What Cutter / Method ??

This topic has 10 replies, 6 voices, and was last updated 6 June 2013 at 18:05 by chris j.

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3 June 2013 at 22:47 #6738
chris j
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@chrisj
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3 June 2013 at 22:47 #121454
chris j
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@chrisj
Starting with a 3" Diameter round steel bar

I want to end up with several pieces about 1" thick with something like a 1/2" shallow (2" wide) in the end of each piece, like an ashtray (does that make sense ?)

So I figure, I set the bar in the chuck square and true and cut the 1/2" deep scallop out of the end face, then use a parting tool to take a 1" slice off the end, job done.

So what method would you employ to cut the scallop out, I can't seem to settle on something comfortable. If I drill a hole in the centre 1/2 deep I can then get a boring type cutter in there and open it up. The pain is I have to use two cutters to do the scallop and a third to part.

What do the panel thing is the easiest method/cutter type. ?
3 June 2013 at 23:24 #121459
Chris Heapy
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@chrisheapy71135
Yes, use a stout boring tool. Be wary of parting off dead to the length required, a facing cut will probably be needed if surface finish is important. I have a 1" 2MT shank endmill which I plunge-cut start a recess like that, then I can use a larger diameter boring tool. However, 3" dia is too big for me to part off comfortably, I would tend to saw the blanks off first and work from there.
4 June 2013 at 01:39 #121467
Ady1
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@ady1
Drill the hole from the tailstock

Once you've drilled the hole even an ordinary pointy left hand carbide tool will be sufficient for the 1/2" recess

bear in mind that you are cutting loads more material on the outer edge than the centre, and you have less torque, so cut more slowly on the outer part

edit: And practice with a few "finishing cuts" before you reach full depth and width and have to do the real deal

Edited By Ady1 on 04/06/2013 01:42:39
4 June 2013 at 01:50 #121469
Ady1
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@ady1
The other thing to bear in mind is parting off

If you haven't done it before, as mentioned previously, you may be better sawing off 7 blanks and doing each one separately

(On a production line they would put the 3" bar through the spindle bore of a big Herbert Turret lathe to keep everything close to the chuck kinda thing)
4 June 2013 at 23:27 #121558
chris j
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@chrisj
Thanks Guys

I had a better day today, probably because I was heartened to think I was doing it about right.
5 June 2013 at 00:10 #121560
nigel jones 5
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@nigeljones5
I find that if all else fails, sacraficing a goat helps…..might only work for Myfords though?
5 June 2013 at 16:12 #121612
chris j
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@chrisj
So I have opened the hole out nicely but the bottom is a bit messy.

What do the panel think might be the best tool to clean it up. ?
5 June 2013 at 16:48 #121614
merlin
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@merlin98989
Also bear in mind that there will be some distortion after removing such a large chunk from the middle so, assuming that it is important, allow a good few thou for final cleaning up of the two large faces.
6 June 2013 at 12:53 #121669
Trevor Wright
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@trevorwright62541
Chris,

The tool you bored out with will clean the bottom face nicely, just do 0.005" cuts till you are happy with the finish. Make sure you have the point of the tool on the centre-line or you will leave a pip if low and chip the tool if high.

I would not attempt to part off that thickness unless you have a pretty sturdy machine. Machine the front and recess, cut off on a saw, turn around in the lathe and face the back to the thickness needed.

Trevor
6 June 2013 at 18:05 #121690
chris j
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@chrisj
Thanks Trevor

I found a great video by Tubal Cain on youtube last night.

What he suggests is to push down the sides towards the chuck (increasing the diam of the hole) and when at the bottom, stop and move towards the centre cleaning the base. Obviously leaving a couple of thou to deepen the hole ready for this. I'm going to give that a try and see how I get on.

I have also secured a Warco 812g single phase bandsaw that I'm collecting tomorrow !!
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