
MODEL STEAM ENGINE PLANS BUILDING MODEL STEAM ENGINES
FREQUENTLY ASKED QUESTIONS
BUYING PLANS TO BUILD THE MODEL STEAM ENGINES AT £10 EACH CLICK ABOVE TO FIND OUT HOW TO BUY THE STEAM ENGINE PLANS
THE ENGINE TOSCA
THE TWO CYLINDER MODEL STEAM ENGINE "JESSIE"
ABOUT THE ENGINES THIS SITE WILL ENABLE YOU TO BUILD TWO STURDY MODEL STEAM ENGINES,"TOSCA" and "JESSIE"
LAYOUT OF THE ENGINES CLICK ABOVE TO SEE THE CONSTRUCTION OF THE ENGINES
SAMPLE PAGE OF ENGINE PLANS CLICK HERE TO SEE SAMPLE OF PLANS.
ABOUT THIS WEBSITE CLICK ABOVE TO SEE MORE INFORMATION
SAFETY CLICK ABOVE TO SEE IMPORTANT SAFETY INFORMATION
METALWORKING SKILLS ARE YOUR METALWORKING SKILLS SUFFICIENT TO BUILDING THESE ENGINES
SCREWCUTTING CLICK ABOVE TO SEE ACCURATE METHODS FOR CUTTING SCREWTHREADS
METALWORKING HINTS AND TIPS SOME INFORMATION ABOUT LATHE WORK AND SOLDERING
MEASURING INSTRUMENTS CLICK HERE FOR INFORMATION ON READING A MICROMETER AND VERNIER CALIPERS.
LINKS OTHER SITES OF INTEREST
COMPLETED PROJECTS THIS PAGE IS DEDICATED TO THOSE WHO HAVE BUILT MY ENGINES

METALWORKING HINTS AND TIPS

INFORMATION ABOUT BUYING ENGINE PLANS

LATHE TOOLS

Building the engines Tosca and Jessie involves turning a number of components on the lathe. I have written this webpage to help those who want to build one of these engines to achieve the best standard of work possible.
Most poor quality turning can be traced back to the lathe cutting tool. It may have the wrong rake angle, be set at an incorrect height or it may have been badly ground or honed. Here are some guidelines to help avoid these pitfalls.
The quality of turned work depends on choosing the correct lathe cutting tool and on the standard of grinding and setting of the tool. The following angles are the main ones to consider when grinding the tool. Accurate methods for doing this are given on this page.

THE CLEARANCE ANGLE - This prevents the region at the front of the tool below the cutting edge from rubbing against the rotating workpiece. It should be large enough to achieve this but small enough to give good support to the cutting edge. A clearance angle of around 5 - 10 degrees should suffice for most purposes. Too large of a clearance angle will cause the tool tip to overheat as there is insufficient material around it to conduct heat away. It may also cause CHATTER marks on the work. Chatter is caused by the lathe tool being set into resonance as it rubs against the rotating workpiece – just as the string of a violin is set into resonance by the moving bow. This happens quite easily for a thin light cutting tool with little support at the cutting edge. You can recognise the onset of chatter by the singing noise the lathe tool makes as it vibrates. The main ways of stopping this are by changing the cutting speed or reducing the length of the tool which protrudes from the toolpost.

THE RAKE (OR TOP RAKE) ANGLE - This is the most important angle in a cutting tool and it determines the quality of the finished surface. The purpose of the rake angle is to allow the material cut from the workpiece to flow easily away from the cutting edge. The easier the flow the smoother the cut and the work finish. Different metals require different rake angles. The engines Tosca and Jessie use only mild steel and brass and the following rake angles are generally recommended for these.

MILD STEEL.......... 20 DEGREES
BRASS............... ZERO DEGREES

Most rake angles given in metalworking texts are only a rough guide and you need to experiment to find the best for your own purposes.
I find that a rake angle a little greater than 20 degrees works best for mild steel.

CUTTING TOOL PROFILE - This is the shape of the cutting edge looking down on the tool. There are many tool profiles but the ones I use most are the rounded profile, the blunt wedge and the corner tool. These are shown below – just place the mouse pointer over the photograph to read the description.

ROUND PROFILE LATHE TOOL FOR MILD STEEL - I FIND THE LARGER THAN USUAL RAKE ANGLE PRODUCES EXCELLENT RESULTS.

ROUND PROFILE LATHE TOOL FOR BRASS (ZERO RAKE ANGLE)

LATHE TOOL FOR MILD STEEL USEFUL FOR MACHINING INTO CORNERS

ROUND PROFILE LATHE TOOL SUITABLE FOR DELICATE WORK ON BRASS

THE BLUNT WEDGE TOOL SUITABLE FOR MILD STEEL

SOME LATHE TOOLS WHICH ARE PRONE TO CHATTER

SETTING THE LATHE TOOL AT THE CORRECT HEIGHT – The cutting edge of the lathe tool must be set at the centre height of the lathe for most turning jobs. If the tool is set too high the front will rub against the work. If set too low the tool will scrape the work instead of cutting it. Slight deviations from the normal setting may be permissible under some circumstances to produce a better finish for some materials but as a general rule keep to the centre height.
Setting the cutting edge to this height involves making some sort of height gauge which is set on the crosslide. A piece of rectangular metal is suitable and it is marked by pressing it down on the crosslide and sliding it along the sharp point of a dead centre fitted in the tailstock.This inscribes a horizontal line at the centre height of the lathe. If you do not have a dead centre sharp enough you can put a piece of round steel in the 3-jaw chuck and cut a sharp taper by setting the miter to about 15 degrees. The cutting edge of the tool is set to this height by the use of shims or feeler gauge blades under the tool. These procedures are shown in the photographs below.

MARKING THE CENTRE HEIGHT GAUGE - A RECTANGULAR BRASS BLOCK

SETTING THE TOOL HEIGHT - NOTE THE FEELER GAUGE BLADE UNDER THE TOOL

GRINDING THE LATHE TOOLS – The main types of materials for lathe tools are high speed steel (HSS) and tungsten carbide. HSS can be ground on a normal aluminium oxide grinding wheel but tungsten carbide needs a special greenstone wheel. I prefer HSS, as tungsten carbide tools are easily chipped when machining irregular shaped work where there is a hammering action of the work on the tool.
HSS tools can be ground on a normal bench grinder by using a special jig which bolts onto it. There are a number of these on the market but I prefer to use a grinding wheel mounted on an arbor held in the 3 jaw chuck of the lathe as shown in the photograph below. ALWAYS COVER THE LATHE BED WITH A CLOTH WHEN GRINDING TO PREVENT THE GRIT FROM DAMAGING THE WAYS.

GRINDING THE TOP RAKE ANGLE (SEE PHOTOGRAPH BELOW) – The toolpost is set at 90 degrees to the topslide and the topslide miter is then set to the rake angle of the tool.
The tool is clamped on its side in the toolpost at the centre height of the lathe. Some shims and packing pieces are placed under the tool to raise it to the correct height.
The topslide feed is used to advance the tool in steps of about 0.2mm towards the grinding wheel and the crosslide feed moves the tool across the wheel. PLACE A CLOTH OVER THE LATHE BED TO PREVENT IT BEING COVERED IN GRIT PARTICLES.
Some lathe tools are held in a toolholder which is usually inclined at 15 degrees to the horizontal and this must be taken into account when grinding the rake angle on the tool.

GRINDING THE TOP RAKE ANGLE ON THE LATHE TOOL

GRINDING THE CLEARANCE ANGLE – This is often unnecessary as the HSS toolbits are usually supplied with a suitable clearance angle already formed. If you need to grind your own then the photograph below shows the arrangement.
Set the toolpost parallel to the topslide and clamp the tool at centre height on its side at 90 degrees to the grinding wheel. Then set topslide miter to the required clearance angle. Use the topslide and cross slide feeds as described earlier.

GRINDING THE CLEARANCE ANGLE

GRINDING THE TOOL PROFILE – This can be done using the bench grinder after the clearance and rake angles have been formed.
To form the round profile you need to grind the front of the tool into a “V” shape. Then grind a flat on the point . You can then “roll” the tool gently against the grinding wheel to form the round profile.
To form the blunt wedge tool grind the “V”shape as before then gently touch the point against the grinding wheel to form a flat 0.5mm to 1mm across.
Both these profiles give excellent results in machining the flywheels of the engines.

HONING THE LATHE TOOL – This is the final process in making the lathe tool. The cutting edge of the tool will be rough after the grinding process and to correct this it needs to be honed.
All cutting edges are formed by the intersection of two surfaces (which may be plane or curved). Both of these surfaces must be made perfectly smooth at the point of contact to produce a good cutting edge and the honing process does this.
The two surfaces are rubbed on an oilstone or very fine emery paper placed on a flat surface. During this process the face being honed must be kept perfectly flat against the abrasive surface as it is moved backwards and forwards (see photographs below).
Any rocking motion will ruin the cutting edge and you will have to regrind it. Slow and deliberate strokes are required.
The surfaces which form the cutting edge should be smooth and shiny after the honing is complete. It will be necessary to repeat the honing process after the tool has been used for a while otherwise the standard of the finish on your work will suffer.

KEEP THE SURFACE PRESSED FIRMLY TO THE OILSTONE DURING THE HONING PROCESS

HONE THE CURVED SURFACE USING A ROLLING MOTION

CENTRE DRILLING

The construction of the engines involves a number of components being centre drilled either to be supported in the tailstock of the lathe or as the initial stage of drilling a larger hole. If you try to drill a hole with an ordinary jobber drill in the tailstock chuck without centre drilling first the drill point will wobble on the work surface.
When using the centre drill in the tailstock chuck the point should have some oil or cutting fluid dripped onto it. The drilling should be done VERY SLOWLY as the point of a centre drill can break quite easily if forced too hard. You should practice rotating the tailstock wheel as slowly as you possibly can and this speed and no more should be used for centre drilling. It is easy to recognise a metalworker who hasnt yet mastered this technique by the collection of broken drills they have accumulated over the years. If the drill breaks then the broken point may become stuck in the workpiece. When this happens it cannot be drilled out as it is hardened steel and the work may have to be scrapped.
The drill should not penetrate the work beyond the countersink edge as shown in the photograph if the hole is to accomodate the tailstock centre. If it is to be used to start a larger hole with a jobber bit then you should drill a little beyond the countersink edge. The hole should be cleaned to remove any slivers of metal as even the smallest piece could destroy the centering of the work.
Apply grease or oil to the hole and tip of the lathe centre. The tip of the centre drill creats a recess which serves two purposes. It prevents the tip of the lathe centre from bearing on the workpiece and forms a well to hold the lubricant.
Finally move the lathe centre into the centre drilled hole using the tailstock wheel. Make sure the tailstock lever and spindle lock are secure. Do not overtighten - the work should rotate freely without any lateral movement. Recheck this at intervals throughout the machining process as the work can loosen due to movement in the tailstock or tighten due to expansion caused by the workpiece heating up.
An excellent website run by The American Machine Co. is listed on the Links page. From this site you can download a 111 page document on all aspects of lathework. There is material for both novice and experienced turners.

SOLDERING

SOLDERING – Making the engines involves soft soldering steam pipes into a large steel plate called the standard and also soldering the brass cylinder block to the cylinder. The basic tools and materials needed for these processes are shown in the photo below
I prefer to use a gas blowlamp rather than a soldering iron as I find it easier and the results are better. I do not recommend using a soldering iron – even a good heavy one for this job – as the large steel standard absorbs a lot of heat and a blowlamp is really the only practical way to supply enough.
I use an active paste flux which means that it reacts chemically with the metal and the solder gets a better grip. Some people think of solder as a sort of glue which simply sits on the surface of the metals but this is far from the case. Solder actually penetrates into the metals it joins to form an alloy with them binding them together with a very strong bond. The strength of a soldered joint depends on how well the solder is allowed to penetrate the metals and this means having their surfaces absolutely clean. The flux does this by removing metal oxides from the surface and coating the metal to prevent any further oxides forming during the heating process.
The solder I use is of the thick wire type and has a melting point of about 250 degrees Celsius. Do not use the thin resin cored type common to most electrical work - in fact any materials or tools used in electrical soldering are totally unsuitable for this type of work.
I have used the soldering of the copper steam pipes into the steel standard to illustrate the techniques required.
Two copper pipes have to be soldered into two closely spaced holes in the steel plate. The ends of the pipes and the steel surface around the pipes are thoroughly cleaned with emery paper and wire wool.
The ends of the pipes and a small region around the holes are coated with the active flux. The pipes are then inserted into the holes and a number of small pieces of solder are placed around the pipes.
The rest of the steel plate is heated first with the blowlamp so that it will conduct less heat from the soldered region when it is heated. This is common practice when soldering large pieces of metal.
After the rest of the steel plate has been heated apply the blowlamp to the junction between the plate and pipes until all the solder melts forming a pool around the pipes.
Stop heating and allow the work to cool. Do not quench in water as the rapid contraction of the metal could fracture the joint.
The work should be carried out on a heatproof mat or firebricks well away from any flammable material. Eye protection must be worn.
When the work has cooled the joint should be thoroughly cleaned to remove any traces of flux as these could cause corrosion in the joint.

THE SOLDERING KIT

THE WORK, CLEANED, FLUXED AND READY TO BE HEATED

THE FINISHED JOINT

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