# Cutting a groove in brass rod?



## Phil Russell (2 Oct 2020)

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


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## novocaine (2 Oct 2020)

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.


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## porker (2 Oct 2020)

Can you make a temporary moving steady from wood to support the back of the rod where you are making the groove ?


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## Droogs (2 Oct 2020)

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






S9042.0 | Dormer Solid Carbide End Mill, 2mm Cut Diameter | RS







uk.rs-online.com


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## novocaine (2 Oct 2020)

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.


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## Droogs (2 Oct 2020)

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'


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## novocaine (2 Oct 2020)

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.


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## AES (2 Oct 2020)

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


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## novocaine (2 Oct 2020)

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


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## Yojevol (2 Oct 2020)

novocaine said:


> 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.





Brian


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## novocaine (2 Oct 2020)

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.


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## Sheffield Tony (2 Oct 2020)

Droogs said:


> 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.


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## porker (2 Oct 2020)

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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## bjm (2 Oct 2020)

I think he means this?


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## Rorschach (2 Oct 2020)

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.


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## Sheffield Tony (2 Oct 2020)

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.


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## Rorschach (2 Oct 2020)

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.


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## novocaine (2 Oct 2020)

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.


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## Phil Russell (2 Oct 2020)

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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## novocaine (2 Oct 2020)

parting off tool. clue is in the name. wrong tool for the job.


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## Rorschach (2 Oct 2020)

novocaine said:


> parting off tool. clue is in the name. wrong tool for the job.



A square ground parting tool can be used for all sorts of jobs, not just parting off.


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## novocaine (2 Oct 2020)

then it isn't a parting off tool, it's a grooving tool or knifing tool as already described. 
a parting off tool has a specific geometry (figure F on my previous image). note the side and back clearance angles, these serve to allow a deeper cut than a standard tool at the expense of strength. 
Here we are talking about a short stub of a grooving tool, no requirement for the back clearance and as we are in brass, no top rake. 
I'd have been kicked out the machine shop for doing this with a parting off tool (even one I'd ground myself).


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## Rorschach (2 Oct 2020)

In the theoretical world you are right, but in the real world, use the parting tool you already have, it will be fine. You don't get sacked from the home shop.


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## Phil Russell (2 Oct 2020)

Oh dear ... I had no intention of starting a bun fight. I have had no formal training in engineering or lathe use. I am self taught and like to think I have a good appreciation of how to make and do things but am learning all the time. I note the debate on terminology but tend to feel that in this case it is not that important. My 'parting' off tool will part 6mm in several materials (depth of cut being 3mm) so using it to cut to a depth of 1.5mm is no big deal. I have used it to cut grooves for circlips, e clips, c clips. I did not know I should have used a different tool for these applications: live and learn I guess.
But thank you all for advice and encouragement.
Cheers, Phil


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## toolsntat (2 Oct 2020)

What's the advantage of leaving the middle bit till last ?
Cheers Andy


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## Rorschach (2 Oct 2020)

toolsntat said:


> What's the advantage of leaving the middle bit till last ?
> Cheers Andy



Speed mostly. You make your important cuts at each end, you can then measure them and check they are within spec. After that removing the material in the middle is fast and requires little care. 
If you start in the middle you have to take more measurements and if you make a mistake when you cut the ends you have scrapped the part after doing 99% of the work.


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## Johnny65 (2 Oct 2020)

You can turn brass with a negative rake HSS form tool, 350rpm is too slow 1000 rpm minimum.


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## Rorschach (2 Oct 2020)

Johnny65 said:


> You can turn brass with a negative rake HSS form tool, 350rpm is too slow 1000 rpm minimum.



You can, but you can't cut a 5mm wide pass on a 6mm rod.


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## HamsterJam (3 Oct 2020)

How clean does it need to be?
Can you make a hacksaw cut on the rotating rod?
Need to adopt left handed grip to avoid reaching over the chuck.


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## novocaine (3 Oct 2020)

Can you not use a form tool for a 5mm cut? I can.
I havent got a lathe here at the moment (its still in nottingham but hopefully not for much longer) so i did this on the less than ideal drill press using my compound vice as a tool post.
Didnt regrind the tool geometry much, just a touch of back clearance as already discribed. Mounted so the face was square to the stock.
Only had 5mm brass rod so i only cut 1mm. I'd say its possible to cut with a form tool. But then, i guess my theoretical knowledge isnt worth much. Good luck with it Phil.


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## Jackbequick (3 Oct 2020)

novocaine said:


> 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.



Hi..the centre if_ just inside_ a countersunk ' other end ', that is just in contact should not bow the thin rod...would you agree novo?


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## Jackbequick (3 Oct 2020)

porker said:


> 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




I thought the same and thought it an easy fix...Apparently I was also 'wrong'. The answer here is great patience and sensitivity...'gently gently' and perhaps 'a little at a time' with a live centre tip tucked just inside a tiny counter-sink ...just enough to maintain the horizontal. The option also might be to go to a tiny lathe made for fine work...could be one of which he knows or at some 'man-cave'.


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## novocaine (3 Oct 2020)

No reason why not but for a chunk of wood with a v cut in it id make a rough and dirty steady. Im lucky in that i have a hollow spindle, so id run the long end through the chuck and have 2" stick out in front. If i didnt have that option I would most like put a stedy right by the cut and rest the long end in the jaws of the tailstock chuck. 

We are making this complicated though. As shown already, it can be done with a form tool a sensible rpm and a slow feed with the right geometry.


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## Jackbequick (3 Oct 2020)

yes...actually setting it inside a collet might be easiest to hold it steady (?)


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## Phil Russell (5 Oct 2020)

Sorted yesterday afternoon. I used a thin parting tool as a grooving tool to cut 1.5mm into the outer edge (rh side) then moved it inwards the width of the tool blade, continuing this action until I had reached the lh edge. Brass rod was supported on rh side by a moving steady. Groove finally cleaned up with a 3mm wide hss cutter. 
Thank you for all the comments and help. 
Cheers, Phil


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## AES (5 Oct 2020)

Well done mate. The most important thing is that you've ended up with what you needed!


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