Member postings for jomac

Hi, just a few thoughts I might pass on. First why not use a chrome/moly cylinder and a cast iron piston, unhardened, apparentley the expansion rate is minimal, so the piston should not jam up,also wear is acceptable, anything over 5cc you could use an aluminium piston and make your own cast iron rings, (modelenginenews has lots of articles and info on this subject), in all cases the piston fit is very important, so lapping carefuly is a must.

See Dave Fenner's articles on building the Sugden special in last years MEW and the problems he had with piston fitting and lapping, Geometer and modelenginenews, has lots of info on this subject.

I am in middle of making the Boll-aero 18, useing crome/moly cylinder and cast iron piston, The chrome 22mm rod I got out of scrap bin at the metal suppliers and the cast iron????? I will cut off an old V8 oil pump. If the oil pump is cast iron thats good !!!!! (I will still use it even if it's not)  because some of the holes through the pump are up to 100mm long with diameters varying from 1/2" to 5/8", these were ground for a good fit of the shafts,(make good cylinders), Jens said he uses front wheel drive shafts, a cheaper alternative is rear half shafts, especially trucks, these are some times much thicker, E.Westbury and L.E. Sparey used these for making collets, but they were heat treated before and after, I think with modern cutting tools, machening these as is, should not be a problem. 

Its been 3 months since I finished  the crankcase out of Al and main shaft out of a high tensile bolt (old engine) and nearly completed the cylinder, but it got hot down here, up to 40 degrees C in the shade, but much hotter inside the 2 car garage, so I have been insulating the walls and roof of my large metal built workshop, I am about to start finishing this engine, let you know how ends up. Sorry for rabbiting on, I hope this topic is a help.

John Holloway.

Hi again.

I was getting a bit confused, about the grit size, on the concave diamond grinding wheels, but I had another look at the e/bay sites, and found descriptions of the wheels. The coarsest wheel is 100 grit, the finest is 600 grit, also as a cross reference they also sell 10" flat and half round diamond files, (A$11) the medium grade is 120 grit the fine is 300 grit , so as the price for a 100mmX35mm with 10mm on the outer face and 5mm on the edge is only A$13-A$15, plus postage A$11- A$15, that seems very cheap, although there are dearer one's, probably because of the shape of the grinding edges ???.

Anyway for the equivalent of 5 quid (my keyboard don't have the pound sign), I think I will go with 200 grit wheel to start with.

Because I can't  find ordinary concave/cupped wheels here in oz, the cost of the item plus  postage from the UK could make it a bit pricey, Besides I mainly only want to sharpen end mills and drills, The next step is to design a cutting machine, I know, Harold Hall has a simple design, so does one of forum posts its also simple, The Bonnelle which is on a disk with real cutter grinders is a bit to complex.

Any more info from the forum would be great.

John Holloway

Hi, I intend to build a tool and cutter grinder, and am thinking that a diamond cupped wheel is the way to go.

E/bay has a good selection of 100mm diamond wheels. The only trouble is, that there is is also a large selection of  "grits" rangeing from 100 grit up to 600 grit. The problem is which grit to use for sharpening end mills and drills, and maybe HSS lathe tools.

Am I right in thinking that the finer grits are to used for polishing precious rocks and gem stones.

So any ideas would be very welcome, and the right info could save me/us  money.

Oh!!! for a decent Tool & Cutter Grinder.

I looked at a few designs and ideas in ME & MEW also H Halls, all seem to have some limitations and easy of manufacture.

So  Graham Howe, was good enough to point me in the direction of MaryPoppinBag on the E/bay site, where they sell all sorts of goodies,One of these is the CD on tool& cutter grinders, which has the complete manuals of many industrial tool sharpeners, More importantley it also has 65 pages of drawings and instructions for the Bonnelle T&CG, the photo's show a very interesting machine that can sharpen lathe tools, drills, milling cutters, reamers etc etc. By the way I am in no way connected to the above people.

The Bonnelle looks complicated, but not as much as the Quorn, so when I can get some spare time, I will look in the scrap box and harrass my local steel merchant, and see what eventuates, Maybe Harold Halls grinding tool holder could be a start , then the Bonnelle or a variation on all of them.

As for sharpening by free hand, I can do it reasonable proficentley, but its a real hassle cause when my fingers get  hot I know the tool is probabley way overheated and I need to start again.

Which reminds me, that years ago while working on site, 30 miles away from  the workshop, and trying to sharpen drills up to 30mm diameter, that we had worn,  broken, or chipped, and were doing this on the side of a 9" angle grinder, or the side of the portable steel drop saw,  now that was a pain in the butt, Why they chipped, was mainley because the holes that were punched in the beams or brackets were usually undersize, maybe the chap punching the holes in the workshop was useing worn imperial size punches and not the metric equivalent, who knows  ??? We  should have had more backups or at least a decent grinder.

Iv'e seen spin indexers on E/bay and in ME and MEW, so are they better than a geared type.

I built on indexer which is a cross between L. Sparey and G Thomas types, but without the indexing plates, I only use the available gears for the two lathes. It works, just doing the maths is the problem.

Now I think a spin indexer with a 36 hole disc uses the vernier holes in the following way, You start with the pin at hole 0 then turn the disc to the next hole which is number 1, and so on, to hole number 9, and continue, by starting back at hole 0 again, turning your blank continuously as you go does this the give you 360 divisions. What happens if you have less holes in the indexing disc, ie, 25.30.40 etc.

Iv'e never seen one in action, only dividing heads, So can some one please explain if I am on the right track.

Also could I suggest to the editors is it possible to do an article, with drawings on how to make one of these, BUT without castings, just out of scrap or what you can buy from a steel merchant , here in OZ shipping costs are horrendous. so a casting is out for me.

In the model engineer Feb/March issue, Dave Fenner described the GRINDALL for grinding the Sugden special pistons etc, He refered to the genuine item in MEW issue 81, and more importantly Alan Booths home made one that appeared in issue 93.

So is there a possability of uploading the article for the home made tool into the website articles. Ive tried to get issue 93 on E/bay but to no avail.

I have  intended to build a Sugden Special for some time, but have been busy making change gears and milling attatchments for my Hercus 260.

The above mentioned tool would be very useful and interesting to manufacture.

Thanks John Holloway.

Richard, the drawings and articles for the Vega Twin are in the following Model Engineer.

Part 1,  3 Jan. 1986, Vol 156, No 3768.

Part 2, 7 Feb. 1986  Vol 156 No 3770.

Part 3. 7 March.  1986 Vol 156  No 3772.

Part 4. 4 April. 1986 Vol 156 No 3774.

Part 5. 2 May. 1986 Vol 156 No 3776.

Part 6. 6 June. 1086 Vol 156 No 3778.

I have copies of these articles in JPEG form, plus line drawings of the plans in Adobe format. 

There is a problem, I dont know how I can  attach these in replies to postings, because if it was me, I would do it.  But, does it infringe copywrite and will it annoy some readers or protocol.

The solution to the above problem could be solved if Dave Clark included these articles in the Model Making section, or some friends or other forum members over there in England may have the relevant issues in their library.  As a last resort I could email or surface mail them to you, But again, putting your private details on a web site is generaly frowned upon so I leave it  you to decide.

Some of the photos of the finished Vega look fantastic. GO FOR IT.

I joined the modelenginenews and puchased the DVD for $A70, this gives me access to the members only site, which has hundreds of articles from Model Engineer and other sources, they cover just about every article and plans about IC engines and relevant  articles on, machineing, casting, cams, etc etc, As an added bonus I recieved for free the whole of the Motor Boys book, in addition there are many more detailed plans for IC engines whose building details are on this site.

If you join this site you can download the monthly updates which at times can be from 4 to 27 mega bites in size, or, Ron will send you for a reasonable fee a CD update.

I know it seems like a plug for this site, BUT, I have learned a heck of a lot, not just IC engines but also machineing.

Granite slabs that are cut for buildings and monuments, should be dead flat.

I used to work for the largest granite cutting and finishers in the Southern Hemisphere, as a welder and mantainence operater, They produced all the granite for the new parliment  house, so when the 2x3 meter square panels were polished in 1 to 5 grades the tolerances were plus or minus 1mm over 1 m, for the front face only, the backs were left as cut.

But !!!!  when the panels were laid flat and leveled with wooden wedges, because the way the saws could cut ofline, most of the panels varied in thickness from corner to corner, That was not a big problem as you could not see the backs and the fixers would pack them out to fit.

Anyway  if you have a section cut from a large panel to be used as a surface plate etc etc, the top surface should be very accurate, Just make sure you are not trying to level it from the bottom surface ie, there could be a variation in the thickness of the corners. 

Does all that make sense,???  cause trying to type and think at the same time leaves a lot to be desired. Women can knit, talk, watch TV and feed the kids all at the same time.

Hi, I tried the eathlink site, Its excelent, !!! I will have to read it again, slowwwwly, Its full of info.

Also I can get The Springs and spring making  from The Austalian model engineer, they are located here in Canberra. Australia.

I was surfing themodelenginenews.com site and came to Colin Ushers site, in it, if you look you can find Alan J Mundays Model engineer utilities, these are fantastic ie, threads, gears, tapers, etc etc plus a calculator for springs, all of these utilities need input then they calculate the printable results.

Thanks for your help. John Holloway

Make sure the wheels are co-planar ie, in line, parallel and dont wobble.

Tension varies between models and blade thickness so check the manual or ask another bandsaw owner.

My large wood/metal bandsaw (home made) started doing what yours is doeing, so after doeing all of the above I had a new one made up, the problem was, that at some stage the blade had got too hot (cutting  large blocks of wood) and the rear of the blade had stretched minutely,  As a result, no adjustment will fix it. The blade tries to go to the high side of the wheels and because the toothed edge is now smaller in diameter than the rear, the blade jumps  off or can go the other way, hard against the guides, causeing more localised heat.

I cannot use coolants on my bandsaw, so I cut slower with less pressure.

I hope the soution to my problem is some help.

First up  I would like to thank Model Engineer for putting in the plans for the Zephyr 

in the magazine, here in Australia I have only just recieved  the Feb/March issue.

Now  if I want to make a 4stroke ie, a Westbury type, single cylinder, there is a mass of information on modelenginenews.com.au. But I cannot seem to find how to make valve springs.

My question is, what are they made of, how do you coil them, and how long are they, and more importantly how many pounds/kilos pressure do you need, to make them operate properly. I know, It all depends on the engine capacity ???