adjustable square for SHS / box sections

I've seen combination squares with a wide flange on the head that will do what you want . Here's a link to one on Amazon , kinda pricey but you might be able to find one cheaper .

Not following you exactly,.. some links that may help or give you some more ideas.

Fireball Tools has some really innovative squares for welding and metal working:

Hi all

Working with Rectangular Hollow Sections Square Hollow Sections box sections ...

The rounded corners make using an adjustable square / sliding square problematic.

Given number of machine parts I have to make quite accurately based on SHS's, thinking of a tool specially optimised for marking distances from the surfaces. ie. whatever presents as "top", slide along marking down the "sides". Typically the middle of the "sides".

Accuracy - well using a chalk / soapstone is plenty good enough. Have to bring magnetic-base drill to the job most of the time, and with using a shell-cutter / trepanning cutter with a central "pin" to locate on the centre-pop - accuracy there is less than chalking gives. So - would hold thing in place and chalk-mark.

I could trim offcuts of angle-iron to make single-dimension tools - eg. marks 25mm from "top" surface. Advantage with this or "settable" tool is spin around 180deg and mark the other "side" and the two heights/levels should match-up.

Hope described this well enough.

------------------------ Compact versions of a carpenter's bulky framing square are called "L Squares".

I use a double or combination (90+45) square with the scale protruding the required distance and scribe across the end. It can be held vertical to bridge the rounded corner. This type and size is pocketable.

A "prick" punch can locate the crossing of fine scribed lines to 0.1mm or so with care and a magnifier, or by feel along the line. Then "center" punch the dimple to better locate the drill bit. These make a good starting hole for larger bits.

A light weight portable drilling guide like this lets a drill bit (or pointed tap) center itself on a punch mark. I don't own a mag base drill and clamp the guide to the beam to drill the full sized hole square, well enough for 3/8" bolts in 0.375" holes through both flanges of 4" channel. The bolt shanks measured 0.372". That was the gantry trolley beam center splice assembly.

The cast or molded enclosures I mount snap-in meters in are too flexible in the milling vise to mill accurately with a DRO, scribing locates features on the uncompressed surfaces.

When working on large stock outdoors I keep my tools safe and handy on a small wheeled cart or folding camp table. This is my most heat-resistant and convenient to carry with one spare finger.

Exactly what I was thinking of. Might even be able to swap out to a longer scale if needed. I had (maybe still have somewhere) a combination square with an 18 inch scale.

Woodworking scribers and marking gauges with wider bases might work.

Thanks everyone for all tips.

One is, given saw cutting long lengths of "box" is accurate transversely but less so "vertically" due to spring in section and distance outrigger is from saw, position "flash" at "side" as sawn so have "square" end as do "measure along" direction AND drill can go through both sides of "box" on drill-press, not risking hitting "flash" on opposite side.

I will look if adjustable square with a wide "foot" is available. Would need a "foot" about 2inches / 50mm wide for when doing big Rectangular Hollow Sections with big corner radii.

Bigger overall point - thanks a lot everyone.

Regards, Rich S

Thanks everyone for all tips.

One is, given saw cutting long lengths of "box" is accurate transversely but less so "vertically" due to spring in section and distance outrigger is from saw, position "flash" at "side" as sawn so have "square" end as do "measure along" direction AND drill can go through both sides of "box" on drill-press, not risking hitting "flash" on opposite side.

I will look if adjustable square with a wide "foot" is available. Would need a "foot" about 2inches / 50mm wide for when doing big Rectangular Hollow Sections with big corner radii.

Bigger overall point - thanks a lot everyone.

Regards, Rich S

------------ You could make a wider foot from flat stock clamped to the square with screws and large washers cut D shaped.

My procedure for cutting short sections from long lengths is to first balance them on the bandsaw table, then place a Toyota Land Cruiser telescoping screw jack under the end. When the stock is moved to cut the support will nearly balance it and the vertical force at the saw vise will be minimal. If I had two finely adjustable supports the second would go under the end to be cut off and I would sight down the stock to lift out any sag.

I work on uneven surfaces outdoors and can't permanently set up an outrigger, plus the roller stands and conveyer table I have are for a wood saw and don't adjust low enough. The bandsaw had larger wheels added to roll to the job, which may be on a dirt path in the forest. It's a 4"x6" which is light enough to move if not the best to use.

The one time I had to cut full mill lengths of 4" square tube and a W10x33 beam (W250x49) I used the hydraulic platform stacker to lift and level it on the saw table.

------------------------------

The base on my 4x6 horizontal bandsaw can twist from floor/pavement unevenness and make the blade cut unsquare vertically. I fix it by checking blade rise and fall with a square clamped upright while moving the base feet around until the blade descends adequately parallel to the square for the job, whether cutting for machine parts or firewood.

The general solution for permanently installed machine tools is to level the machines' working surfaces, the level and plumb bob being inexpensive instruments that very accurately indicate direction.

An expensive one:

My South Bend lathe has an alternate method that works on a ship. The tailstock end of the bed is on a lengthwise pivot and restrained by setscrews. Loosening them lets the ways untwist, then the screws can be gently run in to contact.

I could make one, but shipping across the pond would probably be a deal breaker.

I could make one, but shipping across the pond would probably be a deal breaker.

Yep. I read your other reply. No big deal for even a hobby machinist.

What he is doing is pretty coarse I think. Could probably do it with an old wood workers marking gage and a nail for a scribe. Hundreds of years of fine wood working was done that way with a story board to repeat measurements from piece to piece for "production" work.

Thanks for supportive wishes. Appreciated anyway. See my post responding to all.

Hello everyone Your various ideas caused a thought to "gel". I will try this. Get a smooth piece of plate a bit wider than the box-section. Place your "ordinary" adjustable square on it, at the edge. Make the blade/rule of the adjustable square protrude beneath the plate lower surface by the amount you want to mark-off - eg. 25mm. Bring "free" plate's edge to align with "side" surface of box you want to mark, with the already-set adjustable square on it, and with hand pressure keeping eveything touching where it should, slide along with chalk under tip of adjustable-square blade. Spin plate with adjustable square through 180deg and do same marking down other side. Those "heights" on the two "sides" will agree - probably the most important thing. Mark distances from the end of the box at which holes are and centre-pop at the intersections. Drill. Done.

Hope this makes sense...

Will see whether this works - and report back, volente dio.

Hello everyone Your various ideas caused a thought to "gel". I will try this. Get a smooth piece of plate a bit wider than the box-section. Place your "ordinary" adjustable square on it, at the edge. Make the blade/rule of the adjustable square protrude beneath the plate lower surface by the amount you want to mark-off - eg. 25mm. Bring "free" plate's edge to align with "side" surface of box you want to mark, with the already-set adjustable square on it, and with hand pressure keeping eveything touching where it should, slide along with chalk under tip of adjustable-square blade. Spin plate with adjustable square through 180deg and do same marking down other side. Those "heights" on the two "sides" will agree - probably the most important thing. Mark distances from the end of the box at which holes are and centre-pop at the intersections. Drill. Done.

Hope this makes sense...

Will see whether this works - and report back, volente dio.

-------------------------------- It should, you've given yourself a reference surface.

Depending on desired accuracy and repeatability (Chalk??) you could fasten a

A possibly less fumbly approach would be to use hermaphrodite calipers to scribe from the plate's inner surface, which permits direct length transfer and saves an element of alignment.

If you mostly need the center this should help.

I center holes in mounting brackets etc by balancing a 6" ruler across stock in the milling vise and equalizing the edge readings from 3", like the center finding ruler but counting backwards on the 6" end. This gets me centered within a millimeter or better on rough edged or compressible stock. As with the previous trick the ruler doesn't have to be exactly squared.

A primitive but effective way is to roughly center a pencil point near the center with your little finger sliding on the edge of the stock, then repeat from the other side. You can refine the guess between the two lines and repeat. Chalk is good for circling and not losing a location with finer marks, like a fine point Sharpie.

I'll add here that placing a ruler marked to 0.1" on the stock lets me locate from the 0,0 reference corner with the mill's table dials without counting turns. jsw

What he is doing is pretty coarse I think. Could probably do it with an old wood workers marking gage and a nail for a scribe. Hundreds of years of fine wood working was done that way with a story board to repeat measurements from piece to piece for "production" work. Bob La Londe

------------------------------------ I learned the old methods from a semi-retired Swedish cabinet maker in 7th grade. One friend's father was an architect, another's building a wooden sailboat, and mine was remodeling old houses, so we all paid close attention and competed with each other. The standards of accuracy were bright light leaking through gaps between the work and a straightedge or the blade of a square, and a press fit that holds together, both difficult with worn metalworking machines. In 8th grade we took Drafting and repeated the competition for top grades. When I learned machine design and construction I needed (and received) no instruction while working in the Drafting department. The lessons also helped when I went into CAD circuit board layout and the design of RF-tight enclosures.

Recently I figured out how and practiced cutting large wood beams with a pruning bow saw as smoothly and squarely as with a machine. That went faster than the attempt to align my bandsaw and conveyer table on rough sloping ground. The weight of the beams threw off the alignment.

Hi all - update Monday 10 February 2025 20:29

I found some Ali extruded angle, hence sharp inside corner. Trimmed one side to give 25mm down side of from surface the angle si resting on. Took a bit of fiddling and measuring, but once made, blessing. Then my two adjustable squares went to mark in the length direction where the holes go. Every indication is it's very consistent and is accurate.

The important things are

• that the holes on opposite sides line-up
• that the holes at at specified centres. All others are significantly less critical.

With the angle "measure" having chalked one side I spun the angle around so it sat on the same "top face" but extended down the other side.

The method mentioned seems to meet the requirements.

Hi all - update Monday 10 February 2025 20:29

I found some Ali extruded angle, hence sharp inside corner. Trimmed one side to give 25mm down side of from surface the angle si resting on. Took a bit of fiddling and measuring, but once made, blessing. Then my two adjustable squares went to mark in the length direction where the holes go. Every indication is it's very consistent and is accurate.

The important things are

• that the holes on opposite sides line-up
• that the holes at at specified centres. All others are significantly less critical.

With the angle "measure" having chalked one side I spun the angle around so it sat on the same "top face" but extended down the other side.

The method mentioned seems to meet the requirements.

-------------------------------- The test is to use it to draw all the way around and see if the start and end meet.

The "angle-aluminum" with its "drop-down" from the "top" surface marks down from that top surface. This is a longitudinal mark. It will always "match-up" (?).

I am painfully aware that these best-meant descriptions, where you'd want a sketch, can be impenetrable.

Best wishes,

The "angle-aluminum" with its "drop-down" from the "top" surface marks down from that top surface. This is a longitudinal mark. It will always "match-up" (?).

I am painfully aware that these best-meant descriptions, where you'd want a sketch, can be impenetrable.

Best wishes,

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I can visualize a solution that fits the description. I post here for practice describing with only words.