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Cutting a groove in brass rod?

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Phil Russell

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A little project requires me to cut a groove in brass rod and I wondered about the best way to do it using a mini lathe. The rod is 6mm diameter and I need to cut a groove 1.5mm deep x 5mm across approx 25mm from one end.
I thought my first attempt using an HSS cutter travelling directly into the rod was going to work (approx 350rpm, tool set at centre) but just at the last moment the rod snapped. The end of the rod was supported by a rotating centre.
I have concluded that filing is out. I am pondering using a parting off tool, approx 1mm thick to cut each side of the groove first then cut out the centre portion.
How would you do it?
Cheers, Phil
 

novocaine

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1.5mm is half the rod diameter. I'd mount it as close to the chuck as I can, put a steady on the other end ((just a roller for it to settle on), I wouldn't put that end on a centre as your putting force on the rod that will make it want to bow, hence the break.
I'd grind a grooving profile at 2mm and take 3 cuts overlapping. worst bit will be the first cut.
 

Droogs

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Do you have a Dremel type tool? If yes then I would do the following:
1. Create a cradle from wood block with a core box cutter and glue the rod into that along with stop blocks either end taking step 2s dimension into account,

2. Either use a Veritas/Dremel plunge base or make a sled out of ply to hold the dremel tool and use a 3.2mm shafted end mill in the dremel of the appropriate width.
3. Mill the slot using the Dremel in the same way as a leveling sled until I got to depth.

a set of endmills can be got for a few quid from BG or from here, just look for the needed width

 

novocaine

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I'm reading it as all the way round rather than a keyway Droogs.
if I'm wrong, then I wouldn't be reaching for machine tools at all, I'd use a file. :)
 

Droogs

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Ah, it's that word groove, has a defined and definitely specific meaning in woodwork - grainward so along length away from the edge of the piece or it would be a rebate. Dado accross, not sure what a turner calls them tho'
 

novocaine

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agree with you there and it's not the right word but it'll do because I can't think what the right word would be right now. :)
 

AES

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Perhaps (???) I'm REALLY slow this morning, but I (still) can't work out if the OP is trying to cut a "groove" into the circumference of his rod, or a "groove" (e.g. keyway) along all of/part of the length of his rod. Perhaps I'll come back to this one later :(
 

novocaine

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The 350rpm suggest circumference. Unless he's milling on his lathe (possible) but then the live centre seems an odd choice. :)
 

Yojevol

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agree with you there and it's not the right word but it'll do because I can't think what the right word would be right now. :)
I think it's called a FLAT. This is my interpretation of the dimensions. If it is a flat that is required and not a groove then the 5mm dimension is superfluous.
Drawing1.JPG

Brian
 
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novocaine

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but that wouldn't fit with 1.5mm deep x 5mm across approx 25mm from one end. there are to many dimensions for a flat that would be 1.5x25mm and still not be doable on a lathe in standard guise. I still think it's something like an oring groove (oh, groove is the right term for that :) )

I'm shutting up till the OP comes back. :)
 

Sheffield Tony

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Ah, it's that word groove, has a defined and definitely specific meaning in woodwork - grainward so along length away from the edge of the piece or it would be a rebate. Dado accross, not sure what a turner calls them tho'
By across I take it you mean across the water in the USA. Here its a housing. A dado is the bottom bit of a wall. Oh how MikeG will be missed ;)

I was assuming he mean a groove around the rod, not along it ? It would better explain why the first go snapped off.
 

porker

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I thought it was a sort of keyway, so started putting a solution to mill the slot by putting the cutter in a collet and clamping the rod on the cross slide but the description sounds like a sort of partial parting off if I understand the description correctly
 

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Very thin parting tool as you need to to keep the cutting forces to a minimum. Make the groove at each end to final depth and then make successive cuts to remove the material in the middle cutting just a little shy of final depth. Finally use the parting tool like a turning tool to remove the final little bit of material to give a smooth finish. The side clearance on your parting tool will be enough for such a small cut.
 

Sheffield Tony

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Seems like a strange way to me. I would have thought starting at the end furthest from the chuck, and making successive (slow, light) cuts would mean you are never putting the torque through a 3mm bit of rod instead of the full 6mm ? But I'm not a machinist.
 

Rorschach

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3mm should handle it fine if using a small tool. You could do it in different ways but I would do it that way to establish the end points and work to them, the job would go faster.
 

novocaine

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the bible has a bit about grinding tools for brass in it. (good book, worth owning, the bible)
they call it a knife tool where I'd always known it as a grooving tool profile. Profile D.
20201002_121336.jpg
 

Phil Russell

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Apologies for not being clear and causing confusion. bjm has got it right in his picture above. I am coming to the conclusion that Rorschach is the advice I will follow. I note comment about the revolving centre.

Out of interest and to pass the time this morning, I took some 6mm brass rod and drilled it through at 3mm then mounted the bits of 6mm rod on the 3mm rod, soldering them in place. Not a very elegant solution I admit but it would work.
Many thanks for all the advice and sorry for creating confusion. I intend to continue with a direct lathe solution .. it's a matter of honour now.
Cheers, Phil
 

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