Parallel Fail! We goofed! Machining & Grinding a 24" Parallel. WW129 

Just a tip for others: when machining cast iron, it pays to take a sufficiently deep first cut to get well under the skin. It can be really hard on tool edges otherwise. (It's abrasive due to the sand content, and sometimes hard due to rapid chilling). The glazing might have been partly due to the failure to take a deep enough cut, as well as the high rotational speed.

I have done parts like you are doing. Since you are starting with a rough casting there are surface stresses within just from the casting process. We would machine all 6 surface and then let it relax a couple weeks outdoors to experience hot and cold or send it out to heat treat it to have it normalized; which is not the same as annealing. Once ready to work on it, begin the grinding using light magnetism or residual magnetism with blocking, just like you did, and grind the working sides and ensure they are square and parallel to each other. Then hand scrape the surfaces to remove high spots and to produce the extreme flatness (less than the .0001" on the indicator), squareness, and parallelism and to create the microscopic pockets so they will hold marking medium (prussian blue, red lead, alcohol, etc.). A parallel for clamping and machining doesn't really need scraped as a ground parallel is going to be close enough for most machining work. Part weight and clamping will also flatten out the parallel's small amount of twist. Where I work, the scrapped parallel is usually a tool for inspection. The ones you find in the catalogs with half moons-scrape marks are for making them pretty; not flat and more accurate. Seeing the scrape marks makes one think it is a precision tool. The Starrett Master level is scraped to make it super flat and to prevent the level from vacuum or wringing itself to the part being levelled. Thanks for sharing in your video.

Paul is very good at explaining his process. Thanks for sharing John!

What an Awesome adventure! Thanks for taking us along! Fred

Great video John...really like seeing different people in their element. Older guys with generations of experience are way cool.

John, talk to and video with this guy every chance you get. He's got the knowledge we want.

my mother used to run a grinder back in the day. she told me that the first thing somebody new in the shop learned is that if somebody yells, you go head to the floor because 90% of the time when someone yells, a part is flying at mach 10 trough the shop.

John, that is the most informative video I have watched on surface grinding. Thank you for taking the time to record and edit the footage so we can learn from your experience. 👍

Your glasses are fabulous

That grinder was fantastic. What a tool! I want one just because....thanks for the video John.

My favorite video from you! So interesting. I'm a machinist in high school. I have to take a precision grinding class for my automated manufacturing engineer degree and now I look forward to it much more!

Those gauge blocks he showed you are the bomb !! I use them to set up my bore mics or bore gauges , but let me tell you they are pricey , but they are awesome!!

I'm really digging the glasses at 6:50. :P

Cabin Fever! Thanks for the shout out John! Hope to have you back sometime! Great to see Paul this weekend as well. Great show and still recovering! Keep up the great work!

Hey dude. I'm writing this only 5 minutes into your vid. Know you have learned from your mistake which is good. In Australia we call this soft footing. Very important to use the flatest face if possible and then most importantly befor clamping is to shim the work piece or set on Machine Jacks depending on the job. Then you can proceed to clamp it down using a Dial Indicator at each clamp to check for Deflection. Same deal when levelling say a Lathe. You level on three feet first so you don't have soft foot. Then bring the other jacks down checking your levels for deflection so you only just take the weight without twisting the bed of the machine. Levelling things is an art in itself. Happy Machining.

Enjoy watching your videos. I'm in Cleveland, nice to hear you're close by. Keep up the good work and have fun at the scraping class!

Fascinating. I always learn so much watching your content.

I left my mark on the back of our surface grinder at work. I completely relate. Great video.

Very cool video, never knew so much went into grinding. And warpage I have ran into many times from heat. Welding a table to weld parts on, burned in one side and had it all clamped down and went to pick it up and the 7'x3' twisted like a corkscrew and turned it into a teeter totter making opposing corners lift by 8"! I had to stand on it, and it sprung flat, burned in the other side and clamped it to my frame. Crazy how 3x4x 1/4" angle can bend so easy with bracing through the middle of it all.

Wow John, this maybe my fav video you've done, but I love grinding. Paul is obviously extremely knowledgeable and seems like a super nice guy. What a treat to be able to get expert help like that. You should talk him into starting a channel lol. That'd be awesome to get some more surface grinder info in addition to the great content from guys like Stan and Rob. Thanks for sharing John.

Really liked seeing the learning experience! Relaxing the magnet is crazy!!

I love these videos where you show where you goofed and how to you came to fix it. Keep up the great work and never forget; everyone goofs, it is not just you ;) .

This is a really cool video. I'm loving just learning more.

Excellent video on grinding a piece "flat"....................It gets super challenging when you grind a really thin piece!

This is what I love about your videos John, I always feel like we are learning at the same time. Still trying to get my head around the twist in a cast part. Very interesting stuff. Keep up the good work. (nice T-shirt by the way ;) )

I'm really looking forward to any videos you do on scraping.

There is more learning in this video that I had every realized. Thank You & Debolt Machine. My mind is racing this morning, great stuff! Lautard, in one of his Bed Side Reader Books, shows how to inspect a surface plate. Great tip when buying used (If I ever move, how the heck will I lift that 300# thing!)

The guy is a master. Your straight edge will be a work of art when completed, I'd be happy with it now though. Recently picked up an Abrasive 1 1/2 myself and looking forward to doing work similar to this when it's going, Putting 3 PH in now, Excellent video Sir... Thank You

Hay Jon, enjoy you class and enjoy the time with the others there

A tip I've learned for cast iron is to throw a couple of fridge magnets around the mill or lathe. It catches the dust and helps prevent it from getting in your machine.

That is a brilliant way of describing the twisting of materials John, always had to try to use my hands/fingers/draw a picture, but that is top notch!!!

This is a great video, young machinist learning from the older and experienced one... :)

John, thanks for showing one of Paul's catalog pages in the video. I just ordered one of his tramming rings. Been wanting one of these for a long time -- nice coincidence. Have fun at Kieth's don't get too blue.

A thought I had to automate the magnetic release based on hold down power vs spark/sparkout level....could really create accuracy, precision and repeatability as well as not having to rely on manual ability / expertise....CNCs are awesome!....some day I might get around to making some sort of program for that idea!....thanks to everyone involved in this video...it truly was awesome and insightful!

Fascinating!

For parallelity, after grinding one side flat, is it best to turn the part end-to-end when the other side is ground, or not.

what a cool friend to have around.

Haha, I just love those old lady glasses you have at Pauls shop 😅

John you are a great student to your trade. You are proof that school ain't just about tuition. I look forward to your videos every week. those jo blocks that you were shown, the first set, I have seen them bought new for Pratt & Whitney at the low price of $11,000. No...... the coma is in the right spot. that being said, I've also seen them for as low as $2500.

Fascinating video!

Takes me back a few years when I was starting in tool making. We had a surface grinder about the same size which I used to use occasionally but mostly used a smaller surface grinder. A work colleague made the mistake of powering down to a diamond dressing tool but the power down locked in place. Never saw anyone move so quick, the dressor held on the magnetic chick but the wheel had a nice groove half inch deep, lol. I was working on the small grinder behind him at the time. Used to do all sorts of thinks like relieve the sides of the wheel so we could grind the stops and other various parts. My favorite task was using a cutting wheel and going through 20mm injector pins in one cut.

John, I enjoy your talks on Fusion 360 use so much that I resided to venture into machining. I guess I am hocked. Thanks for the work you do and honoring your grandfather. Keep up the good work. By the way, my birthday is coming up it will be 77.

AWESOME video content Bro!...thanks

Thats good that you know your limitations and take the advice from specialists.

ice one John. Its a pain in the ass to get castings parallel. I cant wait for the scrapfest footage I attended a 2 day scraping class here in Australia unfortunately we couldn't afford to fly richard across the pond. I assume you did this before getting your new grinder. One tip is place a thin rubber sheet under the job between the magnet it helps it pulling flat

Speaking of scary grinder stories. I had a machine tool instructor who was working on a grinder with his teacher, when the wheel exploded and took the guys scalp off, killing him. Well one night when I was working in the tool crib, sharpening endmills, we went out to the grinding room to cut off the end of a milling cutter, and just as that short piece of endmill came off, it wedged the wheel, and exploded. We looked at each other like some ghost had just passed by, and decided to let him live another day.

I always loved machining cast iron.

Learn every day. That's where the fun is.

Hi, You may be interested to know that on a grinding machine such as that the Z axis is actually backwards and forwards, Y is up and down and X is left to right. The spindle orientation normally dictates which axis is which. Cheers. Crispin

I've got a lot to learn about grinding Great video

Man this safety glasses at 6:48 LOL :D

Nice vid! On warped or irregular parts I like to use a couple screwyballs (outsidescrewball #16) under the part, and then clamp it to an angle. It keeps the part from getting sucked down on the chuck.

Awesome. Perfect timing, I am just bidding on that exact same surface grinder :D

dude, if you started filming this video in your at-home shop, wow! that's totally sick! and if you got lucky enough to film where you work, well that also awesome. keep the vids coming; I don't have that sort of resources (yet?) but it gives me a better idea of what I need and how to achieve the results I want.

A camel back straight edge is much wider and has a relief angle cut, so you can spot into dove tails. A large parallel like what your making is very useful.but not as a spotting transfer gage for tool rebuilding. I've found when using a Bridgeport, the table will flex the farther you get it out. The saddle is actually very small for how fare the table can travel . Looks like fun, Richard king is A character you will love the class.

note at the start of the grinding the dull orange colour of the sparks that cast iron gives off whereas steel gives off a brighter more yellow spark, you can use this as a way to identify cast iron from steel if you are unsure what you have.

Joe Blocks! I have an old set of these with Pratt and Whitney's name on them. Didn't expect to get that out of this video. Big thanks to Paul.

Assumeing that is a raw casting you had made it needs to be normalized before Machineing and or grinding. It has to relax it's internal tensions from being poured. Put it in the oven at 500 degrees for several hours (after supper to bedtime for example) to relieve the stresses. Hope this helps some, keep up the good work

Great video.

I believe that the irregular design of the hump back better prevents movement from temperature fluctuation.

Nice webbing on those parallels, may I suggest if you ever make them again have the webbing stop short about 2 inches from the end. This will give you enough room for a half inch bolt down hole when you need to secure them to your work surface. Good point out concerning the placement of the diamond on the surface grinder!

Very fascinating.

i just imagine your shop in a few weeks with machinery all torn down while you scrape the ways to perfection. got to get your surface plate lapped though. loose machinery bugs me no end. but it cannot be avoided sometimes.. thanks for a great video

John rocking the 70's disco safety glasses :D

wow! that fine feed would come in handy so often. what a nice machine

So funny. I was going to ask you for Paul's name. I couldn't remember it and misplaced his business card. DOH! We have a few small one off parts to get turned around quickly. I got busy (I was at Sam's shop) and didn't get to ask and here it is. So, thanks. 😊 John

cast iron sparks out forever. and it's springy. I spent 5 years in a grinding shop and had lots of flattening jobs for cast iron. a fun challenge at times

Good video John is this what caused you too buy a grinder?

wow. I enjoyed this episode.

There was no way to clamp the piece at both ends hanging it "on the air"? Maybe some 123-blocks with screws pushing at both sides of the vertical faces of the bar? (I.e. applying a transversal force at bar's ends and keeping it lifted up from the table surface).

Back at my first job I ground 14' stright edges. 1 tenth per foot was the tolerance. They took about 9 hours each to grind. They sold for $4000 each in 1985.

Is there some sort of fast-setting goop you could put, say, between two layers of aluminum foil, to let you clamp it securely without twisting or bowing it? Like a liquid shim?

Glad it turned out ok in the end after all.

You should have put the piece on a surface plate after you have milled it. While on the surface plate you use an indicator and shim stock to make the part sit flat. You mark all of your shim stock locations then transfer the shim stock and the part to the surface grinder and turn on the magnet just like normal and grind the piece. In. Once the surface sparked out check the part on a surface plate re-shim and regrind as needed. Doing it this way will allow you to see how flat the part is while not being chucked up. Do note that you only have to shim one side and when you grind the second side there should be no shim stock.

Those are some sweet ass safety glasses.

Now that was interesting!!!!

I spent a day as a apprentice trying to get a casting flat doing the exact same thing kept clamping the twist out only for it to come back when realised. One of the old timers took pity on me in the end and showed me how to shim using a indicator so your just getting a tiny deflection when clamped down

I'm curious to see how stable these are with time.

Yeah, surface grinding is more about the "feeling" and hearing, than dialing in a value...learned that in the past, too.

Table droop can cause the high center from milling to grinding. Just depends what you are seeking as far as over all tolerances and what you are using it for.

Regarding a camelback vs a parallel is that the camelback is much deeper. Stiffness is proportional to the square of the depth. The rib is going to be thinner on the camelback than the 2nd parallel side so the whole thing will be lighter and stiffer. If you are working in scraping all day everyday that parallel is going to be exhausting to work with. Also, I think if you use that parallel in the shop for mill setups etc it will not keep its precision. A precision straightedge should be used for scraping and otherwise kept in a box or otherwise kept away from dust and chips. And my Grandma had glasses like that! Great video.

If you run a cupped length of wood through a thickness planer, the rollers flatten out the cut and the blades remove a thickness of material. When the stock emerges, thinner, but still cupped. You have to flatten one side on a jointer first and then thickness the material that is flat on one side to get the other side flat and both sides parallel. When you took the twist out of the parallel with the clamps or magnet, you did essentially the same thing as thicknessing a cupped board. You should have shimmed the piece stable on the table without changing the shape or twist and the first grinding of the top side would have flattened it and then could have been used for reference to flatten the opposite side.

The granny glasses kill me !!!! LOL

I am starting to undestand why grinding is more precise than other methods. The grinder is basic just a wheel, so the contact surface is smaller and average by itself. The table is the thing that moves making it the center point. Really interesting.

Machining gets you close, grinding or burnishing gets you real close. :-) Your parallels were likely fat in the middle from the knee rocking on the Bridgeport. Holding less than .001 over several foot length on a knee mill can be a real challenge. I did a video about that called "how to do precision work with a worn machine"

When you come to GA I would be thrilled to meet you! I live about 20 minutes away from tifton.

Clamping the ends with some sort of cam action clamp pressing against each other on each end will probably get rid of the twisting problem. But then it will have very little sideways holding force so you need to use minimal tool pressure if you are going to mill it.

john very interesting video cool.

Hi John, just wondering, once they were true and straight could they be chucked together side by side and ground to be really parallel?

I've done hot glass and had to deal with the stresses and relaxing that happen as it cools, I never even considered that it would be an issue with cast iron. I guess it is pretty much the same thing though.

Sweet safety glasses.

The hump back is a definite purpose flat straight surface used to check lathe ways and other machine surfaces.

Get some glass for the table for the end checking as they are nice and flat.

The reason for the "camel back" straight edges is to prevent them from bending under its own weight. Things you think are solid, aren't. Rich set up a bridgeport table on a work bench and indicated it with his KingWay tool. Then he had all 10 of us stand at the other work bench. Our weight on the concrete floor was enough to move the indicator a couple tenths. We were not touching the workbench. Your parallels are so nice and flat it will almost be a shame to scrape them. Then again, scraping them to exactly the same height will be challenge. A fun project for me was doing a 6" angle plate. It took awhile, but I got all surfaces flat, parallel and perpendicular within a 2~3 tenths. It still amazes me that can be done with hand tools. Andy

With any contact, especially with a wheel that wide, surely heat is a factor without coolant to start?

Is that a salvagnini in the background?

Interesting "parallels" to wood working (wood typically has lots of twist and movement). Normally you start by jointing (never heard of a metal jointer), and then make it parallel in a planer. However, when you have a board wider than your jointer, you shim it on a thick flat board and run it through the planer. So I would think you could easily shim it on your Bridgeport table and then mill it.

John. That surface plate is filthy. My mentor would have kicked my ass back when I was an apprentice if I was checking parts on a dirty granite plate. Any metal transfer or oil, or grit, or plain old dirt will make your job harder than it needs to be.

just wondering - could you submarge the straightedge in something like block of cement, that you could use for clamping, to prevent warping?

Surface plate has stains??