Fly cuter tool?

[the-green-monkey]

This is a long shot but, are there any millers on here in North East England who happen to have a fly cutter I could borrow to skim an A-series cylinder head?

[chrisryder]

Why not get it ground?

[the-green-monkey]

Because I'm doing it at college, hence why I have the milling machine and not the tool. They have a grinder but the stroke length is not enough to do in one pass and I'm not too keen on going over twice.

[MarkyB]

Will you be able to do it in one pass with a fly cutter then?
My brother in law did mine on a very aged machine I think he just used a small cutting tool and fed it through quite slowly.
It wasn't very pretty but has worked very well.

[Trickydicky]

You would need a very large dia cutter to do it in one pass, also the surface feed would have to be very slow to get a good surface finish.
How much needs to come off it?

[the-green-monkey]

I should be able to do it in one pass but as Trickydicky says I will need a rather large tool, I just hoped someone may have done it themselves and had a tool handy. I may just have to rig one up myself using a cutting tool from a lathe, much like this one but large enough to pass over the whole head: http://www.okiegauges.com/images/FLYCUTTER.pdf
Thing is, it probably doesn't really need it, I just want it to be perfect since it's off and there's no rush to get it back on, it only needs a couple of thou off at the most, simply because there is a tiny dip near the little oil flow bit (I really cannot think of a more appropriate name for it, apologies) and a few little scores between the third and fourth cylinders that I'm worried may cause a loss of compression.

[Trickydicky]

Hi,

If it doesnt need doing then dont, jobs like this have a habit of ending up biting you in the a***e, if it only needs a couple of thou then grinding is the best way of machining it. On a Milling machine If you get the speed and feed wrong on the first pass you may end up having to take off more than needed.
Run the engine first then make a call on skimming the head.

Richard

[MarkyB]

That tool looks very much like what he used, I wouldn't bother for a thou or two.
I think we took about 30 thou off to raise the compression a bit.

[tomas.geoghegan]

Hi,

If it doesnt need doing then dont, jobs like this have a habit of ending up biting you in the a***e, if it only needs a couple of thou then grinding is the best way of machining it. On a Milling machine If you get the speed and feed wrong on the first pass you may end up having to take off more than needed.
Run the engine first then make a call on skimming the head.

Richard

VERY SOUND ADVICE . TOMAS

[the-green-monkey]

Thanks for the advice guys, I'll just leave it for now. As I said before it wasn't urgent, just wanted to have a go really but I don't want to balls it up.

[bmcecosse]

Fly cutter can be used - but you need many passes to get a significant amount off, and then you should finish it off on the grinder. To try to take any significant amount off with the grinder will take for EVER! Best way is to mount the head to a lathe faceplate - and spin it!

[MarkyB]

Blimey, that sounds exciting!
It's a big chunk of metal to have whizzing round in the room!

How much would you suggest removing?

[the-green-monkey]

Thanks bmcecosse, that cleared a few things up for me, I don't think I will be mounting it to the lathe mind. As MarkyB says that sounds very "exciting" a bit too exciting for me.

[Matt]

Need a big old lathe for that BMC... but I suspect you have access to loco wheel lathes?

[Trickydicky]

Hi,

The only way you could machine something as big as a cylinder head would be as previously stated, is on a milling machine. The head is stationary while the cutter passes over the head and it also maintains the surface and cutting speeds.
It would be ill advised to try and skim it mounted on a faceplate on a lathe as the surface speed slows the nearer you get to the center of the object you are machining while the cutting speed stays the same resulting in a poor surface finish.
Also you need to take into consideration the fact that there will be a hardened skin on the head due to the heat generated from normal use of the engine, as marky says, he took about 030 thou of his which may have been enough to get underneath the skin.
If you must machine it then grinding is the only way to ensure a good surface finish.

Richard

[Alec]

Hello Richard,

theoretically what you say is true about machining in a lathe, but in practice, with cast iron it will not be a problem. And as today most use carbide tipped tools the surface hardness will not be noticed. Certainly it is not the most accurate way, a milling machine or surface grinder is inherently more accurate and either will give an acceptable finish for a cylinder head.

Alec

[bmcecosse]

Yes -we did use a BIG lathe for the head skimming - and then finished off on the surface grinder.