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View Full Version : jig borer VS vertical mill for cylinder head work



emj
02-10-2009, 03:04 AM
Are vertical mills(a 2hp BP clone) sturdy/accurate enough for cylinder head work, for example--- valve seat cutting, valve guide resizing or valve seat replacement. I'm finding my mill may not be accurate enough for valve seat cutting via Serdi-type 3 angle cutter. Jig borers appear to have the spindle perpendicular to the table without the need for tramming like a vertical mill. My BP clone will not allow the spindle to be fed down slow enough with the feed handle. My smaller mill has a fine tuning handle in the front to allow very gradual feed of the spindle in addition to the regular feed handle on the side of the machine. The boring head on it has no forward or side movement, just up and down so it may prove to be a better choice. Just wondering if a jig borer would be a better choice for this type of machining if only given the choice between a BP mill or JB mill.

tattoomike68
02-10-2009, 03:16 AM
The real pros have a jig borer or a sunan hone.

I dont care if I had a brand new mill, I would send that work to the guys who do that type of work.

Thats my take on that.

Forrest Addy
02-10-2009, 04:39 AM
There's no accuracy demands in cylinder head work to justify a jig borer. Hell, I could do most anything there is to do on a cylinder head on a husky drill press. It's the idiot car mag writers that propagandize the technical end of engine preparation and foment fads until the bar has been raised so high that no-one can afford to go racing except those with deep pockets or those willing to impoverish themselves. A jig borer is definitely overkill for almost anything automotive. It would be laughable if it wasn't suddenly a technical fad and bragging point. "I had my head work done in a jig borer."" "Cool!!" (What the heck is a jig borer? Sounds like the real deal. I better get my stuff done on a jig borer too.)

That said, Mike is right: a specialist shop would probably do a better job prepping cylinder heads for racing engines than a hot GP machinist. They will have the jigs and tooling, experience and contacts that would best realise your hopes and dreams into practical hardware.

If you have access to a jig borer and it's well equipped with tooling including a rotary tilt table, have at it but be aware that things can go slow on a jig borer if you really want to take advantage of the accuracy. Personally I'd prefer a turret mill. You can swivel and tilt the head to any angle you wish making funny valve stem angles and combustion chamber volumes easy as falling off a log.

Adding. I was in an aytomotive machine shop some time ago and they had what looked like a herky drill press head on a bridge arraangement. The bridge was mounted on columns above a precision ground table. A fixture that registered off the head face had a two axis tilt arrangement and an airlift that allowed the fixture to move over the table with near zero friction, The operator mounted piloted tooling in the chuck, aligned to the valve guide angle, positioned the table and with the air shut off the table's several hundred pounds ensured against movement. Therafter using piloted tooling the operator could bore out and replace valve guides, recondition valve guide bores, bore for valve seats etc. Slick rig and not that expensive.

Here's a vid http://www.youtube.com/watch?v=RK0djZ2Ha_Y

chief
02-10-2009, 06:56 AM
Dump the clone and buy a good BP mill, 99% of the accuracy lies with the machinist, not the machine. A jig borer is good if you doing something like line boring motorcycle engine cases but for for other work Forrest kind of nailed it. The next question is are you making parts from 6061 alumium billet or are you using plain old 6061 alumium round stock, the local race car experts tell me their is a difference.

HTRN
02-10-2009, 09:15 AM
Forrest is on the money - most of the cylinder head work is done off of piloted tools that use the valve guides for location.

Goodsons sells a rollover fixture to do headwork in Vert. Mill (http://www.goodson.com/store/template/product_detail.php?IID=2957&SID=343190044190eda6b19c122e316fb773)


HTRN

MickeyD
02-10-2009, 10:47 AM
Years back when I was into hotrods I used to have my head work done by an old man (or at least I thought he was old back then) who did everything except surfacing with guided tools and an ancient drill motor and the work was always perfect. I think that a lot of these improved ways to do things are invented just as a way to sell more tools (but there is nothing wrong with more tools).

derekm
02-10-2009, 11:24 AM
Advanced head work might include changing valve angles and of course this leads on to piston crown modifications but none of this is "high precision", more emphasis is on consistency. Even making your own valves is not "high precision".
This is because the heat and the flexing in the application means there must clearances and those clearances are not tiny compared to what is achievable with readily available tools.
The flexiblilty of turret mill or turret/Horizontal combo seems enough to get to the nearest 0.001

Although a bit off topic - The owner of X-trac who was at the time making gearboxes for F1 Williams, MCClaren, Indy cars etc... said he was required to deliver product that was far more accurate, to tighter tolerances and closer fit than was ever needed, advisable or desirable, but if they wanted to pay top dollar who was he to deny them.

emj
02-11-2009, 01:46 AM
[QUOTE=Forrest Addy] Personally I'd prefer a turret mill. You can swivel and tilt the head to any angle you wish making funny valve stem angles and combustion chamber volumes easy as falling off a log.[QUOTE]

My clone mill is a turret type mill and the tilting head appeared to be the problem. I re-trammed it with a dial indicator at four locations and the spindle appears to be perpendicular front to back and side to side. With this mill I can not lower the spindle slow enough to get the 3 angle valve seat cutter from chattering or is that a speed problem. The pull handle shakes pretty violently. I think the smaller non-tilting head mill will feed slower for the 3 angle cutter but the spindle has some run out which is a concern when reaming up valve guides. My clone mill doesn't have a lot of travel once the ball head adapter/ball head are put in the spindle so I figured a jig borer would be a better choice than the clone mill. A jig borer is less expensive than ditching the clone mill for a BP at this time. I guess I'm trying to make a silk purse out of a sow's ear! Thanks, emj

cuslog
02-11-2009, 01:26 PM
Are you feeding the quill down by hand ? What if you "peck" a thou or 2 at a time against a stop ?
I too am interested in this subject. Have you looked at the BHJ stuff, lots of neat fixtures. http://www.bhjproducts.com/bhj_content/products/cylinderhdtooling/chf.php

Forrest Addy
02-11-2009, 02:54 PM
Slow is no problem but let's look at your spilndle speed pronlem first. Is it chattering because you are trying to cut too wide a swath? Is there a hole in the end of the cutter and maybe a setscrew to hold a home-made pilot for the valve guide bore. There several ways to do that incliding brazing in a slug of material to extend the cutter from which a pilot can be machined.

Slowing the minumum spindle speed: You can remove the fan from the motor and fan exposing the stub end of the motor shaft. Then you can spin it using pulley reduction and an axilliary motor. If the belt is accesibnle yu can turn the spinfle by hand using the belt to pull 0on.

If the motor is single phase you can't use a VFD to slow it. If it is three phase you can. You are kinds of in a box if you wish to use a one piece cutter on a limber dick spindle like an R8 but there are tricks requiring only a little consideration and imagination. You know your trsources. I bet there's sonthning in your shop that can help you solve yout problem.

brucepts
02-11-2009, 07:11 PM
Head over to the forum on http://www.speedtalk.com that's were the Pro's in the high performance cylinder head business hangout.

Most of the Pro's swear by a mill setup for performance head work. But it all depends on the level of precision you are after?

Fasttrack
02-11-2009, 07:49 PM
Well just to clarify... if your asking whether or not you should buy a used jig-borer, the answer is YES :)

If you asking whether or not you need a jig-borer for doing head work, the answer is NO

emj
02-13-2009, 03:57 AM
Slow is no problem but let's look at your spilndle speed pronlem first. Is it chattering because you are trying to cut too wide a swath? Is there a hole in the end of the cutter and maybe a setscrew to hold a home-made pilot for the valve guide bore. There several ways to do that incliding brazing in a slug of material to extend the cutter from which a pilot can be machined.

Slowing the minumum spindle speed: You can remove the fan from the motor and fan exposing the stub end of the motor shaft. Then you can spin it using pulley reduction and an axilliary motor. If the belt is accesibnle yu can turn the spinfle by hand using the belt to pull 0on.

If the motor is single phase you can't use a VFD to slow it. If it is three phase you can. You are kinds of in a box if you wish to use a one piece cutter on a limber dick spindle like an R8 but there are tricks requiring only a little consideration and imagination. You know your trsources. I bet there's sonthning in your shop that can help you solve yout problem.


I'm using a Goodson 3D Fast Cut system. The mill has a RPC, no VFD. I have the mill set on the low setting with the belt on the smallest motor pulley so it's not turning all that fast. I think the jig bore mill in conjunction with this 3D Fast Cut system is the way I probably will go. Have Sioux grinding stones, valve refacer/stem cutter but looking for something a little quicker with more repeatablitiy. Jig bore may be better suited for working a set of raw 129 Bowtie BBC heads I have had for a few years now. I don't trust the BP clone turrett mill to accurately drill holes in these castings or even accurately ream valve guides in order to use the 3D fast Cut setup. Thanks, emj

emj
02-13-2009, 03:58 AM
Well just to clarify... if your asking whether or not you should buy a used jig-borer, the answer is YES :)

If you asking whether or not you need a jig-borer for doing head work, the answer is NO


I agree on BOTH of your statements!! Thanks, emj

Forrest Addy
02-13-2009, 08:08 AM
"I don't trust the BP clone turrett mill to accurately drill holes in these castings or even accurately ream valve guides in order to use the 3D fast Cut setup. Thanks"

You say "accurate" but you don't qualtify it. With a little care a turret mill in serviceable condition will position within 0.005" with ordinary care and 0.0005" using precision techinque. Much depends on what you use for references and the condition of your machine.

As for the need for high accuracy, you're talking gas flow here. Smoothnss of contour and shape of port are far more conducive to good flow than sweating a few thousandths.

A jig borer is a hell of a machine but it's not magical. You have to use the same sweat and technique dialing in the existing references as when using a turret mill. Once dialed in of course the jig borer is capable of an honest ten times closer rolerance for positioning and geometry of machined features if that's what you truely need. If you wish to acquire a jig borer by all means do so but for the right reasons. Don't think just because you have a jig borer your ability to accomplish accurate work will automatically become effortless.

I took a brief look at the Goodson line of porting tools and they look to me like they're intended for use when piloted off the valve guide bore. Thus the port detail they machine is automatically centered on the valve guide. Doesn't this render the means of driving to nothing more than a source of rotating power - like say a hand drill ot a big T handle?

I don't want to poo-poo your legitimate concerns but many times I've seen people devoted to hgh specific output engines led down the garden path by frivolous fads engendered by motor sport reporters garbleing technical processes and quoting seriously dismossive remarks from annoyed tuners.

What I'm saying is, don't be seduced. There's quite often simple and economical ways of performing work that others use expensive technology to accomplish. Technique supported by imagination is the real driver of process and progress.

emj
02-14-2009, 03:42 AM
My problem started after I reamed up my valve guides on the BP clone. Even though the spindle trammed out perpendicular to the table, I believe it reamed offcenter. It would seem if the valve guide is reamed up correctly and the pilot fully seated in the guide I shouldn't have the violent shaking in the spindle lowering handle. The cutter did cut deeper on one side vs the other side of the seat. Luckily for me I didn't cut to the total diameter of the valve margin so the seat can be salvaged. My concern is only and has only been related to having a concentric/centered pilot so I can drive the 3D cutter properly. If a jig borer will allow this, I'm willing to do it. As for fads/ motorsports reporters....???? As far as I'm concerned, this thread is closed. Thanks, emj

abn
02-14-2009, 06:55 AM
I'm not necessarily experienced enough to open my mouth here...but, reamers don't locate holes. Especially ones as slender as a valve guide reamer. The only time I would use them rigidly is if I had drilled or single pointed the hole IN THE SAME SETUP, that way you are using the precision of the spindle. Otherwise I would use a floating holder, or even do it by hand. "Reaming off center" would not seem, to me, to be a machine tram or accuracy problem, but rather the precision of the machine fighting the location of the hole.

Spin Doctor
02-14-2009, 11:48 AM
I don't think that the average machinist whether he is working on automotive speed shop tasks or not has any idea of just how much of a Royal Flaming Pain in the Arse it is in a production environment to get the valve seats and valve guides to priint in terms of concentrictity and angularity. With aluminum cylinder heads the valve guide bore and seat is machined (bored or reamed) and then the valve guides and seats are pressed in. The next step is to finish machine the seats and guides. This is done in one shot but there are problems that can occur. One is if the vavle guide is slightly off in one axis (but with in tolerance) in the first operation the finish operation may be slightly off location from the first. When the slide with the boring heads comes in to cut the valve seats it is also acting as gun reamer for the vavle guide. The seats will get machined at that machine sations postion. If the vavle guide is slightly off the gun reamer is not going to machine the hole dead nuts to the valve seat. It WILL FOLLOW the bore in the guide bushing to a large degree.We are talking solid carbide tooling here so the amount of defection is not as much as HSS or HSS w/ cardide faces would be. But it is enough to cause concentricty problems. In actual practice I don't think is means much as the valve gets hot when the engine is running and will bend in the area of the stem to head allowing the valve to seat. Now the tolerances we are talking about here are something on the order of +/- .0015 IIRC for the valve seats and guides. Try holding that on machinery running 70 to 90 parts per hour. 80+ hours a week. In varying temperatures and varying degrees of tool edge shapness. And that is only one of the headaches faces when mass producing machined components

PackardV8
02-14-2009, 01:04 PM
Yes, it is possible to do automotive head and block work on a mill, if one just wants the challenge and the bragging rights. I can't find any economic or quality benefit to doing so. FWIW, I've been in racing and restoration for many years. I've done valve guides and seats by hand and on a mill and in a KwikWay Head Shop and in a Sunnen. I like doing them myself, but the bottom line, the investment in tooling to do it correctly makes it a losing proposition for the few times an individual will be using it. Don't even think about trying to compete for business with established shops. Five rebuilders have gone under here in the last three years. After looking at their tooling going at bargain prices, it still didn't pencil out. I've found a local machinist who does beautiful work fast and reasonably and he still gets all my head and block work. These guys are still out there and the end product will be better and the net cost will be lower when you find the right shop.

As always, your shop, your money, your decision.

thnx, jack vines



thnx, jack vines