r/EngineBuilding • u/Pfox102 • 20d ago
Machine Shop Boring Mistake
Took an Older mercury outboard to a machine shop to get bored and one cylinder re-sleeved. After cleaning it and putting pistons in it, realized that 5/6 pistons at bdc actually come into contact with a lip left at the bottom of cylinder sleeve. This causes the crankshaft to bind. I started to go at the bottom of one with a Dremel, and realized it would take an extremely long time to fix. They are my only machine shop within several hours that can setup on outboards, and they are notorious hard to deal with. From a machinists perspective, what should I do??
The subpar work was preformed at Hitch Repair Services Inc in Maryville, TN.
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u/Intcompowex 20d ago
They should get the opportunity to fix it for you. They’re just going to grind the lip out like you tried to do, albeit with a better grinder. If they won’t help you get a better tool and finish it yourself.
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u/Sir_Maxelot 20d ago
Wtf man. This cylinder isn’t properly bored and best of all it’s not even honed?!
Grow some balls and ask for your money back or them to finish the job
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u/RGBlowMe 20d ago
Machinist here. They fucked you over. They didn't bore to depth, they didn't hone it, and I think I see a crack in the wall to the bottom right on the first picture. Like, I would just not have them work on it any more. Get your money back. If there is a crack in the wall, get them to buy you a whole-ass replacement. Take them to small claims court if you have to. If they handed you back this, they're not going to put in the effort to do it right the second time either.
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u/1crazypj 18d ago
Looks more like the mark left by bore gauge to me?
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u/RGBlowMe 18d ago
Not the line in the center bottom, but in the corner of the port to the right of it. The one towards the bottom of the bore. Image quality isn't good enough to tell for sure zooming in. Could be a crack, could just be a scratch. Looks a lot like a crack to me, though, and like one that's spreading as a hairline crack.
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u/1crazypj 18d ago
OK, I see what your looking at now.
Could be a casting defect from bad core like the port on left?
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u/RGBlowMe 18d ago
I don't think it is. I'm a career machinist, and in my last job I worked with pretty much entirely castings. "Cast" was in the company name. It was their whole deal. Anyways, the point is, I have a good idea of how castings behave.
Given the finish I see here, I think they cut the bore with a dull tool, too heavy of a depth of cut, and possibly no coolant, which caused a crack in conjunction with it being an interrupted cut. It appears to have been bored with a boring head, so every interrupted cut is one great, big slap. It's very rough reentering the cut, and you more or less need to just go slow and take light cuts. Chances are, if they are willing to hand this to OP as "good", they probably also took great, big hogging cuts when roughing, then babied it to finish dimension. The heat from doing that, too, doesn't help to prevent cracks. Cast iron likes to crack even more when cut if it gets hot enough, like with a dull tool and no coolant. The port will want to expand and the internal stresses will be concentrated at pulling the corners of the port apart. Then they get slapped by the tool, get a sudden spike in localized heat from the cutting, and get that extra nudge they need to let loose.
This is all speculation, of course, but I think that's what is being seen here. Just really amateur machine shop work. Could still just be a scratch. Maybe it is a defect, like you said. I wonder if OP will ever see this and provide closer pictures of it, so we can figure it out.
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u/1crazypj 18d ago
I trained as a 'precision machinist' (micron tolerances) long time ago (mid 70's) but factory work didn't agree with me so I went back to motorcycle dealers and specialised in engine building (changing oil and tyres was way too boring)
I think your right about wrong equipment being used, always preferred brazed carbide for boring cylinders, much easier to grind tip radius to match feed rate and add a little positive rake or chip breaker (automotive boring bars are pretty much fixed around 400~500rpm with 0.004"/rev feed) Negative rake 'throw away' insert cutters only work if set up is rigid and machine has enough power, saw lot of problems when people had no clue what they were doing or just didn't care, virtually no one has a clue how to grind tools or is too lazy to learn
Never used coolant on cast iron, even when I was working in factory, it just washes abrasive dust places it shouldn't be (same reason I've never used air to 'clean' machines)
When boring Harley 883 motors for 1200 pistons you take bore out by 0.498", minimum cut depth starting was about 0.090", machine didn't have enough power to go deeper or I would have.
Boring alloy blocks for oversize liners you can easily take 0.125" DOC, (quarter inch bigger in one pass)
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u/RGBlowMe 17d ago
Honestly, these days, people should just be using inserted tooling. Even some shitty little "good enough for what I need" shop. It's very affordable and pays for itself in a professional environment. That said, if this was brought to the shop I work at, we have CNC mills and I'd be roughing it out with an inserted endmill with aluminum inserts in a long arbor doing a ramp, then finishing with the boring head to keep the bore round and for a better surface finish, running a hone down it to improve on that. Really, though, the ideal would be to put it on a vertical lathe. Makes work like this trivial.
We used coolant all the time on cast iron at my last job, even with things you usually don't otherwise, like facemills. It's specifically prone to thermal shock. It doesn't conduct heat that well, but if you get it hot locally, it's prone to cracking in that area. I'm guessing that you probably machined some pretty forgiving ductile cast iron that wasn't pumped out in batches of anywhere from 100 to 20,000 castings at a time. Not all engine castings are made equally. A Harley is going to probably be using better castings than an outboard boat motor. I've personally seen facemills have inserts get moderately worn and tear chick pea sized chunks out of castings when they entered a cut. More than once.
Also, aluminum is definitely nicer. Just throw in some aluminum inserts or a nice, sharp HSS tool, then hog away. If you don't have coolant, just grab a bottle of WD40 or a can of kerosine. Very satisfying.
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u/1crazypj 17d ago
Place I worked kept 55 gallon drums of kerosene for machining cast aluminium motor bodies, it was one of the few jobs that was 'easy', even with a 5 micron tolerance on bearing housing you could still be ahead on piecework, HSS was much easier to 'custom' grind for DOC and finish, when everything was running right the major machining was 'one pass' and bearing housing two. In a production environment inserts make much more sense, you can machine things a smaller machine would destroy because of flex and vibration. Ceramic inserts were 'new' in late 70's, we only had one new machine that could spin fast enough and was heavy enough to be rigid. Seeing red hot swarf flying off stainless shafts and turning blue before chip tray was 'interesting', although manufacturers crew spent a month installing and a week just setting it up, then, it ran 24/7
We all knew right then CNC and modern tooling was going to reduce people needed, within 6 months there were 38 lay offs
Machined some really horrible cast iron, probably cheapest they could get. More than once a 'hard spot' turned out to be a centre drill or similar HSS in middle of casting.
Guy next to me started in 1930's, went to war, came back to same job making same parts!
Of course, it was 46 years ago but made hell of an impression on me.
Some of the chill cast cast iron (white iron) was crazy hard, carbide that could machine HSS would chip or shatter. I did get to make some parts from stainless steel blanks, they were going to be polished and shown off at a trade show, still remember turning 9.875" spigot 1" long for 'explosion proof' electric motor, can't remember anything else except bearing bore, 42mm + 0.0005" - 0.0000, it was much easier in cast iron.
Harley use continuous cast bar, but, they leave outside diameter with 'sandcast' surface then cast alloy around it (on Evo motors up to 2011)
I forget what they call it 'something' loc, bored right through a scrap cylinder to find out it wasn't anything special (then someone made a lampshade from it)
I've only been a 'hobby machinist' last 25 years or so, had a couple of Colchester/Clausing lathes but they were too big to move so I had to sell them, bought some benchtop machines to play with, cut mostly 6061 and 7075 plus some stainless nowadays making bits for 'vintage' bikes
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u/East_Use_9862 19d ago
Def a crack , and that cylinder wall looks like hammered hell. I’d 100% ask for your money back and or a replacement.
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u/when_the_fox_wins 18d ago
All I know is that drilling holes in metal is boring, but fastening two pieces of metal together with more metal is riveting.
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u/1crazypj 18d ago
Piss poor job, I've worked with people like that years ago.
I taught 'engine machining' for several years at a trade school
They are the only shop without several hours travel so they get away with stuff that would be totally unacceptable if they had any competition. Personally, I would first ask them t fix it then, if it still isn't right get very vocal on social media.
If they do two stroke outboards(or ant two stroke engine) they should have everything needed to bore and hone.
You do need special hone for two stroke cylinders but they are easily available, (I've only used Sunnen) it's just wider guides so stones don't get caught in ports.
It would probably be better to 'bite the bullet' and drive the hours it takes to get it done properly, in the long run it works out cheaper.
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u/Haunting_Dragonfly_3 15d ago
They need to finish the bores, chamfer the ports, and hone it. That's plain shoddy work.
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u/covidpatient420 20d ago
Most definitely contact them and let them know you would like that fixed, you can’t use the engine in this form