Grizzly Surface plate? Snag or Pass

[C-Bag]

I’m still very green at machining and have a shop full of lo buck used and heavily used Chinese and Taiwanese machines which I buy cheap and repair and upgrade. My first 9x12 grade B plate I bough from Shars and still use. I had to have at least one reliable reference for what I do. It has become my rough in quick reference and also use it with sticky back sandpaper for rough in surfacing before I go to a cast iron lapping plate. My main 18x24 grade A plate I bought used from a local machine shop when it went out of biz with stand for $65. It is kept covered and not used very often and had just been checked and certified right before I bought it. Yeah I’m not doing stuff for NASA but when I really want to know where there is a problem the surface plate is usually the final word when my various straight edges can’t find the answer.

 

[C-Bag]

After my morning constitutional (dog walk) bits and pieces of the previous comments have spurred further thoughts.

It’s always helpful to state as precisely as possible why you are contemplating a purchase. OP did an admirable job of outlining. But as we all know just about everything in this hobby is a deep subject and often my rabbit holes are triggered by Craigslist ads. When you start out you need everything and don’t know what’s relevant to what you think you are going to do.

Surface plates are a very deep and sometimes esoteric subject as I think OP is seeing. And a knackered surface plate is worse than useless. It can lead you astray. You have to know what you’re looking at with a used plate and a plate that is in a shop with a bunch of different users that is not kept covered and used with care with no inspection sticker is suspect. So should be priced accordingly. Even just used should be less than half of new and if un inspected recently less. It is expensive to have a plate inspected and resurfaced and most import plates they won’t even bother with.

 

[rwdenney]

I bought an inexpensive granite plate at Woodcraft for about a hundred bucks--12x18x3. It's within a couple of tenths, and I'd call it a good plate "for shop use" as opposed to "for inspection use". I thought I'd never use it. I use it all the time, for everything from checking wood plane flatness to assembling stuff that needs to be really square. Add a surface gauge with a scriber, and a height gauge (mine is a Starrett but it's a vernier scale so nobody wants it and I got it cheap) and it gets even more useful. I've been quite surprised by how often I use it--it has definitely not been a waste of a hundred bucks.

Have I graduated to needing a better plate with more accuracy and a larger surface? If I was scraping surfaces that needed to be really accurate, a surface plate with some bluing is the standard. But I can blue up my plate and identify the high spots on a surface even if I'm using my thumb behind a piece of sandpaper to lower that spot. So, I don't yet need something bigger or more accurate for what I do, but I wouldn't be without the one I have.

Rick "has never yet regretted buying precision measurement equipment" Denney

 

[thebrick53]

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.

However, anybody saying you hobbyists don't need a surface plate is talking out of their arse and you should probably consider it a sign they'rw not a reliable source of useful information!

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:

Absolute Beginners, Start Here!

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!

Wow I was not expecting such a passionate response! I have broken your comment down into a couple things that I would like to respond to.

First, what type of beginner am I. Well I had a thought on it and I would say I am not an utter beginner. More like a freshly pasteurized beginner. I have watched machining videos for about 4 years now with Blondie Hacks at my back bone with TOT, Inheritance, and Mr. Pete. I have also spent some time in a shop that still dose manually machining job shadowing.

Second, reason for wanting one. I personally want to make model steam engines and in my mind scribing and checking parallelism are a huge part of that. I can see myself using it for assembly of parts that need to be very square. These is definitely part of me that wants a surface plate because I thought it was necessary for any machine shop though.

Third, MAGNITUDE!!!! I have never though about metrology like this. I just put it to granted when I saw some one measure something that they just grabbed the right "magnitude" for the job!

With that and all the other opions I have seen here I will hold out from getting a SP just yet. Thank you for the passionate response once again!

 

[thebrick53]

How much accuracy do you require?
I do some precision work but most is +/-.005 and I utilize a poor-mans solution for a surface plate since I pretty much use it for scribing lines. I'm old school and it would would taboo to scribe lines with the edge of my caliper. I went to my Lowe's store and purchased 2- 12X12 ground marble floor tiles. I glued them together to gain some thickness and rigidity. I spent less than $10 and the accuracy across the surface is .001". Not perfect but well enough for what I do. If you opt for this option I would take a reliable straight edge and verify the flatness of the surface. The important part is that the surface is a ground surface with no coating of any kind. The tile I have is ground and polished.

This great to know! Definitely will use this when I need to do some flat sanding or similar preposes.

 

[thebrick53]

@C-Bag

but when I really want to know where there is a problem the surface plate is usually the final word

This what I think in my head makes it such a more useful tool! I will sure keep you second comment in mind when it comes time to purchase one.

 

[Aaron_W]

9x12 is a useful size to determine if you even need a surface plate. For the kinds of projects you describe being interested in, it may be all you need.

Small, not too expensive and worst case as mentioned it can become a lapping plate, paperweight, soldering platform etc.

I have a 12x18" cast iron and a 9x12 granite surface plate. They don't get used often, but they are occasionally useful and cost me very little. $55 is way to much though for used, you can get a new 2" thick 9x12" from Grizzly for $35 and a 3" thick 9x12" for $54. They are small enough that they don't get hit with special shipping fees.

Now getting a 24x36" surface plate and finding out you don't need it, that would be a nuisance, although I suppose you could use it as a tombstone.

 

[Ulma Doctor]

If you’re just setting up shop and want a surface plate, the grizzly plate will suffice. The plate is most likely precise enough for work coming from a hobby/garage shop .

You can even try your hand at scraping, but that would start a path to a grade A surface plate and a rabbit hole of epic proportions.

 

[coolidge]

Speaking of flat and straight a few years ago I purchased a 48 inch Starrett 1/4 inch thick straight edge that's flat to .0008 over the 4 foot length. I also abandoned wood workbenches for BuildPro welding tables which are flat from .000 to .0015 across the 22x46 surface. I have two of those for workbenches now. Straight, flat and true just makes everything else easier.

 

[m1kemex]

Thing is, seems like OP will not be doing any high precision job any time soon, so he doesn't *need* the surface plate right now. Need is completely different from *want*. Besides, anyone can do basic layout on the free surface plate that comes with every mill: its table.

A few sets of 1-2-3 blocks will probably more useful at this stage.

P. S. Hardened craftsmen get the job done with whatever they have available. The lack of a tool doesn't make a job impossible, just harder.