Any subject.

Sorry, no metal working. Took a load of rubbish to the tip. Did some gardening. Just seen the finish of the GP. Now going back out to the shed to clean up the mess I've made doing wood-spoiling for a couple of 9' long bookshelves.

Mark Rand RTFM

OKay, a hypoid oils question.

I've been working on a 50 yr old large marine gearbox, reassembling it now with various new bearings etc. The oil spec is vague, basically non-critical, SAE 20 or 30 'engine oil or good gear oil'. There's been an issue with the reduction gears grating heavily in ahead gear, this seems to have been down to a combination of worn bearings and the output gear loose on its taper. All that has been sorted, but the output (spur) gear has wear marks, the best word I can think of for them is 'striations', it's a pretty fair bet that these will mean the gears are still noisy. I happen to have a drum of EP90 hypoid oil which I would like to use, thinking it might give the oil film a better chance of survival between the gear teeth than if ordinary engine oil is used. Two issues- will it be of any benefit as regards the gears?

Second, the ball and roller bearings mostly have brass cages, is there an issue with EP oils there? I know it can cause problems with some plain bronze bearings but there are none in this box. Also is it likely to cause any problems with the friction clutches (Ferodo-type materials)?

In round figures the box is transmitting about 300 bhp, input at 600 rpm, 3:1 reduction. Sorry, not model-sized.

Thanks

Tim

Well I've often wondered it's it worth fitting an R8 spindle to a Triumph or Student and increase the stiffness by a factor of 7?

John S.

Sounds like a cracking great idea John,especially if you weld it in.I find an easier way is to put them in the skip first and all the other junk on top,this helps to stiffen them up a bit.And....if you`re lucky the scrap merchant doesn`t notice the bottom of the skip is light scrap so you get top bucks for the whole load. I knew there had to be a reason for R8 spindles existing in the first place but I just couldn`t think what it was. Mark.

The reason the R8 spindle was invented was for a lecture by the Machine tool Builder association in Paris [ Texas ] in 1938 They wanted to compare the best qualities of a NMTB 40 with a hypothetical bad design.

Throwing together a non standard diameter, a taper that matched nothing, a drawbar for a non standard thread and dimensions only suited to hold farm gate on hinges they came up with their hypothetical bad design.

Bridgeport's saw it, not realising what it had been invented for, fell in love with it and the rest is history

What I was told when i used to rebuild british /jap bikes with wet clutches was that EP oils would weck the plates.

Mike Cole

Alright then. We've got a fused-deposition modeller at work that we use to make boxes, brackets etc. for various electroniccy things we build. You just design in SolidEdge and send the stl file to the printer. Many hours later, you've got whatever you designed.

What is the design flow if I were to use something like a KX3 cnc mill to do a similar job? How do I convert the design into G-codes? I'm used to doing something similar with a T-Tech PCB milling machine but I can't see what I'd need to buy to move to using a small mill.

Chris

Understood.I had thought it was the other way around.Bridgeport had built this machine and when they came to put the taper in the spindle discovered there wasn`t enough metal there for a proper machine tool taper so looked around to see what they had.In the bar rack they found a bit of bar with a taper on it (it wasn`t meant to be tapered but that`s American steelmakers for you) and this bar fitted their spindle.GR8 they said we have a tool holder that nobody will/can copy,so that`s how the GR8 taper was born.Over the years it got shortened to just R8.

Never understood why they persisted with R8 when they proved that QC30 (and therefore proper 30INT) would fit. I suppose they reckoned that they'd "made a standard" which to some extent is true. But I'm with you that it's a crap one.

Charles

If you are using stl files that means 3D and a CAM program that will convert stl to 3D moves in G Code. Problem 1 is cost, the ones that can do this in fine detail with speed and control are very expensive. The cheaper ones that do this tend to be more 'arty' and have less control over the toolpath but are very quick and easy to program.

Take a look at this website to get an overlook of what is needed.

They do have a working demo you can play with on the site where you can play what if with a couple of sample jobs.

I have done a couple of small patterns on a converted X3 CNC for some vintage car parts using this and they came out well.

John s.

Just to add to the story,

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk

Try that again.....

Why did we end up with so many variations on a theme with the INT30, 40 and 50?

Apart from the basic one, there are QC versions, and yet another set with different holding threads.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk

How much? For example, a second FDM is gonna cost me 20K and I'm pretty sure things'd be faster and better surface finish with a small milling machine in a lot of cases.

We've had stuff made outside but it seems very cheeky to ask a company what design flow they've used so we can buy the same and never give them any work in the future.

Thanks.

Sounds good to me.

Chris

One CNC is about =A32500, FeatureCAM is about =A35K as a rough guide.

JOhn S.

Thanks, John. Now I can start looking at putting a shopping list together.

Chris

I closed early and took most of the day off to visit an amateur radio junk sale - my junk box needs refilling. Guy there had a wonderful vehicle, one of those toy sized pickup trucks, the sort you want to pick up and push along the road to wind up the flywheel, powered by a RR Viper jet on the back. It just fits. So just manoeuvre that traffic warden to the hot end... Or would the suck end be better?

Regards,

David P.

From memory, the sulphur in EP oils will react with all brasses and bronzes.

Cliff Coggin.

Use the hot end. It has greater range. You have to get quite close before being sucked in.

Henry

I thought the idea of extreme pressure additives was that they reacted to a small degree with the exposed metal to form a protective coating?

Best wishes,

Chris