Dremelling Aluminium spinner question

Hi,
I spent quite a bit of yesterday cutting the propeller holes in an Aluminium
spinner. For the uninitiated these spinners are around 1/16th of an inch thick
in ally that's about as hard as it gets, idk why. They're not a particularly
convenient shape to hold securely which is why I prefer to use the dremelloid.
Anyway, I've tried multiple ways in the past including hacksawing then filing,
dremelling with a sanding drum, and so on. At the LME a few weeks ago I managed
to pick up a couple of small carbide "slot mills" suitable for the beanqueue
dremelloid and so I tried these. They are the type that have multiple teeth
spirally arranged around a 2.5mm (ish) cutter with a 3mm shank to fit the
collet. They work great for a few seconds but clog almost immediately and cease
to cut, so I am back where I started.
The obvious way of doing the job is to buy a piercing saw and then file back to
final shape afterwards, but I just thought someone might know a way to stop my
carbide cutters clogging, or else know of a different type of cutter to try ?
Or failing that, a sure fire method of performing this tedious and irritating
job with the minimum of frustration using hand tools ?
Thanks in advance,
Reply to
Boo
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It is pretty odd to state that any aluminum alloy, esp. 6061 which is likely what you are dealing with, is as "hard as it gets".. there are few aluminum alloys that would be classified as hard, although high silicon aluminum might be referred to as such in comparison to softer alloys.
What is a "dremelloid" - is that supposed to be some kind of cute name for a Dremel tool?
Firstly, high speed steel tools do a better job of cutting soft aluminum than carbide, although carbide will work okay. How fast are you running your dremel tool? You should not try to machine/cut aluminum at 8 million rpm. You need to keep the surface speed of the cutter moderate to avoid heating and melting the Al at the tool/material interface which is most likely the cause of your tool clogging. And, a coarser mill is preferred to a fine one, so if the cutting teeth are of a fine variety and you are running the tool at high speed there is your problem. Normally, the amount of metal you are talking about removing should take only a few minutes. You could even rough saw the opening, then use a small Dremel drum sander on lower speed to finish cut. You should not be having so much grief with this job, I think you need to slow down your tool and perhaps use a coarser cutter.
MJD
Reply to
mjd
Very simple my young Padawan alloy porter. You need to keep the carbide cutter lubricated with paraffin when cutting aluminium. There are a vast range of carbide porting burrs available with 3mm shanks for cylinder head work. Google for carbide burrs. For making holes there's a pointed one I use which tapers over about 1/2" from a sharp point to the 3mm shank. You can thus make any hole size you like up to the 3mm or hack slots through things. A quick porting 101 on clogging burrs.
1) Running the burr too fast. The faster you go the quicker the metal removal but at a certain point the alloy softens as it comes off and the cutter clogs. My pro porting gear (Foredom) has a variable speed controller. I can run it up to the clogging speed and then back off a bit. If your Dremel doesn't you might be a bit stuffed in this respect. With 3mm tooling it's unlikely to be a problem though. I do most of my work with 6mm tooling and burrs up to 3/4" diameter so the correct speed is vital.
2) Soft alloy. The better the heat treatment the less clogging you get, in general anyway. Maybe your alloy is not as hard as you think. Sometimes however very hard alloy heats up and softens as you cut it so the clogging problem comes back. Less speed and more lubrication is the answer. High silicon alloys like LM25 cylinder head casting alloy don't tend to clog anyway and I do most of my porting dry because it's easier to see what you're doing. Low silicone forging alloys like HE15 and 30 clog more so you run wet. Whatever the material you'll always get faster stock removal wet than dry though.
3) Tooth profile. Teeth for alloy cutting are ideally very coarse i.e. not many per inch of circumference to stop clogging. Teeth for iron and steel are much finer. However with lubrication you can use any burr you like and in fact most of mine are general cut or cross-cut. The coarse cut non ferrous burrs certainly do remove material at a fearsome rate in comparison though. I'll use one of those for fast stock removal and then go back to my favourite general cut oval burr for fine detail shaping. Sometimes it's a big advantage to not have the stock come off too fast when you're trying to home in on a shape.
4) Lubrication. Paraffin is the best thing. Any light greasy hydrocarbon will do just fine though - diesel, kerosene, heating oil etc. Brush on frequently with an old toothbrush or spray on with a a window cleaner bottle. Even a clogged burr will miraculously unclog itself as soon as you chuck a little magic fluid on the job.
Try again with the right techniques and I'm sure you'll find the Force is with you.
Reply to
Dave Baker
In message , mjd writes
'Dremelloid' seems to me to be as good a generic term as any for the countless number of such tools available on the market. It is certainly a term I shall adopt in the future.
Reply to
Mike H
I was hoping it wasn't a name for a greivous injury inflicted upon one's self caused by sitting on a running Dremel tool... :-o
Reply to
mjd
Me too Mike :) I prefer it to Black & Decker or any of the zillions of brand name imitators, which could cause confusion. "Dremeloid" will be my choice in the future :) Cool - Boo! ;)
Reply to
Ed Forsythe
Great reply Dave! I think MJD was right on about the speed but your dissertation covered everything. I have had the same problem with my Dremels for years (like 50+)so I just gave up and started buying spinners that fit e.g. True Turn :) Now I'm going to resurrect all those badly dremelled jobs using the lubrication/speed techniques. Thanks MJD and Dave for enlightening me!
Reply to
Ed Forsythe
For lathe work when you can put an ultra sharp edge on an HSS turning tool for one final clean facing cut I might agree but for porting work with burrs then definitely no. Steel burrs have a very short lifespan even on alloy and blunt in no time. Metal removal rate is also much slower. I have a number of them in various shapes but mainly a 3/4" ball cutter system which I acquired because the carbide equivalent wasn't on the shelf when I needed it. The shank has a screw end and the replaceable balls screw on to that so you can fit a new one when the old one blunts.
I use them sparingly when I need to shape a large internal radius accurately but they don't do a very good job even though they're pro quality coarse-cut non-ferrous burrs from my usual carbide burr supplier. Metal removal rate is dire and they make a horrible screeching noise into the bargain. They pretty much insist on being run wet to get even a reasonable amount of material off the job. Basically all they're fit for is final smoothing and shaping.
By way of contrast I've never had a carbide burr wear out in over 15 years of dry porting abrasive high silicon alloy cylinder heads. In fact I do most of my porting with just one of my 30 or more burrs. It's a general cut oval 3/8" burr on a 4" extended shank so it can reach all the way down most ports and after 15 years and hundreds of cylinder heads it's like an extension of my own arm. Quite often I'll be shaping one port while I'm looking down another to see what I want to do to it. The burr knows its own way round a port by now. It's like an old faithful horse that'll still get you home when you fall asleep at the reins.
It's still as sharp as the day it was made and that includes porting a fair number of cast iron heads too although I do those very rarely these days. I'd say it's removed at least 95% of the material that my entire collection of burrs has shifted.
If I ported cast iron heads on a daily basis then it might well have needed replacing by now but as things stand I'm sure it'll outlast me on aluminium ones.
HSS had its day but that day was half a century ago. Carbide is vastly superior in every respect.
Reply to
Dave Baker
I meant as hard as ally gets. Let me know your address and next time that engine spits the prop I'll send you some of the shards and you'll see what I mean.
Reply to
Boo
...snip rest of helpful words...
Thanks for the good advice, I will have a go at slowing the 'loid and using parafin next time. It sounds odd but it never occurred to me that I'd be running such a small bit too fast, or that carbide bits on ally would benefit from lubrication while cutting.
It may be a while but I'll try to remember to post my experiences when I next do one.
Cheers,
Reply to
Boo
Yeah I could be out of date - it may well be that I've used good HSS cutters and carbide that are not up to par - considering the variety of materials we cut at work and the number of people using tools who knows. Also, I do a lot of lathe work on small aluminum parts and for sure I do prefer the surface finish from a final cut using a good steel tool, while for hogging duties the carbide insert tools are the choice. Our lead machininst at work, who does absolutely beautiful machine work, uses HSS mills exclusively on aluminum work - although I may be drawing the wrong conclusion from that, since cost-wise they are also more expendable.
Reply to
mjd
Easy there buddy.. I meant it seemed "odd" that it would be so hard, thinking that these days most of these spinners are spun from 6061 bar stock, but perhaps that is not the case. Is it bar stock or cast? I know there are certainly harder alloys than others but I'm used to a Dremel chewing through most aluminum I've encountered with little effort. I wondered if it was pot metal or something like that, I'm using that term for utility grade metal where the properties can wander all about.
Reply to
mjd

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