How to profile a head

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mickyb
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Sun Jan 18, 2009 8:20 pm

you can also fit a piece of ally to an engineers square, with the square on the side of the piston file the shape of the crown in the alloy, you can the use that as a jig to grind the profile onto a piece of H igh Speed steel. When you set the tool up in the lathe you only need to make sure its square to the chuck and you know the profile will be correct

156 D
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Sun Jan 18, 2009 8:21 pm

davidblythe wrote:also what is the best way to hold a cylinder to top and tail it
I`ve been thinking about this one for someone that does one or two in there own garage workshop....because to buy the proper mandrell that will do the job so you can do hundreds a day will cost......so the easiest way out is get a piece of timber the size of the bore by making your own with the lathe( a lathe can be used for either metal or wood).....go gently when your near the size so that it is a nice fit....the end at the chuck can be reduced to fit if it`s to big to go straight in the chuck....but anyway to make it it must be in the chuck and tailstock in the first place......if you have no means of holding or clamping the barrell tight to the wood while you turn it just put some water on and it will swell to hold the barrell tight you will only have to wet either end for it to work......when your up and running just very carefully nibble away until you have topped or tailed it.........sounds a bit Heath Robinson but on your own in the workshop you have to make things up......by the way if you have to glue lengths of wood to get the diameter, make sure you make an octagon out of it before you put it in the lathe otherwise..... BANG!!...............
Nostalgia is a thing of the past!....

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jonny snatchsniffer
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Sun Jan 18, 2009 8:48 pm

i used to get my barrels done by some bloke called dave near newlands corner he was old school and did it on a lathe, he did me a suzuki 190 and knew his stuff very well

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Knowledge
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Sun Jan 18, 2009 11:29 pm

David,

I picked up this very wide lump of machine steel and shaped it to a cylinder head contour.
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The tool can be positioned in the tool-post at slightly different angles to suit pistons with different dome shapes. This saves having to re-grind the profile on the end of the tool for every type of piston. OK, you might have to re-grind it for certain pistons, but you'll be surprised how many pistons you can made it work for.

With a tool this wide cutting across such width, the lathe must run as slowly as possible; around 60rpm or less. It makes a bit of a row while it cuts, and there is a lot of vibration, but it should be OK. Feed it in slowly though, or your fillings will fall out.

This is my head holding tool, with another view of the cutting tool. It uses the top four fins of an old barrel as a base. You can use a 150 barrel for small block heads, and an old 200/225 barrel of the big-block heads. All the other components are inter-changeable.

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Sorry if you've seen this before, but if you want more info, pm me.
Martin
Last edited by Knowledge on Fri Jan 23, 2009 1:19 am, edited 1 time in total.
Martin

156 D
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Mon Jan 19, 2009 5:11 pm

I would be careful as you are a novice with lathe`s.......the chatter caused by a full width tool would be considerable and you won`t like it......also it may leave deepish chatter marks which you will have to smooth out and considering people talk about 1.2.....1.3....1.5mm squish you may not get the desired amount.......i am not in the least saying a full width tool is wrong ....but what i am saying is unless you have a few heads to practice on i would cut a little at a time...have you heard of the term "a little and often" or "don`t be greedy"..the amount of chatter generated may even move the location of the head on it`s jig.........part of using a lathe is getting one hand to turn in sequence with the other to get a curve and you will only aquire this by patience and practice....but if you do not take chances then you will get to your aim more accurately and safely and the lathe will still be in one piece!!..........Hope this helps?...........
Nostalgia is a thing of the past!....

Stringy
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Mon Jan 19, 2009 5:57 pm

I have been thinking about how to machine cylinder heads without using a 'form' tool for a while.

The best way i could think of doing it was to make a tool similar to a ball turning tool but backwards, rather than turning the outside of a ball reversing it so that it cuts an internal radius.

If you do a google image search for 'ball turning tool', be careful how you type it :lol: , you should see a few different designs.

Boo
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Fri Mar 06, 2009 12:04 am

If i was machining a head i would set it up in a 4 jaw chuck holding it quite firm and clocking the face and stud holes true.Then make a template out of card or thin steel the same profile as the piston crown then grind a tool to the exact shape as the template. Set the tool in the tool post start lathe then machine the squish band with the tool untill you have the correct profile.Before you take the head out the machine just check the squish with the gauge to make sure its correct .By using a 4 jaw chuck you can hold the head more rigid eliminating chatter (vibration) and getting a good machined finish.
To machine faces of a barrel you need a mandrel.
Get a scrap piece of steel bar slightly bigger than the bore of your cylinder set it in the lathe and turn it down to about .001" below the bore size of your barrel and a bit shorter than its lenght.It needs to be a good fit and a smooth finish with no burs as not to scratch the cylinder,slide barrel onto mandrel spiggot end towards chuck and very lightly clamp to mandrel just enough to drive it(you could use a large jubilee clip round the spiggot to clamp it but remember barrel needs to be a tight fit on the turned bar to do this or you could brake spiggot, or clamp it by other means) then just flick the faces of the barrel with tool, they will then be square to the bore.
Lambrettas are for life!

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