Morning chaps.

I popped into my local engineering place yesterday to see if they could make me some mild steel outers and stainless crush tubes for my suspension. I showed him the top hat bushes they were for and he asked if I want them made up too.

I didn't know you could do that as they look cast. He rekoned if I got the type of plastic they can cut it.


Is it OK to do this?
is it a certain type of polyeurathane to make suspension bushes?

If they can do it it may be a bit cheaper than whats available so I'm pretty interested.

Any Ideas?

Yes it's OK

Don't think you need a specific polyurathane but make sure the shore rating is right for your application (firmness)

I believe the trick with machining it is to freeze it and work it while it's still hard.

Taken from the superflex site:-

These helpful hints will ensure safe, accurate machining of polyurethane rod.

1 - TOOL: Parting tool must be in the form of a razor sharp knife blade. The machining tool should have a 30 degree rake on the leading or top edge. Use of light oil will assist deep parting off.

2 - SURFACE: 500 ft/min e.g. - 2000 RPM on 1" bar.

3 - LENGTH RATIO: Simplest to machine with 2:1 diameter to length ratio, e.g., 2" solid rod projects 4" out of chuck. (The poly rod will move away from the tool if any lower).

4 - TRAVELLING STEADY: Don’t use traveling steady when machining long tubular lengths. The friction created where the steady comes into contact with the rod, will melt the polyurethane.

5 - MANDREL: When machining outside diameter on long tubular parts, machine on a "Mandrel".

6 - DRILLING: When drilling, force drill into rod to create required internal diameter, then allow drill to dwell for a smooth finish. The polyurethane material will actually melt to size.

SPECIAL NOTE: When working with 70 Duro, for best results and for ease of machining, place rod to be worked on, into the freezer section of a refrigerator the night before.

SAFETY PRECAUTIONS
• When machining any polyurethane component DO NOT INHALE
• any vapour or smoke which could be created.
• Always wear protective clothing and glasses

Could be a goer then.

make sure you use the correct grade polyeurothane, the wrong type could split

Dont know anything about grades of eurathane.

How do you find out whats the right stuff?

Been in and spoke to the boss who said me cant really be arsed turning the plastic. Says it makes a real mess of the machine. He did all the other bits though.

Ah well.