How Easy Is It To Machine Parts?

[CzechItOut]

First off, I'd like to state I have no idea what I'm talking about...

While watching Wheeler Dealers this morning, Ed needed a piston ring for a Range Rover's air suspension pump. However, the individual part wasn't available so he had to purchase a whole re-conditioned pump for £120.

I'd have thought that a simple piston ring contains a couple of quids worth of metal and would be simple to manufacture, even if made to order. Therefore, if you sold it for even £30, it would be significantly cheaper than a whole re-conditioned unit.

Or am I talking rubbish?

[Speedy11]

I don't know if this is the same part but 1 piston ring and 2 o rings for a Range Rover air pump for £12.50 plus the vat

http://www.island-4x4.co.uk/suspension-compressor-...

It is probably made by stpart so won't last 5 mins though

[Krikkit]

It's very, very hard to produce that kind of thing at home - you have to find exactly the right material (i.e. the right alloy etc) to create your part, then you have to make it with the right tolerances etc to be functional. No mean feat in the garage, you would need very good tolerances on something like a piston ring to be worth bothering with.

The future will be 3D printing replacement parts for cars etc, but they will generally be of a lesser tolerance requirement than something like a piston ring, bearing etc.

[AW111]

In theory you are right, but paying a machinist commercial rates to :

Measure part
Select material
Setup machine
Make part
Heat treat

will come to over 120 anyway

[GadgeS3C]

AW111 said:

In theory you are right, but paying a machinist commercial rates to :

Measure part
Select material
Setup machine
Make part
Heat treat

will come to over 120 anyway

As well as having invested in all the expensive equipment required and the training to use it.

[AW111]

If, however, you work in the appropriate environment and the machinist likes beer, one-off parts are easy

My custom exhaust was welded for a bottle of Jim Beam, and I have had various parts machined for a slab (24 cans of beer, for non-Aussies)

[GadgeS3C]

AW111 said:

If, however, you work in the appropriate environment and the machinist likes beer, one-off parts are easy

My custom exhaust was welded for a bottle of Jim Beam, and I have had various parts machined for a slab (24 cans of beer, for non-Aussies)

I'll buy the beer if you pay for the postage!

[AW111]

Beer - the universal currency!

Unfortunately, my mechanical skills stop at spannering , but I have dynoed a couple of mates cars after hours, at a slab a time

[morgrp]

A piston ring is prob a bad example as would be tricky to fabricate as they effectively need to have a certain amount of spring and tension and would need a specialist fabrication technique - that said I have lathed up and fabricated loads of little bits and pieces over the years so not out of the question

[Tickle]

Did my Mechancal Engineering apprenticeship back in the day as a tool maker. Custom machined parts like most manufacturing processes be effected by economies of scale.

If there is an order/demand for a lot of said component it could be produced in big numbers by CNC's offsetting the cost of the expensive initial CNC/tooling set up being absorbed into the the price of many components. Other costs too will benefit from larger numbers of components being made, materials, semi-skilled labour once tooling is set up, overheads etc etc.

For just a one off of bespoke component there will be a big cost associated with it. The set up costs, skilled engineers sell out rate, materials (if materials not in stock too much material will be bought as a supplier will not sell 'just the amount needed') and possible bespoke tooling. These factors will all be incorporated into the price of that one component.

There are methods for producing in-between the two extremes I've mentioned, small batch production techniques. But as the OP mentioned there probably isn't much demand for the component on Wheeler Dealers so to answer, it would probably cost a lot.

.....If you can find a thirsty apprentice though, we often did Friday afternoon jobs for beer tokens!

[Garvin]

The piston ring in question is not metal - it is a rubber/plastic material that makes the air tight seal between the cylinder bore and piston in the compressor pump. Not dissimilar in concept/operation to a bicycle pump. They need to be manufactured precisely and are not something that can be easily machined. They are readily available for the P38 (Mk2) Range Rover but, apparently, not for the L322 (Mk3) Range Rovers onwards.

[jas xjr]

Quite a long time ago I had a mk2 golf gti . There was a fashion for adding various interior bits and pieces in aluminium . A friend of a friend made me a hollow tube which sleeved the gear stick . You could buy one for less than £20 . How much would it have cost for mine had it not been made in the chaps lunchtime? He reckoned at £600 for the design and machine time .

[Tickle]

jas xjr said:

Quite a long time ago I had a mk2 golf gti . There was a fashion for adding various interior bits and pieces in aluminium . A friend of a friend made me a hollow tube which sleeved the gear stick . You could buy one for less than £20 . How much would it have cost for mine had it not been made in the chaps lunchtime? He reckoned at £600 for the design and machine time .

He is probably right!

I remember making a polished aluminium sphere gear knob, I'd say it would of cost £300 more than the £30 Demon Tweeks were selling them for.