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Help with surface plates in Derby

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Phill Spowart27/07/2021 14:15:28
26 forum posts
2 photos

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"

Mike Poole27/07/2021 15:32:22
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Moderator
3057 forum posts
72 photos

A good quality surface grind will probably be flat enough for most practical purposes. A scraped finish will look nicer, be flatter and a better surface for bases to glide over but unless you fancy the challenge it could save a lot of work to not go further than the grind. The surface of my plate is not scraped but doesn’t look surface ground either, it seems devoid of any type of machining marks.

Mike

Brian H27/07/2021 15:41:11
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2214 forum posts
113 photos

I know that a scraped finish is traditional but is it really necessary for what you are doing?

Many years ago I scrounged a surface plate that had gotten into the hands of sheet metal workers (never a good idea).

I took it to a small local company that has a Snow grinder. These are large grinders with segmented stones and grind horizonataly. so is perfect for this type of work and they are large so will do the work in one pass, meaning that it is a lot cheaper that normal surface grinding.

You can scrape them in if you have a master table to work from, or use the traditional method with 3 plates but I've never found it necessary as I'm not chasing tenths.

Brian

Phill Spowart27/07/2021 15:46:18
26 forum posts
2 photos

I want to try and get my machines and tooling into good order, so I figure the best way is to start with a master surface I can rely on. Then I can be sure that any problems are my own ineptitude. I'm also finding that the current variations in finish are making it hard to tell if I'm applying the blue evenly.

Baz27/07/2021 16:05:55
558 forum posts
2 photos

Rather than grind the surface how about a planed finish. I find that the height gauge tends to stick on ground plates whereas I don’t get anywhere near as much sticking on the planed plate.

Andrew Johnston27/07/2021 16:06:21
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6235 forum posts
676 photos

My 36"x24" Windley Grade B (workshop) surface plate doesn't look like it's been ground or scraped:

surface_plate.jpg

There are a series of horizontal lines about 5/16" apart, almost as if it's been planed. Unless you're rebuilding machine tools part by part I'm not sure how a surface plate helps with machine tool setup.

Andrew

Baz27/07/2021 17:15:10
558 forum posts
2 photos

Andrew that is a planed finish, I have a Windley workshop grade bought back in the early seventies, not as big as yours, only 24 x 18 but big enough for a set of loco frames!

Phill Spowart27/07/2021 18:02:52
26 forum posts
2 photos

"Unless you're rebuilding machine tools part by part"

That is the ultimate aim, yes

Pete.27/07/2021 18:13:42
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625 forum posts
102 photos

Why not get a granite surface plate, you can buy a brand new 00 laboratory grade granite plate for under 300 quid.

Howard Lewis27/07/2021 18:21:59
5237 forum posts
13 photos

There is a sequence for lapping a surface plate absolutely flat, but involves lapping two others together and using the result to lap the final one.

Very much an iterative process, obtaining an improvement at every stage.

So neither quick nor easy.!

Full marks for aiming for the best that you can get with the facilities available. Go for it.

A machine tool needs to more accurate / precise than the work that it is required to produce. Tolerances and clearances, may be minute, but they build up into quite sizeable figures. 0.0005 on a shaft and 0.0005 on the bush in which it runs will give 0.001 clearance. Do that on the location of the bush in the Headstock, and on the Headstock / Bed locations and things start to look less than precise!

Howard

duncan webster27/07/2021 18:22:54
3456 forum posts
63 photos

Best of luck finding a planer nowadays, and if I had £300 spare I wouldn't blow it on a surface plate

Phill Spowart27/07/2021 18:34:33
26 forum posts
2 photos

Been looking out for granite plates, but not got anything yet. Once my big plate is flat, I figure I'm well away, it's just getting to that stage.

Pete.27/07/2021 18:40:16
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625 forum posts
102 photos

Where have you been looking? a simple Google search, the first few results Cutwel, in their surface plates, 630x400 00 grade £262 in stock, I believe delivery is included.

 

Surprisingly cheap imo

Edited By Pete. on 27/07/2021 18:40:54

Phill Spowart27/07/2021 18:46:45
26 forum posts
2 photos

They come up on bankruptcy auctions sometimes. Right now I've not got room for one, once new workshop is built I'll get one. For now, I just want a good plate to work off. Didn't really intend buying a big cast iron one, but it was found in a junk shop for a tenner!

Pete.27/07/2021 18:55:36
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625 forum posts
102 photos

I'd be interested to know how much it will cost you to have an 18" surface plate surface ground then scraped in, if you find out will you report back please.

Pete Rimmer27/07/2021 19:12:22
1047 forum posts
58 photos

Scraping in a 18" plate is a lot fo work it's huge surface area. Granite plates by comparison are quick to lap in and reportedly wear more slowly. Certainly they can suffer clumsy handling without taking damage more than an iron plate can.

Dave S27/07/2021 19:12:40
204 forum posts
41 photos

Eley metrology can probably recondition your plates, but I bet it is more cost effective to buy a new granite one.

My 4’x2’6” table has a planed finish. It’s flat (for some values of flatness - workshop grade and well out of certification. .
It makes an excellent stand for the 18” granite I actually use...

Dave

Pete Rimmer27/07/2021 20:30:18
1047 forum posts
58 photos

I recondition surface plates from time to time I tink I have seven in my workshop right now. Small iron plates I scrape, granite plates I lap with diamonds. Invariably they are out of certification, some by many years and I can tell you this - I never yet saw a used plate that wasn't out of specification for the last ticket that was on it and only one that came close.

Remember this when buying any used plate - you absolutely cannot rely on the 'grade' sticker and should completely disregard it as part of any selling spiel. Grade A, grade B it doesn't matter - they almost all need re-working.

old mart27/07/2021 21:19:18
3316 forum posts
203 photos

You could try lapping them together as they are nearly the same size, using fine compound and light oil. It would be a help if you could post photo's of them.

Bo'sun28/07/2021 07:59:24
496 forum posts
Posted by Howard Lewis on 27/07/2021 18:21:59:

There is a sequence for lapping a surface plate absolutely flat, but involves lapping two others together and using the result to lap the final one.

If I remember correctly, I think the procedure might have been down to Mr Whitworth,

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