Machining – Riggs Machine and Fabricating, Inc.

Tensile testing (aka tension testing)

11/07/2022RMF

We recently got to work with a local steel company to help create samples for the tensile testing of their rolled products. I wanted to look at what the samples were going to be used for once they left the shop.

Tensile Testing measures tensile strength, breaking strength, maximum elongation and reduction in area. There are several variations of these tests, including how the loads are applied across the materials. Below is an example testing unit. The prepared bars are held in the arms and pulled apart.

Universal Tensile Tester — CC BY-SA 4.0 Ganitz

These tests are performed after rolling to ensure uniformity and consistency in the product line.

Other reasons for performing these tests are:

– to find out how well a product will perform

– to see if it meets the client’s standards

– to test a new design

Pallet of Bars to be Cut — A pallet of bars to be cut for testing.

To perform the tests properly, the samples must be prepared for the testing device (tensometer). The ends are wider to be easily held by the device, while the center is cut thinner to allow the deformation and fracture to occur at this point. To help repeatability of testing, the samples must be as similar as possible.

Cutting a Bar for Testing Cutting a Test Bar

The tester will apply an even and consistent force across the sample until it fractures. The elongation that occurs, as well as the amount of force that was necessary to create it, is used in the final calculations.

bar cut for testing

These calculations will help with the following tests:

Yield Strength – The point at which deformation in the part occurs.

Ductility – Percentage of elongation.

Strain Hardening – How much the part hardens with plastic deformation (plastic deformation – a yield point, once passed, is some fraction of the deformation that will be permanent and non-reversible)

Modulus of Elasticity – The point where the material will no longer return to its original length and permanent deformation occurs.

Ultimate Tensile Strength – The maximum stress that the material can withstand while being stretched or pulled before breaking.

thick bar for testing

Thick Bar for Testing - Side Shot

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Mill Caps – Handling the Heat and Pressure of the Modern Forge

02/25/2022RMF

As molten billets of steel race through the plant, they are formed into their final shape through a series of ever tightening rolls and presses.

Rolling plates - a hot slab partially finished, Steel Works, Homestead, Pa. - Library of Congress — Rolling plates – a hot slab partially finished, Steel Works, Homestead, Pa. – Library of Congress, Prints & Photographs Division (rep. # LC-USZ62-69674 )

"Rolling Mill with Coil Box" by mouser-nerdbot is licensed under CC BY-NC-ND 2.0 — “Rolling Mill with Coil Box” by mouser-nerdbot is licensed under CC BY-NC-ND 2.0

The stands that hold these forming rolls are under extreme stresses as they progressively squeeze the metals into shape; be it flat sheets, bars, round stock or rails.

Mill Cap - Finished - Front Shot — Mill Cap – Finished – Front Shot

Mill Cap - Finished - Rear Shot — Mill Cap – Finished – Rear Shot

At the top of these stands are the mill caps – holding the components together, absorbing constant shock and vibrations as they maintain pressure on the searing metal as it is is worked beneath it.

The original cap was a cast part. This machined version will be stronger and less susceptible to cracks and weak spots due to the possibility of bad casting. It is also made of a finer grade of metal than the old, worn piece.

On Mill - Ready to Start — On Mill – Ready to Start

Using the drawings, we will CNC a new component from a 22 inch burn-out weighing over 19,000 lbs. (Not many suppliers can provide a single piece of metal that large.) Hooks were welded on the sides so the block could be moved throughout the shop.

Burn Out - Top Shot — Burn Out – Top Shot

Burn Out - Side Shot — Burn Out – Side Shot

These higher quality mill caps will provide a better support system and a more dependable and stable stand. In the long run, they will help provide our client produce a better product and maintain a longer running mill.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Model 1841 Field Gun Cannon

06/08/2020RMF

1841 Field Gun - Test Fire

Built by Steen Cannons & Ordnance Works of Ashland, KY, (http://steencannons.com/) this is the test firing of a model 1841 field gun cannon. Riggs Machine milled and turned the cannon from a raw casting. This particular model is made out of cast iron. Steen did a beautiful job with the final assembly.

Here is the unit out of the horizontal mill after getting the trunnions machined. It is ready for the CNC lathe.

1841 Field Gun - partially machined

It’s been very exciting working with Steen. They do excellent work and we hope to continue our relationship with them. We never know what type of jobs will hit the shop, but these cannons have been some of our favorites!

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Precision Shafts to Get You Running Again!

05/30/201912/17/2021RMF

They say “wheels make the world go round”, but without shafts, nothing would ever move.

A shaft connects a mechanical power source to gears, wheels, turbines, rotors and much more. Shafts can be as simple a basic round bar or as complex as containing exacting bearing fits, keyways, sleeves, grease fittings, snap ring grooves and splines.

Often, the shafts we see have been in service for many years, sometimes running non-stop. Unfortunately when these older shafts break (as shown here), there aren’t drawings available and not a lot of time to get the new shaft machined and the unit running again.

This shaft broke and we got it in 2 sections, still in the housing. After disassembly, we made hand sketches. While the housing was cleaned and checked, we created 3D drawings and then machined a new shaft.

Here is the new shaft ready for inspection. After passing final inspection, the housing was reassembled and the unit was ready for production use.

Finished Shaft – Ready for Unit Assembly

Hopefully a broken shaft won’t take one of your machines, or worse, your facility down. But if it does, Riggs Machine has the experience to get you running again.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Shims – more than just a strip of metal

04/12/201904/17/2019RMF

SHIM – A washer or thin strip of metal used to align parts, make them fit or reduce wear.

These, sometimes extremely slender, strips of metal are very crucial in industrial operations. From getting a pump to line up perfectly or to make a surface level, a shim must be exact.

Shims come in a variety of materials, but most commonly from metals such as carbon steel, brass and stainless steel. And they also vary greatly in their thickness from up to 1/4” thick and down to .001 thick (imagine an industrial foil).

.003 thick shims – for precise applications

And the tolerances they must hold are key to their functionality. They cannot deviate across the surface, their dimensions must be held.

Often industrial shims come in sets of varying thicknesses. They can be added individually to get the final adjustments perfect.

They also come in many different shapes, often having to be custom designed to fit around existing bolt holes and other features. We like to add the small hand holds (show below) to make installation and adjustment easier.

At Riggs Machine and Fabricating we understand Industrial Shims and their importance in setup, maintenance and repairs. We understand the tolerances and design elements that separate a shim from a strip of metal. Yes, there is a difference. If the shop you are working with now doesn’t agree with that, then you are working with the wrong place. Time to call Riggs Machine.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Rail Welding Shears

02/01/201904/17/2019RMF

Used when creating a Butt Weld between two sections of train rail, this shear takes a lot of abuse. At the same time, it must follow very tight tolerances to maintain the profile of the rail (especially when a high speed train is running across it).

A butt weld is created in the field using a mobile electric flash-butt welder. The two sections are joined and electricity is applied to the rail ends. The flash-butt welder squeezes the sections together at very high pressure, permanently joining them, but this also creates a seam at the joint with a segment of slag.

Rail w/Hot Slag after Butt Weld
(notice the manual shear in the background)
“Thermite Rail Welding” by PetrS. 2013 licensed under CC

The RAIL WELDING SHEAR is clamped onto the rail and slid along the rail, by the mobile welder, cutting off the hot slag leaving only a small remainder that will be later ground smooth.

These shears are precision cut out of Nitronic 60 – a high strength metal known for it’s wear resistance – with a wire EDM machine. The EDM unit cuts parts slower, but with more precision than a waterjet or laser cutter.

The final grooves are added via a CNC and the units are then inspected. A hard-surface weld is added and machined to create a precision cutting edge. The parts are assembled to complete the rail welding shear.

These are ready for the rail and making the travels of passengers and goods go smoother and safer.

This video shows a portable flash-butt welder in use. Notice the Rail Shear clamped on the rail before the unit is lowered on the section.

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Tapered Tube Plugs – Not as Simple as it Seems

11/20/201804/17/2019RMF

Used during repairs and outages, this simple looking device becomes a necessity. The Tube Plug is hammered or welded into the open section of pipes in boilers and heat exchangers. They plug the end of the pipe to either stop the flow of steam or coolant. If the plug’s seal is not tight the coolant can seep into the material and contaminate it.

What makes this seemingly basic item so important are a few factors. First, its fit must be right. Sure they are tapered, but they must fit without damaging the existing pipe or sliding too far in. Also, the material specifications for Tube Plugs can vary greatly. While some plugs can be made out a carbon steel like 1018, other plugs must match the existing pipe section (i.e. A350 with more carbon content) or even stainless steel, nickle or other metals. If the wrong type of metal is used, it could lead to corrosion, rust, leaks or a possible reaction with existing materials in the system.

Even the machining isn’t always as simple as it may seem. Bar stock in not always available in a size close to what the job requires or the material type needed is only available as plate. In that case, a plug larger than the finished size would be cut from the plate and then turned turn by hand on a lathe. Time consuming, yes, but necessary for a professional fit.

At Riggs Machine & Fabricating, we not only have the experience, but we ask the questions to make sure the job is done right, the first time. Don’t trust those supposed simple jobs to just any shop. Call Riggs first for the dependability and quality your facility demands.

*(Morton, John, 2 Electrolyte Heat Exchanger Tube Bundles in the 8×6 Foot Wind Tunnel, 1975) – http://catalog.archives.gov

Riggs Machine & Fabricating – Serving industry in KY, OH and WV for over 45 years!

Explosion Proof Hatch – Pyrite Ducts

07/27/2018RMF

Here are some newly machined explosion-proof hatches for pyrite ducts.

In preparing coal for energy production, pyrite, a sulfide that contributes to air pollution and acid rain, is removed before burning. The separated pyrite is forced through ducts to waiting hoppers using high pressure fans. These ducts have negative pressure in them. If a chunk of pyrite gets stuck in a hopper then unit has to be shut down and the duct removed from the unit to be cleaned.

Photo by James St. John / CC by
Sphalerite-Pyrite

With the addition of these hatches, if a chunk of pyrite gets stuck in the hopper, it is only a temporary shut down while the hatch is opened and the material is washed out. Once the hatch is sealed, the unit is quickly brought back on-line.

These hatches have also been used as inspection doors on gearboxes, giving quick access to the internals for routine maintenance or adjustments. The locking tab on the hatches also helps keep the unit secure.

A Phonographic Finish!

06/29/201804/17/2019RMF

No, not what is used when a race is too close to call (that’s a photo finish). But a machined finish added to the raised face on a flange to give an extra level of security to prevent leaks and maintain effective seals.

The Phonographic Finish is actually a serrated finish, either concentric or spiral (much like the grooves on a record), that will grip the gasket between pipe sections firmly.

These finishes are typically added on a lathe to specifications set either by the company ordering the flange, the manufacturer or ASME B16.5 guidelines. Below is a render of the completed flange with bolt holes. I would have included a photo of the actual completed unit, but as soon as it was finished, it was rushed to the job site! But that’s why we’re here. Everyone knows who to call when a custom part is needed in a hurry.