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Author Topic: Chrome liner re-bore  (Read 222 times)
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Fourfingers
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« on: August 07, 2019, 03:18:41 PM »

I read somewhere recently that chromed liners are not really suitable for re-boring.  Possibly due to thiness of chrome?
My experience would tend to support this. 
Any experience out there?
Thanks
Ff aka jc
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TimWescott
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« Reply #1 on: August 07, 2019, 03:46:53 PM »

No experience, but you can apply some logic: a "chrome" liner is brass or aluminum that's been plated with chromium.  Plating is thin.

So on the first pass of your boring tool you take away all the chrome, and you're left with the underlying sleeve material

If you were going to renew an ABC or AAC liner, there'd need to be a step in there where it goes off to the plating shop to be re-chromed.  This is the point where I say "OK, time to switch to electric", or at least "dangit, I'll just buy a new piston & liner".  But if you're really intrepid you could try to find a plating shop.
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Konrad
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« Reply #2 on: August 07, 2019, 03:57:48 PM »

We need a bit more detail as to what you are asking. But there is no reason you can't bore out a cylinder. Now I assume you are talking about a model airplane cylinder with its insert liner. These do have a practical limit set by the wall thickness of the liner. We are talking about the stability of the liner.  

Are you looking at steel liners, brass or aluminum?

You never want to deposit more than 0.3mm layer of real hard chrome on to a surface. Internal stresses tend to want to pull the plating off the surface of the parent material. You will want to deposit enough chrome to allow the finish grinding of the liner to be on size with about 0.16 max thickness of chrome for most wear surfaces.

Yes I have a lot of experience with this as I would often replate my FAI F3D Pylon engines. Please note that any deposited chrome plating will need to be ground to size as chrome does NOT deposit evenly on the surface. Please don't confuse real chrome plating with what is often passed on as chrome when it is in fact electroless nickel plate.

Friends don't let friend fly nickel,
Konrad
« Last Edit: August 07, 2019, 04:09:43 PM by Konrad » Logged

Cut it twice and it's still too short!
qazimoto
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« Reply #3 on: August 23, 2019, 08:33:38 PM »

I read somewhere recently that chromed liners are not really suitable for re-boring.  Possibly due to thiness of chrome?
My experience would tend to support this. 
Any experience out there?
Thanks
Ff aka jc

When people talk about model engine "re-bore" (an auto engine term) they really mean "honing" and piston replacement with a slightly larger one. Chromed liners can't really be honed because they are usually too hard, so a slightly larger piston is fitted. The latter process can be repeated multiple times. I have a 2.5cc diesel with chromed liner that's on it's third piston and it's still a top performer.
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Konrad
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« Reply #4 on: August 24, 2019, 12:12:37 PM »

Hard chrome cylinder liners can be honed. One usually needs a rigid hone such as found in most automotive machine shops used to fit the wrist pin bores on the connecting rods.  It is recommended to use a diamond stone. This would be done to try to reestablish a cross hatch pattern or true up some slight out of round condition.

ABN P&L where the liner is plated with electroless nickel can NOT be reworked in this way, as the plating is far too thin and delicate.

Where does one find oversized pistons? I knew that Fox, Picco and most of the Italian stallions offered oversized piston for their ABC offering.

All the best,
Konrad
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qazimoto
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« Reply #5 on: August 25, 2019, 03:14:12 AM »

Hard chrome cylinder liners can be honed. One usually needs a rigid hone such as found in most automotive machine shops used to fit the wrist pin bores on the connecting rods.  It is recommended to use a diamond stone. This would be done to try to reestablish a cross hatch pattern or true up some slight out of round condition.

ABN P&L where the liner is plated with electroless nickel can NOT be reworked in this way, as the plating is far too thin and delicate.

Where does one find oversized pistons? I knew that Fox, Picco and most of the Italian stallions offered oversized piston for their ABC offering.

All the best,
Konrad

Honed or ground? On planet diesel most c/l clubs or communities have an individual who reconditions engines by lightly honing the cylinder and making an oversize piston from cast iron. PAW also offer this service. Some of the European engine fettlers can make and chrome new Aluminum or brass liners with suitably matching pistons. Depends on the engine but Nelsons and Rossi p/l can be done.
« Last Edit: August 25, 2019, 03:29:13 AM by qazimoto » Logged
Konrad
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« Reply #6 on: August 25, 2019, 09:32:29 AM »

Good to know.

Honed and ground are are both machining process that use a stone. With "Honing" the center line is free floating (Self Centering). In grinding the machine quil/table defines the cylinder axis.  
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Cut it twice and it's still too short!
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