Surface plate refurb…

[wayne ollerenshawParticipant @wayneollerenshaw89933]

I am looking at a cast iron surface plate that needs by look of it a tidy up. I read a lot about scraping etc to resurface them.

As i am new to it. Why is milling the surface not ok ?

[Michael GilliganParticipant @michaelgilligan61133]

Because a Surface Plate worthy of the name needs to be much flatter than a Mill can achieve.

MichaelG.

[wayne ollerenshawParticipant @wayneollerenshaw89933]

so no then. shame as it is a good price. thought to mill then sand it.

 

so surface grinding best bet ? Its not going to be for ultra precise work.

 

i should go look at it maybe and see how bad it is. looks rough but  cant tell in pictures.

[noel shelleyParticipant @noelshelley55608]

iF IT’S anything BUT SMOOTH, FLAT AND SCRAPED  Then drill a hole in the middle and use it as a mud weight. Otherwise if you do not need the accuracy then use it as it is ? Noel.

[Roderick JenkinsParticipant @roderickjenkins93242]

Scotchbrite and oil will take any surface rust off without affecting the flatness.  Even a bit of pitting will not really affect its use as most things you will put on the plate will bridge any small depressions.  Not all workshop grade plates are surface ground or scraped.  Mine is planed and looks striped but is smooth to a 0.0001″ (tenths) dti.

Rod

[BazyleParticipant @bazyle]

A bit of plate glass is normally recommended for model engineers…..

[Roderick Jenkins]

On Roderick Jenkins Said:

Scotchbrite and oil will take any surface rust off without affecting the flatness.  Even a bit of pitting will not really affect its use as most things you will put on the plate will bridge any small depressions.  Not all workshop grade plates are surface ground or scraped.  Mine is planed and looks striped but is smooth to a 0.0001″ (tenths) dti.

Rod

Planed finish plates are normally grade B at best. The total flatness spec for Grade B plated up to 18″ square is 0.0002″ so even if it’s not delfecting a tenth indicator over the visible lines it’s highly unlikely to be flat to that limit.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, it does depend on exactly how flat you personally need it to be, and the size, as a large surface plate area will take more work than a smaller one will, in the link below, it shows a 7″ x 4″ approximately, one that I did on my Major milling machine.

https://www.model-engineer.co.uk/forums/topic/surface-plate-2/#post-622337

Using the dial gauge with my small surface gauge, hardly moves the pointer, wherever it’s moved over the whole surface, and I can feel a slight air suction between the surface plate and the surface gauge, when lifting it off, from anywhere it is placed. I’m not proclaiming it’s absolutely flat, but it is good enough for my needs.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Nicely done, Nick

Your second one is particularly interesting … it looks like Whitworth’s classic pattern.

MichaelG.

[wayne ollerenshaw]

On wayne ollerenshaw Said:

…  Its not going to be for ultra precise work.

 

i should go look at it …

True

MichaelG.

[Mike HurleyParticipant @mikehurley60381]

Unless you intend to be working to aerospace specs, probably more trouble than its worth. Plate glass is perfectly OK for general modelling work.

If you decide to try the plate, have you thought exactly how you would check its flatness once you had worked on it? Hand scraping takes time, care & patience to do properly. If you’re interested read this interesting short article on wiki at

https://en.wikipedia.org/wiki/Flatness_(manufacturing)

regards Mike

[Mike Hurley]

On Mike Hurley Said:

Plate glass is perfectly OK for general modelling work.

Very true. I would recommend looking at small Mitutoyo surface plates. We have a couple and I bought them because it surprised me how cheap they were. Even though it was pre Covid looking at their website the prices haven’t changed much.

Looking around, generic Chinese surface plates from the usual suppliers are £60 and up for a 12″x12″ one. I’m not sure why anyone would waste time with a lump of old scrap that would probably cost the same.

[duncan webster 1Participant @duncanwebster1]

First thing to do is work out why you want a surface plate. I’ve got one which I very rarely use. Even when I worked at place which made 15″g locos we had one but very rarely used it

[Chris Evans 6Participant @chrisevans6]

Wayne, If you are within easy reach of Lichfield Staffordshire I have a cast iron surface plate that I would give you. Unused for ten years and sadly I must give up my workshop and all of my machines.

Chris.

[wayne ollerenshawParticipant @wayneollerenshaw89933]

Sorry late getting back to you guys. And gals maybe???

 

Mad busy and popped straight out to get the plate. Defo needs something as a fair lot of dings in it. Nothing that cant be fixed though.

Yes some may say its a mud weight, as already have but i like a challenge and to fix stuff.

 

It cost me £40 so no big deal.

 

I just use some Kerosene as its all i have at the minute to scrub it down to see whats what.

 

 

seen that and thought well, a bit of a blast with the DA and 240g with kerosene will do no worse than it is.

 

 

Its not to bad for being flat really looking at it with the piece of machined Sapele i have here 🙂 🙂 ;);)

 

So now to decided when to sort it out.

Happy with it anyway. even if for a nice work surface wen faffing.

 

[wayne ollerenshaw]

On wayne ollerenshaw Said:

Sorry late getting back to you guys. And gals maybe???

 

Mad busy and popped straight out to get the plate. Defo needs something as a fair lot of dings in it. Nothing that cant be fixed though.

Yes some may say its a mud weight, as already have but i like a challenge and to fix stuff.

 

It cost me £40 so no big deal.

 

I just use some Kerosene as its all i have at the minute to scrub it down to see whats what.

 

 

seen that and thought well, a bit of a blast with the DA and 240g with kerosene will do no worse than it is.

 

 

Its not to bad for being flat really looking at it with the piece of machined Sapele i have here 🙂 🙂 ;);)

So now to decided when to sort it out.

Happy with it anyway. even if for a nice work surface wen faffing.

 

On Chris Evans 6 Said:

Wayne, If you are within easy reach of Lichfield Staffordshire I have a cast iron surface plate that I would give you. Unused for ten years and sadly I must give up my workshop and all of my machines.

Chris.

Thanks for that Chris i am over a couple hours away. Although i probably would of taken you up on it if i seen this sooner. I maybe could do with some gear though…..have you any sales adverts going.

[wayne ollerenshaw]

On wayne ollerenshaw Said:

a bit of a blast with the DA and 240g with kerosene will do no worse than it is.

It just needs light work with a stone to take the high spots off the marks.

[noel shelleyParticipant @noelshelley55608]

That’s not a mud weight ! You did well for £40. Good luck. Noel.

[Chris Evans 6Participant @chrisevans6]

Hi Wayne,

My Bridgeport mill and Excel lathe are advertised here. Small stuff, angle plates, rotary tables, Donkey saw etc to follow.

Chris.

[bernard towersParticipant @bernardtowers37738]

dont know how accurate people work to at home but I machined a 8” x 6″ surface plate at home from a raw casting and it seems to be flat enough for the work I do. I thought if you were going to scrape a surface plate you had to have some kind of master reference?

[Pete RimmerParticipant @peterimmer30576]

That plate will be fine for general setting out/measuring tools stuff like that if you just knock off the burrs with a stone or burr file. It’s a long way off being fit for scraping duty though.

[Steve355Participant @steve355]

Flat and smooth are not the same thing. It have have a surface that’s rough as a badgers and still be engineering flat. Well not quite, but you know what I mean. It may well be absolutely fine.

To scrape it you need a certified flat surface that is bigger than it, which you don’t have. To check flatness you need some fancy tools which you also don’t have.

Scraping is a really interesting process, I scraped my vintage surface  grinder back into tolerance. It took months and unlimited patience. To do that I bought a granite surface plate as I didn’t trust my cast iron surface plate which was similar to yours.

I’d say …. Decide on your tolerance. If you are happy with 0.0005 for the work you do, get a 0.0005 feeler strip (or thinner if you can find one) and some good quality straight edges (e.g. engineering squares) and see if you can find anywhere you can get the feeler strip under the edge. If not, it’s usable for you. If you can, it’s probably scrap.

if you are using it for, say, marking up work with a height gauge, testing flatness and squareness of parts you are making, that’s a very different proposition from using it as a reference for bluing and flattening other surfaces – which is why I got my granite one for scraping the surface grinder.

my 2p anyway.

Steve

[Alan DonovanParticipant @alandonovan54394]

Posted by Noel Shelly.

…  Then drill a hole in the middle and use it as a mud weight.

Hello.

The term ‘mud weight’ ………  I hate to show my ignorance but this term has been used more than once in the above thread,  is this a slang term for simply scrap iron, or a slang term (maybe?) for a specific item of engineering equipment.  I have not heard this term before.  Wickipeadia only references the weight of ‘drilling mud’ for Oil Wells for the term.

Regards.   Alan.

 

 

 

 

 

[Alan DonovanParticipant @alandonovan54394]

Posted by Bernard Towers.

…….  I thought if you were going to scrape a surface plate you had to have some kind of master reference?

Hi Bernard

You are absolutely correct in what you say, but there is a method of producing flat surfaces by means of using three plates.  By systematically checking one against another and scraping to suit you eventually end up with a flat surface to all three.  The ‘three plate method’ is also referred to as the ‘Whitworth Method’.

If you are interested in more detail, there is quite a bit on the internet.

Regards.  Alan.

[Iain DownsParticipant @iaindowns78295]

On Glass for surface plates, I bought a piece of about 15 mm thick 30mm x 50mm (or thereabouts) a few years back.

It was as flat as the Himalayas!  Well – clearly an exaggeration.  But it was out of flat by at least 0.25mm over the  surface.

A colleague of mine who used to be a glass quality inspector (who knew) and later a CNC engineer told me that the requirement for flatness of glazing glass was around 0.5mm per metre.  Which this bit met.

I ended up throwing my bit away as it was no use.

Clearly this is not a universal experience, but thought I should mention.

 

Iain

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