Gallery, Projects and General > How do I??

Engraving aluminium question

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AdeV:
Hi All,

Right, I'm wanting to engrave a logo onto a fairly small piece of aluminium (approx 95x40mm). Due to the size, there's some fairly intricate detail, to the point where it looks like I'm going to need a 0.3mm cutter to get decent quality. The engraving BTW is going onto the cam cover of my Jaguar engine; and that throws up its own complications: I don't want to have a separate stick-or-screw on piece; I want it to be part of the cover itself. Whatever cutter I use has to stick approximately 2" out of the spindle nose, if I'm to be able to use the bulk of the 95mm width (actually I've got nearer 100mm, but I've taken 5mm off to cover spindle clearance issues).

I reckon there's 3 ways I can approach this, using in all cases a 0.3mm end mill:

1) Mount end mill in a home-made holder, in a standard DA collet holder. Upside = cheap and easy, Downside = potential cutter-killing runout, max RPM=4000, very slow cutting speed
2) Buy a spindle-speeder, mount cutter in spindle speeder collet. Upside = accurate, 20krpm top speed for faster cutting, less likely to kill the cutter. Downside = £2150 + 20% tax....
3) Make a dremel holder that fits on the spindle sleeve. Mount cutter in dremel. Upsides = cheap, high rpms, accurate if rigid. Downside = complex to make, tool breakage if I accidentally raise the spindle too high...

I must admit... I'm leaning towards #3...

Any other thoughts/ideas entertained.

PS: it's got to be a physical engraving. I intend to cut the logo, paint the entire cam cover British Racing Green, then mill off the paint around the engraving & across the rest of the patterned top, leaving the logo in contrasting BRG with a silver background.

RobWilson:
Hi Ade

I used these http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Engraving-Cutters#Solid-Carbide-Engraving-Cutters with good resultes at 4300 rpm in the we denford cnc mill , ruff out with a 1.5mm end mill and finish with the engraving cutter . Still slooooow going  :palm:

Rob

Spurry:
Ade
I've used a piece of silver steel of a diameter to suit a collet, say 12mm or 1/2", then drill to suit the smaller diameter cutting tool. Depending on how accurately you can make the hole on whether you need a spot of Loctite to secure.
Pete

AdeV:
Hi Rob - I've seen a few places offering those "D" style engraving bits; are they reasonably strong at the sub-0.5mm size? As in, stronger than a typical PCB routing bit, for example?

I did contact a company who sells end-mill style bits at 0.3mm diameter (with 0.6mm flute length), G-wizard suggests I can push these reasonably hard, although I'd still expect to be sitting around for a few hours waiting for the results.

Pete - that was kind of what I was thinking. The PCB bits usually have a 4mm or 6mm shank, so I'd drill a suitable hole in a piece of steel, of a set depth, then cut down the outer diameter to suit whatever handy DA collet I have lying around doing nothing; in theory, I can do this without disturbing the work in the lathe so concentricity (provided I can spot the hole accurately) should be fine. I guess I'd need to ream it to size to get a perfectly round hole. Final ops would be to drill & thread a side hole for a grub screw, then each PCB bit would need a flat ground onto the side to lock it with said screw. That should, in theory, mean that if I do snap a bit, I can replace it without disturbing the Z-axis setting, given the likely small depths of cut, that would be important I feel. Balance at 4000rpm shouldn't be an issue, but if it's more than say 0.0001" out of concentricity, I'm sure I'll be snapping bits left right & centre at such slow speeds :(

That was my Plan A BTW... I was hoping to get some info from the company that makes/sells the bits before I splash out the £11 per cutter for a 0.3mm size...  :bugeye:

philf:
Ade,

I second the use of a proper engraving cutter rather than an end mill. They are much more robust and, particularly if you buy them from China or HK, are very cheap. I have made them out of broken carbide end mill or drill shanks and they work fine.

How deep do you want to engrave? Obviously the diameter increases with depth and if you want a 0.15mm radius max engraving 0.5mm deep the tip would be very small.

Why does the tool have to stick out so far?

Cheers.

Phil.

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