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View Full Version : Anyone turn your own crankshafts? on a lathe?



ibewgypsie
04-20-2003, 05:46 PM
I am pretty good at building chevy motors.. Problem is the machine shop costs eat me alive. I got a 55 gallon barrel to soak them out in, Just wondering if anyone knows what the tooling to set a crank up on a lathe looks like? Got any pictures? The local guy who used to do mine had a belt sander with a stainless strip, I wasn't interested so I didn't pay any attention to the jig to hold the crank.
Mostly, I think 305-350 chevys.. and 5.0 fords.. hate to diversify too much from the motors I know.

Michael Az
04-20-2003, 05:50 PM
The ones I have seen use a big grinding wheel.
Michael

Doc Nickel
04-20-2003, 06:40 PM
A crankshaft grinding lathe is a pretty large and involved chunk of machinery.

If your lathe can swing enough, you could get away with working just the mains on a regular machine, assuming you compensated for droop and sag.

But to do the throws requires some wild equipment- The one I saw essentially had a large faceplate with a movable head that slid sideways on a micrometer track kind of like a boring head. On this slider was a 3-jaw chuck which held the nose of the crank. The "tailstock" end had something similar but with a "center" rather than a chuck.

With a little care and an understanding of how the adjustments worked, one could center any of the throws just like you dial in a part in a four-jaw. I wasn't familiar with the procedure but there has to be something about dialing both ends, so the crank isn't twisted.

More importantly, one doesn't just turn the throw with a tool like machining a bar of cold-rolled. Surface finish is critical on cranks, and they're almost always done with a grinder. The wheels on the unit I saw were fully two feet in diameter in order to clear the throws.

The "belt sander" you saw was very likely a final-stage polishing process.

Doc.

BC21OSH
04-20-2003, 06:44 PM
The crank grinder that I have watched work was made by Landis and it too had a very large wheel that turned fairly slow. The guy that ran it had been doing it for as many years as I had been alive.

Bernard

John Stevenson
04-20-2003, 07:02 PM
I served my time running big Churchill crank grinders grinding the cranks on Rolls Royce Merlins.
These took a 2" wide by 30" diameter grinding wheel. They had hydrostativ head bearings and it took at least 1/2 an hour to get these warmed up enought to get them to run true.
All seven mains were ground at the first setting with wooden finger steadies on either side of the main being ground.
Next the six throws were ground in three lots of two pairs.
To get these to run true the centres holding the crank were wound down on a set of slides so the whole crank was out of centre but the two throws were clocked up true. The next two sets were done at this same setting but the crank rotated in the jig to bring the next set in line. When the throws were being ground you had to fit balance weights to the driving and tailstock ends to compensate for out of balance forces. These were very old machine but still deadly accurate.
Final polish was put on with 1000 wet and dry paper run wet in a massive pair of wooden nutcrackers. Crank ran at about 50 to 70 revs and you stood there holding these nucrackers until you had a polish you could see your face in.

Later on I saw a modern smaller crank grinder what worked by some elaborate compensation mechanism whar the crank always ran true. The wheel head advanced and backed off as the throw was rotating so the wheel was always following the diameter.
I spoke to the guy using it but he wasn't as keen on it as the older machines but it was quicker to setup.

As for doing grinding them on a lathe - forget it.
Polishing is OK

John S

ibewgypsie
04-20-2003, 07:35 PM
Droop and sag.. I guess that explains why the pictures I have found of Model A crankshafts being ground were spinning on thier end. (a good challenge to engineer?) So.. Spinning would complicate matters with inertial load.
My large old dusty 24 inch 4 jaw lathe I think can swing about anything I put on it. The 2,000 dollar grinding wheels, well.. I'll have to figure a way around that. I am hunting something to fix the crank so setup won't have to be done on each rod journal. The mains.. well no problem. I too have made clothes pin type polishers with tacked in emery cloth.
Spinning homemade indexers? in a adjustable dovetail slide? On each end? Perhaps I need to measure the droop on a v8 crank?

[This message has been edited by ibewgypsie (edited 04-20-2003).]

docsteve66
04-20-2003, 07:40 PM
Several months ago I posted story about when we broke down in Scotts Bluff Neb in maybe 1938- 40. Rebuilt the engine under a sign board. The engine used shims to set bearings clearance. Man came out and polished the crank in the engine. Had a machine that mounted on top of the block, sanding belt ran around the journal, top was on springs so it could follow the throws. The engine was rotated and belt was moved at same time. I do not remember how the belt was joined to move from throw to throw. It took out the marks that dad was afraid would destroy the bearings. The machine was used to re-do farm equipment on a routine basis. I was under 10 years old so memory may be faulty. But it was done. I doubt it would meet modern specs- for one thing rods were probably babbited. I know as late as 1955, many shops had machines to cut inserts to size- which would not work on modern multilayer bearing materials.

gamachinist
04-20-2003, 09:25 PM
Hi guys.I need an excuse to buy a digital camera and learn to post pictures.If enough of you want to see them I'll post pics of my crankshaft grinder and the steadies,dressers,cross slides on the chucks(they move in two directions) etc...Of coure I'll have to clean it up really good so it won't look so bad.A video would be better but I don't know if I can pull that off.Thanks,Robert.

PolskiFran
04-20-2003, 09:31 PM
I remember seeing a crank turning attachment for South Bend lathes in one of their old advertisements. The attachments didn't look too complicated. You could probably fabricate something. But it looked pretty involved to set the crank up in it.

George Hodge
04-20-2003, 10:49 PM
You might be able to get around buying a 30 in. wheel,by using an abrasive belt setup. I've seen crank grinding lathes go pretty cheap at auctions.

Doc Nickel
04-20-2003, 11:50 PM
Not necessarily. The belt can't always assure concentricity, and typically can't be set to grind a rolled fillet where the throw meets the counterweight.

Belts would be fine for final finish/polish, but I sure wouldn't want to turn a crank down .010" with one.

Doc.

Thrud
04-21-2003, 12:02 AM
ibewgypsie:
Instead of grinding you can hard turn the journals and throws with CBN inserts. You need a very ridgid machine for this.

The crank can be milled in a CNC mill with a 4th axis table.

In europe production cranks are made from hardened forgings in two steps - a roughing mill with an oscillating "D" shaped cam that has hundreds of inserts along its arc and then hard turned to finished shape with CBN - no grinding required.

No easy way to do it quick without CNC.

Oso
04-21-2003, 12:36 AM
John S:

When did those things go out of production? I sort of assumed they were gone by about the time of the Korean war.

I suppose spares might have been made for quite a while though.

Carl
04-21-2003, 02:31 AM
Here's a photo of a crankshaft grinder like one I ran a long time ago. The head and tail stock centers were adjustable to center them for the main journals or offset them for the crank pins. The large wheel at the front center moved the entire bed including headstock, tailstock, and crank from side to side. The crank to the left of the wheel moves the grinding wheel into position, the small wheel at the top to the right of the grinding wheel is the fine feed. The two knobs in front of the crank are a steadyrest. there is a dial indicator to the left of the grinding wheel with three jaws that clips on the journal and shows your progress as you grind. http://www.allstates.com/storm_vulcan_15c_crankshaft_grin.htm

Charles Ping
04-21-2003, 03:51 AM
I know someone who did made a crank on his lathe - OK it was a small, flat plane, 4 cylinder & 2 main bearing crank but it was a crank.
His comment was that everyone has a crank in them - that was his crank, and he wasn't going to do it again!
Fifteen years later it's still going fine.

Charles

abn
04-21-2003, 05:39 AM
You might check out the Winona "In the block" grinder type machines that Docsteve mentioned...There were a couple on ebay a short time ago. I don't know how the results compare with a freestanding machine. The abrasive belt machines are for polishing cranks. Here's some intresting pictures and links from the web:


http://www.okumamerit.com/e_manufacturing/c/c001_03.html

http://www.azspa.it/products/cx.htm

http://www.azspa.it/video/azbig.mpg

John Stevenson
04-21-2003, 06:41 AM
Oso,
Reread my post again and realised I'd been telling lies. Post should have read Meteor and not Merlin.
Hard smack on back of wrist -- ouch http://bbs.homeshopmachinist.net//biggrin.gif

The Meteor was the detuned version of the Merlin. Same size 29 litres, same everything except pistons, cams and the Meteor had a wheelbox instead of a supercharger.
This wheelbox drove hydraulic pumps and all sort of ancilary devices.

The Meteor was fitted to the Centurian tank which is still in service with some obscure countries. We kept it until well after the Chieftain came into service around 1969/70

There is a company near here that has a couple of these that they hire out for company play days. Might save up and relive my misspent youth http://bbs.homeshopmachinist.net//biggrin.gif

The Cent was one of the few tanks whose transmission was setup to do neutral turns.
In neutral if you pushed one stick and pulled the other it spun on it's own axis.
As apprentices we used to get these on the prooving ground and spin them into a hole http://bbs.homeshopmachinist.net//biggrin.gif
The trick was to see just how deep you could get one and still get out. One lad got one about 12' deep and had to be dug out - that stopped that game.
Next trick was the ferret scout cars, we used to use the old Donington park racing circuit. We had a site hut there with kettle etc, the blokes used to go in and brew up and leave the apprentices to have a drive around the overgrown circuit.
We used to play dobby http://bbs.homeshopmachinist.net//biggrin.gif
Main rules, hatches down only the slit for viewing. Engines alway running - no listening. Count to 100 whilst everybody hides then go find them - remember only the slit for viewing. Idea was to spot one of your mates before he saw you. Then you rammed into him and he had to count to 100 whilst you hid. Immense fun but that got stoped when the guys back at base used to complain about the crash damage to the scout cars.

John S.

ibewgypsie
04-21-2003, 10:07 AM
Found some grinding rock 12 inch, 75$ each. Got to measure to see if it can clear the counterweights. My tool grinder is about 3/4" wider than the rock. Belt polisher, yeah I can do that.
DOvetails as per movie ABN posted center concerned journals, Neat.. Not rocket science. I guess dovetails need to clamp to lock in clearances once stroke is found. Indexer point for each journal location? probably a 12 point one? clamps? they must be custom per motor. It looks like both ends are driven in there too..
Next question, how to you ensure your rocks are round? run them lots faster than the surface speed on the crank? How important is that? If the crank goes around and around centered won't the journal be round?
Eccentric grinding made HANK the CRANK famous. He has made strokers as long as I remember.
Problem is setting up for each stroke, and not eccentric grinding by mistake.

Carl
04-22-2003, 04:49 AM
Be sure and take everything into consideration before attemting to grind or turn a crankshaft. As Doc Nickel stated, be sure you get a good fillet radius were the journals meet the counterweights, a busted crank will really ruin your day. The stroke of each crankpin must be exact or you will have a different compression ratio in each cylinder(raises hell with ignition timing). The indexing (angle) between crankpins must be exact or you will throw the ignition and valve timing off between cylinders. The surface finish on the journals must meet spec to or you will eat up bearing inserts.

Carl
04-22-2003, 04:57 AM
In regards to your question about determining if the grinding wheel is round: crankshaft grinders are equipped with diamond truing tools, one to true the face of the wheel(this also trues it to perfectly round), and a radius tool to establish the fillet radius on the corners of the wheel.

ibewgypsie
04-22-2003, 06:41 AM
I have tore down hundreds of engines. One of the largest rebuilders in America even puts different sized pistons in them. I had a truck that you could not see out of the rear view mirrors, sure enough it had a jasper engine. One std piston some 20's and two 60 overs. the two 60s were not on opposite sides.
This was not the first time I saw this. I guess they saved some money and used what they had.
A internal combustion engine goes though it's own machining process as it wears. One that is real good takes a long time doing it. They all wear out. A real bad one machines out the bores and crank-cam-valves even faster.
You would be surprised to know I have had my cranks turned by local shops them measured the 0ut of round and wanted to not build a engine. Sometimes for whatever reason there is a .008 flat spot on the crank. When you run a engine you have to think of the rod beating the crap out of the journal. every time it fires. The hi pressure oil in the journal protects it some, not all. When you think of it, it is a marvel they run as long as they do.
And, the local shops no longer place a mirror finish on the cranks, when you get them back they have a lead dull sheen to all the surfaces. Not to my liking either, slick is better to me. (I was proved wrong about shiny combustion chambers thou, they do crack more)
I think I can and do, a better job then that. I won't turn the cranks unless they are right.

yf
04-22-2003, 01:37 PM
Most likely the reason they last as long as they do is that according to the Machineries Handbook article on lubrication, under high pressure, oils viscosity increases. Its explained as, the long chain molecules get intertwined or something like that. (I'm no engineer) http://bbs.homeshopmachinist.net//confused.gif

So the higher the bearing pressures the more flotation the journal will have in the lubricant. That is why precision surfaces on journals are so critical. Any high spot will puncture the lubrication film and allow metal contact and aslo tend to plow lubricant aside and allow more contact.

It probably explains why a lot of abused machinery still exists in running condition.
When I read the article a while back (26 edition) I thought it was intresting and then a whole bunch of things suddenly made sense.

Thrud
04-22-2003, 06:35 PM
yf:
Petroleum oils do not have long chain molecules - they are just stubby molecules (waxes mostly) compared to the Diester and PAO (Poly Alpha Olefin) ultra high molecular weight synthetic molecules.

Con rods and journals run a hydrodynamic bearing - that is the crank and rods float in a pressurized ring of oil which prevents metal to metal contact except at startup and low pressure. Under those conditions, the "plastic like" Synthetics that are ionic in nature, stick to the metal better and prevent scuffing during cold starts and high pressures.

gamachinist
04-22-2003, 07:09 PM
Hi all.I've been thinking about this for a while now and finaly thought of some thing positive to say.John Stevenson's stories about the scout cars got me to thinking about my dads A P C races at Fort Hood.That got me to thinking about his breakdown coming home after he was discharged.Very little cash towing a house trailer with a flat bed truck back to GA.Some where about half way home it started knocking.Having been a mechanic all his life the only thing he could do was patch it up to get home.Sooo, he took the pan and head off,removed the offending rod,wraped a piece of leather around the crankpin with a hose clamp to cover up the oil hole and put it back together and drove home.( My brother got the surprise of a life time when he pulled the heads off of a 292 Ford thinking it had a burned valve on two cylinders opposing each other.He calls laughing so hard he could hardly talk.It seems someone went to the trouble of making two wood slugs to fill the bore up after doing the same thing to that truck.)Then I thought about the in frame crank grinder(Thanks abn).If you had one of these units,it would/could be made to work on a large lathe.It would have a dresser made for it.It would follow the rod journal as the lathe rotated the shafteliminating the need to rig up cross slides and counterweights.It could be mounted to a carrige to grind the main journals on the same plane.You'd still have to stop and measure many times to keep on size,but it would be a small price to pay.As for stroke correction,most shafts I grind are usually not equal in stroke length by .010 or more.Usually it's one off just enough that you can't correct it and grind them all to .010 undersize.Obviously it's not that critical on a STOCK engine.Race engines are another matter.As for the .008 flat spots ibewgypsie refered to,they must be starting the polishing belt moving and then starting the shaft rotating.Either that or it could be too much stock removal with the polishing belt and it is dishing out at the oil hole(or maybe something I haven't come across yet).I don't mirror polish my shafts but several people I trust say my shafts are smoother before I polish that most peoples after they polish.I take my time while grinding and keep the wheel dressed and balanced.I may even be able to put you in touch with an equipment dealer in Dahlonega that can sell you one.(Email me if you are interested).Good Luck,Robert.

wierdscience
04-22-2003, 11:06 PM
Talk about your cheap rebuilds I tore down an engine the other day and the sucker had knurled piston skirts!I thought that went out in the 40's.I have seen odd pistons in the holes before and have also seen it from the factory,had a slant six once that came in from Dodge with one .060 over piston!Not to common but it does happen.

docsteve66
04-23-2003, 12:23 AM
Some of the Marine enging makers say rebore a single cylinder and rebuild. They make over size pistons same weight as originals.

I have never believed in increasing power by boring- the volume of iron removed is not very large. Increasing bore AND stroke is a different matter. .060 bore might make a difference, but .01, .02 improvements are lost in the noise of unequal fuel distribution and like items.

gamachinist
04-23-2003, 12:32 AM
I saw a knurled piston for the first time in many years the other day too.Customer walked in with it and one new one to relpace it.You have to measure everthing in an engine.Ford will grind the crankshafts .010 on either the rods or the mains sometimes.At least they do all of them instead of one or two as Chrysler did in the sixties.I've come across Fords and Chryslers with all the cylinders .020 oversize before but not one or two.Chevrolet ground the mains.009 under on some steel shafts in large journal 327 and 307HD engines.I guess they wanted to increase oil clearance after the shafts were ground standard.After you do this for a while,you see some really strange and half a things from all of them.Mercury marine say it's alright to bore one cylinder oversize on a warranty cliam on one of their outboards!(Cheap you know whats).The japs fit pistons and bearings with size jumps of .0003 sometimes.I guess they couldn't machine to tighter tolerances so that was how they controlled them.Beware of really cheap mail order kits too.A few years ago a customer brought in some Chevy 350 pistons from a kit that were made in Japan.Those were the only GROUND aluminum pistons I have ever seen.Man did they look rough compared to modern Diamond turned pistons.I've got a piston grinder stored here that looks Army surplus.Glad I don't have to do that instead of picking up the phone and ordering the size I want!Gosh I hope nobody gets mad about the car talk.Robert.

ibewgypsie
04-23-2003, 12:50 AM
Uneven displacement produces uneven power pulses. (a major source of harmonics) Once I had a Plugwire come off the panhead, the lil french girl hollers as I was trying to put it back on.. No No No.. I will give you what you want, just let it shake ten more seconds.

Motors should (are) be designed to counterbalance Factory displacement and design pistons. I believe in static balancing, machine balance is even better.

We recently put a S&S super rod kit into a shovelhead (harley) and it (crankpin) was much larger, after much research it was decided it was within the 15 gram tolerance (lot of weight to me). Well it shakes so bad you can't see out the mirrors. (light rigid frame)

You got to love the new rubber mount harleys. I wonder thou, what all the thrashing and shaking does to the internals thou. (motors goes 50 in rubber, bike sitting still)

I found a good site on static balancing a harley (same priciples as V-8) http://www.viebach.com/harleyindex.htm It looks right, is it?.

Thrud
04-23-2003, 05:40 AM
ibewgypsie:

The crank should be balanced on a grinding wheel balancing jig - the knife edge is not good enough for the crank. The balancing jig has very low drag ball bearings that a shaft can rest on. A properly set racing bicycle wheel will oscillate for some time just from the weight of the tubular tire core valve weight. You need fine bearings to get fine results. The crank should be ballanced the crank and flywheels fully assembled.

The rods should be checked first that the bores are parallel to each other and the bore centerline must be perpindicular to the large or small end face. Center to center distance is then checked. Once both rods have been measured and corrected for errors then they can be matched for weight with big end bearings installed. Weight is usually only taken off the big end cap. the beam should never be educed in section. Sometimes the addition of heavy metal is a better option than removing weight off of marginal assembies. The pistons also need to be checked for proper wrist pin to piston deck dimensions. Adjusting piston weight is tricky and best done on the inner surfaces. Wrist pins should also be weighed and equalized.

BTW, I love the sound bite on the site!

ibewgypsie
04-23-2003, 10:09 AM
Thrud, Yes.. Home balance is like home machinist, you lust after the big toys, you have what you can dream up.
Them S&S rods had no fillet in the beam. Solid. Actually fuel rods I think, not street models.

Thrud
04-24-2003, 04:21 AM
ibewgypsie:
Yes, I agree, but you can precision balance them by making your own balancing jig. They are handy for your grinding wheels too (the best reason to make one). All my stones are on balanced hubs for my bench grinder - they are readily changed for grining different materials.

You know, I would love to build some 1/4 scale harley motors - love the sound, man!

Carl
04-24-2003, 05:14 AM
Speaking of 1/4 scale Harley engines, have you seen this site? http://www.replicaengines.com/products/knucklehead.htm

ibewgypsie
04-24-2003, 06:59 AM
Geeze Carl... I can build a full sized engine for that.. NICE site thou.. I will be sure to save it. (more toys I can't afford)
S&S engine cases were $679 in 2001. I had less than 1500 in my last evo engine.
Thrud, would you power a airplane? Them knucks were notorious for leaking oil, just like a pidgeon? Death from above. You know I always thought the V-twin was a slice of a radial engine anyways. Roller bearings and all.

wierdscience
04-25-2003, 11:33 PM
I have an old friend that actually trained in a Stearman trainer,he said the first time he saw it reminded him of Harley jugs in a circle,he also found out what the white scarves you see the pilots wearing were for! http://bbs.homeshopmachinist.net//biggrin.gif He also said the plane had a little eyebrow windscreen,It was to hide behind when you needed to read a map http://bbs.homeshopmachinist.net//biggrin.gifYou know how you see guys rolling over radial engines by hand,well its not for vapor lock like the myth says, its to make sure the bottom cylinders aren't full of oil before startup.

[This message has been edited by wierdscience (edited 04-25-2003).]

Thrud
04-26-2003, 06:45 AM
Carl

Thanks for the url, nice! Inspiration!

ibewgypsie:
I don't want it for a plane, for staring at and freaking little kids out - they love that!

I collected model airplane engines for a long time, but I have no idea who stole them on me (relative or aquaintance during a move). I have been thinking of collecting the new 4 cycle model engines - pretty cheap these days.

a.hebert
01-24-2006, 10:20 PM
<font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
I am pretty good at building chevy motors.. Problem is the machine shop costs eat me alive. I got a 55 gallon barrel to soak them out in, Just wondering if anyone knows what the tooling to set a crank up on a lathe looks like? Got any pictures? The local guy who used to do mine had a belt sander with a stainless strip, I wasn't interested so I didn't pay any attention to the jig to hold the crank.
Mostly, I think 305-350 chevys.. and 5.0 fords.. hate to diversify too much from the motors I know.
</font>

Hey man i have a old crankshaft grinder to sell probably less than your lathe attatchment you are asking about. I grind crankshafts in my diesel shop. Machine is in fair shape grinds god enough to do chevys but not heavy diesel shafts.Probalby would cost you less than your lathe attatchment drop me a email can send pics a tooling list

------------------
old men need toys too:900 h.p mustang

a.hebert
01-24-2006, 10:27 PM
<font face="Verdana, Arial" size="2">Originally posted by Doc Nickel:
A crankshaft grinding lathe is a pretty large and involved chunk of machinery.

If your lathe can swing enough, you could get away with working just the mains on a regular machine, assuming you compensated for droop and sag.

But to do the throws requires some wild equipment- The one I saw essentially had a large faceplate with a movable head that slid sideways on a micrometer track kind of like a boring head. On this slider was a 3-jaw chuck which held the nose of the crank. The "tailstock" end had something similar but with a "center" rather than a chuck.

With a little care and an understanding of how the adjustments worked, one could center any of the throws just like you dial in a part in a four-jaw. I wasn't familiar with the procedure but there has to be something about dialing both ends, so the crank isn't twisted.

More importantly, one doesn't just turn the throw with a tool like machining a bar of cold-rolled. Surface finish is critical on cranks, and they're almost always done with a grinder. The wheels on the unit I saw were fully two feet in diameter in order to clear the throws.

The "belt sander" you saw was very likely a final-stage polishing process.

Doc.</font>

Hey Doc you are absolutely right crank journals are a RC 30 to 55 depending on crank application. And believe me it isn't all that easy to set up the rod stroke if you never done it before. I grind cranks have a large Berco it still takes a good deal of adjusing to get within the .001 you need to start grind and finish is everything i grind to .0005 and use a polisher w/ sanding belt to bring to a good finish and to final size. most all crank grind to within .0002 pretty fine machine work you ahve to maintain proper crank to brg. clearance to keep oil pressure thakes a lot of practice to get good

Dawai
01-24-2006, 11:23 PM
Hi..

New name.

I am interested, you are a ways off thou. This machine weighs ?? You can email me at ibewgypsie@hotmail.com Pretty large machine for a long haul. I did go to PA after a bridgeport.

Kenny G
05-07-2012, 05:51 AM
I know this thread started 9 years ago but just thought I would share my experiences of trying to do something similar.
The answer was right in front of me, (so I thought) I had an old Wilson 8.5" x 48" lathe and a modified Duplex Tool Post Grinder! Having invested too much time & only managing to grind small 4 cylinder cranks, I would have been better to take the crank to the local shop and hand over the 's to get the job done!
Trouble was, the only shop I would use was 180 miles round trip away which ment I wasn't productive for the best part of that day?
No matter how hard I tried, the time involved to dial in the crank was taking far too long. How was I going to manage a V8 or V12 crank?
Out went the Wilson and in came the Churchill CRM Crankshaft Grinding Machine. :D
If anyones interested you can follow on http://bbs.homeshopmachinist.net/showthread.php?t=46462&highlight=Churchill+Grinding+machine

sasquatch
05-07-2012, 09:59 AM
Wow!! Maybe David Cofer will check back in here and give us a update, i miss his interesting postings.

Anyone know what became of him???? (ibewgypsie).

saltmine
05-07-2012, 12:01 PM
Since most of the people who used to know how to operate a real crankshaft grinder are either dead or senile, finding one in serviceable condition would be an exercise in futility....if you were able to get one working, you'd still need to learn how to work it.

Knurled pistons? I used to do them a set at a time. Especially where the piston skirts were worn a bit, and the customer didn't want to pop for new pistons. The old timer who taught me always claimed that the knurling would hold oil better than smooth skirts, anyway. Thousands of small block Chevy's, many still running after all of these years. International and Dodge engines were bad about odd sized pistons, bearings, and lifter bores. You never knew what you'd find when you pulled a rod cap off of one. My apprentice one time was having a bit of trouble putting the lifters back into a Dodge 318. I finally got tired of his endless taking it apart and putting it back together, and went over to check on him. The 318 had an oversized lifter bore in one of the banks, and my apprentice was going nutz trying to figure out why some of the remaining lifters either slopped around in the bore, while others wouldn't even fit. A quick game of "musical chairs" (but with lifters) soon had everything back to normal.
When I was working in a Chevy dealer in So Cal, the owner took on a Hyundai franchise. Early Hyundai's were pathetic (and I'm being kind).
We got one in the shop that had a squeal coming from the bottom end. I had one of the guys pull the pan, and eventually located the problem....an undersized bearing in # 1 connecting rod, with a shim made out of a Coca Cola can. We ended up replacing the crank and rod in that one. But you could still read the Coke logo on the back side of the shim, when it came out.
We also had one with a misfire come in once. Come to find out, the husband of the gal who was driving it went to change the spark plugs and twisted off the base of one. Stuck in the cylinder head, the rest of the plug refused to come out, but it turned merrily as the engine ran. The husband drove a 3/8" lag bolt through the middle of it, and glued the spark plug wire on to the lag bolt. Presto! a three-cylinder Hyundai.

I wouldn't bother with a crankshaft grinder. Removing more metal from the crank is bad enough, if you do it right. If you're learning, it could be disastrous. Besides, to offset the cost of purchasing a crank grinder, and all of the wheels and fixtures, plus, learning how to operate it, well....you'd have to regrind a whole bunch of crankshafts to justify it. Especially when you can go to one of many suppliers and buy a brand new, high quality steel crankshaft for a little more than a reground crank would cost. And the new crankshaft would be accurate in every dimension, square and straight.
Besides, there are scores of used engines out there that don't need reground crankshafts.

John Stevenson
05-07-2012, 12:12 PM
Since most of the people who used to know how to operate a real crankshaft grinder are either dead or senile,

Hey I resemble that remark !!

I'm not dead.................................

EddyCurr
05-07-2012, 12:43 PM
Since most of the people who used to know how to operate a real
crankshaft grinder are either dead or senile, finding one in serviceable
condition would be an exercise in futility....if you were able to get one
working, you'd still need to learn how to work it.It ain't necessarily so ...

This Bertoni & Cotti RTM225 Crank Grinder (S/N 504B) is available fully tooled
in my neighborhood. From a working shop, definately NOT a spray can rebuild.
An interested party could be put in touch with the motivated seller. I imagine
training and follow-up support could be arranged, too.

For those who would rather build their own, I've included some close-ups showing
the mechanism for positioning the crank.


http://www.slalom4me.com/imaged_a01/jpg/other/tools/grinders/2012.05.07_Berco_01.jpg

http://www.slalom4me.com/imaged_a01/jpg/other/tools/grinders/2012.05.07_Berco_02.jpg

http://www.slalom4me.com/imaged_a01/jpg/other/tools/grinders/2012.05.07_Berco_03.jpg

http://www.slalom4me.com/imaged_a01/jpg/other/tools/grinders/2012.05.07_Berco_04.jpg

and a picture of the left side, too (http://www.slalom4me.com/imaged_a01/jpg/other/tools/grinders/2012.05.07_Berco_05.jpg).



I wouldn't bother with a crankshaft grinder. Removing more metal from the
crank is bad enough, if you do it right. If you're learning, it could be
disastrous. Besides, to offset the cost of purchasing a crank grinder, and
all of the wheels and fixtures, plus, learning how to operate it, well....you'd
have to regrind a whole bunch of crankshafts to justify it. Especially when
you can go to one of many suppliers and buy a brand new, high quality steel
crankshaft for a little more than a reground crank would cost. And the new
crankshaft would be accurate in every dimension, square and straight.
Besides, there are scores of used engines out there that don't need reground
crankshafts.Sound and reasonable advice - for dime-a-dozen applications.

.

Kenny G
05-07-2012, 02:12 PM
It ain't necessarily so ...


Sound and reasonable advice - for dime-a-dozen applications.

.

Eddy, I whole heartedly concur. Thanks for posting the close up pics of the sliding centre's.
Here's the challange I have below. Can't get a follow round grinder to cope with it so just had to get my own! :eek:
https://lh4.googleusercontent.com/-WZOK4vhEJzM/TcVLra1dh2I/AAAAAAAAAMU/2ofkiSmacq0/s512/Image0103.jpg

https://lh6.googleusercontent.com/-JlYGg3OlCfY/T6_rgUlpvII/AAAAAAAAAc0/0dVkjTpxxR8/s640/DSCF5794.JPG

Both items were destined for the scrap. Just think, could have ended up in China making those cheap cranks!!
I know what I'd rather have, hence the decision?? :D

Forestgnome
05-07-2012, 03:50 PM
I suspect that the machine shop costs that are "eating you alive" are probably just making a living for the shop doing the work. And that would if they were keeping those machines working so many hours a day. I don't see how you would do better by investing in something for low production.

Kenny G
05-07-2012, 06:00 PM
I suspect that the machine shop costs that are "eating you alive" are probably just making a living for the shop doing the work. And that would if they were keeping those machines working so many hours a day. I don't see how you would do better by investing in something for low production.

Apart from grinding Crankshafts, this Churchill machine can handle plain grinding between centres up to 60" with a 10" swing, it can also taper grind to 9 degrees. Machine weight is 7.5 tons and I'm lucky I've got the room for it! As I'm based just outside Glasgow, Scotland, there are only a few shops in Scotland doing crankshaft grinding. Only one that I know off has a Berco offset machine, the others are all the follow round type?
It's been a steep learning curve and one made all the more interesting with the input from this Forum! :)
Click on: http://www.youtube.com/watch?v=wvYQ5YjFn1U

becksmachine
05-07-2012, 07:37 PM
Wow!! Maybe David Cofer will check back in here and give us a update, i miss his interesting postings.

Anyone know what became of him???? (ibewgypsie).

See post #38.

Dave

justanengineer
05-07-2012, 11:17 PM
Sound and reasonable advice - unless you are planning on making a business of it.
.

Fixed it for ya.

Dime a dozen vs ultra rare one off crank is irrelevant. The point was that you have to grind a heck of a lot of cranks to make back the purchase price of a good machine, unless youre shopping for machines at the scrapyard. The last crank grinder I saw that didnt need a ton of work and was decently tooled sold for a bit over $20k. Even at a few hundred per, thats quite a few cranks reground to pay for the machine. Considering I can have several automotive sized cranks custom forged and fully machined to my print for the same $20k, its a "no-brainer" for the hobbyest.

Kenny G
01-12-2013, 03:39 PM
Fixed it for ya.

Dime a dozen vs ultra rare one off crank is irrelevant. The point was that you have to grind a heck of a lot of cranks to make back the purchase price of a good machine, unless youre shopping for machines at the scrapyard. The last crank grinder I saw that didnt need a ton of work and was decently tooled sold for a bit over $20k. Even at a few hundred per, thats quite a few cranks reground to pay for the machine. Considering I can have several automotive sized cranks custom forged and fully machined to my print for the same $20k, its a "no-brainer" for the hobbyest.

The challange was always about saving an old iconic piece of iron that played a major part in Britain's engineering history and the part it played in the grinding of Rolls Royce Merlin Crankshafts for the war effort and prove that it could still turn out the same quality of work some 75 years later! Thanks must go to a very understanding wife, son and apprentice's from PJ Training, Johnstone, Scotland.

https://lh6.googleusercontent.com/-JlYGg3OlCfY/T6_rgUlpvII/AAAAAAAAAc0/0dVkjTpxxR8/s640/DSCF5794.JPG

https://lh4.googleusercontent.com/-y7JsFPgWsFQ/T6_r-sgKGuI/AAAAAAAAAc8/QJZxyqc9vIA/s640/DSCF5795.JPG

https://lh3.googleusercontent.com/-MwLOEd6Had4/TvGfHpBjtCI/AAAAAAAAAVI/sNQYJl3usKk/s576/Churchillpictures07.jpg

http://bbs.homeshopmachinist.net/threads/46462-Churchill-Crankshaft-Grinding-Machine-Restoration?highlight=Churchill+Crankshaft+Grindin g+Machine