Cast Iron Surface Plate clean up and inspection

[rmcphearson]

Greetings,

I just brought a 24x36x5 Challenge brand CI plate home. It has what looks to be the original baby blue stand and there are 2 ID tags on the front reading 94-A and 4302. The underside webbing is in a rectangular pattern and is also painted baby blue. There is some paint overspray and crud on the top that I can't get off with paint thinner, a plastic scraper and a scotchbrite. Any suggestions to get the surface cleaned?

Thanks,
Roland

 

[sfriedberg]

Don't be afraid to try a razor blade scraper.

 

[Demon69]

A stanley or razor blade to get the worst off, then stone respectfully with mineral spirits, I like aluminium oxide.

 

[Milland]

Any reason you've not used actual paint stripper? The stuff sold now may take more applications then the old (dangerous) brews, but it still works...

 

[metalmagpie]

Torch with a soft flame to soften the paint, then plastic blade to remove it. Won't get it all but will get most and make getting the rest easier. Dishwashing detergent will eventually remove paint. Tilt your plate and cobble up a system with a pond pump and a hose and bucket and let the dishwashing detergent run over the overspray?

 

[rmcphearson]

A razor blade on the end of my Biax hand scraper worked well. It gouged the surface (barely) if I got wild with it. No need for chemicals. Thank you for the suggestion. There is a plethora of scratches and gouges but not deep, looks like I have a pretty good surface overall. Next step is to stone it.

Thanks,
Roland

 

[lucky7]

How do you plan to check your plate for accuracy?

I have a couple of Challenge plates that I’ve rescraped and seem to be stable. Like em!

L7

 

[rmcphearson]

I stoned them with the bottom/virgin surface of some large Norton sharpening stones that I have with a touch of mineral spirits.

How do you plan to check your plate for accuracy?

I have a couple of Challenge plates that I’ve rescraped and seem to be stable. Like em!

L7

I don't know yet. My shop here at home is sparse, I don't have hardly anything here yet to do even basic checks. I've been thinking about lapping it and then have it checked professionally. I've scraped a couple straight edges using this plate and then checked the SEs on my granite plate at work. The print pattern I get from my CI plate and my granite plate at work is a little different but not way off.

 

[lucky7]

If you have a granite plate in current A grade spec at work and lifting gear, I’d be renting time on it from the boss/owner and rescraping your iron Challenge plate from it. What folks around here used to call Saturday morning jobs.

L7

 

[projectnut]

Greetings,

I just brought a 24x36x5 Challenge brand CI plate home. It has what looks to be the original baby blue stand and there are 2 ID tags on the front reading 94-A and 4302. The underside webbing is in a rectangular pattern and is also painted baby blue. There is some paint overspray and crud on the top that I can't get off with paint thinner, a plastic scraper and a scotchbrite. Any suggestions to get the surface cleaned?

Thanks,
Roland

I've had the same plate for a number of years. According to the manufacturer there are 2 different models. Model TP-2436-GR is "precision ground" and should be accurate to within .001". Model TP-2436-SC is hand scraped and should be accurate to within .0005". I have the hand scraped model that was last certified in 2016. It's been in my shop since 2017, but I've never checked it for flatness. They are heavy in that they weigh 475 lbs.

 

[dcsipo]

If you have a granite plate in current A grade spec at work and lifting gear, I’d be renting time on it from the boss/owner and rescraping your iron Challenge plate from it. What folks around here used to call Saturday morning jobs.

L7

Even with a biax it may take a couple of fo Saturday mornings. I have not scraped anything that large. My CI surface plate is only 15x12 or so, but even that was a bitch to get on and off the granite. One thing I learned, you have to be able to rotate the plate for every spotting or you might be chasing a slight pretzel on your target. Make sure your reference is large enough.

 

[dcsipo]

I stoned them with the bottom/virgin surface of some large Norton sharpening stones that I have with a touch of mineral spirits.


I don't know yet. My shop here at home is sparse, I don't have hardly anything here yet to do even basic checks. I've been thinking about lapping it and then have it checked professionally. I've scraped a couple straight edges using this plate and then checked the SEs on my granite plate at work. The print pattern I get from my CI plate and my granite plate at work is a little different but not way off.

If you have a 4' SE scraped to the granite you could verify the surface plate. You might not be able to accurately measure from it because of the potential sag of the SE, but you can spot it in the union jack pattern.

 

[lucky7]

I have scraped stuff that big, and you’re correct, it takes time. For this guy’s project I think it depends on access to a Biax (I wouldn’t do it without), how worn it is, and how many ppi the guy wants. It won’t be a two Saturday morning project. ;-)

I find larger square surfaces the most difficult. Can’t hinge directly off a plate, need to futz around checking with shorter straight edges etc.

L7

 

[rmcphearson]

I've had the same plate for a number of years. According to the manufacturer there are 2 different models. Model TP-2436-GR is "precision ground" and should be accurate to within .001". Model TP-2436-SC is hand scraped and should be accurate to within .0005". I have the hand scraped model that was last certified in 2016. It's been in my shop since 2017, but I've never checked it for flatness. They are heavy in that they weigh 475 lbs.

Thank you for that info.

Regarding spotting this thing on top of a granite plate. No way I’m moving this thing again. I’d rather be slathered with butter and locked in a cell with a hungry Whoopie Goldberg.

I may divide it in half and scrape each side using a 18x24 master or some variation of that. This thing IS beckoning me to scrape it or lap it. I can hear it calling me at night when I’m trying to sleep.

I’ve also thought it might make one hell of a base for my Cataract lathe (which needs a base).

 

[dcsipo]

Thank you for that info.

Regarding spotting this thing on top of a granite plate. No way I’m moving this thing again. I’d rather be slathered with butter and locked in a cell with a hungry Whoopie Goldberg.

I may divide it in half and scrape each side using a 18x24 master or some variation of that. This thing IS beckoning me to scrape it or lap it. I can hear it calling me at night when I’m trying to sleep.

I’ve also thought it might make one hell of a base for my Cataract lathe (which needs a base).

You can scrape it flat using a long SE and a small surface plate. Spotting and leveling become a lot more complex. There was a youtube video, I cannot find right now, where two guys scrape a 4'x8' or so cast iron plate using a small something like 12"x18" plate as a local reference and long SEs and differential levels to assess overall flatness.

I do not get the woopie butter thing...I like butter and do not care for whoopie much, I do not know how much she likes butter. But this is disturbing on many levels