From: Dave Baker
Subject: Re: Block boring
Date: 02 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: cstemple <cstemple@pacifier.com>
>
>  I need to bore a cast iron single cylinder engine block 0.020,
>Question should I attempt to bore it to the 0.020 over in one pass or
>take light cuts on the cast iron? I have a Bridgeport mill to use for
>the job. What type cutter is best to use on cast iron? and what speed
>should it run?
>Thanks in advance


My best advice is not to do it. Take it to an engine reconditioner for the
small amount it will cost. A mill won't have the rigidity to get an accurate
bore. You'll get chatter marks. You'll have to leave 3 or 4 thou to be honed
out anyway to get rid of the tool marks whereas a jig borer will bore to within
a thou. You'll pay as much for the honing as you would for the whole job
anyway. You'll spend hours making up a boring bar long enough, you'll have to
clock the concentricity very accurately - spend the time fishing and save
yourself the anguish. Been there, done that, got the teeshirt - got a proper
boring bar now and would never go near a mill for that sort of job again if my
life depended on it.

BTW - if you are thinking of running the engine with a bored finish without the
proper honing work and cross hatch pattern may the engine gods bring a plague
of boils and pestilence upon you :)


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Block boring
Date: 02 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: Robert Bastow <Tubal_cain@hotmail.com>
>
>All that plus..
>
>A pukka engine reborer will have the required "False Head"..A block of
>thick steel, prebored to clear the bar..that he can torque down on the
>block to bring it to its actual running configuration while it is being
>bored and honed..All in less time than it will take you to bolt it down
>on your mill table so it don't move..too much!

No he won't ! - only once in a blue moon and only for very common blocks do you
find anyone with a "torque plate" to bore and hone them with. In the USA you
certainly have plates for standard V8s cos there are shit loads of em about.
Over here I have never seen a block bored with a torque plate in 20 years of
building engines. 1 or 2 firms have plates for certain types of race engine if
you think the extra cost is worth while. There are too many types of engine and
not enough of each one for it to be cost effective to make the plates up.

For road use, (and most race engines) torque plates are a complete waste of
time anyway. For some thin walled engines taken to flat out drag race spec they
allow you to gap the rings a tad tighter but it's debatable if any extra real
power shows up at the end of the day.


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Block boring
Date: 02 Feb 1999
Newsgroups: rec.crafts.metalworking

In a message dated 2/2/99  3:30:44PM, you write:

> From:	ben@lucent.com (Jan Ben)
>
>> BTW - if you are thinking of running the engine with a bored finish
>>without the proper honing work and cross hatch pattern may the engine
>>gods bring a plague of boils and pestilence upon you :)
>>
>> Dave Baker at Puma Race Engines (London - England)  - specialist flow
>> development and engine work. .
>
>Dave, I asked the same Q awhile back, most people's comments were similar
>to yours. But I got the mill just for this kind of work/play, so I am
>determined to learn on my OWN mistakes :) My attidude is that's it's a
>hobby and a challenge, tho' I know it's worth it to bring it to an auto
>shop.
>
>Having said that, can I ask you to share your experiences of trying to
>bore it on the mill? Again, it would be infinitely more useful if you
>told me what to do to optimise it rather than not to do it. What blocks
>did you work with? I have a couple of Rover/GM 3.5l v8s and an Alfa v6
>(which is wet sleeve, I just need to bore the block to receive the bigger
>sleve).
>
>Again, I am not disagreeing w. your comments, I'd like some advice on how
>to do it better on the mill. thx Jan


I used my turret mill to rebore but only because I have professional honing
equipment and can take the last few thou out to achieve a final size and cross
hatch. My mill only has a 5 inch quill feed so is too short for most bores
anyway. I used to just wind the knee up by hand and try to aim for about 4 thou
over finished size. Finish and chatter wasn't important as I just honed all
that out. I don't think you will get close to achieving a bore good enough to
fit a liner into. My mill has an R8 quill and this is too flimsy to achieve a
bore finish good enough with the length of bar needed to bore a block. A 30
international might have a better chance.

I did try with blocks and the quill horizontal and the table feed acting as the
boring feed but still the flex in the tool prevented a good finish. A mill a
friend had, had a quill with 4 tapped holes on the underside and we made up a
boring bar that bolted to these. Now that was sturdy and you could get a decent
finish but nothing like a jig borer. If you must proceed then try to make the
bar as sturdy as possible and rather than just use the normal quill location
(R8, 30 Int etc) try to make a bar that clamps round the bottom of the quill or
bolts directly to it so it acts as an extension of the quill itself.

You won't cut 20 thou as a finish cut - thats a decent cut even for a jig
borer. Aim for just a few thou as the final cut and work towards your final
size in stages. Also remember that there will be a good bit of spring in each
cut so if you take a second pass with the tool at the same size, chances are
it'll take out another couple of thou. I used to get caught out by boring to 5
or 6 thou from target size, adding that to the tool offset and then finding
that I was 2 thou oversize on the last cut. There's no doubt that a determined
man can bore on a mill but it's a thankless task. Remeber that jig borers have
quills located in bearings a long way apart so there is little quill flex even
in a deep bore. Mills don't have good enough quill bearings for deep boring as
they are really only designed for "surface" level work with short tooling.

I know where you are coming from though because I too am a bugger for trying to
do everything at home even when I don't have a piece of equipment designed for
the task rather than admit the need for anyone else's services. Good luck
though but you WILL scrap blocks in this attempt so don't start out with any
decent ones. Finally, it is hard to keep a block round and without taper if you
have to hone a lot out of it. Hones, even professional ones, are prone to
making a block smaller at the bottom and the best way is to bore as close to
finished size as you can dependant on the depth of the tool marks which of
course must be honed out. A professional will bore to a thou and the bore will
still be good after honing. If you only bore to 3 or 4 thou the honing becomes
megga hard work. You won't save any money by telling a pro that you will do the
boring if he hones - he'll just charge you 3 times as much for honing lots of
metal out.

Now of course you could go out and buy honing equipment too - that'll put you
back at the start of another fun filled learning curve I can tell you !!!


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Block boring
Date: 03 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: address.is@bottom.of.message (Dick Brewster)
>
>In article <19990202153553.28489.00003231@ng09.aol.com>,
>pumaracing@aol.com says...
>
>>>From: Robert Bastow <Tubal_cain@hotmail.com>
>>>
>>>All that plus..
>>>
>>>A pukka engine reborer will have the required "False Head"..A block of
>>>thick steel, prebored to clear the bar..that he can torque down on the
>>>block to bring it to its actual running configuration while it is being
>>>bored and honed..All in less time than it will take you to bolt it down
>>>on your mill table so it don't move..too much!
>>
>>No he won't ! - only once in a blue moon and only for very common blocks
>>do you find anyone with a "torque plate" to bore and hone them with. In
>>the USA you certainly have plates for standard V8s cos there are shit
>>loads of em about. Over here I have never seen a block bored with a
>>torque plate in 20 years of building engines. 1 or 2 firms have plates
>>for certain types of race engine if you think the extra cost is worth
>>while. There are too many types of engine and not enough of each one for
>>it to be cost effective to make the plates up.
>>
>> Dave Baker at Puma Race Engines (London - England)  - specialist flow
>> development and engine work. .
>
>
>I have to wonder if the distortion form the head being bolted on
>isn't less than the normal thermal distortion form the engine
>being at operating temperature. Maybe they should bore engines at
>operating temperature too (:-)


Some people do that too - I only know of one company over here though who
advertises boring a block at running temperature. Another waste of time in my
opinion. Blocks don't run at an even temperature over the length of the bore
and the bore walls go all over the place as soon as they have high speed piston
thrust and vibration acting on them anyway.

I look at it this way. Bore wear takes place mainly in a very limited area at
the top of the ring travel. You can strip a newish engine down and find 1 thou
of wear over just a quarter of an inch of bore length but the power and
cranking pressure won't yet be much affected. That means the rings can cope
with moving in and out over that 1 thou in such a short distance. Even at 3
thou wear you see little drop in power. I stripped an engine recently with 8
thou wear and that certainly was smoking a bit but power was not too bad still.
Maybe 95% of original output.

So does even less than 1 thou of ovality or taper over the whole length of the
bore cause the rings any problems? I doubt it somehow.

I don't dispute that in theory the perfect bore should be round and straight at
operating temperature and with the stresses of the head and mains caps bolted
on. Whether the few tenths error you end up with by not boring with these
stresses in place makes the slightest difference is open to opinion. My
opinion, after seeing what engines can cope with in terms of machining error
and still run at peak power is as I say above. Also most engine reconditioners
don't get a bore anyway near round and straight at the best of times. 1 thou
taper or ovality is par for the course when I check other people's work. That 1
thou is still going to be there if they bored with a torque plate on - just in
a different part of the bore I suspect. Call me a cynic.


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Block boring
Date: 03 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: pdrumm@dwave.net (Peter Drumm)
>
>That depends on where he takes it :) Jig borer? Not around here, no
>way. The auto engine rebuilders use a boring machine that bolts onto
>the block and is run by a 3/4" handheld electric drill, the they hone
>em in a Sunnen machine. The small engine guys use a drill press for
>both operations. Sometimes a mill -is- the better choice!


And there's me thinking that America has such a huge marketplace that everyone
uses CNC machinery. Even the smallest engine reconditioner here would either
use a self contained bolt on boring bar like a Van Normann, Buma etc or a floor
standing jig borer.

I've never seen a bolt on boring machine with a hand held drill to run it; and
a drill press to bore with ?? You sure they don't just run the hone with the
drill press ? Thats a perfectly good way of running a hand held honing system.


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .

From: Dave Baker
Subject: Re: Block boring
Date: 04 Feb 1999
Newsgroups: rec.crafts.metalworking

>From: Jan Ben <ben@lucent.com>
>
>Hey Dave, how does the VN bar align on the mains? I know it centers on
>the bore and the deck, but doesn't it somehow indicate on the mains too?

No the VN doesn't indicate on the mains (nor any other clamp on type boring bar
AFAIK) If you want to bore exactly over the centreline of the mains then you
have to clock up the block on a mill or jig type borer.

I have a "Wandess" BTW. Same type of thing as a VN but more accurate and with 2
speeds and feeds. I have used VNs and they are fine but the feed is a bit quick
and you need to hone out 1 thou or so to shift the toolmarks.


Dave Baker at Puma Race Engines (London - England)  - specialist flow
development and engine work. .