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Member postings for Jeff Dayman

Here is a list of all the postings Jeff Dayman has made in our forums. Click on a thread name to jump to the thread.

Thread: ZA12 - a new option for model engineers?
11/04/2010 14:06:02
Hi Ramon,
 
ZA-12 ahould not be used where the temp is higher than 100 deg C, because it has a low melting point, and its properties degrade rapidly above room temperature. It has low creep resistance as well, so if you use it for a cylinder head the bolts holding it will seem to loosen over time. This is actually not the bolts loosening, it is the alloy relaxing and squeezing out under the bolts! ZA-8 has better creep performance but is also not a high temp material. I would not recommend any ZA or zinc alloy for cylinder heads or other model IC engine parts. High silicon aluminum would be far more suitable, as used in mower engines and trimmer engines.
 
 
10/04/2010 20:25:17
For manufactured goods the ZA family of metals are used because they have good properties for this class of work  but the main reason is they are relatively cheap compared to steel, aluminum alloys or copper alloys. They are better in strength and bearing properties than even high grade engineering plastics, but can be moulded (die cast) so are cheap to make per part, and often no machining or little machining is needed after casting. This is why you see them in cars and consumer goods. I have designed and had made many parts in these alloys over 25 years professionally. For consumer products with a limited life they perform well.
 
Personally I would not use any zinc or ZA alloy on any heirloom ME project because they all corrode to some extent, some rapidly in wet or salty / soapy enviroments,  and rapidly lose their properties as they do so. Also they creep far more than any other class of metal. They are not suitable for use near high heat (like near a boiler). Getting paint to stick to them can be difficult.
 
In short I wouldn't go near the stuff unless it is a quickie throwaway project. If you're planning to eventually have your project sit on your great grandkids' mantel use cast iron, steel, bronzes and copper.

Edited By Jeff Dayman on 10/04/2010 20:26:54

Thread: Drive belt tensioning dolly wheel
07/04/2010 22:04:50
How about shortening a tubular roller from a conveyor belt? good bearings already in those...
 
or a wheel from a commercial paint roller?
 
or a wallpaper roller tool?
 
Hope one of these works. Failing that , you could make a solid aluminum one with a pressed in ball bearing quite easily. A 2" offcut of 2" dia alloy would not be too expensive.
 
Cheers Jeff
Thread: Making the Hand Crane
05/04/2010 01:46:45
Looks great so far Neil, nice job.
Thread: Newest EU legislation
01/04/2010 12:01:10
I heard a rumour today that the EU in Brussels is tabling some new legislation about some commonly used materials.
 
Rumour has it they want to ban the use of iron and steel because they contain carbon, and carbon is flammable.
 
This has serious implications for model engineers. Personally I am worried about the safety risk of wearing a fire blanket in case my lathe bed bursts into flame. The fire blanket could get caught up in the chuck jaws.
Thread: MEW 162 - Phoenix Battery Drills
22/03/2010 14:31:08
in my opinion low voltage devices should never be fitted with mains plugs or receptacles, to prevent the risk of them getting plugged into mains. If it can be it will be.
 
There are so many low voltage connectors around, and some really cheap ones for cars, I would encourage people to use those instead.
 
The "weatherpack" style are reliable even in wet weather, and have no exposed male metal terminals. They are recessed in the plastic shells to resist shorting when disconnected. Spade connectors are also available now with nylon shells around male and female terminations, are very cheap and can be crimped without special tools. Panduit and Faston are two brands.
 
I believe a statement should be made that the mains plug arrangement in the article was for experiment only and that low volt connectors are recommended for anyone making drill mods as described.
Thread: Thread dial indicator
22/03/2010 14:23:20
Your dial gear does not have to be helical if you angle the shaft at the appropriate helix angle for best mesh. Rather than try and measure/do the math/set it up it may be easier to just make the mount bearing adjustable with a pivot and clamp screw and set the angle for best mesh.
 
The gear does need to be a close mesh on the leadscrew, with least possible backlash, for good thread start accuracy. The adjustment above may actually enable this on its own, by permitting backlash to be taken up helically rather than axially as usual. (Easy to make as well.)
Thread: Line Borer
18/03/2010 12:28:57
what model and year car are you working on?
 
north american cars from 1900 to 1930's had generally loose tolerances, but after that got a lot tighter.
 
do you have a rebuild manual? all specs should be there if so, and that will dictate what lashup you need for line boring.
 
my grandfather was a car mechanic 1917-1976 and I watched him do a number of old engine rebuilds. for some Ford models he would centre the bar in the existing bearing caps with a tapered wedge at each end of a fitup bar, and this would allow bolting a bearing plate at the wedge-derived centres to each end of the block - there were tapped holes provided in the block. old babbit was then removed, fresh babbit poured in undersize. He then swapped in the boring bar for the lineup shaft and drove it with a portable drill to bore the new bearings. A quick blue-up and scrape, a two-cigarette paper clearance check with the crank and caps, and in went the crank for good.
Thread: Thread notation
08/03/2010 15:33:02
For the record I am NOT a lover of any particular thread system, or metric, I use what is to hand for models. Professionally I use what is specified if working to others drawings, or what system the client requires for new designs. If I were to put BA thread callouts on new part/product drawings I would expect a big fuss from toolmakers both in Canada/USA and the far east however, so I never do.
 
#2-56 UNC is close to 7BA dia and pitch although a little low on OD ad finer than 7BA, but I do have changewheels taps and dies for it. This would be my first preferred equivalent is making a model that had 7BA specified.
 
#3-56 UNF is also close, but a little larger OD and I don't have taps and dies for it. (although I could get them at low cost from any industrial supply house)
 
finally there is always M2.5 x .45 ANSI coarse metric per B1.13-1983 which is a very close match, but I don't have any taps or dies for it. (I could get probably get them at  an industrial supply house but they will likely ask "what the hell's that for?")
 
All of the above threads can be cut with 60 degree flank single point tools.
 
I have no tooling for 47.5 degree BA threads and get by fine by substituting by comparison as above.
08/03/2010 14:01:55
Christephens-
 
Not opposed to reasoned debate at all, but suggest you start a new thread if you want to digress away from thread topic, which is special fine threads on model drawings.
 
Personally I don't care about Whit and early threading history. I am making stuff in the here and now.

Edited By David Clark 1 on 08/03/2010 20:58:26

Thread: Dave Park's 2-Stroke
08/03/2010 13:15:00
personally I appreciate error warnings - in case I ever want to use the drawings.
Thread: Thread notation
08/03/2010 13:13:15
Does it really matter who invented what system or when?
 
Diverse threading systems are here and likely here to stay for the forseeable future.
 
Much easier to adapt and learn all the systems you can, and tool up as needed.
 
If you come across a drawing with a thread you don't have tooling for, look at the closest diameter and pitch ones you do have and substitute. Common sense really.
 
Much more productive to do that than worry/wring hands or try and start arguments on obscure hobby websites.
Thread: Bandsaw speed control
07/03/2010 19:37:02
If you do make an electronic controller and get the speed down far enough, you will not likely have enough power to saw. You would be better to rig up a jackshaft and pulley transmission with a stock motor.
 
Is the bandsaw a three wheel type with aluminum frame and plastic wheels? If so, it will not last long sawing metal.
 
You would be farther ahead making a saw with a simple angle iron frame and two plywood wheels. Yes plywood wheels. A friend and I built one that way almost twenty years ago for exclusively metal cutting and it is still going strong. We made two 24" (as I recall) wheels of 3/4" thick plywood faced with neoprene rubber strips glued on with contact cement. The rubber provides plenty of grip for the saw band over half the wheel, a huge contact area, and the large radius gives a 12" throat for the cut. Each wheel has a steel hub and shaft inset into it and large 3/16" thick washers each side 6" diameter bolted thru the wood to support the plywood and drive the saw. We drove it with a 1/3 HP washing machine motor and two stage pulley drive, a 2" to 10" first stage and a 3" to 12" second stage. Bronze bearing plummer block were used on all shafts. This drive gave 150 sfm with the motor we used, a little fast but with a GOOD QUALITY industrial bimetal blade works great in any metals including stainless and A or D tool steels. We made some blade and wheel guards of galvanised sheet steel to keep fingers away from the blade. Also 3 ball roller brgs were used a blade guides just over the table and adjustable up and down. I'll see if I can get him to make some photos to post here.

Edited By Jeff Dayman on 07/03/2010 19:40:39

Thread: Thread notation
07/03/2010 14:55:07
Sorry I don't know about the origins of the letter and number drill rationale. Could be just another adopted working standard from a particular company.
 
I forgot to mention the below 0 size threads in UNC/UNF. These go down to 0000-160 that I know of. Again it is based on .060 as number 0, and you subtract the multiple of .013 as you go downward from number 0.
 
ie 0000-160: .060-3 x .013 = .021" od x 160 tpi
 
I have some 00-90 screws used on a couple of my models and that is as low as I want to go (I can hardly see if they're threaded!)
 
There is also the UNEF series of threads which have finer pitch for a given OD similar approach to the ME threads. You can still buy UNEF taps and dies from industrial tool suppliers  though which are generally far less money than ME suppliers due to their higher sales volume. 
 
Charts for UNEF and most other threads are of course in Machinery's Handbook and probably on the web if you seacrh around a bit.
06/03/2010 20:33:31
Just in case any newbies don't know, there is a simple rule for UNC/UNF numbered threads. The base number 0 is .060" OD. the numbers indicate what multiple of .013" to add to the base dia .060" to find OD.
 
example #4-40: 4 x .013 +.060 =.112" OD 40 TPI
 
                #10-32: 10 x .013 +.060=.190" OD 32 TPI
 
check em on yer chart if you don't believe me...
 
easy now you know the rule eh?
 
As far as where this system came from I assume that it was started in a big USA hardware maker's factory in the 19th century and was gradually adopted as a working standard (and still is in North America although Metric is creeping in slowly-cars and office equipment are designed in metric and use metric fasteners. Steel and other metals are still made and sold in inches. Fasteners are available in both systems but metric are often more money. Domestic plumbing is all inch including threads)
Thread: Smart & Brown Nut
06/03/2010 13:46:57
I'm not sure, but this may be a passive backlash eliminator. the thin end after cutting at the factory could have been given a press or bash to slightly deform it toward the main part of the nut. This would result in a very slight deformation of the thread pitch. When assembled to the leadscrew the thin end would spring back to conform with the thread pitch, but the interference force would take up some backlash. This would be rather rough on the leadscrew, but maybe they used a hardened leadscrew.
 
On other antilbacklash systems in different machines separate springs and other devices do the same thing.
 
The angled slot on top is an oilway as Keith mentioned.
Thread: Thread notation
06/03/2010 13:38:46
well since the first "colonials" comment offered no real value I thought I should chime in.
 
For the standard engineering threads generally a pitch is related to the diameter and is usually rather coarse, for strength and ease of cutting, tool longevity etc. If these coarse threads were used in the scaled down walls of model parts, there would be very few engaged threads.
 
In ME designs often a special finer -than-standard thread is used, ie 40 threads per inch or 32 threads per inch, which give more engaged threads in thin walls. it also helps keep diameters small and closer to scale in things like piston rod glands, because the fine threads are also shallower than coarse ones.
 
Hope the info helps.
Thread: Stellite
06/03/2010 13:30:32
I think Stellite has pretty much been replaced by carbides and CBN tooling these days. I haven't seen it offered for years at the metal houses I deal with.
 
What are you boring that requires stellite? (maybe someone here can offer a different solution from their experience.)
 
It also used to be used in some car valve seats and valves but new alloys and surface treatments made it obsolete.
Thread: What type of STEEL?
05/03/2010 12:00:52
I would suggest you spend some time with at least Wikipedia to get the basics of metallurgy.
 
At this stage of your knowledge the book Machinery's Handbook would be a very wise investment. It has a mountain of info on metals and every other aspect of mechanical work. The sections on drills taps threading etc. are invaluable. This book is pricey but worth every penny. I have used mine almost every day of a 30 year working and modeling life.
 
 
Thread: Oil Traps
01/03/2010 12:27:05
Looks  great Fred, sorry I don't have any oil trap info just wanted to send my compliments.
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