Hi
Thanks Mal
The cylinders need to be bored to 1 3/16". I have never done anything like this before so its going to be a bit of a steep learning curve.
From what I can see boring the cylinder with a between centres boring bar and the cylinder mounted to the cross slide is the best way.
So I am going to need a between centres boring bar. After a bit of research I settled on a design by G H Thomas
I had a bit of steel bar 13" long that would do although at 30mm diameter a bit too thick.
To start I mounted it in the lathe 3 jaw chuck and fixed steady and centre drilled
The largest drill I have is 25mm so I turned the end of the bar down to a little under the 25mm
Then turned the bar round and centre drilled the other end
Turn a soft centre to 60° and number stamp the position of number one jaw
The bar can now be held between centres with a dog at the chuck end. The dog is driven by one of the chuck jaws
The bar is turned down to a little under the 25mm
I used the powered leadscrew on my lathe, much easier than winding by hand,.
A bit of video
In the mill the bar is cross drilled 3/16" to take the cutter and a flat machined across
Then drilled and tapped to take an M6 grub screw
There is quite a lot of info on what shape to grind the cutter to. A while back I made some tangential cutters that use round tool steel and have got on really well with them. A very good finish can be achieved both turning and facing so I opted to use the same. I have a little jig I made for sharpening the tool steel
An accurate method of setting the cutter would be an advantage. I started with a piece of ally and cut it into this shape
Then with a series of drills upto the 25mm drilled the hole
The adjusting screw is brass screw cut 40 TPI. which means 1 turn is .025". Turned down 1 end to just under 3/16". A piece of 1 1/4" round brass is drilled and tapped 40TPI. the 2 pieces screwed together and silver soldered
The ally is drilled and tapped 40 TPI through the top and drilled and tapped M6 underneath for a clamping screw
I was trying to figure out how to mark 25 divisions on the adjusting screw so drew it out on the computer
Then a flash of inspiration, print it out on photo paper and stick it on
Thats the boring bar completed which took most of yesterday to make.
Today I set it all up in the lathe and gave it a go
I'll post the results in the next installment
Cheers
Rich