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10-29-2003, 11:44 PM #1
What is the common method for boring iron cylinder liners? The first step would be to create a fixture to hold them, but what type of machine and tooling is used?
10-29-2003, 11:55 PM #2
I don't think that cylinder liners are generally over bored. My experience is that they are discarded and replaced with new liners.
The wall thickness on the liner is not really enough to support much in the way of overborring.
I'm sure that it has been done. And I'm sure that it is not much fun.
I once remachined the top surface of a set of sleaves to accept a high performance head gasket arrangement for a tractor puller. I did end up making a special fixture and cutting them in the CNC mill.
10-30-2003, 12:25 AM #3
I'm thinking of a custom application with a 2mm overbore. New liners are only available with .5-.75-1.0mm over. And at $150+ per cylinder (8) for new piston/liner assemblies, boring the existing liners and using $22 pistons is quite tempting. The rebuilders and hot-rodders do bore these things. I have a picture of them being done in a specially made fixture that does nine at a time. I was just sorta wondering what type of cutter they use. I don't think this is something I would attempt to do myself, just curious mostly. I've bored intake manifolds and throttle bodies, but I don't know if the Bridgeport and boring head I have would be accurate enough for a cylinder.
10-30-2003, 12:32 AM #4
Bore and hone them (to spec) AFTER they're installed. Unless you have a boring machine, you can use a mill. If you're making blanks, you can use a lathe with a boring head in the tailstock.
How big and what are they for? You can get premade blanks.
ops, didn't finish mine until you already posted. Your BP isn't acurate enough? Wow, don't let that get out around here. Most shops that do this full/part-time have a jig that simulates the crank. The tooling (guide) clamps to this "crank" so that when the cylinder is bored, it's perpendicular to the crank center-line. They will also use a simulated head to place mounting torque on the engine block and cylinders.
[This message has been edited by CCWKen (edited 10-29-2003).]
10-30-2003, 12:49 AM #5
When I said custom I meant not on the shelf at Autozone. I do have the OEM liners to work with, no need to make blanks. Cadillac 4.9 liter V8. Aluminum block, iron sleeves, iron heads. They call them semi-floating liners. 92mm diameter, want to go to 93mm or 94mm. They cannot be machined in the block, as they are only a slip fit, the only thing holding them in place is the heads. I think the most difficult part of the whole process would be holding the sleeves, but I still don't know what type of cutter is used.
10-30-2003, 12:50 AM #6Jose Guest
Back in the dark ages of Ralph Nadars' Corvair, we spent over 8 months searching GM's warehousing trying to find six new cast iron cylinders for the air cooled flat six. Young man at an independent parts house suggested boring the original jugs. He had a biker friend with machine shop and tooling to bore Harley Davidson cylinders. Had 'em ready the next day, worked great.
Dry cylinder liners, as I remember them, are quite thin. After installation, the new liner, generally, was never bored. A wet liner is thick by comparison, for obvious reasons.
10-30-2003, 02:43 AM #7
Oh.... Oh yea... Floaters are different. In that case, SCRAP IT and get a real engine!
10-30-2003, 04:08 AM #8
you can bore those thin liners.......
but if you don't wrap them with a bundle of themair rubber band bracelet things borrowed from the brake drum lathe
you will not be happy with the finish or the noise
easier to put in a lathe but I'd do it in a mill everytime and suffer the pita of clamping them......
I assure you it can be done
10-30-2003, 09:34 AM #9
I've bored dozens of liners atone time or another. I just made a pot on a 4 Jaw chuck clamped the liner to it using all thread studs and bored them with a nice beefy bar.
An alternative is to mount the liner in a saddle on the carriage and line bore them with a double length plus overrun between chuck and tailstock.
Either way your set-up has to be accurate so the bore finishes concentric with the exterior mounting features. Leave 0.08 to 0.10 mm for honing alowance. Use a real cylinder hone (like a Sunnen portable hone) that ensures roundness and cylindricity and the requisit crosshatch finish (for proper ring break-in) not a glaze breaker.
10-30-2003, 11:47 AM #10
When I was doing tooling for DANA, they bored the sleeves to about .020" (.5mm) under and then honed. We do about the same thing here except its not cast iron. We have "pot" fixtures that locate on the OD and clamp to the ring. A good automotive shop that has a Sunnen cylinder king hone should be able to hone 1.0 mm in about 15min.
10-30-2003, 12:25 PM #11
Forrest......... those caddy liners are really thin and relatively long........ if left undamped........
they will chatter enough to take the tip off your carbide in just a few revs
I competely rebuilt a 4100 engine back in the mid eighties before anyone remanufactured them. I would rather be beat in the head with a pillowcase full of soup cans.
any flimsy engine that will lose a crank main journal if one of the drive belts is slightly overtightened........ well.......
needless to say....... I laughed at the next caddy owner that heard it could be done and showed up at my shop
10-30-2003, 06:54 PM #12SCRAP IT and get a real engine!
11-06-2003, 02:58 PM #13Lead screw Guest
Make a jig for your lathe carriage using a boring bar between centers that exactly simulates the liner bore in the cylinder block, clamp the liner in and bore away!
11-06-2003, 04:03 PM #14
Thin walled liners? I'd still bore them in an engine lathe. Make a pot (a full diameter full length slip fit lathe spindle fixture) for the liner. Then I'd bore it with a 2" dia boring bar sticking out of the compound.
I'd make the pot of aluminum about 0.0005 undersize for the smallest liner, bore it a trifle undersized and hone it to size with a Sunnen portable cylinder hone.
Then I'd bore and hone the liners using the same set up protecting the lathe from the abrasive.
The advantage of aluminum is it expands faster that cast iron. Heat it up 100 degrees over ambient and it expands 0.003" so you can pull the finished liner out. You have to wait for the pot to cool off on the nextone before you can start work.
You'll need a 17" lathe to bring this job off and it should be level and in good condition.
Since the liner is fully supported by the pot there will be no chatter arising from the liner itself.
As for the bar, it has to be stiff. A spaghetti 3/4 bar will be nothing but a huge PITA. The tool post is inadequate for a bar 8" long. Make one specially for this job that attaches directly to the compound. I make them from pipe or square tube with a blank with a tool slot machined in it welded to the end. I use a block of steel on the compound end that has a 13/16" hole in it for the tool post stud. I weld the pipe (long enough to bore the cylinder in one cut, right?) to the block at the right height to be on center.
If you want to get a bit fancy, fill the pipe about 1/4 full of shot gun shot. This will dampen the bar to a surprizing degree.
Watch it. More shot is not better. Load the bar 1/4 full of shot and no more. If you use too much shot the individial pellets will interlock and move as a unit. You want individual random motion of the shot to blot up vibration energy.
11-07-2003, 12:50 AM #15
I made a fixture, jig, or "pot" as you call it. It's turned from steel because that's what I had around. A liner slides in to 1/2 the depth of the liner, which is as far as they are machined on the outside. I then have a ring that sets over the top of the liner and several bolts to clamp it down, just like a head and head bolts would do on the engine.
I turned one out to 1mm oversize just for practice using a 3/4" bar, the largest I have. It did get a bit of chatter, but not as bad as I expected. I really like the idea of making a heavy boring bar from pipe. I'll still need to wrap the part of the liner that is not inside the fixture to keep chatter to a minimum.