You say you got your first mill and lathe but is that the first mill and lathe you've used in your life or first mill and lathe you've personally owned?
Some of us are utter beginners when we first set up our shops, some walk in to our newly created shops with experience already under our belts (I was and still am, a year later, a rank beginner).
If you'rea beginner like me, then at this point in your hobby 'career', right now you don't
really need a surface plate. There are plenty of other things you can spend your money on that will be much more useful.
Since nobody else has asked,
is there something you want to achieve that you reckon you need a surface plate for or have you just got the impression it's an early requirement for any well set up workshop. Or do you just damn well want one because they're 'machinist cool' (and indeed you're right, they are.
)
As an aside, anybody buying a new Chinese 7x mini lathe probably
would find a surface plate very useful early on, but that's more an indictment of the QC of Chinese 7x mini lathes, than a recommendation for early purchase of a surface plate!
As for small used surface plates generally?
Smaller used plates have a much higher chance of being knackered to a point of uselessnes: there's a minimum size of likely scratch, chip, dent or ding that can matter to any size surface plate, and much less space for any damage on a smaller surface plate, therefore, any damage will have a greater effect on the fundamental usefulness of the plate.
One thing I'd say is that a surface plate really ought to be reasonably flat to within
much less than a thou over its surface overall. For high quality used plates, it doesn't matter if there are a few dents or scratches; you can avoid using those areas but generally, you're probably looking for the deviation from flatness to be
at most half a thou or really a couple of tenths. Same goes if you're buying new but more so since you paid for a new, pristine surface plate.
The reason is for that is that you want your metrology kit to be about one magnitude of order higher resolution, one magnitude of order more precise, and one magnitude of order more reliable/repeatable (probably okay at half a magnitude of order but whole magnitudes of order are easier to reason about). If you're working to single digit thous (0.001) then your metrology kit should be relied on to give you at least half a tenth (0.0005) resolution, precision and repeatability.
If you really
do want a surface plate (and to be fair, if you stick with this hobby for any amount of time, you will end up if not actually
needing one, finding a surface plate
very useful), then something about 12" by 12" or bigger would be much more useful.
You can pick up bigger cast iron plates used, or there should be a fair number of new import 12"x12" or 16"x12" granite plates available for sensible money.
One thing I noticed on the Amazon.co.uk reviews of the various import surface plates, was that during the pandemic, the quality of these plates dropped significantly, but now seems to have come back up.
BTW, nobody from NASA will be using these import plates but they'll do for hobby purposes for
most hobbyists.
If you buy new, it
is possible you might be sent a low quality or even damaged one (the packaging has got better in the last couple of years but there's no accounting for delivery services), so try to make sure you can send it back for a replacement, if so.
So, I'd steer you away from this particular one in general and wait until you definitely need one. If you're sure that time is now, then the rest of my post might be helpful.
Oh and if you haven't watched these three videos yet, I 'd definitely recommend watching them:
If you've never even touched a machine tool before, but want to learn, start here!
youtube.com
BlondiHacks has a lot of really good videos (the lathe skills playlist and the mill skills playlist are very good for beginners; I go back and rewatch some of them from time to time) but her "Absolute Beginners Start Here" playlist really is great.
Also this:
is worth watching for her thoughts on the reasons we as beginners but tools we don't need!
