Author Topic: clamping round bar  (Read 7427 times)

Offline boatmadman

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clamping round bar
« on: September 29, 2009, 12:48:27 PM »
Hi,

New to this forum, so hi folks.

I have a peatol lathe with various extras that allow me to mill on it. Now, I am not very experienced in this metal work stuff, so I need some help!

I want to machine a length of 40mm round bar into a rectangular block - not too hard - except my mill vice isnt deep (?) enough to hold it, so, is there a way to hold this thing, or do I need to go anf buy a bigger vice?

Thanks for any help.

Ian
If it works, take it apart and find out why!

Offline Darren

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Re: clamping round bar
« Reply #1 on: September 29, 2009, 12:50:18 PM »
Do you have a four jaw chuck, if so you could turn it square if the chuck can hold 40mm?
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Offline raynerd

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Re: clamping round bar
« Reply #2 on: September 29, 2009, 12:53:00 PM »
People on here will give you better advice but I think a V-block would help and that is what I would be using. Then clamping my V-block to the bed or vice....I could be wrong, normally am!




Offline Darren

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Re: clamping round bar
« Reply #3 on: September 29, 2009, 01:18:09 PM »
Yes a V-Block is certainly a handy device but I don't think it will help here as Ian wants to machine the round into a square?
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Offline boatmadman

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Re: clamping round bar
« Reply #4 on: September 29, 2009, 01:22:25 PM »
Darren,

I think the 4 jaw chuck might be the way to go, I have one tucked away somewhere.

Must learn to think laterally!

Thanks

Ian
If it works, take it apart and find out why!

Offline raynerd

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Re: clamping round bar
« Reply #5 on: September 29, 2009, 01:37:33 PM »
my bad, didn`t read properly, thought you could have an overhang out of the V-block and square that up then part of

bogstandard

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Re: clamping round bar
« Reply #6 on: September 29, 2009, 02:15:54 PM »
Ian,

Are you using the solid ali block type of vertical slide, as normally supplied for the Peatol lathe (called a Taig in the US)?

If so, you will need to make some deeper vice jaws (at least 25mm deep for holding 40mm diam bar), unless you stand the bar upright and clamp on the ends of the bar. I don't think the jaws on your four jaw will be deep enough to hold more than the two bar ends, and even then it might not be very secure.

Bogs

Offline boatmadman

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Re: clamping round bar
« Reply #7 on: September 29, 2009, 02:24:51 PM »
Bogs,

Yes its the solid ali block vertical slide.

Deeper vice jaws, another easy solution!

I will have to check my 4 jaw chuck to see if that is an option, but bigger vice jaws sounds favourite at the moment.

Ian
If it works, take it apart and find out why!

bogstandard

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Re: clamping round bar
« Reply #8 on: September 29, 2009, 03:33:43 PM »
Ian,

If you get stuck with the making of the jaws, if you can make up a sketch of the ones you have now, including size and depth of cap screws and head recess (if any), I will see what can be done.


Bogs


 

Offline boatmadman

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Re: clamping round bar
« Reply #9 on: September 29, 2009, 03:44:38 PM »
John,

You are a star.

I have just tried a bit of cast round in the 4 jaw chuck, it worked ok, but I was a little concerned about the tool thumping into the workpeice twice a rev - doesnt feel right to me, even when taking very small cuts.

Should this worry me? Or is it just lack of experience?

Ian
If it works, take it apart and find out why!

bogstandard

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Re: clamping round bar
« Reply #10 on: September 30, 2009, 02:30:12 AM »
Ahah! the dreaded interrupted cut.

Just three things, you need to make sure the job is really secure, make sure you get your cutting tip as close in to the toolpost as possible, to keep things as rigid as you can, and I think you will find that tipped tooling doesn't really like to do it. It tends to chip the edges away.

You might find a problem holding size and shape on a small lathe due to tool flex. This is where the cutter starts its cut at full depth on the first edge of the material, then as it cuts, the edge is forced away slightly from the cutting face. Once the first face is cut, the tool springs back to it's original position of a full depth cut, then repeats the problem over again. It usually gives a slightly curved edge on the leading cut face. I hope you understood that.

The way around it is to rough cut first until very close to size, then super-superfine finishing cuts so that there is not as much loading on the cutting edge that is trying to deflect it.

With a small lathe, you will find that jobs like this do tend to take a bit longer, as you don't have the overall rigidity to take big cuts. Once you start to realise the machine limitations, and stick rigidly within it's capabilities, then you will start to make some real progress, and get nice work off it.

Many years ago, I owned one of these Peatol lathes, but didn't make much use of it. So I let a fellow model boater have it, and he produced some fantastic work with it, he even made a very nice double acting oscillator with it. When he started to use it as a hand graving machine as well, that was when he really produced his best work. But for you, that side of things will come a little later.

Bogs