Metal thing

[Jake]

Hi metalheads - not in my comfort zone and input appreciated.

I need to make c100 of the Things below to extend some reclaimed cast iron railing pickets. The pickets have a short (5mm or so) base the same shape as the main column of the Thing but a few mm smaller, and they are drilled about 20mm to take an M8 bolt. So the plan is that the Thing has an M8 threaded part on the top to attach and align it to the cast picket, and I'll add some structural acrylic adhesive to glue the top surface of the Thing and the base of the picket together for much longer than matters to me (I cannot spare the time to weld them and make fair especially with cast to steel welding complications). Then the bottom of the Thing needs a solid connection to a decent fixing down into the stone coping and brick wall below it. - say M16 rod. (This all needs to be reasonably robust, but every couple of meters there will be a solid 30mm or so reproduction cast pillar in the railing run with a backstay to take any real loading.

The Thing needs to more or less match the profile of the base on the reclaimed pickets, which is just a 25mm by 60mm end-radiused rectangle, so Things are the same but 30mm x 65mm to give a distracting step. Most Things will be 120mm high. Some Things on the sloping wall up the steps to a front door will be 120mm on the short edge and longer on the other to match the 30 degree or so slope.).

So, the question is how best to get Things manufactured at least cost and with least time and cost input from me. The fact the radius on the sides of Thing is different from the width of Thing means it is not simple turning. However, the quantity seems to be enough to get within shot of reasonable CNC costs. So:

• Subtractive for either the top thread and bottom protrusion cannot be anything other than insane given the size differential with the main column
• Additive seems more simple - threaded rod could be used for both protrusions.
• Welding on of protrusions would introduce another process. It might be cheaper than boring and/or threading but unless recessed (complication involving more machining) the weld bead would stop the top and bottom surfaces mating neatly with the picket base and coping stone top respectively.
• Alternatively a through-bore through the column and forming the M8 on the end of the M16 rod would work with the column just being a spacer, But, lots more metal to remove from the column, albeit a simpler machining operation. But max drill depth constraints probably mean it would need to be drilled twice, ie from each end, on CNC (on the basis of 4 or 5 times drill diameter being max depth). And two machined parts not one cannot help costs wise.

So my inclination is to go to some prototype/low quantity type CNC shop and get quotes for the Thing minus protrusions, with a 20mm deep M8 threaded hole in the top surface and a 32mm deep M16 threaded hole on the bottom surface for the rod going down into the supporting wall.

Feedback welcome on any other ways of achieving this or of saving cost in making it.

 

[paulrbarnard]

Hi metalheads - not in my comfort zone and input appreciated.

I need to make c100 of the Things below to extend some reclaimed cast iron railing pickets. The pickets have a short (5mm or so) base the same shape as the main column of the Thing but a few mm smaller, and they are drilled about 20mm to take an M8 bolt. So the plan is that the Thing has an M8 threaded part on the top to attach and align it to the cast picket, and I'll add some structural acrylic adhesive to glue the top surface of the Thing and the base of the picket together for much longer than matters to me (I cannot spare the time to weld them and make fair especially with cast to steel welding complications). Then the bottom of the Thing needs a solid connection to a decent fixing down into the stone coping and brick wall below it. - say M16 rod. (This all needs to be reasonably robust, but every couple of meters there will be a solid 30mm or so reproduction cast pillar in the railing run with a backstay to take any real loading.

The Thing needs to more or less match the profile of the base on the reclaimed pickets, which is just a 25mm by 60mm end-radiused rectangle, so Things are the same but 30mm x 65mm to give a distracting step. Most Things will be 120mm high. Some Things on the sloping wall up the steps to a front door will be 120mm on the short edge and longer on the other to match the 30 degree or so slope.).

So, the question is how best to get Things manufactured at least cost and with least time and cost input from me. The fact the radius on the sides of Thing is different from the width of Thing means it is not simple turning. However, the quantity seems to be enough to get within shot of reasonable CNC costs. So:

• Subtractive for either the top thread and bottom protrusion cannot be anything other than insane given the size differential with the main column
• Additive seems more simple - threaded rod could be used for both protrusions.
• Welding on of protrusions would introduce another process. It might be cheaper than boring and/or threading but unless recessed (complication involving more machining) the weld bead would stop the top and bottom surfaces mating neatly with the picket base and coping stone top respectively.
• Alternatively a through-bore through the column and forming the M8 on the end of the M16 rod would work with the column just being a spacer, But, lots more metal to remove from the column, albeit a simpler machining operation. But max drill depth constraints probably mean it would need to be drilled twice, ie from each end, on CNC (on the basis of 4 or 5 times drill diameter being max depth). And two machined parts not one cannot help costs wise.

So my inclination is to go to some prototype/low quantity type CNC shop and get quotes for the Thing minus protrusions, with a 20mm deep M8 threaded hole in the top surface and a 32mm deep M16 threaded hole on the bottom surface for the rod going down into the supporting wall.

Feedback welcome on any other ways of achieving this or of saving cost in making it.

View attachment 160219

Made in three parts us certainly the way I would go.
Rods with threads into the body part.
The rods could be made by hand, simply cut to length and threaded with a die. 100 pieces wouldn’t take too long but of course it would take no time at all on a capstan lathe.
The body part would be a simple job for a CBC Mill.

Edit: you mention making the thing slightly larger than the picket to get an obvious join. Why not go the whole hog and have square corners on the thing. It would simplify the part to the extent you could make them with a saw, drill press and taps.

 

[ChaiLatte]

If you can relax the dimensions a little, the rounded rectangle could be made real old school.

Use 2 1/2" x 1 1/4" rectangular bar and a 5/8" radius corner rounding end mill in a vertical mill or concave radius cutter in a horizontal (e.g. HSS CONCAVE RADIUS HORIZONTAL MILLING CUTTER | eBay - choose 1 1/4" DOC from the drop down box £54).

The reason I use imperial dimensions is that affordable second hand metric tooling is quite difficult to find.

With two cuts in a horizontal (or four in a vertical), that would give you a stick of the correct outside proportions as long as the mill has travel.

Saw to length, drill through nominal 16mm (coolant-fed drill in a lathe to blow out the chips, held with soft jaws for speed). Use a stepped stud.

If it was possible to use a single diameter (change the 8mm to 16mm), even if that means drilling out the pickets, that would save cost. In that case, maybe 16mm rebar could be used - the resin will bond well to the ribs. If you can make a single diameter work, crop the rebar at twice the required length and then saw in half. The sawn end to pass though the Thing and into the picket.

If the 8mm cannot be eliminated, then the end of the 16mm rebar could be turned down to 8mm. The rebar could be cropped to length rather than sawn as the burr on one end from the cropping will be removed when its diameter is reduced.

I am guessing that the projecting proposed threaded rod in your sketch does not thread into anything. Having any male threads engage with any female threads means you have to consider clocking between the Thing and the part below and aove it (i.e. everything goes tight before the parts are ligned correctly).

 

[--Tom--]

Find a blacksmith and get some dies/ top tool made for their pneumatic press or power hammer, they can then forge out matching parts

 

[Jake]

Thanks all.

I had not considered forging Tom, will look into that.

The rods can just be off the shelf studding Paul, none of it will show. I think a square spacer/base would look too brutal but it's worth considering costs-wise.

Chai - I had thought about rebar and milling the 8mm thread on the end of it, and just structural gluing it into a plain hole in the spacer bit. Unfortunately the picket can't really take much more of a hole and they are already drilled and tapped too. I think threaded both into the spacer and into the picket base should avoid clocking issues (plus the structural adhesive will give some flexibility as it can gap fill). But so would the turned end, plain hole and just putting the spacer on after the rod is screwed into the picket.

Thanks again for all the helpful comments. Food for thought.