Grinding practice on scrap cast iron

Reposted with a better title.

I've been practicing with my J&S 540.
I don't have a master square, so I thought I could make one using 3 import squares - matching each one to another in round robin.
To do that all I needed was a flat flat. Seems like a grinder would be a way to make one of those...

I have assorted scrap waiting to be turned into new things.
In the pile is an old clutch pressure plate - a reasonable lump of old cast iron.
I hacked it into 3 pieces:



Then used my mill to make them 'mostly' straight:



(anvil for scale )
I also made them roughly the same height, and cut a small flat on the curved edge.

Then bunged them onto the grinder:



Taking care not to add heat I proceeded at around 3 thou DOC / 150 thou stepover. 46 K SG wheel.

Turned out nice:



And blackout flat:



All 3 match with no light, and blue against each other really evenly.
Think that shows my grinder doesn't have significant wear.

Next I need to learn how to grind square and arbitrary angles. (tips gratefully received)

I think I have enough offcuts from this scrap to make a pair of 10mmx20mmx30mm mini 123 blocks.

Dave

I might have set that up differently but done is done and it worked so a job well done.

You might grind one clutch sections to be flat on the other, the rounded side. Grind a notch at each end to take a roll perhaps .5000 or 1.0000 so when screwed to each notch making the roll center to center an exact number of inches so the end product would be a sine bar. Great for setting angles.

Might take another chunk of scrap and add a post to hold an indicator and make a surface gauge, one with having a rounded nose or a v notch at one end and a post for an indicator can be used for checking a part to be dead square.

Here is a veide with another surface gauge you might make up, one with having a redius buit into the surface gauge.
YouTube

surface gauge with using a ball.
YouTube

With not having a test master you can just check one flip is +.xxx and the other flip is -.xxx so you in between is zero. checking off the oposite paralell sides on the one same side..
Perhaps good to check your 123 blocks and find the most squae one and use that for a master if close enough for your needs..might even hone in that one side to zero error.. could mark it with gun cold blue.

I would scrape them and then blue them again
Bleuing on ground surface gives plenty of fals readings
Peter

For grinding "square" it's my habit to begin with grinding the two largest surfaces parallel for the largest reference surface. Can't really give advice/tips until we know what you have in tooling, indicators, surface plate, vise, etc. Also need to know your intended level of precision.

Couple of suggestion:

1) Would have secured those pieces more solidly but as already posted, what's done is done.

2) Long grind paths create more heat = more potential thermal expansion. Position pieces for shortest grind path

3) Grind the large faces parallel first to hold in a "grinding vise", this can/will ensure perpendicular 3rd surface

4) When grinding real cast iron (not cast steel) you'll want a different wheel. What do you have?

5) DOC at .003 (inch) can/will generate a lot of heat on a long grind path. If the surface is hot to touch then you either need to reduce depth of cut, angle piece for shorter grind path, change wheel, use coolant, or all of the what I've mentioned. Your intended level of precision determines what needs to be done, if anything.

Qt:[Grind the large faces parallel first to hold in a "grinding vise", this can/will ensure perpendicular 3rd surface]

Some vises can be set on their side to hold the 3rd side up facing the wheel and grind it square.

Or to double C clamp to such as an angle plate or a 123 block.. clamping high enough that the mag does not try to pull it down off angle. with checking the side to the right with another 123block or a hand square.

Its not a bad idea to throw a C clamp on a chancy set up, perhaps to another thing being held to the mag.

Your set up is a little bit suicidal, you might find a better way to hold the work, when it rocks up it will blow the stone and send parts flying...Phil

Phil in Montana said:

Your set up is a little bit suicidal, you might find a better way to hold the work, when it rocks up it will blow the stone and send parts flying...Phil

Click to expand...

One of many set-ups may have been placing two on the chuck with flat sides facing in and the have a flat parallel between with a C clamp fore and aft.
then place he third with one done and grind the last.

But trusting one's grinding skills and giving a two finger test push that set up worked fine.
Some times felling you have a chancy set-up grinding only on the grind side can help.

I suspect the Op was comfortable with his set-up.

* That waste part between the three rounded parts could make a nice little square check gauge with putting a post in that hole and a set screw to hold it tight.

Having a trusted for square 123 block you can set a parallel along side the 123 block, then set a part to be groung that already has side 1 and 2 done. Set side 1 against the 123 block and clamp it so side 3 and side 5 are sticking out enough to grind them with just flipping your 123 block.
Then set the part on the chuck and grind oposite to Sside 3 and 5.
Yes alwayse use two C clanpe ...and sometimes you need a third C clamp so you can take one off that is in the way of yoiur grind with not letting the pare free to turn.


Aarallel clamps can be handy:
Precise Toolmakers Parallel Clamps Jaw Opening 1-3/4" Jaw Length 2-1/2" - TPC-002-1 - Penn Tool Co., Inc

I guess I didn't really think enough.
The 123 block was on the chuck to help me set the parts to the same place. Then once the magnet was on of course it was stuck there.
Its not obvious in those pics, but the parts have a flat on the bottom:



Its a bit over 2" long. I first had the parts the other way up - long flat side down, and ground this piece, before flipping them to grind the tops.
They didn't slide or move when mag'd on. I was pretty robust in checking that given the small contact area. On the mill its always add one more clamp...
I can see now however if they had moved then the 123 would have acted like a ramp and pushed them up into the wheel.

I am running flood coolant on the grinder - it helps to stop the grit and dust migrating too far. I checked the parts during the grinding, and at no point did they become even warm to the touch. Wheel wise I currently have the 46 grit SG that's on the grinder, a 60 Alox, the pink alox from previous posts, also a 46 grit IIRC, and a few random wheels which came with the machine - 100 grit x 1/4" Alox and I think a green SiC but without markings.

I need to start making some jigs and fixtures for watchmaking, so my intended level of precision is probably pushing what can be achieved in a none temp controlled shop.

Tooling wise as well as the grinder I have 48x10 Russian mill, English 10EE sized lathe (CVA) and the assorted clamps, hand tools and such that you might expect in a small shop. I do not have very much precision metrology equipment - up to now most of my stuff has been make this bit fit that bit that is already in existence, and no we don't have any drawings for it.
I do have 1-2 and 2-3" tenth reading mics, a shop set of gage blocks a couple of tenths indicators, and 3 not quite finished master squares that are roughly 5 tenths in 7" off square - that is the project the flats are for.
I need to get / make a grinding vice - I have a large bolster of 2085 mould steel (similar to AISI420FM) which looks like the thing to use - its hardenable to 48HRC, and is supplied at 30HRC.

Bluing and scraping is currently still somewhat of a mystery. Every time I touch the blue tin I end up looking like a smurf…

Hopefully you can see that the piece on the right has a very thin layer of blue on it:



Just placing the other flat on top and applying light vertical pressure causes the 2 to 'wring'.
I have lifted the bottom one up with the top one in this picture:



And its all but impossible to get a photo of the transfer - but you can sort of make out the 'grain' pattern in the lower bit of this picture:



Its very even all over, and as I only need flat to rest the squares on as I make them match I think this is good enough?

One of the scrap pieces does have a boss in it, so that would make a nice little surface gage I think:





Dave

IMO, if they wring, you're doing pretty good.

Dave I know you are way past this kind of advice but a lot of new guy read these posts so good to give simple advice when someone gets the chance
Buck

One can always use block-in blocks and many sizes are good. And making them you practice squaring things.

Another way to hold things even for non-magnetics is to set a pair of 123 blocks, or any blocks with the part between and put a C clamp or two to pull tight.
Just double C Clamp a part to one block is also good.
Most often you should double clamp a part because grinding tend to turn a part held with one ckamp.
A V-notch block made with 45* notched wheel can become a V block with just a c clamp over the part. Such a rectangular block with a few V notches at different heights and sizes is a very handy fixture you can make.

*Great photos dave, and I am enjoying your posts.

Finding a chunky piece of cast you might make up a spin index. Might fudge up a small 4 jaw chuck to use with it , and perhaps make it sized for collets.

YouTube

An angle plate and a couple C clamps makes a fine vise for surface grinder use. They are more precision than a vise because a vise can bottom bend when tightened, angle plates don't do that.

Good way to use a vise is to not over tighten and then put a block-in at the go side. a shim strip set on the moving jaw face will help keep the part square to the solid side. I often would lightly tighten and then slide and angle parallel at the go side if the part over hung the vise.
but mostly I avoided vise use for any close parts.

Buck,
I think you over estimate my skill. I have been running a grinder for maybe a couple of days total time, over maybe a couple of months.
Always pleased to learn things, and receive advice. My training is in software, making real things is my relaxation.

Dave

And you must know that I like taling about surtface grinders.
QT:[Always pleased to learn things, and receive advice.]
Then try this ..Down feed your fresh derssed wheel with it not running (parked)and hand wheel rub your part at one end and then the other..when you master this you can feel a different part height of .0002..you also feel where the part is highest so very littls chance of a wreck due to a high place...and know about where you will make first grind..
Doing the feel you can also measure a taper..perhaps .xxx different height in 3 " of travel so it is a xyz taper..so often much better or as good as measuring a taper with a micrometer.

Buck

Not trying to burst a bubble, and I could be wrong, but it is hard for me to imagine the process and parts shown resulting in parts flat enough to wring.
If you didn't de-magnetize them, I would suspect residual magnetism is allowing you to pick up that part.

Couple of points:-

Ground parts will often 'wring' together, it's usually residual magnetism, not actual wringing. Even cast iron will do this. A few taps on the unground parts with a hammer will often fix the problem. It's a greater problem with a coarse poled magnetic chuck.

Seing light through a 1/2" deep gap between two plates is extremely difficult, unless the gap is several thou and the surface is not rough.

You should be able to get a photographable blue transfer if you slide the parts together.

Edit:- ok, three points and zach types faster than me.

I did run a B4S micromaster that could make ring togeter parts... it was likely the closest surface grinder I have used.
Problem was that it had the belts drive so it would not hog grind as well as some other machines. I think it was five or seven HP....but you could not get all the HP to the wheel.

I ran a brand spanking new Jones & Shipman 540 Hyd Surface Grinder but never tried it for ring together parts.

To me that is a fals reading

Peter

Peter from Holland said:

To me that is a fals reading

Peter

Click to expand...

Agree..the ring together parts usually have a near mirror finish.
Zach and Mark Rand likey right about the need of de-mag.

It’s not residual magnetism. The parts weigh 550g / 1 lb 3. There is a little residual - if you wipe them through some cast iron filings then it will barely pick up a few...
Agree the width for light block is quite large, If you put a ********* paper in one end then there is a clear light gap which disappears when the paper is pulled out.

Anyhow they are flat enough for me for now. I’ll try and get the “proper” camera out for some pictures of blue - it would be instructive to heat what people who know think once they can see the blues surface and transfer.

Dave