[jamesd256]

Hi,

I need to make some brackets for a video camera rig from aluminium on a tight budget.

Essentially we are talking about some blocks of aluminium big enough to take 2 15mm holes spaced at 60mm. They will take 15mm diameter rods which support other camera gear and accessories. The plan is to make a cut at each end from the outer edges of the pieces and tap a hole for a thumb tightening bolt to secure the rods.

I am planning to source a cheap drill stand and twist vice. I am hoping I can get enough accuracy from this type of set up.

I am happy with tolerances of up to a millimetre, so I am not expecting CNC levels of accuracy. As long as things can be tightened rigidly, small inaccuracies can be adjusted for.

I can't afford to anodise, but anyway it's a bit overkill, so I'm going to go for spray finish. Any thoughts on the most cost effective spray which will offer at least some scratch resistance? Or maybe chemically dying the metal is better at hiding scratches?

Are any guidelines / links / tutorials which could be recommended for drilling largish holes in aluminium. Do I use a small pilot hole to centre the drill, and then go straight to the full 15mm? Or do I buy a set of progressively bigger drill bits and work up to 15mm? I'm planning to make quite a few of these, so purchasing guidelines on drill bits would be appreciated.

To make my lateral cuts, I was thinking buying a cheap jigsaw table to attach my cheap jigsaw to. This is just to make the cuts properly square and to be able to use a guide rail to get a straight cut.

Thanks in advance for your thoughts, and thanks for reading.

Cheers!

[doorknob]

I'm no expert, so don't take the following as gospel...

How thick are the aluminum blocks going to be? Do you have a diagram that you could post?

I have some (limited) experience drilling some 10mm diameter holes similar to what you have described into a 100mm x 150mm x 12mm thick 6061 aluminum plate.

How precise do you need the 15mm diameter of the holes to be? How precise do the hole locations need to be? (I think that you said tolerances of up to a mm, but I'm not sure whether that applies to the diameter or hole location or both) Conventional drill bits tend to drill holes with imprecise diameters. They also have a tendency to "wander" away from the desired hole location.

If you need a precise diameter for the holes, you may want to look into drilling a smaller sized hole than desired, after which you could use a reamer to enlarge the hole to the desired finished size. One problem that you might run into with your proposed setup, though, is "runout" or other misalignment of the drill chuck that you are using. For very precise drilling it helps to have a very rigid spindle and supporting equipment.

That said, here are some tips that may help you:

- it helps to use a center punch as close to the intended hole positions as you can get, in order to minimize wandering of the drill bit when you first start making the holes

- start by drilling pilot holes at the center-punched locations

- the best drill bit to use for a pilot hole is probably what is called a "spotting" drill that has a relatively shorter length than standard "jobber length" drill bits

- when I didn't have a spotting drill bit, I have used a "center drill" bit for making pilot holes (a center drill bit is designed for drilling a hole to hold the end of a workpiece in a tailstock-mounted lathe center - the drill has a very thick body so that it does not flex very much)

- you will want to use progressively larger drill bits to enlarge the pilot hole step by step until you reach the final desired size. To determine which drill bit sizes to use for each successive drilling step, first look for a drawing that labels the parts of a drill bit and find the part called the "web" of the drill - one recommended practice is to make sure that the length of the web matches (or is slightly smaller than) the diameter of the previously-drilled hole that you are drilling out to a greater diameter. I don't think that you can look up the web length of a particular drill bit in a table, rather it's something that you will probably have to measure on individual drill bits.

- if the aluminum block that you are drilling is somewhat thick, you may find that "peck drilling" (drilling for a short depth, then withdrawing the drill bit, then drilling another short depth, and so forth) will give you better results than simply trying to plunge all the way through the entire hole.

- as for choice of drill bit material, I would look for plain "HSS" (high speed steel) bits, and avoid bits coated with titanium nitride or cobalt bits

As far as surface finish goes, maybe you should reconsider anodizing if you want a hard surface. I'm no expert, but I do not know of any surface treatment that you can apply that can give you the hardness of an anodized finish. You may be able to do the anodizing by yourself instead of using a job shop to do it, but that's a whole different discussion.

Hope that helps...

[jamesd256]

I'm no expert, so don't take the following as gospel...

Thanks for taking the time, you obviously have more useful experience than me on this.

How thick are the aluminum blocks going to be? Do you have a diagram that you could post?

25x25mm cross section, 90mm length. Here is a quick draft:

I have some (limited) experience drilling some 10mm diameter holes similar to what you have described into a 100mm x 150mm x 12mm thick 6061 aluminum plate.

How precise do you need the 15mm diameter of the holes to be? How precise do the hole locations need to be? (I think that you said tolerances of up to a mm, but I'm not sure whether that applies to the diameter or hole location or both) Conventional drill bits tend to drill holes with imprecise diameters. They also have a tendency to "wander" away from the desired hole location.

The tolerance I mentioned applies to the hole centers. Less so for the hole diameters. As you can see from the diagram, the slots which facilitate clamping the rod will allow for a slight variance of hole diameter, but hopefully not a millimetre.

If you need a precise diameter for the holes, you may want to look into drilling a smaller sized hole than desired, after which you could use a reamer to enlarge the hole to the desired finished size. One problem that you might run into with your proposed setup, though, is "runout" or other misalignment of the drill chuck that you are using. For very precise drilling it helps to have a very rigid spindle and supporting equipment.

This is where I'm wondering if a drill stand will have the rigidity to at least get that 1mm tolerance. I don't think a reamer will be required though.

That said, here are some tips that may help you:

- it helps to use a center punch as close to the intended hole positions as you can get, in order to minimize wandering of the drill bit when you first start making the holes

- start by drilling pilot holes at the center-punched locations

- the best drill bit to use for a pilot hole is probably what is called a "spotting" drill that has a relatively shorter length than standard "jobber length" drill bits

- when I didn't have a spotting drill bit, I have used a "center drill" bit for making pilot holes (a center drill bit is designed for drilling a hole to hold the end of a workpiece in a tailstock-mounted lathe center - the drill has a very thick body so that it does not flex very much)

- you will want to use progressively larger drill bits to enlarge the pilot hole step by step until you reach the final desired size. To determine which drill bit sizes to use for each successive drilling step, first look for a drawing that labels the parts of a drill bit and find the part called the "web" of the drill - one recommended practice is to make sure that the length of the web matches (or is slightly smaller than) the diameter of the previously-drilled hole that you are drilling out to a greater diameter. I don't think that you can look up the web length of a particular drill bit in a table, rather it's something that you will probably have to measure on individual drill bits.

- if the aluminum block that you are drilling is somewhat thick, you may find that "peck drilling" (drilling for a short depth, then withdrawing the drill bit, then drilling another short depth, and so forth) will give you better results than simply trying to plunge all the way through the entire hole.

- as for choice of drill bit material, I would look for plain "HSS" (high speed steel) bits, and avoid bits coated with titanium nitride or cobalt bits

As far as surface finish goes, maybe you should reconsider anodizing if you want a hard surface. I'm no expert, but I do not know of any surface treatment that you can apply that can give you the hardness of an anodized finish. You may be able to do the anodizing by yourself instead of using a job shop to do it, but that's a whole different discussion.

Hope that helps...

I don't actually need any guaranteed scratch resistance. I think anodizing is not for this round. Maybe if I go into production I'm now thinking that my bicycle is about as ding proof as I would need for this, and it's only sprayed.

Tons of useful info. Many thanks.