Author Topic: Granite surface plate, cheep!  (Read 19137 times)

dkwflight

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Granite surface plate, cheep!
« on: August 02, 2006, 12:28:08 AM »
Hi Group I've been thinking about a lapping plate, where to get one?

I just drove by a place that is making counter tops out of various colored granite from around the world. I stopped and asked  for a scrap piece. Got one 2' square for nothin!
I was so pleased I gave the yard guy a $20

From what I have seen in many houses the top is pretty true by the reflections in the surface.
I think If I was going to use it as a true surface I would want to set the plate in grout for extra support as it is only about 1" thick
Dennis
28/2 powersolutions JKSon -20k gen head
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GuyFawkes

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Re: Granite surface plate, cheep!
« Reply #1 on: August 02, 2006, 01:44:38 AM »
That is NOT a surface plate.

domestic granite is a completely different grade.

sir needs one of these


18" square, 150 quid

if they are any good they usually come with certificate AND case, like these



you can also get cast iron ones


which are bloody useless if the thing you're trying to analyse is magnetic....
--
Original Lister CS 6/1 Start-o-matic 2.5 Kw (radiator conversion)
3Kw 130 VDC Dynamo to be added. (compressor + hyd pump)
Original Lister D, megasquirt multifuel project, compressor and truck alternator.
Current status - project / standby, Fuel, good old pump diesel.

dkwflight

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Re: Granite surface plate, cheep!
« Reply #2 on: August 02, 2006, 02:05:10 AM »
Hi Guy
I know about those.
I don't think they can be had for 150 Quid?, over here.
I thought that since I would be useing an abrasive compound to lap my heads I really did not want a high quality surface plate.
How ever the piece of granite ment for a counter top would be flat enough for most home shop aplications.
If one wanted to go through the process of flattening three pieces useing finer and finer grits, one could arrive at a perfectly flat surface plate. Substituting labor for $ or Quid. The process is discribed in several places. also used for making straight edges.
Thanks
Dennis
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kyradawg

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Re: Granite surface plate, cheep!
« Reply #3 on: August 02, 2006, 02:10:21 AM »


Peace&Love :D, Darren
« Last Edit: August 03, 2006, 02:04:20 AM by kyradawg »

dkwflight

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Re: Granite surface plate, cheep!
« Reply #4 on: August 02, 2006, 02:26:35 AM »
Hi Dawg
Glass will work just as well. I have a book on restoring old machinery that describes the process of scraping ways using a good straight edge and a purple dye to indicate high spots. With enough patience and a little skill you can get any surface to within almost any tolerance you need.
For a home shop or a Lister head how flat do you want?
Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time

MeanListerGreen

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Re: Granite surface plate, cheep!
« Reply #5 on: August 02, 2006, 02:30:04 AM »
Harbor freight has surface plates.  I think they were around 40.00 last time I looked, of course that was 5 years ago.
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MeanListerGreen

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Re: Granite surface plate, cheep!
« Reply #6 on: August 02, 2006, 02:33:45 AM »
Hi Dawg
Glass will work just as well. I have a book on restoring old machinery that describes the process of scraping ways using a good straight edge and a purple dye to indicate high spots. With enough patience and a little skill you can get any surface to within almost any tolerance you need.
For a home shop or a Lister head how flat do you want?
Dennis

That purple dye is called dicom (not sure about the spelling though.)  we use it for lay out as well.
MLG Gib Key Pullers

GuyFawkes

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Re: Granite surface plate, cheep!
« Reply #7 on: August 02, 2006, 02:37:31 AM »

For a home shop or a Lister head how flat do you want?


You either have a worktop /  benchtop, or a surface plate, in the same way you either have a straight edge, or a strip of steel or wood.

but

I don't think you understand how to use a surface plate.

it ain't something you plonk a lister head on and see if it rocks

it is a datum, from which all other measurements can be made
--
Original Lister CS 6/1 Start-o-matic 2.5 Kw (radiator conversion)
3Kw 130 VDC Dynamo to be added. (compressor + hyd pump)
Original Lister D, megasquirt multifuel project, compressor and truck alternator.
Current status - project / standby, Fuel, good old pump diesel.

dkwflight

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Re: Granite surface plate, cheep!
« Reply #8 on: August 02, 2006, 02:53:43 AM »
Hi Guy
Since I have neither a surface plate, nor a machine shop, mills , lathes or a drill press. I don't have much need of the accuracy that can be had from a lab quality plate and Johnson blocks.
A good straight edge would be enough to tell me if a head was warped. I don't have a good straight edge either. I do know how to make one if the need comes up.
We are talking about how to do things in the "How to" section?
If you want a short course on how to make a straight edge or a flat plate I can oblige.
Some of us don't have the $ to purchase the best tools for our shops. I thought to suggest a small $ alternative for those of us who would like to do a job without spending a lot of $$$$#!
Thanks
Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time

GuyFawkes

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Re: Granite surface plate, cheep!
« Reply #9 on: August 02, 2006, 03:31:52 AM »
Hi Guy
Since I have neither a surface plate, nor a machine shop, mills , lathes or a drill press. I don't have much need of the accuracy that can be had from a lab quality plate and Johnson blocks.
A good straight edge would be enough to tell me if a head was warped. I don't have a good straight edge either. I do know how to make one if the need comes up.
We are talking about how to do things in the "How to" section?
If you want a short course on how to make a straight edge or a flat plate I can oblige.
Some of us don't have the $ to purchase the best tools for our shops. I thought to suggest a small $ alternative for those of us who would like to do a job without spending a lot of $$$$#!
Thanks
Dennis

"Lab quality"? nope.

The point of a surface plate is that it gives you a datum. (http://www.m-w.com/dictionary/datum)

Once you have a datum you can measure, and measuring tools are cheap, especially second hand.

Before you go anywhere near a machine shop, mill or lathe you need a reason to go there, and that reason will either be because something is not as it should be, or because you want to modify something, either way you need to measure first.

Don't make this an argument / discussion about cheap tools, because it isn't.

By definition you CANNOT make a surface plate or straight edge, without using something known to be straight or flat as a reference.

You can make a pretty good flat surface or straight edge sure enough, but there is something you MUST understand about engineering.

"very small inaccuracy" might be used to describe something, such as the flatnesss and uniformity of a home made surface plate.

the non-engineer will interpret "very small inaccuracy" as a good thing, eg closely approaching accuracy.

the engineer will interpret "very small inaccuracy" correctly, as small but significant and unknown level of inaccuracy GUARANTEED IN EVERY MEASUREMENT"

eg GUARANTEED INACCURATE

========================

There is a thread elsewhere about rocker wear and geometry.

Rocker are levers, and levers multiply errors.

Without a PROPER surface plate and a PROPER engineers right angle, you, BY DEFINITION, have no way of ascertaining if either your valves or your rockers are operating in a vertical plane, and until and unless you can guarantee this, and rectify it if required, you have precisely ZERO chance of setting them up in the vertical plane correctly.

===========================

wherever you are in the states, keep you eyes open and for 200 bucks you can pick up a good used surface plate, same again will get you a set of good used vee blocks, mic, dial, vernier and a couple of angles.

if you don't buy these tools and learn to use them, your machinist will have no option but to use his, and all he will be able to measure are the bits you hand him and your drawings, not the bits you keep at home, and he will charge you his hourly rate for this measuring.

want to know if your piston is of uniform height and if the ring grooves are cut square, want to know if your rods are straight, want to know if your valves are the right length and straight, want to know if your rocker geometry is right, want to know if your barrel is the correct length, etc etc etc etc? then you need a *proper* surface plate, or, like me, access to one in your local machine shop
--
Original Lister CS 6/1 Start-o-matic 2.5 Kw (radiator conversion)
3Kw 130 VDC Dynamo to be added. (compressor + hyd pump)
Original Lister D, megasquirt multifuel project, compressor and truck alternator.
Current status - project / standby, Fuel, good old pump diesel.

dkwflight

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Re: Granite surface plate, cheep!
« Reply #10 on: August 02, 2006, 04:03:03 AM »
Hi I think you are missing my point. You don't have to buy accurate tools. They can be made. They were made by the craftsman who needed them first.
You are right about what is acceptable accuracy. When you decide what is acceptable you are at the first stage. The second stage is how to get the accuracy you want.
The first lathes were made by people who did not have the tools to make them. They had to make the tools they needed first!.
The first tool needed was a straight edge!
To make a straight edge you need three pieces as straight as you can make them visually!
Then you lable them 1, 2, 3!
Then you take 1 an 2 and with prussian blue rub them to gether on the edge you want to true.
Then you file and stone them to get the high spots down. When the surfaces are congruant you have to switch to 1 and 3 repeat the process.
 then switch to 2 and 3 and repeat untill all three pieces are straight. the prussian blue rub will show when all three pieces are straight. The main ingredient is patience

The whole idea is to get a straight edge. This edge is then used to check what ever surface you arre working on be it a surface plate or the ways on a lathe or a drill pressĀ  or what tool you want to be accurate.
Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time

listeroidsusa

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Re: Granite surface plate, cheep!
« Reply #11 on: August 02, 2006, 04:05:35 AM »
Surface plates can be had relatively cheaply these days. Look up Enco, Wholesale Tool, MSC, and other major tool supply houses. A size compatible with a Listeroid can be had for little outlay, but like having a lathe or mill, the thing is useless without the accessories than will need to go with it such as indicators, height gages, angle irons, (not the steel structural  kind) and other tooling.

I've got a 36 x 60 lab grade surface plate that is 12" thick and sits on a special stand. Just the angle irons, verniers, height gages indicator stands, ect set me back over $1000.00 for used tooling on Ebay, and that is not all Suburban brand accessories. Suburban, Starret, Brown & Sharpe, and Fowler are some good brands to look for on Ebay.

Guy is right about the accuracy. That is why any good surface plate will have its accuracy directly traceable to the Bureau of Standards. Just because it looks smooth and flat doesn't necessarily mean its good enough to trust for accurate measurements. A good plate will be ground, lapped, and hand scraped to a known accuracy by using a certified plate. It is then checked with optical flats that measure to the millionth's of an inch. Considering the work it takes to get a flat accurate surface the surface plates are a bargain.

Mike

dkwflight

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Re: Granite surface plate, cheep!
« Reply #12 on: August 02, 2006, 04:41:46 AM »
Hi I still think you guys are still missing my point. The first optical flat was made by a guy who decided to do it. He used a process similar to what I discribed earlier. By using your time instead of $ you can get the accuracy you want with minimal expense.

We are talking about a flat surface to true a Listeroid head!

I am not setting up a machine shop to make precision insturments.
And yes you can find wonderful stuff used, Hopefully not abused. Who knows if the standard you just bought was dropped? You have to ship it out to a lab to be checked against a standard. Right? A granite surface plate is very hard, but in use the insturments are slid around to use them. How much was it used in this manner? Was it used where abrasive dust was allowed to settle?

Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time

mobile_bob

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Re: Granite surface plate, cheep!
« Reply #13 on: August 02, 2006, 05:05:41 AM »
as a thought, you might take your granite top to a shop that has a surface plate and have them check it to see how close it is. just a thought, they probably wont charge you much to prussian blue and check it to see if it has high and low spots at least.

actually it is amazing how many precision tools have been made using just such a plate, the english are known for having done so.

those english dude's build some fantastic stuff using some rather rude methods, and attain some pretty high precision.

another thing to consider, folks like leblonde made their own lead screws (alot of folks had theirs made outside), they produced batches of 100, and checked each and every one against a standard. picked the few that were good, and installed them in machines to produce the next batch. the next batch had a higher count of quality lead screws and on it went.
before long they had exceptional quality lead screws

detroit diesel has a section on producing surface plates as you describe, useing 3 plates, and alot of time and patience will produce 3 high quality plates, good enough for there injector work which is well under 10 thousands of an inch.

myself i would think that for listeroid use a plate that was within a thou flat, would be useful and probably produce work that exceeds the oem quality in engine parts.

surface plates are used to blue parts as a precursor to scraping, i have taken a tour of a large machine tool rebuilder and seen it done.

also the machine tool rebuilding book by connelly has a world of info that is good to have as a reference, great book for  a hundred bucks.

i am not going to rain on your parade, i think it has merit using granite tops, perhaps one could get 3 similar sized ones and finish them to withing .001 without an undue amount of effort. certainly this level of precision is probably good enough for most jobs on the listeroids. i think your idea has sound merit and is a good thing, thanks dkwflight

i have to admit tho that there are several grades of granite surface plates available, those that are within .001 are not to pricey

but as a DIY plate, failing having the bucks or availability of a commercial plate, i think it is a good thing.

beets the crap out of using the sidewalk :)

also as i have been critical of kyradog, his idea of using float glass has merit as well, the english dudes use this method to good result. using a thick piece and floating it on a bed of sand, one can get pretty accurate results for alot of things.
thank you kyradog for the well thought out input.

perfect no, close enough for the listeroids, probably yes

bob g
ps. i figure if i am going to beat up on some folks the least i can to is give credit and acknowledge them when they have good idea's.
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

dkwflight

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Re: Granite surface plate, cheep!
« Reply #14 on: August 02, 2006, 05:21:00 AM »
Thanks for the input
Originally I commented on the reflections in the highly polished surface on these counter tops. I believe the reflections I have seen are an indication of how flat they really are. If the lines are straight how uneven can they be.
If you are looking at a surface that is only .0005 out of true you would see curved lines in the reflections.
I thought the granite plate would be good enough for what I wanted. The price was right too!
Some times you have to trust your eyes.
Thanks
Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time