goes below around 55 degrees Fahrenheit; no air conditioning of any sort; while it experiences seasonal ranges in relative humidity between 30 and 70% and I never get any rust on any tools.......


.... I don't have a precise answer regarding what climate conditions you would need to maintain in your workshop (and what to do to maintain them) but I suggest that you research "dewpoint" as a topic and buy a digital temperature/relative humidity gauge with minimum and maximum recording capacity as aides to sort out what is happening to your workshop environment......

good luck

michael

[Gerry Grzadzinski]

Another Topcoat fan. Use it once or twice a year, and it's been years since I've needed to remove rust from any of my tools.

[Peter Aeschliman]

Thanks guys for all of the information and replies. All great advice. I think we've pretty much answered my question about cast iron- the answer seems to be proper preventative maintenance...

Neil, unfortunately I haven't the foggiest clue what the RH is in my shop. But I think I would be interesting for me to investigate.

I do actually have magnetic covers that I made for most of my tools. I need to make one for my sawstop since I gave away the old cover with my old saw when I sold it. I bought some magnetic sheet stock (same stuff used for signs that people stick to their cars for advertisements) and cut it to size.

The tools that get covered still don't stay pristine... they don't really rust, but they seem to tarnish a little.

I think a dehumidifier might might be the ticket.

Thanks again everyone... an interesting thread.