Member postings for CHARLES lipscombe

Danny M2Z you have a PM about the Bandiana Sale

Inwards expansion does not happen in the school ball and ring experiment

Chas

I don't think that Bob Youldon's explanation is the correct one -remember that physics experiment at school describing thermal expansion where a ball will not pass through a ring at room temperature but when the ring is heated, it expands and lets the ball through? The inside of the ring must be expanding outwards for this to happen.

Martin Johnson's theory sounds might explain things, but I'm still not convinced because the bronzes are such good conductors of heat and heat from the cutting zone would very soon reach the outside of say a half-inch bar. I presume that brass does not suffer from this problem because of the way it breaks into chips at the cutting edge.

My experience is that when the bronze starts to grab it quickly destroys the drill lands - after which you might as well stop and have a cup of tea while you ponder the next move

Chas.

Re Brian Woods post of 18th October (sorry haven't worked out how to copy bits from previous posts yet).

Brians experiences with holes appearing to shrink and grip the drill when drilling bronze are exactly the same as mine when drilling Aluminium Bronze. Nightmare stuff to drill. But what is the technical explanation of this?

Surely as the material immediately around the drill gets hot from drilling, the hole would expand and give the drill an easier time?

And why are the bronzes (Phosphor and Aluminium ) alone in this behaviour?

Chas

Hi Andrew,

Thanks very much for this info, I now have the situation in perspective. Also I know 2 things. Firstly that I have a grinding fixture and a baseplate for 3/8 - 1/2 inch dies but no height gauge( both early pattern). Secondly that I have never missed out on buying a height gauge at autojumbles because I did not recognise what it was

I don't know what my chances are of buying a height guage on its own but the search is on!

Best wishes, Chas

HI Andrew,

How many Jigs do I need to sharpen a Coventry Die? Do I need Jig A+B+C? What are these jigs called?

Chas L

Unfortunately Brickies advice is not good, although it is seems a popular belief. All it will achieve is to form the skin on the surface of the paint which is in contact with the air-space i.e. halfway down the tin, where it is almost impossible to remove without getting bits of skin in the paint.

As S.O.D. says, there are many types of paint but talking only about the oil-based household and hobby paints: The last thing the paint manufacturer does before sealing the tin is to add a small amount of methyl ethyl ketoxime which is an anti-oxidant. This does not interfere with the drying because it is highly volatile and quickly leaves the drying film. The ketoxime is sufficient, together with the small air-space in an unopened tin to stop the paint drying (aka skinning). If you open the tin, use half of the contents then reseal the tin, you will have lost the ketoxime while the can was open, and there will be enough air above the paint to cause skinning.

There is only one way to avoid this, and that is to open the full tin and decant the contents immediately into smaller, well-sealed containers until they are required. Or buy smaller tins of paint

Chas

Roger, Your unknown thread is very likely to be metric.

AMAC carbs in particular (not Amal which came later) often used metric threads.As others have said it might well be a non-standard metric thread.

What make/size carb is it? A photo would be good.

Chas

The whole subject of whether people circulate a venue/room whatever in a left to right or right to left fashion is covered in a most elegant experiment in Parkinson's Law. A brilliant book, available in Penguin which just about everyone has heard of but few have actually read. Certain to be worth the effort of chasing down.

Chas

I have a Picador type drill sharpener which appears the same as the typical type of Picador in Graham Meek's article and is die-cast alloy (Mazak). The pivot was vertical. It never gave satisfactory results for me and only my lack of skill at hand sharpening prevented me from dumping it. I modified it in accordance with Graham Meek's article and low and behold - perfect results every time.

Slightly different - when I was a kid my cockney grandmother used to use the expression "Black as Noogit's Nocker". It took me years to work out that she was referring to "as dismal a prospect as being committed to the notorious Newgate debtors prison". Interestingly that prison had been closed about a century earlier so she must have inherited the saying from her grandmother.

Chas

Neil: Thank you for your very helpful reply. I will post again when I finally solve the problem but I feel fairly confident you have supplied the answer. Per ardua ad excellence

Once again the forum comes up trumps!

Chas

Ian H: I have sent you a private message.Chas

To not done it yet, I think somehow I have accidentally started a new thread. If you check back posts for the past few days using the same thread title you will see the start of this topic.

Sorry for that, Chas

Thanks to all those who responded.

Neil: The photo shows 2 original parts (brass), the 3D print and a failed stainless casting. The part is a lever fulcrum for a carburetter control which was current from 1909 to 1914.

Typically about 50% of the S/S castings I get back are OK and the other half have the "lace curtain" effect shown.

Thanks for clarifying what you did with your casting - a good example of horses for courses I think

The prints were originally 2-shell i.e. the walls were 2 layers thick with a hollow centre. I went to 5-shell then solid prints but without any conspicuous sucess. I believe it is usual for foundries to apply vaccuum at some stages of their process and this would mean that a small pinhole could lead to a major defect in the casting.

I agree that it would be better to use a company that did the printing and casting in house but the few companies that I have found in Australia to do this, all charge like wounded bulls. I am a hobby-level producer, basically in it for the fun and the satisfaction of creating things with my hands so high costs are not on.

Jason and David Colwill: Print quality is OK but not as good as some I have seen. I don't know what thread size he prints at. Anyhow, I don't work on the surface of the prints before they go to the foundry. The foundry uses a product called Patch Wax to repair damaged waxes before casting (made by DARENT WAXES in the UK if anyone is interested). I have tried this on the 3D prints but it is difficult and time consuming to do this and get all facets of the prints covered. Again I have had limited success with this idea.

My next move is that I am waiting delivery of an el-cheapo vacc pump and vacc chamber from e-bay. I propose to immerse the castings in molten Patch-Wax, apply vacc and watch for bubbles. Then I can drain off the surplus wax and send them to the foundry for casting.

To summarise, I am finding 3D printing brilliant, even indispensible for prototype work(*see below) but I am still struggling with production

*The original is for the left-hand side of the handlebars but I wanted a right-hand version. Without 3D printing I would have to fashion a RH version, probably from solid and probably need several goes before I got it right.

Best wishes, Chas

Edited By CHARLES lipscombe on 15/04/2018 06:30:05

Finish per se is not really the issue because the final stainless castings have a sand-blasted finish and I need to polish this off anyway. However useful to know that such waxes exist. Thanks, Chas

Edited By Neil Wyatt on 17/04/2018 13:52:32

Following several pieces of very valuable advice from different forum threads, I am currently trying to make 3D printing work in conjunction with lost wax casting,

Current state of play is that the finished stainless steel castings (prepared from PLA "waxes" are often rejects, being incomplete in some areas or deeply pitted.

The foundry blames porosity in the 3D prints while the 3D print guy blames the foundry for not completely melting out the "wax". Doubtless this situation can be resolved by more time and effort, but I would like to negotiate from a position where I know what I am talking about

SO MY QUESTION IS: IS POROSITY IN 3D PRINTS A KNOWN CAUSE OF PROBLEMS WHEN USING THEM FOR LOST WAX CASTING?

I have seen Neil's articles on 3D prints to Lost Wax castings but whilst excellent for Neil's needs they look much to low a standard for what I do - which is:

Making otherwise unobtainable parts for vintage and veteran motorcycles, especially control levers etc, so the parts are often about 50x50x10 mms in size and complex shapes.

In conclusion, I agree that I should be doing my own 3D printing so that I have control over the quality but an often unstated fact with 3D printing is that for model-making purposes etc you first need to create a CAD drawing. For someone like me starting from ground zero this is a considerable handicap.

Best wishes to all those forum contributors who have helped me in the past, especially to mechman48

Chas

Edited By CHARLES lipscombe on 14/04/2018 10:16:12

Edited By Neil Wyatt on 17/04/2018 13:52:00

This is not directly related to the previous postings but is related to the thread title

I make stainless motorcycle control levers etc from 303-grade in the obsolete patterns used by veteran and vintage m/c enthusiasts.

After polishing the levers the crevices etc usually contain unsightly deposits of polishing soap. I clean up the castings by placing them in a Lidl ultrasonic cleaner with warm water and a generous dose of washing up liquid which does the job nicely. I then rinse the parts in water, leave to dry, then bag up.

Is it fact or urban myth that washing up liquids contain salt? I have never seen or had reported a case of corrosion on my levers etc. I think it very unlikely that the washing up liquids available in Australia are different to those used in the rest of the world.

I have seen adverts for cleaning solutions for ultrasonic baths but does anyone know what these contain and weather they would cause an explosion/fire risk used in a (pretty basic!) Lidl bath?

Chas

Thanks to all who replied to my post and especially to David Standing 1 for the link which gives all the info one is ever likely to need for hobby purposes.

While searching for my original post I learned two things 1) that the search engine is very specific and won't pick up e.g drill under drills

2) That there are numerous postings on the same topic under different headings e.g spotting drills, spot drills, centre drills.

The late and great John Stevenson's posting on spotting drills is a concise summary of the situation

And for my next purchase..........

Chas