Circle Heat tTreatment

I'm currently machining a crank case casting for a rare Motorcycle and despite checking a couple of times regarding the groove depth for the Circlip/retaining ring I seem to have made it slightly too large by about 1/16" on the diameter.

I was thinking that maybe the best thing to do would be to heat the clip up to Bright red and let it cool down slowly to bring it back to a soft state so that I can expand the ring by placing it around the jaws of my 3 jaw chuck and opening it out slightly. Once done I would then heat it up to red heat and quench in oil then temper it to around 400 degrees centigrade and quench to lock in the temper.

Anybody any ideas if this will work or not. I don't want the clip loose in the groove just in case the bearing it helps retain starts to rotate i the groove and wears away the sides of the groove or worse still decides to pop out into the crank case.

Bob,

What size is the groove and what size ring did you intend to fit?

Mark

PS. the ring you have (or most you might buy) will probably be quenched in liquid salt in a process called "Austempering" rather than oil quenched

Edited By Mark C on 20/10/2016 11:37:34

Just bend it cold.

Done it loads of times.

John,

That may well work but it would be good to know how big the thing is before hand - just bending them is risky unless you know the provenance of the ring. All rings are not created equal, you have probably been lucky!

Mark

Can you turn a ring that is slightly larger OD than the groove, slightly larger ID than the correct ID the groove should be, cut a section out of the ring to allow it to be sprung closed a little and pop it into the groove? The circlip will then push it outwards and hold it in place when it is installed?.

Or purchase the next sized circlip?

Or next sized metric circlip if original is imperial and vice versa. Sometimes you get lucky.

I would first try to work the inside of the ring with a small hammer, so the inside curve of the ring expands and the diameter gets larger. Niko.

if the circlip is in good nick I would not touch it but make a 'filler' strip for the groove/housing.....just a strip of mild steel of correct width and thickness and nicely bent around a fromer of the right size, then fitted carefully into the groove,...and the circlip will be in the right position.......

Edited By Bob Stevenson on 20/10/2016 12:49:46

If the circlip has been edge rolled from section wire, you may get away with "stretching" it, if blanked from sheet, no way.

Make up the difference by rolling a "Packing ring" from a suitable diameter piano wire and insert into groove then use circlip in "correct" bore.

Regards Ian.

Hi Mark,

the bore is 2 13/16" I.D. and the groove is 2.95" I.D. I don't need to expand it too much, when the clip is in the groove you can see that it has about 1/32" float in the bore of the groove. I did try expanding it cold but am scared to expand it too far in case it breaks.

I have thought about packing the groove but am also afraid that the packing could come out and get into the crank case. The clip is made from flat plate.

I will search the web for the next size up but the thickness of the clip is .070" is not common.

2.95" is near enough 75mm. Standard thickness is 2.5mm, you might be able to get it surface ground

Bob, you might want to look at a DIN472-72 which would fit a 72mm bore. It would have a free OD around 76.5mm but is thicker at 2.5mm (an extra 0.72mm) and would normally require a groove of 75mm. You could then increase the groove width (it does not matter if it is a little wider as long as the position of the fitted ring is correct - so, wider on the bearing side) or you could grind the ring to match the 70 thou. if you have the facilities. If you grind a metric ring, you will remove the phosphate coating but if it is in an engine it should be lubricated resulting in little detriment.

As John mentioned, you could also try stretching the ring (it is most likely a wire part rather than blanked from strip at this size - unless it is an import from overseas). But that would definitely be "bodging" in my book and if you have a lot invested in the job why take the chance on stressing the ring when you have other options available?

Mark

Goijemiddag Speelwork.

your suggestion to work the inside diameter with a small hammer worked a treat. I worked on one side only tapping quite heavily with a 1/2 Lb hammer and the spreading of the metal increased the opening between the eyes by about 1/4". I used a flat surface and worked one side only so that the flat unhampered side will be the one that I will fit against the bearing when I fit it.

Herte Bedankt,

Bob

And if you do grind a pressed steel circlip, it helps to note that one of the outer edges will be sharp, and the other rounded, from the pressing process. It might be best to grind the rounded face, so you finish with two sharp edges (and then it makes no difference which way round it is fitted).

Not everyone seems to care about this detail, but the rounded edge is clearly more likely to be pushed over the edge if things get 'interesting' as well they might in this case.

That said there are circlips which are ground on their outer diameter, so this does not apply to them.

Finally, is there any way you could add a filler-piece (a thin shouldered washer, perhaps?) inside the circlip which would prevent the clip from contracting inwards? This might save the day as you are clearly pushing your luck, here.

Cheers, Tim

Tim, the radius you mention is required to clear the radius in the groove. If you are using ground rings, they often require special grooves to ensure no interference. For rings of larger size (from roughly 30mm up) they are generally made from coiled wire so you get two radius edges as there is no blanked edge on the working diameter.

I have a particular expertise in these if anyone wants to discuss them further (as does "Circlip" - surprisingly with that name! ).

Mark

Photo of original would help. Never remember edge rolling 70 thou material but original could have been "Discus" ground. Can still remember the pain of "Flattening" coiled rings of thicker "Wire".

Regards Ian.