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Cutting a groove in brass rod?

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novocaine

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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).
 

Rorschach

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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.
 

Phil Russell

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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
 

Rorschach

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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.
 

HamsterJam

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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.
 

novocaine

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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.
20201003_094850.jpg
 

Jackbequick

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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.

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?
 

Jackbequick

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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


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'.
 

novocaine

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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.
 

Phil Russell

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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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