bertiedog

Stainless steel can be a pig to machine, but if the bar stock is from a model engineering supplier then it will be OK. There are two main types magnetic and non magnetic, and most machinable bar stock is the non-magnetic type. Magnetic is used where heat or vacuum hardening will be done later on after machining.

There are dozens of grades and surplus or scrap must be assessed and tested by machining. In sheet form, magnetic grades are more easily machined.

There are also free machining grades with graphite, molybdenum, sulphur, or lead added.

Unknown source Stainless Steel is a mares nest, God help you if you ever get Inconel grade alloy, it is used for turbine blades, and heat resisting parts in jets, and is only machinable with diamond tooling. The moral is to buy from a supplier that deals with model engineers and is able to give the grade and/or assurance it is machinable.(Reeves, Maidstone models, Chronos, etc.,)

Now if the stainless is in tube form it may be very difficult to machine without carbide tools, lower speeds, and lubricant to cool the tip.

The reason is the extruded/ formed nature of some tube may work harden the metal. making it difficult. This is one reason that stainless steel wheel tyres are not made from tube, but from bar stock.

The tool shapes are normal for tipped carbide, if using HSS steel tools, then have less top rake. HSS will work with free machining stainless steel. If the material has a hard crust due to work hardening, then the tool rake angle must be increased to get the point under the crust as the work turns.

Aluminium is often dismissed as too soft, but is fine for tooling, jigs, and parts that will not be stressed as much as steel. It can be use to make parts for lathes like tool holders, and tailstock adaptors.

Stephen.

I am afraid the supplier has told half a story, all Perspex,(Lucite), Acrylic plastic, machines, but cast acrylic is preferable for complex shapes etc., or where heat stress later on is expected.

The extruded forms including sheet and rod may suffer from relaxation with heat after machining, slight dimensional alterations or warping. The extruded plastic has internal stress in it, and this may be released by machining and heat.

The cast Lucite, especially the optically clear type, has no internal stresses at all in it and will retain all machined shapes.

But for the purposes of models the effect can be dismissed, the extruded acrylic should machine up fine.

Stephen.

Further to my earlier reply about fitting bushes in Bachmann wheels I had a query about Perspex etc, and it is easy to source on EBay, in 5mm and 8mm, 1 metre long at around a fiver including postage.

Acrylic rod, Lucite, and Perspex are the same item. Super glue works fine with it as it is basically liquid perspex in chemical structure. Perspex will also take epoxy glue very well indeed. Most paints will work, as long as the polished surface is abraded with fine emery, wire wool, or machining. The high polish on rods and sheet may reject paint if this is not done.

Lucite is absolutely identical with Perspex, just trademarks for the US and UK, however Lucite (brand) is made in optical high purity grades.

Tufnol is also sold on Ebay 16mm diameter bar, or bigger sizes, it is far more expensive than Perspex, but is extremely tough. It is a resin, reinforced with compressed cloth.

Acetal rod, or Delrin could be used in glass filled grades, but they do not glue well, so force fits would be needed for the bush and the axle fit.

All round the Perspex is best unless you use Tufnol, or it's close cousin Bakelite plastic.

All plastics should be cut in the lathe with razor sharp tools at lower speeds to prevent melting.

Water is a good lubricant/coolant, add a dash of detergent. Do not use any oil, these plastics are slightly porous and it may interfere with painting/glueing later on.

I am told that the Harris axles have a plain end, so the machining should be easy, just mount accurately in chuck or collet and machine way enough for the adjustment. The Peatol will manage it straight away.

Stephen.

I am not sure of the exact nature of the Harris axle, but was told that it has a taper end similar to the Protofour 4mm wheel system.****see important end note as well as following notes.

I am assuming that these are the cast iron wheels, mounted on tapers, and with a split axle, of which I have no exact details to hand.

• But it will be well within the capabilities of the Peatol Lathe, as long as collets or split collets are used to mount the axle for machining the end. The Peatol may be small, but it is accurate.

A four jaw chuck could also be used, or a three jaw(soft jaw) with freshly machined bored faces.

• The axle stub would have to be gripped true, and checked with a dial gauge in the case of the four jaw.

With no four jaw the best would be a tube split collet made in the lathe, a short brass collar (or steel), fitted to the three jaw, centre drilled , reamed and then removed and slit down one side with a saw. The reamer is run through to clean the collet.

• The collet is replaced in the position it was machined in, by marking the collet before removal.
• The axle will now enter the hole, and the pressure from the three jaw grips the axle and it will run true.

However now comes the problem, and it's big, duplicating the taper further up the axle stub to reduce the back to back.

• The taper must be measured and the tool slide set to match exactly and this is skilled tool setting.

If you have a dial gauge it can be used to zero on the base, (large end), of the taper, and then move the dial gauge along with the top tool slide, taking a reading at the outer end, when the readings are the same the taper is the same and the toolslide will duplicate the cone.

This is precision work on even an O gauge axle, and a test piece would be made to use as a plug gauge in the wheel to check accuracy.

In practice the taper would be cut "fat", and the taper adjusted with abrasive blocks to get it to fit to perfection. Very hard oak stripwood is used with diamond paste to grind the cone. You may get away with it with very fine emery paper on a block.

If this sounds difficult, it is at first, but is practical with a bit of experience. The method works with any taper mounted wheel. If the taper has a flat for quartering, it is best the machine the cone first, and then hand file the flat, testing the fit as you go.

Studiolith used to make P4 wheels with cone taper ends, they had to get a Swiss clockmaker to make the axles and cones to the exacting standards to get the wheel to grip on the taper at the fully home position.

Presumably the Harris is similar, and easier to work with as it's larger.

****After all of this I have the feeling that the easier way would be to turn a bit off the ends in the middle of the axle to shorten them, since you say that they are split axles. This leaves the cones intact, and you just machine away enough to adjust.

Stephen.

It may be needed to replace the plastic bush with a new one, and re-drill the plastic with the wheel held in a split collet.

• You need acetal rod, perspex, either scrap or Ebay, or a rod of Tufnol, scrap or ebay, or any machinable plastic, but not poly, PVC or nylon. It must be a hard glueable plastic.
• Machine a bush to fit to the same as the Bachmann, and make it a light fit, and push home with epoxy glue.

Personally I use Tufnol rod, it is a resin reinforced with cloth, made under immense pressure, or I use Perspex rod, which is easy to machine in any lathe. It will look a bit rough at first, but is polished with fine paper etc to give a perfect finish.

Bakelite rod can also be used, but is difficult to come by these days, it is the best though. Bakelite is still made in sheets, and you can cut strips and turn the bush in the lathe from the rough blank.

The Split Collet:

Take a scrap piece of brass , steel, or aluminium, of a diameter that's bigger than the wheels tyre. Again scrap, or buy in, model engineer suppliers often sell offcuts, short bar ends.

Make the blank collet tube,(about 1/2" long), about 2mm bigger than the wheel on the O/D, and then slip it in the three jaw chuck, and mark number one jaw on the tube with a centre punch. You can leave a lip on the outer diameter to locate the collet hard against the jaws.

• Then drill out and bore the tube out till the tyre just enters the tube and seats against the flange.
• Don't forget the tyres may be straight or slight taper, and remove the collet edge where it touches the flange base, to get the best snug fit.
• You now have a collet that the wheels fit, and the collet is removed from the three jaw and sawn with a hacksaw down the length to slit one side.
• The collet can be re-fitted to the three jaw , with the reference punch mark for guidance.
• When the wheel is placed in the collet, the three jaw chuck jaws crush the collet, and grip the wheel very accurately indeed, should be in the range of half to one thou. Do not over do the pressure, the grip is usually very good, as it is so custom sized.

The wheel can then be centre drilled, and drilled through, undersized, and reamed to finish. If you don't have reamers for the size, then proceed with a series of expanding drill sizes, it is nearly as accurate.

• The size should be a good light push fit on the axle, and then retain with Loctite, superglue or epoxy.
• Prepare one sides wheels on axles, and then put in frames, and gently press home and glue, doing the quartering by any method, there are dozens.

A couple of vital points with Bachmann and all Chinese wheels, they are plated Mazak, and do not machine away the chrome finish. The back of the wheel could be machined, but usually no need. The flange could be thinned, but you are exposing the soft metal to wear and possible corrosion.

Some un-spoked wheels may be brass, and more machinable and amenable to changes.

If you want to severely alter the Bachmann, then remove the entire tyre and replace with a stainless steel, or brass or nickel rim etc. Stainless steel, machine grade is the best, and more easily available.

Any other points just ask, the collet can be retained for more work on other wheels.

The same principles apply to all split collets, useful for armatures, axles and wheels or anything requiring accurate holding, and a final revelation...it do not matter a toss how accurate the three jaw is at all......

Stephen.

The Sellers cannot hide behind the so called standard descriptions, the system does allow for blanks to be entered and the seller can add any description he wants to, ( and has to pay to do so of course).

Too many items are represented by poor descriptions, not deception, and it is obvious what TMC are offering, and they are not covering anything up. It is still fair comment to query why anyone would want a Britannia with the Duke name plate on it, but to everyone their own.......

The brand new, and TMC finish is what is referred to, but it is complete (and mentioned) miss representation to sell a un-altered Britannia Class loco as The Duke of Gloucester, but they do cover themselves by saying the plate has transformed the loco to a not strictly accurate model.

It is not the fact that this is wrong, it is the description that needs correction, it is a re-finished Brittania named The Duke of Gloucester, then TMC would be more accurate...

Stephen.

Especially for Gordon, the Esso blue advert and song, care of Utube!!!!

Stephen.

Any recommendations of what to use to degrease my Proxxon lathe? They talk about using paraffin, but the days of Esso Blue or Pink being available at every corner garage have long gone. I can't find a local stockist so any alternatives?

 

Gunk?

Paraffin in definitely best, and acts as lubricate, leaving an oily trace that helps keeps rust at bay. Gunk will remove grease, but leaves the steel un-protected, so will need a rub over with light oil, or a spray with WD40 or equivalent.

White spirit will also work like paraffin, as will "low odour" lamp oil.

With due respect to safety, petrol may be used to initially clean down a machine to remove excess grease.

Best try to find a can of paraffin as a reserve, it makes a cutting lubricant for lathe work, and a bottle of paraffin/car oil mix is a good storage lubricant for most machine tools.

If white spirit or turps/turps substitute is used with cotton rags, make sure the rags are not bundled up semi wet, they should be carefully air dried, as they can spontaneously combust in extreme circumstances.

Stephen.

It appears to be a round form tool for wheels, a segment type, and requires a holder, a bolt through the middle to attach the form tool to a tool holder to suit the lathe.

The tool bar should be the normal tool size, with a hole drilled through the side and a nut and bolt to attach the form tool to it. For small lathes the bar may have a larger head that sticks out beyond the reach of the tool bar.

• The hole could be tapped to take just a bolt as well, both ways are valid. The tool bar should be mild steel, it does not have to be tool steel.

• The form tool is set to exact centre height for the lathe, checked against a tail stock centre for instance, and the form bolted up very firmly.

• The lathe is set to a slow speed,(100+), and the form is plunge cut slowly and steadily into the bar of material to the required depth, measured and checked, and then repeated by the dials or stops for the next wheel.

• The saddle should be locked firmly, and the work advanced by loosening the chuck after parting off each wheel, with a rear parting tool, or for a batch, could be parted off after, say, six tyres are formed.

There are several caveats to form tools, they should be used at relatively low speeds, with a cutting lubricant with steel, or dry with brass. Nickel tyres usually cut dry, but can use cutting oil if the nickel is tough.

When steel is used , then make sure it is a leaded free cutting type, not common mild steel.

• The reason the form is used like this is the form is re-sharpenable by just grind the face lightly and honing with a polished drill blank to de-burr. Never touch the outer form edge, only the segment form.

Should the form tool edge reproduce scratches on the work, it should be re-ground again, till the marks are gone. The form tool will last ages, with dozens of re-sharpenings possible.

Picture should show the form edge level, not raised, the bolt must be a good fit to the hole in the form tool, might need a sleeve turned to make it snug fit. ALSO washers should be used to spread the pressure.

Stephen

http://www.axminster.co.uk/axminster-sieg-sc2-mini-lathe-prod809904/

The Axminster up rated version with the 500 watt coreless motor, it appears to still have the nut lock tailstock, but this can be changed very easily on all Sieg lathes.

Cam lock kits are made, or you can use a dedicated spanner, or make a lock yourself in an afternoon.

http://www.machinemart.co.uk/shop/product/details/cl300m-metal-lathe/path/metal-lathes-milldrills

This is the Machine Mart Clarke, older tailstock, ( but you can change, modify or home build the cam lock), and the older motor, which is perfectly good, Warco claim more for their motor version, but you pay more.

http://www.warco.co....D4121A9297.aspx

This is the Warco, with extras, check for price with vat and delivery, they may have deal.

It has the new tailstock with cam lock.

Also they offer a certificate of accuracy......

The UK suppliers, Clarke, Axminster, Warco, Chester tools, Arc Euro, all supply versions of the basic Chinese Sieg Models, 7x10, 7x12, 7x14, in various small details they differ, for instance Warco have the latest tailstock design, and some suppliers offer the very latest coreless DC motor on the top model.

All would be 240VAC supply for the UK (approved), and all have the US made speed Boards or up-rated types.

The exact spec' does vary, so contact the suppliers, and ensure the tailstock is the new lever lock in the deal....or make an offer for "the older models" the lever can be added later!!!!

I have personally set up Chester, Clarke and Warco versions, no problems at all, just an inspection, clean, and go! Warco will pre-inspect anyway.

Stephen.

Boxes can be vital to collectors, but a Bachmann box? sounds fishy!

This the Bugatti bolt, and matching nuts, as it has been queried by another member, a bolt with a flange instead of the head bearing on the load surface, they are far more sophisticated than plain bolts, the picture is a car set with two sizes of head plus hand tightening butterfly types for covers in a 1920's engine. Most cars have hex heads, some with square heads.

Although famous for his cars, Bugatti was a brilliant engineer, designing engines for aircraft and high speed steam engines of advanced design.

Stephen.

We do seem to be at odds un-needed, everybody has ways of machining parts, all I am suggesting is keeping it within the limits of a home machinist, without a rotary table, CNC or even a mill if they are working with the mill as a lathe.

Small headed BA bolts are indeed made, but I was not describing that, but the making of Bugatti Type bolts use by Bugatti on cars, Aero engines and Italian engineering that Bugatti was involved in.

Two types were made, on for the cars with a constant sized head, despite different bolt sizes. The other type was related to the bolts size, but with a smaller hex than the diameter of the thread.

They all have a washer shaped head to spread the load, and work better than ordinary bolts, especially for appearance, fit of a socket, and the need in the case of the Bugatti cars , the need for only one spanner and socket size for all the main bolts.

Such miniature Bugatti bolts have never been made commercially, anywhere.

A lathe tool holder to make at home, takes 1/8 carbide drill shanks, you can buy broken drills as shows or gather your own, make in steel, with the screw bearing on a brass disk to soften the grip so the carbide does not shatter.

The tip shape is ground on a diamond disk, or green grit wheel, to whatever shape you want, and the finish is as good as the grinding standard. Very good for fine light work.

The body size is simply made to suit the lathe tool holder from 6mm upwards. The retaining bolt I use is 2BA or 5mm metric.

Stephen.

I did cover the other points, at no point have I ever mounted hornblocks between centres, there's no need, the accuracy is up to the milling operator.

Whilst the faces may be accurately set by setting on centres, and rotating for the opposite face, the average home mechanic has not got the gear to do it. If a hornblock ends up with the axle out of line it is simply bad practice in milling. For 3 ¹/₂ and 5 inch gauge the block is fully finished before coordinate drilling the axle holes in the mill and then boring in situ in the mill. Each horn lock is dropped into the jigged vice and gets the same setting applied.

Everybody has a milling vice with the milling machine, but few have rotary tables or division chucks to hand.

Very few models are going to need hex heads milled, even in live steam models, I do use rotary tables to make Bugatti Bolts, with integral washer heads, in 10/12/14 BA for miniature steam engines, these are made entirely by milling the head, no lathe work. In many years in model engineering the people who make hex bolts could be counted as .......very near zero!!

The bolts are made mounted in a collet, with the rotary table underneath to provide the hex division via a direct hex plate to save using the handle, which is de-clutched. Two stops on the bed are set to allow the cut for the bolt faces and the washer edge is a continuous rotation with the handle engaged on the second stop. The bolt top is done freehand with the top tip.

Stephen.

With modern insert tips, it is more to do with chip-breaking with the insert tooling, on a CNC machine centre it is vital to ensure no continuous swarth is made, it would foul the machine badly. The modern machines need swarth size that can be flushed away with coolant reliably. Most inserts have a chip breaker top, a groove which curves the swarth and breaks it up.

There are zero top rake types with no groove as well, often used for rougher cuts.

Any HSS tool will take a better finish than a carbide, but cannot retain it for long. A carbon tool with hardening can take a finish and last well, but with strictly no overheating when cutting.

Most carbide is quite brittle, and chips itself if in any way the cut is intermittent, such as squares in four jaws, or eccentric stock. The first rough could be best done with HSS, and then switch, although one type of material is best with carbide and that is cast iron, which can be very hard at the surface.

Do not throw away the carbide tips when chipped and worn, they can be easily re-sharpened on the small diamond steel disks in a mini drill like a Dremel.

It is worth removing the tips on new tools cleaning the seat, check there is no burrs on the seat or around the screw and firmly fit and tighten. Never trap dirt under the tip, it can cause a shatter.

There are several grades of carbide including diamond, and nitride types, but for most amateur home use it's best to stick to the normal common types. Many of the specialist types HAVE to operate with continuous copious lubricant at all times, as they are designed to work at higher speeds and feeds than any home workshop.

Stephen.

The set is described as side and face left and right, face, and the rough face cut left and right, across the box.

Stephen.

The basic rule with inserts is any corner can cut, and the ones overhanging the bar at the front are the cutting point in action. You have facing and cutting left and right, but the two at the right I cannot see the overhang details. They look like fast cutters for roughing bars.

Centre held types like this go into a shaped ledge in one set position.

No one job is defined by the point on inserts, if the point suits, then use it for the job. All inserts like this should suit most fine finish work as they have formed rounded tips.

With a light lathe take only shallow cuts, only build up as you get more experienced.

Stephen.

Yes, it's one way, but normally division heads, or rotary tables, are used for more than 4 faces and odd numbers, not a square, which would be milled in a vice, the bar held vertically, and automatically give the two axis for four accurate faces without any division being required.

When new to milling it always pays to take the simplest way any way, and few here are going to have a rotary table or centres, let alone collets capable of taking a axle box blank, but they should have a decent machine vice, a basic for all mills.

http://www.technobots.co.uk/acatalog/Shop_Front_Plastic_Bevel_Gears_402.html

Reference for 2mm shaft 1:1 bevels for the rear axle? These would allow the motor to be under the bonnet , with a 2mm drive shaft to the rear axle, solid, with one wheel "loose", they are 12mm dia, the black ones half way down page. With the gear box and 1:1 the speed would be perfectly controllable, you do not want scalextric speeds! ..... plenty of other interesting items on this robotics site.

Stephen.