resurfacing cylinder heads
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    Default resurfacing cylinder heads

    Im a new machinist and am new to grinding although i've studied it. I wanna learn how to shave and grind cylinder heads but my automechanics teacher, not a machinist himself, says that u have to grind in one pass with a huge grinder otherwise if u make multiple passes it leaves "lines". Im talking about grinding on a 1.5hp milling machine since my shop and budget arent big enough for a huge machine. It doesnt make sense to me that if everything else is done right, that it would be impossible to grind a uniformly flat surface with more than one pass.

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    Your teacher is right that a large single pass tool is typically used, but I'm not sure it's 100% required.

    But, your small 1.5hp mill is probably the wrong tool for the job just because most Bridgeport type mills cannot make large flat surfaces reliably.

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    thanks for the fast response and the intel. yeah bigger ones are better cuz one pass is much faster. im getting a jet jmd-40gh in about a month as a step up from my grizzly mini milldrill. im gonna b practicing a lot b4 doing it for $, but if smaller mills are not reliable i will hope it works but in case it doesnt i wont open a business betting on the jet.

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    but just to b sure is there a problem with multipass grinding producing "lines"?

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    Quote Originally Posted by Leecho View Post
    im getting a jet jmd-40gh in about a month as a step up from my grizzly mini milldrill.
    You might want to peruse the Sticky in the general section (where your thread should
    have been started) about Jet and grizzly machines.

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    If you face modern TTY alloy heads on a toy grinder ,the job will have to be done over on a proper machine.....Assuming there is enough margin left......the hard shim gaskets used wont seal for five minutes if the head face is lees than a perfect mirror.

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    From what I have seen, block and head surfacing machines are kind of specialized for that specific task. For example, they will have the spindle trammed slightly off so that the cutter only cuts on the leading side. Also, it's often much more time consuming to set up the heads or whatever to make the cut than it is to actually do the machining. The dedicated machines will have lots of handy fixtures.

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    Quote Originally Posted by Leecho View Post
    Im a new machinist and am new to grinding although i've studied it. I wanna learn how to shave and grind cylinder heads but my automechanics teacher, not a machinist himself, says that u have to grind in one pass with a huge grinder otherwise if u make multiple passes it leaves "lines". Im talking about grinding on a 1.5hp milling machine since my shop and budget arent big enough for a huge machine. It doesnt make sense to me that if everything else is done right, that it would be impossible to grind a uniformly flat surface with more than one pass.
    Hi, not to slam you but it seems you're mixing cutting methods. The machine you mention is a milling machine (well, almost), and isn't typically used for "grinding", which is a totally separate process over milling (cutting with edged tools). And it's not shaving either, although there are tools called metal shapers where that's a fair description of the process.

    The Jet is totally inadequate both from a size, accuracy, rigidity, and in pretty much all other ways for surfacing cylinder heads, unless you were talking about a small lawnmower engine.

    You need to learn more about the entirety of engine rebuilding, machines for the purpose, and general machining practices. Search and read a lot on the web, perhaps especially well-chosen videos on YouTube.

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    Automotive has always been the red headed stepchild of machine work. My surfacer runs on ball screws and uses a single half inch round pcd insert, four inch spindle. Surfacer on left.
    Attached Thumbnails Attached Thumbnails ab974089-eb63-4db2-b883-37b34198b06f.jpg   f2bb21da-0782-47ea-8fe6-1a9e40e82b48.jpg  

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    Nice! What's the max head length you can do on it? And is there a slight tilt to the cutting head so it only cuts on one side, or do you get a crosshatch finish?

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    You can surface a head in such machines but....
    You will only be as flat as the way travel and since you will likely get way out on the ends be aware that most machines in this range will droop at long extensions.
    You need big diameter cutters, 1.5 to 3 times the width is preferred. That cutter diameter eats up a lot of machine travel.
    Two cutter choices here, a flycutter or a aluminum body mill cutter. In the second you may want to set one tool "proud" or high or just use one insert making it a stiff flycutter.

    The machine head/spindle should be setup not flat. You want just a touch deep on the entrance side.
    When the front of the cutter exits everything relaxes, you need just enough twist so that the back end of the cutter never touches.
    The needed right or left twist of the spindle introduces a small concave in to the cut so you want the least amount possible for the finish pass.
    Since all work is done on the front of the cutter the part is not centered on the machine.

    It might be best to go to shop that is setup to do such work.
    Production work is so different, fancy expensive stuff and 30-40 seconds max allowed for this op.
    Bob

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    thanks everyone for not answering the question about lines. looks like a lot of u missed some other stuff, such as the keywords "new", "learn", "practicing"...

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    To the OP.
    As noted you are in the wrong place for this kind of thing.
    I am an automotive machinist now specialized with cnc. I started young like you so take this to heart.
    The problem with the vertical mill method is:
    1: Rigidity. It can be done but you have to jump through some hoops.
    2: Unless you are specializing in small engines you will need a 54 inch table to have enough travel to use a single pass cutter.
    3: I suggest going here and spending a few hours going through threads. Speedtalk.com
    Tons of discussions on how and what tooling as well as fixturing.
    It is read only at the moment due to the forum owners sudden death.
    Also use google like this.> Head surfacing site:speedtalk.com
    That will narrow down whatever subject you are looking for.
    It's a hard road but if that is your thing Good luck to you.

    General info.
    There is nothing wrong with multiple passes on a properly trammed machine. Flat is flat.
    The problem is that somewhere back in time the tilted head,one pass cut came to be and now automotive guys get positively apoplectic if they see multiple passes or a back trail.

    They don't realize or don't want to know that the tilted head leaves a cupped surface in the Y direction. Done right it's not too bad but many machinist may not think to throw a straight edge in that direction.

    Personally, I recommend saving up and finding a Bed Mill. Then you can do some serious work.
    Even better if it is CNC equipped.

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    Quote Originally Posted by Leecho View Post
    thanks everyone for not answering the question about lines. looks like a lot of u missed some other stuff, such as the keywords "new", "learn", "practicing"...
    Seems like you missed the part that this is a place for professionals, not podunk wanna be machinist hobby types with bottom of the barrel machines...

    Actual surface grinding can leave lines, they are all but immeasurable.

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    Quote Originally Posted by Leecho View Post
    thanks everyone for not answering the question about lines. looks like a lot of u missed some other stuff, such as the keywords "new", "learn", "practicing"...
    Well, some of us didn't mention anything about "lines" because the real issue was asking about a machine so far from appropriate that "lines" would be the least of your worries.

    And we are trying to help. It's more than a little annoying when so many folks get useful information but don't understand what they don't understand, and so feel like they have to smack talk back. Not helpful for you to do that, it'll only slow your learning.

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    I can do three feet safely. The head is tilted two, when it hits the switch it raises a thirty second to eliminate dragging. When I first bought it we did some work and sent out to check how flat, one over three feet. Profilometer seems more critical. Spindle is four inch cutter head is a foot. Does well for my low rent shop.

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    Quote Originally Posted by CarbideBob View Post
    You can surface a head in such machines but....
    Aargh. Bob, he would literally be better off using a big sheet of sandpaper and a surface plate than trying to cut with that toy.

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    hey thanks not only for debunking the myth, which was my hunch, automechanics have lots of em, and all the good advice(i know its gonna b hard with lotsa variables), but thanks even more for "As noted you are in the wrong place for this kind of thing. --- I started young like you so take this to heart." Cool words.
    Yeah if i would have known that this site is unfriendly to new guys, as if i was gonna resurface THEIR cylinder heads and f it up, well, there's alot more sites out there. I'll check out speedtalk.

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    Quote Originally Posted by workin stiff View Post
    I can do three feet safely. The head is tilted two, when it hits the switch it raises a thirty second to eliminate dragging. When I first bought it we did some work and sent out to check how flat, one over three feet. Profilometer seems more critical. Spindle is four inch cutter head is a foot. Does well for my low rent shop.
    Thanks for that info. Could I get a clarification or two? When you say head it tilted two, do you mean two thousandths from one side of the 12" cutter to the other? Can't be two degrees, that would cup the surface too much (wouldn't it??).

    And the "thirty second" - that's the spindle being raised after a pass to ensure no chance of a dwell cut? That must be due to not quite enough travel to go fully off the head on either side with a longer head?

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    Perfect


    Sent from my iPhone using Tapatalk Pro


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