Best way to parallel drill holes in box aluminium?

[piggybladder]

Hello all,

I'm trying to make up some homemade 1 metre clamps using cast iron clamp heads I got from Rutlands with box aluminium for the struts. The clamps will take 25mm width so I'm planning on using 50mm x 25mm box aluminium. I've already trial built 2 prototypes using 16 gauge 40mm by 20mm box aluminium, which went okay. I marked out and punched each row of holes on each side and went through the HSS drill sizes from 3mm up to 10mm on my pillar drill. I found this to be not as accurate as it might be. A couple of holes were very slightly misaligned, which translated into a not insignificant sideways skew on the clamp heads. Mea culpa, poor marking out, drilling or unlevel table. It was also tedious having to mark out and drill both sides of the piece and having to lower my platform and re-align the table between drill changes. I'm not looking forward to doing the next 8, which will be the finished articles.

So can anyone tell me the quickest and most accurate way to drill parallel holes in aluminium? I am thinking a stepped drill bit might work better. If it is long enough to completely drill 10mm holes on the top face and partly drill through the bottom face albeit from the inside wall, then I'd only have to mark out one side and not have to change the platform height. I'd only have to flip the piece over and finish the partly drilled holes on the second face. Is this workable and accurate enough or is there a better way?

Thanks in advance.

 

[CHJ]

I'm confused here, why can't you drill straight through from one side, surely your drills are long enough are you indicating that your pillar drill does not have a long enough quill travel ?

 

[flh801978]

Surely any drill will have a usable length of 30mm and any pillar drill will have a travel of at least that?
I would think that with aluminium you could just drill straight through with a 10mm bit in one go rather than stepping through with lots of drills

 

[SteveF]

parallel part is easy I think
clamp a straight edge to your table for the first set of holes
if you cant go through the whole way then flip the piece and reference from same edge

Steve

 

[Bod]

Be sure to have the drill table 90 degrees to the drill bit.
If you use any "packing" between the table and tube, make sure it is evenly thick. Not tapered.


Bod

 

[Brentingby]

I would agree that you should be able to drill these holes in one go. As Bod wrote, make sure the drill is at 90° to the table in both directions. To reduce layout errors, you could make a jig similar to the typical box joint jig. Instead of a finger, place a pin offset from the drill by the desired interval. After you drill the first hole in the alu box, drop the box on the pin and drill the next hole. Repeat along the length as needed.

 

[mayo.mick]

I would agree that you should be able to drill these holes in one go. As Bod wrote, make sure the drill is at 90° to the table in both directions. To reduce layout errors, you could make a jig similar to the typical box joint jig. Instead of a finger, place a pin offset from the drill by the desired interval. After you drill the first hole in the alu box, drop the box on the pin and drill the next hole. Repeat along the length as needed.

That would be my way of going about it too.

 

[Lons]

What the others said, don't see your problem tbh. :?

16g aluminium is like cheese to drill using a pillar drill and sharp bit and if you can't accurately drill straight through through 25mm depth you need to throw your pillar drill in the bin. Watch the swarf btw, sharp and possibly a little warm

You'll need to clean up the exit holes with a flat file or countersink bit which is easy enough.

Bob

 

[piggybladder]

I'm confused here, why can't you drill straight through from one side, surely your drills are long enough are you indicating that your pillar drill does not have a long enough quill travel ?

I think I was being picky and didn't want the breakout on the outside of the second face and my drills aren't very clean cutting, new but cheap s@@t from Screwfix. I guess I could countersink to tidy up if I have to.

 

[piggybladder]

Surely any drill will have a usable length of 30mm and any pillar drill will have a travel of at least that?
I would think that with aluminium you could just drill straight through with a 10mm bit in one go rather than stepping through with lots of drills

I can go through both sides at the same time but my drill bits aren't very good, that's why I was asking about stepped drill bits. I worry that doing a 10mm hole in one go with an HSS will come out ragged or not really round?

 

[piggybladder]

parallel part is easy I think
clamp a straight edge to your table for the first set of holes
if you cant go through the whole way then flip the piece and reference from same edge

Steve

Yes I did this but I think my table was slightly off. Stupid me for not not checking before I started. Note to self before next batch!

 

[sunnybob]

Use a 5 or 6 mm drill first. Then re drill at 10 mm.
SLOW speed. Most people drill most holes way too fast.

 

[piggybladder]

I would agree that you should be able to drill these holes in one go. As Bod wrote, make sure the drill is at 90° to the table in both directions. To reduce layout errors, you could make a jig similar to the typical box joint jig. Instead of a finger, place a pin offset from the drill by the desired interval. After you drill the first hole in the alu box, drop the box on the pin and drill the next hole. Repeat along the length as needed.

Great idea, which I shall use. I must check my table first like I should have done in the first place. My table's rubbish tbh I made it in haste out of some laminated pine offcuts some time ago and planed it flat and coplanar but it may well have cupped a bit during winter in my cold damp garage. I've been meaning to replace this with material which is more stable. Thanks

EDIT: my stupidity amazes me at times - why oh why didn't I just take off my wood working drill table before I started (hammer) ? Probably because I'm a woodworker who can't see the forest for the trees. :roll:

 

[piggybladder]

What the others said, don't see your problem tbh. :?

16g aluminium is like cheese to drill using a pillar drill and sharp bit and if you can't accurately drill straight through through 25mm depth you need to throw your pillar drill in the bin. Watch the swarf btw, sharp and possibly a little warm

You'll need to clean up the exit holes with a flat file or countersink bit which is easy enough.

Bob

I didn't want to flat file the second face and mar the finish, not that it matters really. Just being anal :roll: I can countersink no problem :mrgreen:

 

[piggybladder]

Use a 5 or 6 mm drill first. Then re drill at 10 mm.
SLOW speed. Most people drill most holes way too fast.

I actually started on a 2mm, then 4,5,6,8,10 at 500rpm. Looks Like I was going too timidly. I'm not really happy to do it in one go, my drill bits are sharp but they're cheapos, may not be quite straight (must check them all). Happy to try it in two shots tho. Thanks

 

[sunnybob]

Thats excessive in aluminium. 1/4" plate steel would benefit from that many stages. Only 2 mm per drill could lead to jamming or catching, either of which would throw the hole out of round.

 

[piggybladder]

Thats excessive in aluminium. 1/4" plate steel would benefit from that many stages. Only 2 mm per drill could lead to jamming or catching, either of which would throw the hole out of round.

Yes. I had my woodworkers (or wooden?) head on. I'm used to drillling small pilots for brad point bits. I rarely do any metalwork. That's why I've made such a meal of such a simple task. (hammer)

 

[Bod]

You are excused.

Bod
(Who done many daft things)

 

[Lons]

my drill bits are sharp but they're cheapos, may not be quite straight

Buy a few decent drills fro UK Drills or similar and you'll notice a difference.

 

[piggybladder]

my drill bits are sharp but they're cheapos, may not be quite straight

Buy a few decent drills fro UK Drills or similar and you'll notice a difference.

Just before I saw your post I bought a coupla LG2 Cobalt & TiN jobber bits from Axminster on their recommendation to see what they're like. I previously bought some Fisch brad points from them for woood and boy are they good. Nice thing about the LG2 (apart from price) is they sell em individually, so you can build up a full set over time and they also do common tap sizes. I so hope they're good.