Member postings for Neil Lickfold

clover plate , not my picture, from a google search.

It just goes to show what can be achieved with what appears to be very a very primitive method. I was very impressed by the quality of material that they made , considering what was used.

No doubt , as time goes on, we will rediscover a lot of things.

Neil

How are precision collets made ?

Does any one know ?

Thanks Neil

You just can not have the tool too sharp to cut cooper. It does need a nose radius unless you want to feed it very fine. Some grades of HSS just do not hold as sharp an edge as others. Just like some grades of carbide do not hold a sharp edge. Using a fine hone stone makes a very big difference when turning soft materials.

Making a guide up so the stone is not rocked as the edge is being honed is also a big help in getting the tool sharp. When you look under a powerful loupe at the cutting edge you will see the various marks from grinding and the hone. Getting it as fine a finish and smooth makes all the difference. It should look shiny to the naked eye.

They now make carbide inserts with very high positive rakes for copper, and they are very shiny on the surface finish, and expensive.

Vege oil like canola or olive oil works very well with most materials including copper.

When everything is right, you do not need it to be going really fast to get a good surface finish.

Neil

If a piece of key steel hit against the corner of the plate leaves no marks, then the plate is harder than mild steel.

There are grades of steel plate that comes already pre hardened at about 40 Rc or so. That is very tough going with HSS tooling that is for sure. It should file very easy and be easy to put a ding into the surface. Capcrews are about 40 or so hardness, so it should file a whole lot easier than a capscrew does.

Neil

Sorry, Mine is the Dickson Type.

It used to be a 4 way tool block with a sprag type of arrangement that allowed it to index every 45 degrees.

I removed that little block screws and pin, and replaced it with the Dickson type setup. I did have the Axa type but it was too thick in the holders to get tools to the correct centre height. It just gathers dust for another project oneday.

I will take some pics of what I have done if that is of any help and try to post them tomorrow if all is well.

Neil

For my one, I made a delrin bush that fits snug in the bottom of the tool block, and has drag on the bottom of the original pin. I made a stepped washer for the top.

The best part is, that due to the snugness of the delrin bush, when I rotate the tool post or need to clock it in, it rotates and pivots without the issues of the standard clearance tool posts.

Knowing what I know now, I do not use soluble oil on my lathes at home. I prefer to use either small amounts of vege oil,(canola or what ever is the cheapest at the super market, where needed), or the light cutting oils.

I worked with some production machines that had oil only and others that had the soluble coolant. The machines that ran only cutting oil, had the least wear on the bed ways and were in the best condition. The machines that used soluble oil coolants had the most wear and were worse for it.

Neil

Those diamond dressers on an small handle do a great job of wheel dressing.They are about 1-1/4 inches long about 5/16 or so wide. They are just great and last a long time.

I like using the White wheels for HSS, not sure what they are called to order them. The only issue with using the side of the wheel is being extra careful if there is no side rest support. As been said above, I would not use a star or rotating wheel dresser on the side of any grinding wheel.

Neil

I am not sure exactly how your chuck assembles onto it's backplate. But on my myford std 3 jaw chuck, I put some bellvill washers under the capscrews. Then it allowed me to lossen the retaining screws a little, and adjust the workpiece to zero , then I tighten them up. Older chucks tend to have areas where they run well and areas where they are not so good. Since it was not right, I made it adjustable. On my chuck backplate I trimmed the spigot diameter down a bit to allow for the adjustment.I also trimmed an allen key down to get in behind easily.

Neil, If you can not make it right, make it adjustable.

A part from motor vibration, also check the simple things like the pulley running true on the motor. On my lathe I had to bush and rebore the pulley. I have a piece of ruber between the motor and mount plate . I also have some rubber washer made also to help it become isolated. Now I can have the motor running and the dti does not move on the work piece.

I also changed the one piece belt to a segmented belt. When it comes around to replacing the current head stock belt, it will be replaced with the segmented belt as well.

My lathe had a problem with the adjustment of the 1/2 nut alignment on the lead screw. I put a dti on the screw and adjusted it , so the screw was not pushed in an up or down position. This did help over all .

Neil

Andrew,

The alloy has been specially formulated for the model engines at a very great expense by an individual who has always been looking for the best. He has been kind enough to share this technology to others so that more can enjoy the benefits of this material. It does not fall into any of the commercial number series of alloys, and it is very expensive.

From looking at a Kallenberger internal wheel spindle, it is not as controlled as the main head stock spindle. There is a very small amount of movement detectable with the the fine dti, the head stock has none detectable. As far as I am aware, there are no high speed super precision bearings. To get then to run fast,they have to have a little more clearance, Most precision bearing set ups have some form of spring loading on them to allow for heat expansion etc. Often running them at the highest rpm range, the work piece does not come out as round as it would if it were run at a slower speed. On my Myford setup, I can not run it in the high speed range as it will create heat in the head stock tapered bearing.

Howard,

You are very correct and bring up a lot of very valid points. Diesel injector making was one of the most difficult to produce parts in a production enviroment.I used to work for a company that made injector pump parts and repaired them.

Most normal inserts that you buy are not ground to a sharp edge. There are ground sharp edged inserts for cutting Aluminium. Like wise for the PCD cutters, There are a series that are sharpened with a positive rake geometry that will take micro cuts when sharp. PCD needs to be EDM ground and some are a lot better at it than others .To control the piston, the bottom of the skirt is made bigger than the seal band diameter, as they are a tapered liner, the skirt diameter fits at about the diameter of the transfer ports, giving the piston very little room to rock around. Traditionally the pistons were more of a barreled shape,or were parallel to the pin and then slightly tapered to the skirt, although these did work, the newer design with a large skirt performs better. Another aspect is the pistons have a small relief after the seal band area, about .1 inches long, to force the piston to behave like a ring. This also improves over all efficiency. Model engines get away with stuff that full size just can not, but at the same time create their own unique sets of issues. An interesting experiment was to take the set up that worked in a model diesel engine and try to run it as a glow engine. It did not per well at all. It did run however, but was too tight and showed signs of over heating. But the glow engine did not make good enough compression to get the engine to run as a diesel on the fuel supplied. A special brew with more ether was needed to get it to start. it was interesting to do and see what was the results.

Like I said, my setup is not good enough to make the pistons for the modern racing diesels, certainly good enough for a saturday afternoon park flier.

If you are running a high speed steel cutter at 360 rpm , and it can not take a 1 or 2 mm cut, then your machine does not have enough rigidity.

In smaller machines you would be better off using a smaller 8 or 10mm end mill.

8mm and 10mm tungsten carbide cutters are very affordable now days.

You can run a carbide cutter at higher rpms, The most common cause of cutter damage is by swarf getting trapped between the cutter and work piece, Having a high flow of coolant or even an air fog buster onto the milling cutter will dramatically increase tool life.

Neil

The alloy used in high performance model pistons contains 30% silicon among other things and is very low expansion. Typically the liners or cylinders are made of 9-11 % silicon material. Usually what happens is when the engine over heats, the liner and the head expand, making the liner larger than the piston, and it just slows down, it is very rear to see a seizure. Essentially the top 2mm of stroke or so on the setup effective runs dry with no lubrication. These are the highest pressure areas. Small gains in the effective seal have a huge effect on power output and overall efficiency. In one example of tuning, the same timing numbers were used, but made into a square arrangement, so the bore was almost the same as the stroke, the power output gain with this engine with a small change in the piston geometry made a power gain of approx 7% . The new setup makes more power for a longer service time, a lot of the extended life is due to the profile of the piston and making it so that it rocks less in the cylinder. The high performance model diesel engines are the most critical in piston fits, and the best of those engines are now turned on sub micron CNC lathes and sub micron cylindrical grinders. What I can achieve for the glow plug engines, would not make a world class piston fit to the modern racing diesel engines. The glow plug engines are a little bit more forgiving. For general purpose model diesel engine with a regular liner in a case , my set up is fine, but the newer integral liners where the head is part of the barrel, is a very different matter.

Cylindrical grinders are usually far more accurate machine due to the precision of the work head bearing set up, and the very low vibration from the balanced motors. Very accurate head bearings do not spin very fast to maintain their accuracy.

Changing my lathe to the smoother 3phase motor on a VFD has made a very big improvement in surface finish.

One last thing, the tools have to be very sharp , when they are dull , they tend to burnish as they cut, those will not work as well either. If the tool can not take a 0.002mm cut with the oil, it is too dull. The high silicon alloy is so abrasive, that even carbide tooling does not last very long when trimming pistons. So I rough out using carbide and then use the diamond tooling for finishing, usually leaving only about 0.05mm on diameter for the diamond finishing insert.

I really like the D bit grinders, there is so much that can be done with single lip cutters.

If you get the double sided wheels in either diamond or cbn, the you can grind thread cutting tools and the like. Also do bull nose radius cutters( offset corner radius cutters)

I have been looking for one, but they are too expensive even second hand. The cheap import ones are not as good as a Deckel.

Neil

I do not know the Ra values sorry. But I think the reason it works better is that the interference fit, effectively burnishes the piston to the final running fit size. When lapping , you are taking away these peaks and so the piston can not burnish to get the liner specific fit. I think this is why when you run a piston in another liner, it does not run as good as a new piston that was fitted to that liner. I have not found a way to make the lapped ali pistons work.

Hope that helps.

Neil

It is a combination of fit for the final position and measure ment. Most model engine liners have a taper of Ø 25um per 10 mm or .0025mm per mm length. So to get the piston to the fitted length if it is 2mm away will require removing .005mm off the diameter. It does take a bit of experience to get it right. If the part has a temperature increase from the turning, you will not make it work, as the size while turning will change.

I have a very good mic with a non rotating barrel and use it like a comparator mic. I am in the process of getting a comparator mic with the dial gauage built in.

The other way of measuring but is very cumbersome , is to use a Vee block and a low pressure finger clock graduated in .001mm increments. But the total range on such instruments is usually about 0.1mm meaning you have to be within 0.06mm of size to even use it. I cannot measure better than about 0.001mm or so. I can certainly get to better than 0.002mm . An error of 0.001 is going to be about 0.4mm on the piston fit position.

Everything has to be degreased and be oil free when measuring. To cut at these small tolerances , I use a mixture of canola oil and about 20-25% crc , for the piston trim I use a positive rake ccmt11 PCD insert. Honing oil is also a very good cutting compound, but is more expensive .

I can fit on my Myford a piston easier and get it right compared to using a standard cnc lathe that has 0.001 resolution. To really be able to make these right requires, sub micron lathes which I do not have access to out here in NZ. These pistons could be lapped to size, but those do not perform as well as ones that have been turned to size. In a mass production set up, these pistons are turned in batches with 0.0005mm or so difference in size and the correct graded piston is then selected to fit that liner.

But this process , will help those who need to achieve 0.002mm size on parts if it needs it.

You need a lot of things to fall into place to get the accuracy that is for sure. You need the temp to be some what controlled, I have a small room built in my garage just for the lathe, with a dehumidifier and a heater for winter. I have my own mix of oil I use on the slideways, it is just 30/40 motor oil with lucas oil stabiliser and some stp oil treatment in it.The lathe bed has been levelled with a precision machine level to get the warp/twist out of it .The standard Starrett ones are not really accurate enough.I brought my own and am very happy with the results. Saddle has been re shimmed to get the better tolerances. Cross slide is adjusted to be quite neat but can me slide by hand, then the screw and nut assembled and correctly aligned. I made a M8x0.5mm pitch screw and nut so that the inches dial now matches the micrometer dial in metric.The down side is the slowness of the cross slide in travelling any distance.Compound slide is adjusted to be just sliding but not binding.I refitted the compound slide as it was, there was a slight taper in it,either wear or like that from new.I only use my Myford lathe for my precision work and thread cutting. All roughing out/blanking out is done on another lathe I have.

I hope others can learn from this , and help them to achieve accuracies that otherwise are not easy to achieve.Even making the M8 fine Pitch thread instead of the course 10 tpi that was in there has been a huge step up in accuracy.

As you can tell, I spent a lot of time setting up the lathe to get it do do what I want.

With my set up, 2 thou on the compound is 0.001mm diameter.

The hardest part of it all was getting the head stock bearing lapped and scraped to run true enough, and then having the end play correct.

I can not run my lathe in the high rpm range otherwise it will start to heat up.

If it is backed off to run at the higher rpm, it will not be running true enough.