Help with surface plate renovation in Derby, UK

[greenbat]

Anyone near Derby able to help me with a couple of surface surface plates? Both suffered surface rust and pitting, I'd like to surface grind out the damage then get it blued and scraped in against a decent master. Be handy to get a few pointers on scraping too, only so much you can get off youtube. One is 15 x 18", other is 8 x 12"

[simplyloco]

Jul 27, 2021 13:14:22 GMT greenbat said:

Anyone near Derby able to help me with a couple of surface surface plates? Both suffered surface rust and pitting, I'd like to surface grind out the damage then get it blued and scraped in against a decent master. Be handy to get a few pointers on scraping too, only so much you can get off youtube. One is 15 x 18", other is 8 x 12"

I have restored plates in the past. Surface grinding is not usually necessary. Rust cleans off with  Emery, and pitting holds oil for you! As you have two plates you can blue both together, and scrape them until they don't separate easily. 

[greenbat]

Don't you need three plates to create masters from scratch? The bigger one looks like it has been planed, has very prominent line pattern in it, put a clock base on it and seems to be about 5 tenths/0,01mm variation across. So probably OK without grinding, but still be nice to check it against a known surface. Annoyingly, they have one at work, and we've just started a 2 week shutdown!

[miner]

I haven't yet started hand scraping anything so far but do know a few people who have many years of hands on experience. Going by what they have to say surface grinding the parts first is considered counter productive. It makes it much tougher to get the scrapers cutting edge to bite into the material to start the initial roughing passes. They think if you can fairly accurately surface the parts (.003" or less) by face milling, fly cutting or best having the surface planed is what you want to start with.

[ettingtonliam]

Yes. you do need 3 plates to guarantee flatness, unless you've got a known master plate to work from. Its a lot of hard work.
To be honest, guys, if you've got a plate thats already OK to within 0.0005" but just needs the rust cleaning off, how many of us, hand on heart, really really need anything better?
I've got a planed surface plate, and thats all I've ever used for the last 30 years or so.

[simplyloco]

Jul 28, 2021 10:28:16 GMT ettingtonliam said:

Yes. you do need 3 plates to guarantee flatness, unless you've got a known master plate to work from. Its a lot of hard work.
To be honest, guys, if you've got a plate thats already OK to within 0.0005" but just needs the rust cleaning off, how many of us, hand on heart, really really need anything better?
I've got a planed surface plate, and thats all I've ever used for the last 30 years or so.

Agreed. I clean my 24" x 24" plate off with 320 wet and dry on a cork block! 

[miner]

For general marking out today and especially if one has decent trustworthy measuring equipment then yes I'd agree + - .0005" is probably more than good enough. But Greenbat expressed an interest in hand scraping not only the plates he has, but reading between the lines a bit, then possibly doing more of the same at some point. A proper surface plate is dual usage, marking out and far more important as a transfer with ink of it's known accuracy to any other parts.It's also a great deal of work to try and increase your reference surface accuracy by continually compensating if you know where the problem areas even are. And with hand scraping other than anything else but flat machine tool parts, the next step is having a straight edge that can check both the flat surfaces and dovetails. To be certain of it's flat and straight surfaces it needs to be correct by again checking it against your surface plate. So that initial known flat reference is your non optional first requirement. Without using the 3 plate method to generate your own or another known to be accurate and as He asked about master surface it's impossible to be sure of anything. Most here are unlikely to start from scratch using the 3 plate method Whitworth invented because of the time and work involved as a couple have already mentioned.

I'd say only He can judge about the room he has and budget to do so. But the next easiest with a bit of cost is to buy an off shore produced granite surface plate just slightly larger than his cast iron plates.With that or without having at least easy access to someone else's plate as that master it makes having what he already does almost pointless for actual scraping. For just marking out even heavy float glass could be used and has been for a very long time by many. Add in that scraping requirement and everything instantly changes. At this point it's impossible to get from where he now is to where he wants to go without the above.

As far as His asking about getting scraping pointers? Maybe he can't teach you everything, but I know of no better source than this YouTube channel.https://www.youtube.com/channel/UCD1jVjhwma9Ehj8BQqDMPHw/videos Jan is extremely knowledgeable and has more than proved he can do professional level work. I'd also do a Google search for a free online PDF of the book written by a Dr. Georg Schlesinger titled Testing Machine Tools. Without knowing how to properly check any machine tool and why it's done in that way you can't hope to survey the equipment for what might need correcting. It's fairly expensive at around $100 www.machinetoolpublications.com/ but again it's a non optional reference because it explains how to maintain and correct a machine tools slides in three dimensions. Flat is fairly easy to obtain, doing so in all 3 dimensions isn't. I can also very confidently say these references and grasping what they have to teach would make anyone a better machine tool operator, more accurate, your machines will last far longer, and you'll fully understand how to properly test and align any machine you have which has never been properly detailed in a single or multiple forum posts anywhere I've seen yet.

[greenbat]

Miner is right, I'm interested in restoring machine tools, hence the need for a good master. Or at the very least, getting a deep appreciation for what a hard, horrible job it is, which would be good motivation for paying someone else to do it!

I've been trying to work it out myself with what surface plates I have, practising on a cheap milling vice. Either it has gone OK or I'm getting false results. I been watching several scraping videos, mostly American lads. Still, there's no substitute for someone who actually knows what they're doing looking at your technique and results and giving you a few hints. For example a lot of hand scraping (not flaking, scraping) has a half moon pattern, which I cannot get anything like.
I've also bought or made about 6 or 7 different scrapers, before finding one that works for me. Ones from my local decent tool shop or Cromwell tools lost their edge in minutes, eventually I got a lovely Rennstieg carbide tipped one-and that involved ordering from a company who don't sell to the public via some random geezer on ebay. Would have been much less frustrating to have just bought that to start with.

Thanks for the advice though. I was mostly asking about just in case someone local to me could help-a forlorn hope but you never know. I do plan getting a decent granite bed eventually, but I've a couple of years work building some space for it first. The cast iron plates are just what has fallen into my lap over the years, small one I pinched off my Dad, big one was in a junk shop in Ramsbottom for a tenner! You can't really say no to that can you?

[milky]

I can send you details of a Clive Lamb, based in Essex. He is a producer of straight edges and has run scraping classes recently.
Also if you check out Lookcreations on You tube he has been bringing a Holbrook Back to life (no recent videos ..so may have to search back)

[greenbat]

Already bought one of his straightedges, hopefully be the next scraping project. Need to enquire about classes, that would be ideal.

[miner]

With that granite plate and then scraping your cast iron plates to it they offer some of the same options those straight and dovetail edges do. And that's taking a lighter weight and much easier to move surface to larger work that can't be moved to that granite plate. And the price you paid can't be beat. It sort of sounds like I'm maybe a little ahead of you in my grasp of how 3 dimensional scraping is checked, measured and corrections made. And it's taken me a long time just to get to where I am now. It's confusing at first for sure and not at all as obvious as it seems once you start some in depth thinking about it. Lol once you get enough knowledge to be nervous about attempting hand scraping on other than dead flat surfaces I think that's the time when you've learned enough to finally try it.

I also think it depends on your personality type if you'd enjoy the process or not. Knowing you'd made any machine or part at least a bit more accurate than it was should be satisfying. Even knowing enough to where you understand what scraping can offer is a huge step forward. All machine tools are or should built to simple geometry principles, flat and 90 degree planes. Except it starts getting a bit more complex once minute inaccuracies are added to help compensate for what the machine will do under actual machining physics. The better lathes for example have when correctly made, both there head and tail stocks purposely misaligned in an upward and towards the operator tilt of around .0005" - .001" over a 10"-12" (.013 - .026 mm over 254 - 305 mm) distance on the carriage and cross slide movements. That's done for two very good reasons. First it's a correction to help compensate for what the actual work piece weight and cutting forces might be, and secondly so the machine slowly starts wearing towards a better alignment and not immediately away from that point. In addition it's generally accepted that misalignment also provides faced parts with an extremely minor concave condition so two faced parts will sit flat against each other. A worn or incorrectly made lathe that faces convex is exactly what you don't want. Yet I've seen dozens of posts on various forums talking about correcting lathe head stock alignments before they've run the proper checks to ensure there is in fact a problem or understanding what the misalignment should be. Add in many advocating using grinding paste to "lap" machine tool slides in on the cheaper off shore machines and there's as much disinformation as there is knowledgeable. That lapping does make the machine feel and probably operate a bit smoother since it improves the slides surface finish. But it's an uncontrolled process of where any metal gets removed. Because of the alignment corrections made and oil pockets left afterwards, scraping will do what no other method can.Other than the time and work involved it's a win/win situation.

Besides that granite plate, hand scrapers, carbide tips, sharpening equipment, micrometers, indicators, accurate dowel pins for dovetail slide measurements, level etc. What's often neglected being mentioned is you also need a true as possible 90 degree reference surface. With that you then have the basics of checking, presetting your indicators and making corrections. With a lathe that's been adjusted to turn as parallel as possible, it's then able to machine a quite good enough and usable cylindrical square. While this video is abut checking commercial quality hardened and ground cylindrical squares, www.youtube.com/watch?v=m4mH120Lf68 the methods are still the same for a home made version. And this video www.youtube.com/watch?v=4F-bUiyFmWc shows at least one method of how setting the indicator to that cylindrical square could be done. But there's many other YouTube videos showing variations of much the same as both of those.

[lesstoneuk]

I never bought scrapers, all mine were made from large files. Ground carefully so as to not affect the hardness and finished with a fine whetstone. You may be using the wrong shape scraper to get the half-moon finish. Of all my scrapers, the flat and the three square got most use.