# Surface Plate



## SRay53TxTn (Jan 3, 2021)

How important is a surface plate to a home hobbyist with a new PM728 mill coming soon?
Just trying to get my top ten mill tools in hand before it arrives.


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## Ulma Doctor (Jan 3, 2021)

i would purchase tooling and such for the mill first, then worry about the surface plate.


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## Asm109 (Jan 3, 2021)

I've had a home machine shop for close to 25 years. Still don't have a granite plate. Of course I have all ways had access to one through work so If I had something mission critical I could get it done. But the number of times I needed that could be counted on one hand.


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## Jim F (Jan 3, 2021)

I use a piece of countertop from the sink cut-out.
Works well enough for what I do.
Buy tooling first.


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## SRay53TxTn (Jan 3, 2021)

That is exactly the info I was looking for and now can have some extra $ to spend on tooling.

Luckily that's all the tools I'll ever need. I know ha ha ha.
I keep looking for local deals on machinist tools (CL &  FB Marketplace), however, most look like they have had a hard life and not well maintained.

And of course - Thank you for your insights!


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## Larry$ (Jan 3, 2021)

I have an 18 X 24 surface plate but don't use it all that often. Many other things I'd get first.
Buy as you find a need,


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## projectnut (Jan 4, 2021)

I have a couple in the shop.  One is a 24"x 36" Challenge cast iron model (475 lbs.) on a stand and with lifting pins.  The other is a 12" x 18" no name.  I bought mine from the shop I worked in for peanuts (less than $150.00 for the pair).  In the scheme of things they would be low on the list unless you can get them cheap, and have a way to transport them.  Mine don't get used all that often.  They were purchased for specific jobs and spend a good deal of the time under covers taking up room.


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## macardoso (Jan 4, 2021)

I thought I *needed* a surface plate and used my 6x9" Tormach tool setting plate for everything. Found a new import grade B 18x24" for $90 locally with inspection report so I picked it up. Nothing to write home about but it does as spec'd. Bowl shaped by 2um (0.000078") from lowest point to corner. That's less than a tenth and a whole lot more accurate than I can even measure.

Honestly I haven't used it much. Did a bit of pseudo scraping and a couple metrology cradles for odd parts, but usually it collects paperwork.

Although when I do need it, it is extremely handy to have. For example I have an 8" height gage that covers me on the >6" <8" part sizes. Needs to be used on a surface plate. Also great for flatness inspection using a test indicator on a base. I personally think you need a plate much larger than the majority of parts you work on.

PS: Mine is 140 lbs and an absolute bear to move around the shop.


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## Jim F (Jan 4, 2021)

SRay53TxTn said:


> That is exactly the info I was looking for and now can have some extra $ to spend on tooling.
> 
> Luckily that's all the tools I'll ever need. I know ha ha ha.
> I keep looking for local deals on machinist tools (CL &  FB Marketplace), however, most look like they have had a hard life and not well maintained.
> ...


If you really think you need one, go to a granite countertop maker.
They usually will have a pallet of scraps that might have a piece that works.
Mine is 12x12.


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## Mini Cooper S (Jan 4, 2021)

Take very careful care of your mill’s table and that can serve as your “surface plate” for quite a while. Two places to look for a temporary plate would be a place that makes granite counter tops, use a sink cutout.  Also a monument company, sometimes they have rejects or mistakes that they will sell cheap

Richard


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## derfatdutchman (Jan 4, 2021)

I use the cast iron top of my table saw for things that don't fit on my tiny 6" x 9" cast iron surface plate.


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## Weldingrod1 (Jan 4, 2021)

Keep in mind that granite countertop is not machinist flat, its "pretty good". Don't expect 0.001" accuracy. Better than nothing, and the price/performance ratio is good!

Sent from my SM-G892A using Tapatalk


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## macardoso (Jan 4, 2021)

I believe a good thick piece of plate glass is actually a pretty good surface, or so I have heard. Needs to be backed up against something flat and rigid regardless of thickness.


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## JPMacG (Jan 4, 2021)

I have a 9"x12" surface plate from Little Machine Shop.  It was inexpensive - $30 or $40 I think.  It has been more useful than I expected.   But yes, it is not essential.  Tooling is essential.


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## wildmtn (Jan 6, 2021)

You can also potentially use polished granite tiles from your local big-box store.  Yes, it is not likely as precision ground as a proper plate but they are quite flat.  I actually use a ~14" square one as the backer for 3M abrasive film to sharpen my straight razors.


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## aliva (Jan 9, 2021)

I was thinking of using the head stone from my gravesite, May as well make  use  of it before I die.


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## Badabinski (Jan 9, 2021)

I might be a bit odd, but I absolutely love my surface plates and would consider both of them essential. I'm really good at blowing past dimensions, so layout lines are a must for me. Dykem + a height gauge + a surface plate lets me do all of my layout work very quickly and quite accurately.

I also have a second cheapy surface plate that I use for sanding because I'm a bit obsessive when it comes to flatness of parts.


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## Larry$ (Jan 9, 2021)

Like Badabinski, I like doing layout with the ht. gage on the surface plate. But being a bit lazy I'll often just pencil & paper the readings I need to follow on the DRO. More prone to errors though. I've found putting the origin  (0,0) into both the abs & inc locations saves a lot of messing around when I screwup and loose it on the abs. Planning the sequence of operations ahead of time has improved my results. Found that out after discovering how hard it is to get there when I've machined away my reference.


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## DavidR8 (Jan 9, 2021)

Larry$ said:


> Like Badabinski, I like doing layout with the ht. gage on the surface plate. But being a bit lazy I'll often just pencil & paper the readings I need to follow on the DRO. More prone to errors though. I've found putting the origin  (0,0) into both the abs & inc locations saves a lot of messing around when I screwup and loose it on the abs. Planning the sequence of operations ahead of time has improved my results. Found that out after discovering how hard it is to get there when I've machined away my reference.


I thought I was the only one that machined away the reference...leaving me to wonder "now what?"


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## matthewsx (Jan 10, 2021)

You need a reasonably flat surface for layout but it doesn't need to be surface plate flat for most home shop jobs. I have a small one in my Michigan shop and it's handy but I don't think I've ever done anything that really needed it. I'd buy the height gauge first and use it with a granite/marble countertop piece for layout. 

That being said, if you don't mind something that's not perfect you can get used or new surface plates pretty cheap. I think I paid about $100 for mine, it's small but works for most of my stuff.

John


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## DavidR8 (Jan 10, 2021)

I just bought a shop grade, 12x18 3” thick plate for $100 CDN so they would have to be less in USD.


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## aliva (Jan 10, 2021)

I actually have a 12x18x3 from Busy Bee Tools. Serves my needs. I don't  need the high accuracy as my space shuttle days are over.


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## Jim F (Jan 12, 2021)

29 1/4 X 15 1/2  marble I just picked up the other day.


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## macardoso (Jan 12, 2021)

Should work well, just be gentle with it, marble is very soft.


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## Jim F (Jan 12, 2021)

macardoso said:


> Should work well, just be gentle with it, marble is very soft.


Yep, free is always best.


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## Dabbler (Jan 12, 2021)

Very  early in my hobby I bought a 12X18 offshore surface plate, and I have used it on nearly every project since.  It has made a big difference in getting accurate parts and avoiding mistakes.  Most useful for milling layouts.  A few years later I got an inexpensive set of gauge blocks and improved my results better again.  A tenths test indicator once again helped me do a better job yet.

Most of these things can be done with a set of mics and patience, but it improves confidence with a properly laid out part, and the ability to accurately check it afterwards.  I now have a Mitutoyo AA 18X24 surface plate to work with , and I'd never go back to the old way of guestimation. 

- A surface plate is the foundation for accuracy in your shop.


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## DavidR8 (Jan 12, 2021)

A set of gauge blocks are on my list now that I have a surface plate. 


Sent from my iPhone using Tapatalk


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## Dabbler (Jan 12, 2021)

DavidR8 said:


> A set of gauge blocks are on my list now that I have a surface plate.



Even the cheapest ones will be way better than your best micrometer.  I don't see the need for a hobby MW to buy a high-end set.


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## macardoso (Jan 12, 2021)

I recently picked up an Interapid 0.0001" tenths indicator. My precision in my work has gone through the roof. I still suck as a machinist, but at least I can suck accurately.

A set of gage blocks is next on my list. You can do a nice job of measuring slots and heights on a surface plate and set up a sine bar with them.


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## Larry$ (Jan 12, 2021)

I have a set of gage blocks. Got them to use with a sine bar. To tell the truth I almost always use a set of angle blocks instead. Nothing I have done has required high angular precision. Nice thought though. Maybe some day I'll get good enough to make use of the sine bar. I have used the blocks to measure slots when I want a tight fit. I'm still surprised at how accurately made the blocks and gage pins are, considering their relative cheap prices. Need to make one of those clamps to hold stacks together so I don't just relie on wringing.


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## SRay53TxTn (Jan 13, 2021)

Chatting with one of my car buddies this morning, he knew of one (big piece of granite the owners dad had in the back of the garage) and the owner needs some car parts I have,  we may can make a trade deal. 
I have sold most of my car and motorcycle stuff to fund my hobby machine shop. Keeps me off the pavement in many different ways + makes the wife happy.
Taking a drive to see it tomorrow.


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## Surprman (Jan 13, 2021)

I got this one at a consignment sale two years ago for $50.  (I have not used it yet but I am glad to have it).  Spend your money on endmills and other milling machine tooling for now but keep your eye open for a good deal on a used surface plate locally (don’t get one that has to be shipped - it might cost as much as the plate!)

Rick


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## SRay53TxTn (Jan 14, 2021)

Ended up getting the surface plate from my trip today. It was in a corner of his garage under some magazines and car parts.
No damage to any surfaces and unfortunately no identifying markings. Shop grade?
It looked like an OK deal for car parts trade. Heavy -Not something I want to move around frequently.
Got it to my home hobby area and cleaned it up. I printed up some labels for it and was going to try some basic accuracy measurements, however, of course my $15 Chinesium height tool is dead.
Guess I need some better tools to determine accuracy. Of course it is probably the flattest piece I own.


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## G-ManBart (Jan 14, 2021)

SRay53TxTn said:


> Ended up getting the surface plate from my trip today. It was in a corner of his garage under some magazines and car parts.
> No damage to any surfaces and unfortunately no identifying markings. Shop grade?
> It looked like an OK deal for car parts trade. Heavy -Not something I want to move around frequently.
> Got it to my home hobby area and cleaned it up. I printed up some labels for it and was going to try some basic accuracy measurements, however, of course my $15 Chinesium height tool is dead.
> Guess I need some better tools to determine accuracy. Of course it is probably the flattest piece I own.



I'm certainly not an expert, but I'd bet even an off-brand surface plate is good enough for most shop work, and that one doesn't look to have a mark on it.  It's hard to imagine it not being good enough considering no damage, probably almost no use, etc.


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