How to machine a flywheel ?

[Brian JohnParticipant @brianjohn93961]

It would seem that reamers are no more accurate than drill bits ! What do they mean by H6, H7 and H8 ?

Michael : I was planning to drill the 6mm hole in the flywheel. It seems simpler than boring it. If this did not work for some reason than I would have to reconsider.

Edited By Brian John on 01/08/2015 17:09:45

[Neil WyattModerator @neilwyatt]

Posted by Dinosaur Engineer on 01/08/2015 16:42:35:

Posted by Neil Wyatt on 01/08/2015 10:33:53:

Trouble with reamers is the usual ones we get are H6 and they are a wee bit too loose to ensure something as wide in relation to its thickness as a flywheel is accurately aligned.

Worst is in cast iron, where the freshly machined part is a snug fit and two days latter its become a tad loose as the dust shakes out

Neil

The normal "cheap" reamers are H7 . The tighter tolerance more expensive H6 grade are not stocked by the some of the modeller's stockists. It is possible to stone a reamer to cut a little smaller.

Oops I'm all sixes and sevens…

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 01/08/2015 17:09:31:

What do they mean by H6, H7 and H8 ?

.

Brian,

This table is reasonably helpful.

MichaelG.

[MuzzerParticipant @muzzer]

And of course you need to consider both the shaft and the hole when trying to ensure a given type of fit between the shaft and the hole. The hole is specified with capital letter and a number, while the shaft is specified with a lower case letter and a number.

There are preferred fits ie combinations of shaft and hole tolerances, as shown in the site MichaelG linked to. These apply to threads as well as shafts, so a thread might be specified as M8x1-6g and the mating nut M8x1-6H to ensure the correct fit. We don't normally get into that in the home workshop.

Murray

[Brian JohnParticipant @brianjohn93961]

I have just bought the Optimum lathe for $715 plus $60 delivery :

**LINK**

Unfortunately, they told me AFTER I gave them my card details that delivery cannot be made until the end of the month due to stock availability. That is a bit annoying so I will just have to wait.

There is no face plate or 4 jaw chuck for this lathe so I may not be able to machine the flywheels on it. The supplied 3 jaw chuck is only 80mm in diameter so I think it will be too small to machine 3.5 inch and 4 inch flywheels on it even if they were concentric in the casting ; the chuck guard will get in the way. But at least I can lift this machine by myself when necessary.

Edited By Brian John on 03/08/2015 08:03:05

Edited By Brian John on 03/08/2015 08:03:45

[mechman48Participant @mechman48]

Posted by Brian John on 03/08/2015 08:02:36:

I have just bought the Optimum lathe for $715 plus $60 delivery :

**LINK**

Unfortunately, they told me AFTER I gave them my card details that delivery cannot be made until the end of the month due to stock availability. That is a bit annoying so I will just have to wait.

There is no face plate or 4 jaw chuck for this lathe so I may not be able to machine the flywheels on it. The supplied 3 jaw chuck is only 80mm in diameter so I think it will be too small to machine 3.5 inch and 4 inch flywheels on it even if they were concentric in the casting ; the chuck guard will get in the way. But at least I can lift this machine by myself when necessary.

Edited By Brian John on 03/08/2015 08:03:05

Edited By Brian John on 03/08/2015 08:03:45

I'd have shopped around for other suppliers that would have a lathe in stock & supplied the above as standard… Just another way of getting more bucks out of you for 'optional extras' … not an uncommon trade practice.

[Brian JohnParticipant @brianjohn93961]

The factory does not make a faceplate or 4 jaw chuck for this lathe. It is a new model and they may make them in future but nobody is certain.

[john carruthersParticipant @johncarruthers46255]

Chucks etc are available for your lathe, you may need an adapter plate but I imagine you'll find one that just bolts on, same with a faceplate. You will probably find they are held on the spindle by 3 or 4 bolts. Once you know the bolt pattern you can order accessories to fit.

This sort of thing…
**LINK**

[Brian JohnParticipant @brianjohn93961]

Okay, I will wait and see what the bolt pattern is when it gets here in 3 weeks ! I had assumed that lathes were like cars and parts from one brand do not fit the other brands ?

[Brian JohnParticipant @brianjohn93961]

Amidst all this talk of flywheels, chucks, drills and reamers I have just realized that the axle is going to have to be machined too. How is that done ?

[Brian JohnParticipant @brianjohn93961]

Does anybody in the UK make these live tailstock chucks with the MT1 arbor ?

**LINK**

[Brian JohnParticipant @brianjohn93961]

I have been machining flywheels using my newly made steel mandrels. Everything was okay on the smaller flywheels (50/60mm) but then I had a go at some of the larger flywheels and struck a problem. The 75mm diameter flywheel cannot be held in my lathe chuck ; my lathe is too small. I have tried both internal and external jaws and I cannot get a good safe grip. I only need to face off the hub and drill a hole for the mandrel/axle. I can then fit the mandrel and do the outer rims and the outer surface.

There is a 10mm diameter hub with 5mm sticking out. is it safe to grab the flywheel as per the photos ? I cannot see any other way to do it. The flywheels are aluminium and brass so they are easily machined.

Some of my other flywheels do not even have a hub sticking out so I think a face plate is the only option with those.

Edited By Brian John on 03/10/2015 07:26:06

[JasonBModerator @jasonb]

Have you tried the jaws that you have fitted at the moment but opening them outwards so the step on them grips the inside of teh flywheel?

[Brian JohnParticipant @brianjohn93961]

Yes, I tried that but by the time the step has reached the rim of the flywheel then the jaws are out of the chuck thread.

[JasonBModerator @jasonb]

Looks a lot closer in the photo, use the step nearest the chuck body

[David Clark 13Participant @davidclark13]

Faceplate would be best and machine bore and outside diameter at the same time.

[Brian JohnParticipant @brianjohn93961]

Jason, no it will not work like that. I have fiddled with it many times. it cannot be gripped on that first step (nearest the chuck body) as the second steps (closer to the centre) will not pass through the spokes. With a different spoke configuration it may have been possible.

David : yes, I think a faceplate is the only answer but there is no face plate for this model so one will have to be made. I am having problems getting the chuck off to see what fittings are required as the nuts are on VERY tight ! I will have another look tomorrow.

[Bob Brown 1Participant @bobbrown1]

Why not get a piece of material and machine it such that held in the chuck it acts like a face plate you can then drill and tap some holes in it to clamp the flywheel to it bit like a jig. To ensure the face is square just take a skim off it before clamping the flywheel on.

Bob

[Engine BuilderParticipant @enginebuilder]

Here is a video of a flywheel being machined.

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

My advice: Buy a small faceplate [any suitable size] and make a spigot to fit it.

Clamp the spigot firmly in your chuck and away you go.

… it probably won't run perfectly true, but you will be levelling the Flywheel blank anyway and I think it's the safest option.

MichaelG.

 

Edit: Bob beat me to it.

Edited By Michael Gilligan on 03/10/2015 08:52:22

[HopperParticipant @hopper]

In the absence of a faceplate, you might be able to undo the three or four nuts that hold the chuck to the flange on the spindle. Then use the flange as a faceplate by holding the flywheel to it with some nuts, bolts and washers. Or get a disc of ally from Norweld and bolt it to the flange then face it off and drill bolt holes wherever you need them. Tonkins also often have steel discs on the offcut bench — "holes" from larger jobs on the CNC laser cutter.

Your lathe will take a much larger chuck than the one it came with. I would recommend a four-jaw independent chuck. You are going to need one sooner or later for holding castings and other non-round items for machining. A 125mm four jaw is a very handy thing to have, if it will fit your lathe. If not, a 100mm is pretty handy too.

For the flywheel in your picture, you might get away with holding by the hub like that. Take light cuts and drill gently. You may have to rap on the rim of the flywheel with a soft hammer (aka handle of a screwdriver) to get it running reasonably true before starting to machine the hub.

Or at a pinch, you might be able to make a simple face plate out of a piece of 20mm thick wood with a hole bored thruogh the centre, say 50mm diameter, that you can grip with the chuck jaws from the inside.  Does the tai tai have a cutting board and do you have the skill to explain how a 50mm hole appeared in it?

Edited By Hopper on 03/10/2015 09:15:03

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

An alternative would be to make a 'Bell Chuck' … have a look at the Wade items on this page, and then think bout what you could make by adapting locally available items.

You have already seen the possibilities of various pipe-fittings, so I'm sure you can find something useful.

MichaelG.

[Ady1Participant @ady1]

Would a long fixed centre help? I made mine out of a bar of silver steel.

Can make awkward jobs safer and more secure and still let the toolpost in to work

 

 

Edited By Ady1 on 03/10/2015 10:29:56

[Brian JohnParticipant @brianjohn93961]

The slightly larger flywheels that I have CAN be gripped by the inner rim. I think that this is just an awkward example which will require the use of a face plate or by carefully gripping the hub. I think I can see how a ''face plate'' can be made to fit this chuck ie. the ''face plate'' held in the jaws and the flywheel then attached to it.

I have to go to work now but I will think about this tonight and look at the problem again tomorrow.

A four jaw chuck and a fixed steady for this lathe has been ordered from China but the Australian company does not know how much it will cost or how long it will take to get here.

I will leave the cutting boards alone for the moment as there are other options to explore. I just thought I might be missing a simple solution with the internal or external jaws. I was surprised to find that I could not grip this flywheel with either.

 

Edited By Brian John on 03/10/2015 12:31:16

[David Clark 13Participant @davidclark13]

Hi addy1 it might be hard to bore the hole with a long centre in the way!

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