# cooling slots in aluminium problems



## pmdevlin (Oct 16, 2016)

Hi all,

I have been asked to cut cooling slots in a small cylinder head from a rc plane engine. The slots will create the fins to aid cooling.

I am using 1.5mm cutters on my siege xl mill, and they are 4mm in depth.

I'm a bit of a novice, so we agreed for me to practise on scrap alloy, see how it looks, then if all agreed attack the cylinder head. The problems are these:

I have snapped 3 cutters, now on the last one, I am using a medium speed with no lube/cooling to prevent swarf from sticking to the cutter. I am told the aluminium is T2, this info means nothing to me !

The cutter where just cheap things, should I but a specific type (not expensive as I am on a tight budget) what speed should I be using, slow or fast (sorry no means on measuring rpm) and should I be using a cooling fluid?

With regard to the job, I don't have any digital measuring scales so its pretty much by eye, is there any way I can manually determine the distance between cuts, I cant seem to get these the same, even when following a careful measurement marked on the metal

Many thanks

Paul


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## Brian Rupnow (Oct 16, 2016)

Use spray on WD40 and keep it wet while cutting the slots. Run the lathe at about 120 rpm. Make sure the tip of the tool is exactly at center height.--Sorry Paul--I thought you were doing this on a lathe. If you are doing it in a mill, then if the cylinder is round you are going to need  rotary table. If it is square or rectangular, then yes, the slitting saw is best. In fact, if it is being done in a mill at all, a slitting saw if the correct tool to use.


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## purpleknif (Oct 16, 2016)

Lots of back clearance on the tool !


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## fcheslop (Oct 16, 2016)

In a mill, I would be tempted to use a slitting saw if available if not a high speed low feed rate and a wee bit of WD40 
To space the fins out equally use the machines graduations find youre starting position by using a bit of bar in the chuck Advance towards the part until a cigarette paper just nips then move half the diameter of the bar This is youre 0 position . Keep the cuts small as its a small machine
cheers


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## makila (Oct 16, 2016)

I agree with the slitting saw, it is a bit more forgiving than small end mills and providing you are cutting straight lines, it can be quite neat.

If you have only got a small mill cutting tool, then lots of shallow passes with the tool turning at high speed, and use WD 40

Steve


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## Jasonb (Oct 16, 2016)

If using a milling cutter then run the mill flat out, it will still be too slow but better than nothing, kerosene or WD40, 2 flute cutter.

As said above it will be better to mount the head sideways and use a slitting saw.


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## Toolguy (Oct 16, 2016)

The one thing you can do above all else is to get some TapMagic for Aluminum. Just a little of this in the cutting zone makes everything else not as critical. You will get good surface finish and the aluminum won't stick to the cutting tool. Works great for all non-ferrous metals too, such as brass and copper.


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## pmdevlin (Oct 16, 2016)

many thanks!

I have slitting saws, been in the packet for two years, like a scary monster at the back of the tool drawer

Ill have a practise, lots off practice first, on review, looks like I was way too slow with the speed, and wasn't using wd40 thinking the swarf would clog up the cutter. I think I preferred the cutter as I was cutting from above, and could see the work better, the slitting saw is from the side. 

Is it a similar high speed with the slitting saws, and wd40 again?

Thanks



> you are going to need rotary table



Brian, strangely, questions about this on another post!
paul


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## Toolguy (Oct 16, 2016)

Slitting saws need to run pretty slow, depending on the diameter. Maybe 150 - 300 rpm. Kerosene, WD-40, etc. is not nearly as good as TapMagic, but a lot of people won't spend the money (not that much) if they already have something else sitting there.


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## pmdevlin (Oct 16, 2016)

is tap magic an American thing, doesn't seem to appear on any GB websites after a google search?

thanks


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## Charles Lamont (Oct 16, 2016)

pmdevlin said:


> Hi all,
> 
> I have been asked to cut cooling slots in a small cylinder head from a rc plane engine. The slots will create the fins to aid cooling.
> 
> ...



How deep are the slots, and how deep a cut are you taking?


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## bazmak (Oct 16, 2016)

If you are using small dia end mills then depth of cut should be less than cutter dia,and speed as fast as you can.Light feed and lots of wd 40 for alum
If you are using a slitting saw then full depth of cut in one pass with speed
as slow as you can.Assuming 1.5w x 4mm dp slots


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## Alchymist (Oct 16, 2016)

Haven't tried it on an end mill yet, but when using a hole saw on aluminum plate in the drill press - Windex! Yep, the glass cleaner. Just keep spritzing it on as the cut progresses. Rolls the swarf out of the cut, and cools the saw at the same time. Works good when using the sabre (jig?)saw on aluminum also.


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## llionellis (Oct 17, 2016)

Tap Magic is available through Amazon But £££££££££
https://www.amazon.co.uk/dp/B01M1F533L/?tag=skimlinks_replacement-20


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## Toolguy (Oct 17, 2016)

In the USA, this is $16.32 US. + shipping for a 16 0z. bottle.
https://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias=diy&field-keywords=Tap+Magic+#20016A
It's 55.27 pounds, look at the link above. Still too much though.


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## pmdevlin (Oct 17, 2016)

> How deep are the slots, and how deep a cut are you taking?



Ideally 1.25 to 1.5mm slots, 4 to 5mm deep.

Tonight tried the slitting saws I have for the first time on some scrap, I realised now why they where cheap! Anyway, it was much easier than I had thought, as stated neat and straight. I am using the fine feed for the distance between the slots, after taking out the slack with head locked I can now get the fins pretty much spot on, all the same thickness, so thanks for the info everyone.

Seems to cut better with a medium speed and wd40, going slower resulted in a  jam twice. The cut was thicker than the blade, I seem to have a bit of run out caused by cheap saws, or at least the mandrel |(if that's the correct name)

Tapmagic is out at nearly £400!!!! I could buy a second mill for that



> If you are using a slitting saw then full depth of cut in one pass with speed



so if the depth is 5mm, I have a choice of cutters, one has fine teeth, and rest are much coarser but smaller diameter, does the speed vary according to diameter? The saws say 20000rpm but the machine surely is much less than this?


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## Cogsy (Oct 18, 2016)

pmdevlin said:


> Tapmagic is out at nearly £400!!!! I could buy a second mill for that


 
It comes up on eBay UK, just search Tap Magic Fluid. Prices were around 20 pounds but I'm in Australia so the shipping might be off.


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