New lathe arrived today : The ongoing saga

What is this small ball bearing thing on the face of the lathe ?

Edited By Brian John on 27/08/2015 02:00:33

Its a push type oil point to get a drop of oil onto the scroll . best to clean that abrasive grit off first though !

steve

Bodge : thank you.

More machining today with some good results and some bad. I got a much better finish using the correct tool with minimum overhang and running the lathe in the correct direction. I could not clean up the mess I made of the spokes though.I seemed to have made it worse today plus the hole is no longer in the centre...I am not sure what happened there !

Obviously I will stay away from the spokes in future. Most people do not machine them for a reason.

It is a bit difficult to eliminate that line in the middle on the outside surface. This is the problem with trying to machine it without a face plate or mandrel. Staying away from the chuck jaws is a bit scary too. It is time to think about making a face plate or a mandrel.

I choose an aluminium pulley with a wider surface for next project ; this gave me more room to stay away from the jaws. I also tried to camber it but I think this is a bit ambitious for me at this stage. I almost had it a few times by turning both wheels by hand at the same speed. In the end I gave up on the camber idea but I did end up with a machined pulley with the hole in the middle. However as you can see by comparing it with an original untouched pulley I did take a lot off while getting there !

How do I put a chamfer on the edge of the wheels and the hub ? I am not sure which tool to use. At the moment I am using a hand held file with a round handle and holding it against the flywheel while the lathe turns at a very slow speed. Is this acceptable ?

NOTE : I bought a pile of flywheels and pulleys from PM RESEARCH a few years ago when the Australian dollar was actually worth something. The aluminium ones were very cheap.

Edited By Brian John on 27/08/2015 08:16:10

Edited By Brian John on 27/08/2015 08:31:36

If you removed or disturbed the flywheel then the hole will no longer be concentric with the lathes axis.....especially with a three jaw chuck.

You would need to 'clock' it to return it to its original position ........Another learning experience...

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Brian,

Once you have made that hole ... it needs to be your master reference for any further work.

I trust that our esteemed Editor's alter-ego will be along soon, to discuss the simple device that bears his name.

Meanwhile, may I refer you back to your previous thread, where there was some very relevant discussion.

MichaelG.

Edited By Michael Gilligan on 27/08/2015 10:05:56

I think a mandrel must be the next project but I am not sure how to cut the slots in the end. What size thread/screw should be used on a 6mm mandrel...would a 3mm screw suffice ?

NOTE : there is no 4 jaw chuck or face plate made for this lathe. They do make a fixed and travelling steady but they are not yet available in this country. This is a new model.

Edited By Brian John on 27/08/2015 10:16:09

Brian,

Could it be possible to hold the casting on its inner diameter using the outside jaws, giving you clean pass on the outside diameter?

perhaps the jaws could even pass between the spokes giving you more than enough to grab, depending of course on the layout and options of 3 or 4 jaw chucks available to you.

I tend to mark my chucked stock with pen or paint (sometimes a scribed line or centre mark) and align that to jaw 1 to keep things grabbed in roughly the same place -This is absolutely no substitute for carefully planned machined operations to ensure concentricity and is probably ultimately considered bad practice - I just like it because if I pick up a previously machined bar I can chuck it up in my wonky worn out general use/abuse 3 jaw chuck and align the jaw to the mark and minimal material removal is required to true it back up.

Regards,

Russ

Edited By Russ B on 27/08/2015 10:38:07

I'm very much a beginner so take my advice with a pinch of salt but the way I've found best for making small flywheels. Is first drill the centre hole to the final size you need, then make a very close fitting mandrel with a threaded end. Next bolt your wheel to the mandrel without removing it from the chuck, do all the necessary machining to your wheel then turn it over and do the other side again without disturbing the mandrel.

I've found with small wheels if the mandrel is a good close fit you can achieve a good true running wheel, I wouldn't like to guess at the maximum diameter you could do this but it worked fine for the 3" one I made a few days ago.

Peter.

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A plain diameter, that's a sliding fit in the hole, would suffice ... fix it with Shellac and remove with heat.

[going out now, so can't discuss further; but I'm sure that others will advise]

MichaelG.

I'd use M4 for a 6mm mandrel, and only use the first half of an M3 tap.

My order of machining for a flywheel is:

Clamp to faceplate or inside rim on 4 jaw chuck (or 3-jaw if spoke arrangement allows and concentricity of casting is acceptable.

Machine rim, front face, centre boss and any other bits needing a tidy up (such as inside edge of rim) - basically anything I can reach with a cutter

Bore out centre - this minimises the risk of 'rim wobble'

Reverse against faceplate or chuck if machined face of flywheel allows to maximise chances of machining other face/boss parallel to the first set.

If this is not possible, mount on a mandrel, but DON'T be tempted to touch the outer face. The mandrel should ideally have a flat face against which the previously machined face of the hub can be snugged up.

Neil

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Oh well ... wrong again

MichaelG.

Some use super glue and heat to break the joint later. I prefer an expanding mandrel. Hacksaw or junior hacksaw slots will do. At the sort of size it appears to be a junior hacksaw would be best as 2 at right angles after the hole has been part tapped tends to grip better than one. It needs to be a step mandrel made from material that is near the size of the boss on the flywheel or bigger.

Personally I would do most of the machining on the mandrel just facing the boss and machining the hole while holding the wheel some other way. Just press the machined face back against the shoulder on the mandrel tighten and machine the surfaces of the wheel. The large diameter part of the mandrel need to project enough to allow the rear rim to be machined. Depending on the size of the chuck and wheel that can be done when the boss is machined if sufficient sticks out of the chuck. Also spokes if these have to be done. When doing the chuck work it's best to press the wheel hard back against the chuck as this will square it up. Sometimes no rim will be left sticking out to machine. When you face the other side of the boss the tool will have to cut into the mandrel a bit. Not a problem really as it wont run concentrically once it is removed from the chuck and replaced again.

The expanding action can sometimes be improved by filing a bit of a taper on the socket headed screw that will be used to expand it. Easy to do on a lathe but use the lowest speed. Just hold the head in the chuck without fully tightening it and tap it to run true if needed then fully tighten the chuck - but see later.

It's best to make the mandrel after the 1st machining operation on the wheel as the fit needs to be good and it's not easy to accurately measure the diameter of small holes. It's best to make that part too long so that you can try the fit before running the cut all along it. There are several techniques for obtaining a certain level of fit but the easiest one is to take cuts equal to the fit you want once it's close to the right size. In this case - imperial I'm afraid, 1 thou would be ideal, 2 thou off the diameter. A drilled hole should come out well under 0.010in over sized so measure with a mic to get to that size and then take the fine cuts. Even finer if you want. If it nearly goes on a bit of emery paper or a file will fix that quickly rather than taking an even finer cut.

You are already using the best way to chuck the wheel with what you have but when you close the chuck onto it feel for when the jaws touch the rim, slow down the tightening and rotate the wheel with your hand, only a fraction of a turn is needed. With a bit of practice this will always get what ever you are putting in the chuck running as true as it can. With bars it's best to have one jaw central at the top. That way you can feel when the bar is resting flat on the other 2. Later you wont need to do that but might if the length within the spindle is heavier than what is sticking out of the chuck. That can be tricky on large lathes.

John

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I am still thinking about making the mandrel. The mandrel with a nut on a thread would be easier to make than an expanding mandrel so I might try that first to see if it works. I am not looking forward to cutting a 6mm thread on stainless steel using a die but at this stage I have no idea how to do thread cutting on the lathe.

I have not had much time today as I had to work last night. I had another go at machining the other pulley in the photos. Bit better today as I did not try to put a camber on it and so ended up with a much thicker rim than yesterday. I also took that flywheel which is no longer good for anything and tried to cut two pulley grooves in it with the parting tool. The first groove went okay but the second gave me problems : the tool dug in and stopped the lathe ! I was only taking a bit at a time but it seems that when using the parting off tool you have to be very careful. Was I going in the right direction ?

Edited By Brian John on 28/08/2015 07:33:51

Edited By Brian John on 28/08/2015 07:45:57

You don't need stainless steeel for the mandrel, aluminium will do or steel

Its a large dia for that small lathe to cope with a parting tool, a slower speed would help. You may have been better using a "V" shaped tool taking a little from each side of the vee in turn, this would also grip a belt better.

For the benefit of those following Brian's adventures with this lathe ... here is the user manual.

It includes good exploded diagrams of the parts.

Of particular interest is 8.2 which shows the chuck fitting arrangement. ... The 'Flange' [55] is a seperate component; which suggests that some interesting adaptations may be relatively simple.

MichaelG.

Welcome!

Once you get the hang of things, you will have HOURS of pleasure.

As already said, gain experience on "scrap" metal, rather than expensive castings, or metal of which you have a very finite supply. It is better to learn on material which you are reasonably happy to bin, rather than a shaft for some model or tool for which you have paid highly.

If you can, join a Model Engineering Club, that way you should have first hand access to a lot of experience and help.

Direction of Rotation: ANTI Clockwise looking at the Chuck. (There are exceptions to this but these need not bother you now. When the time comes, you will probably have the experience to know how and why)

Learn how to turn the handwheels at a more or less constant rate, using both hands (a bit akin to pulling a rope hand over hand, one hand taking over from the other)

As you face inwards, the cutting speed will decrease, so the surface finish will probably vary. You will need to adjust your rate of feed to accomodate this.

As you traverse along the bed, the cutting speed will remain constant (unless you are cutting into a taper to bring it parallel).

3 Jaw self centering chucks do not hold work absolutely concentric. A good one will be within about 0.003 inches (say 0.01mm) Total Indicator Reading. As someone has already said, you turn the scroll until you can just see the start coming to the slot for No 1. Slot in jaw 1. Turn scroll slightly. and jaw will start to move in. Stop and turn chuck so that you can see down the slot for No.2.. Turn scroll until start comes into view. Fit Jaw 2, turn scroll until jaw moves in. Repeat for jaw 3..

Always fit tools at centre height, NEVER above. With minimal overhang, if the tool is ground to the correct angle, and meets the work with the correct clearance angle, if it chatters, reduce speed, and/ or feed rate.

Making a centre height gauge might be a time saver, and a useful exercise to gain experience. It can locate on the bed, or on the Cross slide, but obviously can only suit one or the other position, not both. The final operation having made one, (before fitting and setting the blade)is to hold the pillar in the chuck and face the underside of the base, to ensure that the pillar will will be vertical when in place for use.

You have a small lathe, so the manual will probably warn against taking cuts more than 0.25mm (0.010"

The toolpost guard came off my lathe VERY soon after it arrived, but I do have a flat acrylic guard that sits on a pillar on a pot magnet, that gets used from time to time. Hot swarf down the front of your shirt is an acquired taste, but not my recommendation.

The chuck guard possibly operates the microswitch by a face cam on the shaft carrying the guard. If you want to work without the guard (BE careful! It is there for your safety) you may get away with removing the guard, but leaving the shaft, although you are liable to have the foul problem still.

On my larger lathe, I cut the shaft and made up a sleeve to join together the two halves. When it gets in the way,as it does sometimes, I remove the sleeve and guard, leaving just the short end of the shaft. BUT I don't do that when the chuck jaws jut outside the chuck body, and keep well away from the jaws on the face of the chuck.

The usual recommended lubricant for Aluminium is kerosene, it will lessen the tendency to weld to the tool, and improve the finish. For a good finish, the tool should be sharp, and if in any doubt, run slower than normal, with a fine cut and fine feed.

White spirit may be an acceptable substitute for kerosene; try it?

When you are more proficient, you can start worrying about levelling the lathe, to minimise twist in the bed.  But that comes later!

Hope that all my ramblings will be of some help.

Howard

Edited By Howard Lewis on 28/08/2015 19:36:19

There are no modelling engineer's clubs in Cairns ; it is too small. Thank you for all the advice.

1. Why does the lathe have to be levelled off ? At the moment it is not even bolted to the workbench. I want to be happy about where it is situated before I do that.

2. I have removed the chuck guard before but rotating the shaft did NOT get the lathe working. There is something else involved which is why I put it back on. It is going to be a real nuisance when I want to machine some flywheels which are a bit larger.

I tried to make the expanding mandrel today. I do not have any aluminium bar stock but I have silver steel and stainless steel so I used the silver steel. Drilling out the end was easy (2.4mm to take an 3mm tap beginning with a centre drill and finishing with a jobbing drill ) but when I went to reduce the shaft from 6.35mm down to 6mm I went to far down to 5.88 and stuffed it up. I was too concerned about getting a smooth finish and I was not measuring as I go I will try again tomorrow.

3. How long should the mandrel be overall (my thickest flywheel is 45mm) and how far in should I drill the end hole ?

4. Should I drill first and reduce down to 6mm after or the reverse ?

5. Parting off is still a problem. In the end I cut it off when I hacksaw. It does not  matter how slow I take the cuts, the tool still digs in and everything comes to a grinding halt. I am not sure what I am doing wrong here. The other thicker HSS parting tool is even worse. I know I am going to need the steadies but I cannot find anybody that sells them in this country.

6. Cutting the slots in the end of the mandrel is going to be a problem ; I doubt that the hacksaw will do a good job. I have a jigsaw with metal cutting blades but it can be hard to hold a straight line with the jig saw. How long do the cuts have to be ?

Edited By Brian John on 29/08/2015 07:26:38

Edited By Brian John on 29/08/2015 07:27:23

Edited By Brian John on 29/08/2015 07:28:03

Edited By Brian John on 29/08/2015 07:29:31

Edited By Brian John on 29/08/2015 07:35:12

Cut far closer to the chuck.

If that is the reduced end nearest us then you don't have enough to hold.

Myself I would not tap the end for a screw, better to thread it externally for a nut, you can then centre drill the end and use the tailstock to support the end of the mandrel

I was going to try both methods : external and internal threads but the external will be easier, I think.

Parting off:

One of the keys to easier parting off is to ensure you have maximum rigidity.

Tool protrusion in holder needs to be minimum to just reach beyond where you are parting to.

Tool on correct centre height and locked solid in holder with an OK top take for material. Most blades have sufficient side clearances due to their built tapers. You also need front rake/clearance.

The parting slot needs to be as close to chuck/collet holding it which must also be a firm grip.

Lock the saddle if there is a saddle clamp.

Importantly, ensure all slide ways have no undue clearance, I.e jib strips need to allow no excessive play. If you have play you will get snatch. I have seen many a tool holder broken because of this.

When actually parting off manually ( not under feed ) don't be afraid of retracting the tool a few times during the operation to clear dwarf. Also consider moving your tool sideways using your compound about 0.5mm to widen the parting slot slightly. It allows for dwarf clearance to help prevent any jamming.

Good luck and when you perfect it it will be a joy rather than endurance.