Enlarging Holes in Thin Aluminium

The very thought terrifies me with the current gas-strut setup I've got on the SX2P. I started another thread on the subject, but basically, the strut I fitted is slightly over-compensating for head weight, which is being pushed up by default. This seems to be making cutter grabbing almost inevitable when feeding down, since there's nothing but a bit of friction and minimal residual gas pressure preventing the head from moving down. I have effectively no fine control of the head in a -z direction.

I just ordered a set of cheese-based step drills from Amazon. I really wanted a decent one that will last, but these should do the job at least once. I just want to get the engine finished.

Cheers.

When I wrote I couldn't post a link, I could have, but it would have been moderated out under the CoC rules. I'll PM you.

John

Edited By John Hinkley on 13/10/2020 13:49:06

I've lost track of what's going on ... can't post links under CoC rules... ' what's CoC' ?... any thing to do with My Time Media ? what links are /not allowed ... eBay et al ? ... Help!

George.

Thanks John for the PM - those are exactly the ones I just ordered from Amazon. As I mentioned, I really wanted some better quality ones (some of the customer reviews are pretty dire regarding wear), but they'll do for now.

I was wondering where the Arc ones you mentioned were on their website, I couldn't see one with 1 mm increments.

Cheers.

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Dave

Edited By SillyOldDuffer on 13/10/2020 15:00:13

"There are tapered reamers specifically for enlarging holes in electrical panels. You could try someone like RS Components. That sounds like an option - are they likely to grab the metal, or do you just turn them slowly by hand?"

I recently purchased one from RS components at a reasonable price. (they have a couple of diferent sizes, depending on hole size) And yes, they are designed to be turned my hand.

Paul

Get yourself an rc car tapered body reamer, used for opening up holes in thin lexan bodies. These also work great on thin sheet metals like aluminum or brass, you can cut any size from around 2mm - 14mm. No steps on these reamers, just a complete taper the length of the reamer. Available from RC Model shops or plenty on Ebay, just search rc car body reamer, these reamers are pretty sharp & give a very nicely finished round hole.

Martin, Is the rc reamer that you refer to the same as this ? They are not only used for rc models but used in general industry.

Avilable from Rc Components, ebay and local hardware stores.

Paul.

Edited By Paul Lousick on 14/10/2020 04:16:44

Tinman's reamer is it's name.

Hi, every hole you'll every want from 4-30mm in 1mm steps 3 PC HSS Step drill set they also have this 4-12mm step drill

Regards Nick.

Edited By Nicholas Farr on 14/10/2020 07:56:51

I have a set of step drills that came from Aldi, I bought them thinking that they would be "disposable" but to my surprise they have lasted well, considering that I use them in the course of my employment. I wouldn't hesitate to recommend them to anyone.

I also used to use a tinmans reamer when I worked with a mate repairing Land-Rovers. It was a great tool for making bolt holes line up in bodywork. To make life easier on the hands we used to use it mounted in an old style joiners brace.

Martin

Silly Old Duffer...thanks for the clarification.

George.

Paul i also have one of the reamers that you show. The rc car body reamers are slightly different but with the same principle, the car reamers only have a single cutting flute. The rest of the reamer is a full tapered round shape, with only 1 cutting flute these reamers cut very circular holes indeed & pretty sharp for cutting plastics, thin aluminium or brass sheet.

The rc car body reamers will cut from 0-14mm.

Popped into Aldi earlier in Buxton.
Multipack, including step drill, conecut and countersink on offer at the moment.

**LINK**

Bill

My tool of choice is a step-drill, and these are available in 0.5mm steps. I think mine came from a Well-Known Builders' Tools stockist! (They are used by, for example, electricians and plumbers.)

You can also buy step-less equivalents - cone-drills - when you need finer diameter control albeit with a slightly-tapered hole.

A tip with step-drills. They are best used as with any drill, in a bench-drill or milling-machine with the work properly held down, and if you set the down-stop just so the lead on the next step up will take the sharp edge off the hole.

Step drills arrived today from Amazon:



I used some parallels to extend the jaws upwards, and put masking tape on the surfaces to give some extra grip, then re-aligned the pilot holes:



The drain cock holes were less than 1mm from the edge, but the drills worked really well:



Exhaust hole wasn’t a problem, although the metal did flex a bit:



I ended up spraying it satin black, then cleaned up the edges with wet & dry:

I feel lke I dodged a couple of bullets with this, becasue of a) cheap tools, and b) the holes ending up so close to the edge. I can't even remember if I accounted for the clearance hole around the drain cocks when I drilled the holes in the casting...Next time I'd move them a millimetre or so further away.

Anyway thanks for all teh advice everyone, job done.