Rust Removal from Precision Cast Iron Surfaces in 2020: techniques and when to stop

[Brian Holcombe]

Also, as a general rule of thumb a sheetmetal square isn’t qualified to be used as a straightedge. A straight edge is specifically flattened on the edge and usually made with a cross-sectional shape designed to retain flatness.

[Bill Dufour]

Bill, I'll be blown away if that is true. Will make me rethink every piece I've ever made.

A study came out about two years ago that men can destern about 200 colors, women 1,000!
Bill D

[Kyle Iwamoto]

Razor blade. Living in the rust capital, I did think I've heard all rust removal processes. This is the first I've heard of using a razor blade. I think, can't recall hearing that before. Tried it yesterday, it does get rid of the thin rust spots. Works like a champ. I also used paste wax as a "lube". So I spent yesterday chasing those rust spots. That one I got with the razor blade has been bugging me. Ended up giving my saw a cleaning, vacuuming and wax job too. And ironically, I've been using razor blades as a glue squeeze out scraper, chisel cleaner, finish and/or CA on the lathe bed ways remover. Never thought of getting rust spots..... Oh yeah not to forget scraping down a finish drip/run. But I never get those.....
I just love this forum.
Thanks for that Matt!
Now maybe I have some time for that drill press column rust..... Nah. too hard. LOL.

[Devin Brenan]

I worked in an automotive machine shop, many times we were required to resurface parts becuase the mechanic took a scotchbrite wheel to a machined surface to clean off a gasket.

So if you think you aren’t affecting your table, you are wrong.

A light touch with scotchbrite (by hand!) with light oil as a lubricant.

I don’t see the logic in wrecking a surface to make it pretty, I’d rather have it ugly and flat.

Your response was what I was thinking a good portion of responses were going to be like, but you're in the minority..at least in this thread. Just a few of you responded this way. Most agree that it does affect the table (power tool with certain abrasives) but not to any degree that one should worry about for woodworking, maybe only metalworking like your machine shop example. I've got enough ammo now to make a well-informed 1st try, and I'll check things out with a feeler gauge set to see what was affected and by how much. If I can't live with it, I'll have it resurfaced. Thanks for the reply.

[Devin Brenan]

Also, as a general rule of thumb a sheetmetal square isn’t qualified to be used as a straightedge. A straight edge is specifically flattened on the edge and usually made with a cross-sectional shape designed to retain flatness.

Yea thought about that, but that square and some other woodpecker's squares are all I have that will fit within the 16" table between the raised ends. I have a 48" Starrett straightedge that I think was around $350 to $400 bucks...but nothing that accurate in a smaller size. For what it's worth, I did set that 12" sheet metal square down on my granite surface plate and could not get a 2 thou feeler gauge under either end or the center. Pretty good accounting for Lee Valley...or maybe it was just a good one.

[Brian Holcombe]

Yea thought about that, but that square and some other woodpecker's squares are all I have that will fit within the 16" table between the raised ends. I have a 48" Starrett straightedge that I think was around $350 to $400 bucks...but nothing that accurate in a smaller size. For what it's worth, I did set that 12" sheet metal square down on my granite surface plate and could not get a 2 thou feeler gauge under either end or the center. Pretty good accounting for Lee Valley...or maybe it was just a good one.

If that’s the case I would have it flattened because a depression down the center of the table means that you will be making material that is always crowned on one side.

On the other post you missed my point, my point is that the wheels do have an effect, so much so that surfaces that seal on a gasket could no longer seal after one session with the rotary disk. Whatever the surface becomes, it certainly won’t be flatter after that disk is applied to it.

Anyways that is my opinion based on my experience, do as you please with it.

[Devin Brenan]

If that’s the case I would have it flattened because a depression down the center of the table means that you will be making material that is always crowned on one side.

On the other post you missed my point, my point is that the wheels do have an effect, so much so that surfaces that seal on a gasket could no longer seal after one session with the rotary disk. Whatever the surface becomes, it certainly won’t be flatter after that disk is applied to it.

Anyways that is my opinion based on my experience, do as you please with it.

That's what I was thinking on the table wallow...that the boards would come out crowned, but others are saying on their planers with wallowed beds that if the infeed side bed roller is flat and set higher than all parts of the table anyway as is recommended, that they don't notice any ill effects on the boards. I'm gonna try it out, intrigued.

And no I got your point about the wheels; you're saying they can take off enough to matter. If you read some of the other replies, they're saying otherwise, for woodworking at least. Maybe the difference there is that metal mating machined surfaces like in your example won't tolerate that type of abrading. I'm sure those tolerances are much tighter than a cast iron woodworking surface.

I'll measure the surface with feeler gauges before and after my abrasive work to see how I changed it. Curious now. Will post what I get.

[Brian Holcombe]

Ill effect #2 is that parts finished in the center of the table will be thicker than those finished at the edges, so check for that also.

I generally read the ‘good enough for woodworking’ argument as ‘good enough for the work done in shop of the person making that statement’. There is no one Single standard for what is ‘good enough’ for woodworking.

I also read it as a general excuse for simply not wanting to deal with the hassle and expense of repairing the issue. Fine, totally acceptable and understandable at times.

[Patrick Kane]

Your thread made me check my T17's table last night. I have a .003" dip near the blade using my 48" starrett. Its about 2" wide, and im guessing this is front running a ton of rails/stiles. I understand Brian's point and mostly agree with him on the "good nuff" argument, but that .003" isnt worth the hassle of having the table planed. On a saw, im not even sure how the table's flatness would impact the cut. On a rip, i suppose the blade would be set to 90° by referencing off the .003" dip near the blade, so a 40" rip would possibly be out of square slightly. The planer's performance has a much more direct connection to the flatness of the bed. Like Brian said, in theory it will put a cup in each face, but im curious how much downward pressure your planer is able to exert on a board. For example, can the infeed roller really deform an 8/4 board to match the wear in the table? I honestly dont know. Im guessing it can squish a 3/4" board that is 16" wide, but i imagine that an 8-10" board of some thickness would require a ton of pressure to flatten it to the depression in the bed.

[Devin Brenan]

Your thread made me check my T17's table last night. I have a .003" dip near the blade using my 48" starrett. Its about 2" wide, and im guessing this is front running a ton of rails/stiles. I understand Brian's point and mostly agree with him on the "good nuff" argument, but that .003" isnt worth the hassle of having the table planed. On a saw, im not even sure how the table's flatness would impact the cut. On a rip, i suppose the blade would be set to 90° by referencing off the .003" dip near the blade, so a 40" rip would possibly be out of square slightly. The planer's performance has a much more direct connection to the flatness of the bed. Like Brian said, in theory it will put a cup in each face, but im curious how much downward pressure your planer is able to exert on a board. For example, can the infeed roller really deform an 8/4 board to match the wear in the table? I honestly dont know. Im guessing it can squish a 3/4" board that is 16" wide, but i imagine that an 8-10" board of some thickness would require a ton of pressure to flatten it to the depression in the bed.

I have a similar issue when I rip thin stock with the fence very close to the blade, but my problem is the insert plate and not the table itself yet. Try as I might, I can never get the d*mn insert plate perfectly flush with the table and this messes with the 90 degree cut of the blade and sometimes causes saw marks at certain spots along the rip cut as the top or bottom of the board is tilted into it. If the plate is set too low and the thin piece I'm ripping is light enough, the front left corner of the wood drops and tilts down a bit into the plate and then that tilts the top of the wood over and leftward into the blade, giving me a nice little reminder. If the plate is set too high no matter the size of the wood piece, the front left corner of the wood lifts up a bit and tilts the bottom of the wood more into the blade. In either case, when the wood the hits the end of the insert plate/table transition, I get another reminder. I find that setting the insert plate ever-so-slightly below the table is better. Regardless, you end up with two different angles on your edge, one that starts at 90 and then changes along the cut. I'm probably preaching to the choir.

For the planer, I think you're right about the board thickness (thicker is better for a bed wallow). Also realized I made a mistake in my previous post that you read...I said infeed roller when I meant to say the bed roller on the infeed side. Powermatic recommends that thing be set at around 0.08 above the table level, which as long as that roller is straight, would help to prevent the board from being smashed into the wallow.

[lowell holmes]

You can prevent rust from reappearing Johnsons Floor Wax.

[Bruce Mack]

There's rust and then there's rust. I've never had any issues as far as what you are worried about, when removing light surface with the usual means (R/O sander with a red or grey scotchbrite). If the surface is pitted, that could be a different story. What does the planer table actually look like?

Erik

This is a great thread. My Ridgid jointer has rust pox. Where can I buy scotch brite 5" hook and loop discs? I see them on line in quantity, but I'd like to buy minimally abrasive discs in single or 5-pack quantity, locally preferable but online is OK. Thanks.

[Eric Arnsdorff]

This is a great thread. My Ridgid jointer has rust pox. Where can I buy scotch brite 5" hook and loop discs? I see them on line in quantity, but I'd like to buy minimally abrasive discs in single or 5-pack quantity, locally preferable but online is OK. Thanks.

Bruce you don't need the hook and loop disc. The grocery store variety scotch brite pads will work fine with the RO sander.

[Bruce Mack]

Great. I have those in shop. Thanks!

[Richard Hart]

I kept it simple with my dad's Craftsman 100 table saw. (1964) It's a saw, not a moon rocket so I don't worry about hair splitting tolerances.

Soaking amount of wd-40 on the table.
220 grit on a sanding block.
Cleaned with denatured alcohol to get the wd-40 off.
3 applications of Johnson's paste wax. Slides like crazy!

Errata: machined pulleys and link belt. Might pass the nickel test