Machining rubber.

Hi Does anyone out there know how to machine rubber.

Can it be turned in any way on a lathe?

Mike.

Edited By sparky mike on 14/06/2013 17:27:37

i once for a job where they turned it on "quick turn CNC's"

they reckoned that a very sharp tool "moved the rubber" rather than machine it

they were working to 0.002" limits!!

Have read about it a couple of times.

Some older lathe books up to the 1940s/50s have stuff on metal spinning, woodworking and machining rubber

All a bit hazy now... but they do exist

Try it after freezing. Thats the way it is done in industry. dont throw it around though coz it shatters

The job in question is a small quantity of mushroom shaped rubber buffers. At the moment the stem of the buffer is around 8mm, and I wish to reduce it to 6mm. I had considered if a hole punch of the type used for making holes in leather / gaskets etc. could be placed in a vice with the buffer and then the vice tightened to pare away the unwanted excess. It might help if the punch is heated up somewhat ?

I am open to any sugestions.

MIke.

Hi Mike,

I too have tried to turn and drill rubber (hard kind), and as Gray says, use sharp tools. Haven't tried freezing, must try that next time.

Thor

I did try freezing rubber on another job but it did not seem to make any difference to the rubber hardness. What temperature should it be frozen at and for how long? Can a domestic fridge be used?

Mike.

The vice method will work make sure the punch is sharp and use soapy water as a lubricant or it can be ground using coarse emery to start then to smooth.

Olly

Used to turn rubber in a university research lab back in the seventies. We froze it and kept it frozen with Liquid Nitrogen and that is mighty cold. It became absolutely solid and easily machineable. I am afraid at domestic fridge temperature you are on a loser! Dave (WhitchurchLad)

It has to be frozen in the freezer. the other methods used in Industry are, grinding or using a very sharp knife tool at high speeed. The edges of hydraulic seals are cut in this way.

Eric

I many year was a platemaker in the print industry and we used to make rubber plates for flerxo and letterpress, these plates were ground to a thou tolerance using a machine with a spinning drum with abrasive cloth attached this was so accurate that people wouldn't believe it I would suggest you grind rather than cut, maybe a Dremel set up on your lathe ??? David

I needed some rubber parts for my Rover P6 dampers but could not get the original parts, I ended up with similar shaped items that were larger in diameter so I made some steel washers of the finished required dia and then used a length of threaded rod and two nuts to sandwich the rubbers, I then put the lathe on its highest speed and with a sharp tool slowly turned the rubber rather easily.

Martin P

Mike,

If I recall correctly, the old trick was to use one of those metal-backed single-edge razor blades as a tool, and lubricate with [soapy?] water. The blade needs to make a slicing cut, like a woodturner using a skew chisel to produce those lovely long ribbons.

Sorry, no idea what speed to use !

MichaelG.

Mike, Try grinding, where i worked many years ago we made a lot of rubber components from a fairly hard it has to be said, rubber compound and we ground them to shape onsurfaceor cylindrical grinders. No lubrication was used all done dry.

I guess some experimentation will be needed and it may well depend on the type or graed of material you are useing.

John

I have a Dremel drill so will probably go down that road for starters and try grinding it first. It is semi hard rubber so I can probably hold the mushroom shaped head in the lathe and then grind the stem. I have 10 to play with and can get more, so will see how we go !! The buffer is for a classic car I am restoring and the bonnet rests on the buffers.. I could of course just drill out the fixing holes in the car, but as these are all in painted parts , I will not be doing that and will keep to originality.

.

Thanks for all the tips,

MIke.

The Little Samson series one builder (either Martin Wallis himself or Stan Nipper) had rubber tyres vulcanised onto rims, then set up a jig to grind about 1/8" or more of rubber away. A huge and filthy job from what I recall.

I have some 3/8" rubber sheet (an old lorry mudguard found on the road) and I want to cut suspension pads for a riding car out of itm, it hacksaws OK, and it's quite messy - but granules rather than dust so it cleans up OK.

Neil

In agricultural aviation we needed to keep the fertiliser out of the fairings that the cables for the tail wheel stearing came out at the tail of the Cessna 180/ 185, and Agwagon aircraft, so we drilled a hole through a 1" x 1"x2" block of rubber, that had to be made into a D shape with a taper along its length. The shape was made by grinding it with a steel bristle rotary brush. After shaping, a length wise cut was made through to the drilled hole, the block was sprung over the control wire, and slid into the fairing, a hole drilled across it and a split pin put through , no more problems with corroded cable.

The wire wheel is OK until you slip, and get your knuckles. Ian S C

Hi Mike.could you use domed rubber tap washers and stick your 6mm stem on with something like "HAFIX" glue .

Just a thought Maurice.

You could always try making a mould and casting them with something like this

Russell

Mike

I suggest that a rotating version of the leather punch would work.

If you find a bit of tube or turn up a bit of steel bar to create a thin walled tube with a 6mm ID and then put a very sharp edge on it with all the bevel/chamfer on the OD. If the parts are already domed then turn a roughly concave hollow in a bit of bar in the three jaw, that you then put the buffer in. With the cutting tube in the tailstock, revolve the lathe and feed the cutting tube into the job. You will need to experiment to find the best lubricant (which you will have to keep off the driving faces.

Once you have gone in to the required depth the 'rubber tube' you have just created can be parted off with a blade held vertically as suggested by several others earlier.

If you only have a few to do the cutting tube does not need to be hardened.

Ian P