Machine Shop Practice: Making Custom Metal Hardware For Basses

[rwkeating]

Just to follow up, I did pick up the small Harbor Freight 2 in. Mini Benchtop Cut-Off Saw in order to cut 3/8" square aluminum rods. I mounted it to a piece of wood (for more stability) and made an output "table" so that the part being cut wouldn't sag near the end of the cut. I need to make a feeder table too.

I am very please with how it works. If you go slow and let the machine do the work, it makes a very clean cut. Pressing down too hard will easily bog the motor down.

I used the blade that came with it plus I bought a pack 3 to have extras. When I did the cut I used a bit of WD40. I use WD40 for drilling and taping aluminum so I decided to use it here too.

This is going to save me a bunch of time as I used to do this with a hacksaw followed by way to much time filing.

 

[Bruce Johnson]

Just to follow up, I did pick up the small Harbor Freight 2 in. Mini Benchtop Cut-Off Saw in order to cut 3/8" square aluminum rods. I mounted it to a piece of wood (for more stability) and made an output "table" so that the part being cut wouldn't sag near the end of the cut. I need to make a feeder table too.

View attachment 5067010

I am very please with how it works. If you go slow and let the machine do the work, it makes a very clean cut. Pressing down too hard will easily bog the motor down.

I used the blade that came with it plus I bought a pack 3 to have extras. When I did the cut I used a bit of WD40. I use WD40 for drilling and taping aluminum so I decided to use it here too.

This is going to save me a bunch of time as I used to do this with a hacksaw followed by way to much time filing.

That's interesting. So, the little machine does have enough power to saw through 3/8 square 6061. That's better than I expected. That could be a useful machine for a small shop.

Just minutes ago, I was sawing off some 3/8 square 6061 into slugs myself, using the Barker. When I'm sawing aluminum, I always add a couple of drops of cutting oil. I keep a small squeeze bottle with a needle tip, filled with cutting oil, right next to machine. The technique is: I start the saw blade cutting into the bar dry, making the groove maybe 1/16" deep. Lift the saw up, use the bottle to put a few drops of oil down into the groove. Resume sawing down to about half depth. Lift up, a few more drops, then saw the rest of the way through. The purpose of the cutting oil is to keep aluminum particles from welding themselves to the saw teeth, or packing into the gullets. That sequence of two applications of cutting oil minimizes the use of the oil and the mess afterward.

I've cut thousands of slugs of 3/8" square aluminum.

I use cutting oil most of the time when sawing or drilling aluminum. And stainless, most cases. I don't use it for brass. I generally don't use cutting oil when milling or turning parts in the lathe. That gets so messy. I'd rather cut at slower depths and feeds, than have to spend the time afterward cleaning the parts and the machines.

 

[Gilmourisgod]

That little HF cut off saw is a good example sizing a tool to a realistic level of strength and precision relative to the actual need. Obviously full time Pros like Bruce need industrial quality tools, but if im cutting a couple brass nuts a year.... Hand me a hacksaw. case in point: Im doing some kitchen renovation that requires an oscillating saw...for about 20 minutes. $12 at HF plus $8 for the blade, and I may never use it again, we'll see.

 

[ardgedee]

That little HF cut off saw is a good example sizing a tool to a realistic level of strength and precision relative to the actual need. Obviously full time Pros like Bruce need industrial quality tools, but if im cutting a couple brass nuts a year.... Hand me a hacksaw. case in point: Im doing some kitchen renovation that requires an oscillating saw...for about 20 minutes. $12 at HF plus $8 for the blade, and I may never use it again, we'll see.

Tool rentals and makerspaces can also be options for once-in-a-while needs or for access to an array of tools with a combined cost in the many thousands of dollars.

 

[MovinTarget]

Tool rentals and makerspaces can also be options for once-in-a-while needs or for access to an array of tools with a combined cost in the many thousands of dollars.

The "try before you buy" aspect is also nice. For a few dollars you might gain a better understanding of how a tool works/operates and be able to make a more informed decision about what to buy or even *if* to buy.

 

[KidAmnesia]

That little HF cut off saw is a good example sizing a tool to a realistic level of strength and precision relative to the actual need. Obviously full time Pros like Bruce need industrial quality tools, but if im cutting a couple brass nuts a year.... Hand me a hacksaw. case in point: Im doing some kitchen renovation that requires an oscillating saw...for about 20 minutes. $12 at HF plus $8 for the blade, and I may never use it again, we'll see.

I was almost a minute wondering what a high frequency cut off saw might be.

I'm so glad the week is over.

 

[Bruce Johnson]

I was almost a minute wondering what a high frequency cut off saw might be.

I'm so glad the week is over.

Knowing typical Harbor Freight power tools, it probably does emit a lot of High Frequency.

 

[MovinTarget]

Knowing typical Harbor Freight power tools, it probably does emit a lot of High Frequency.

I guess its a good thing I was born with almost no HF in either ear? My Fourier analysis shows both ears shelving about half way through audible frequencies... HARBOR FREIGHT, HERE I COME!

 

[rwkeating]

Funny, I don't know what the Harbor Freight saw sounds like. I grabbed my safety glasses and without thinking automatically put on hearing protection before using it. Do I dare take a listen ?????

 

[Bruce Johnson]

Okay, we've gone through a quick overview of the tools and machines, so you know what I'm referring to when I use them. Now it's time to get into some metalworking. I'm going to start off with those aluminum bridge sets that I showed you in the first post. I'm going to show the whole process of making them in full detail, these steps in particular:

• Sawing the bar stock into slugs
• Vise technique: holding blocks in vises using stops and parallels
• Squaring off the ends of blocks
• Drilling technique: Spot Drilling, Machine Drilling, Types of drill bits
• Milling aluminum in a milling machine
• Sanding and deburring the edges
• Finishing the flat surfaces; filing and sanding

If you are curious, these bridge/anchor block sets are for my friend Michael DeTemple, for his P55 basses. If you haven't seen them, the DeTemple P55 is a high end ($6K) early P-bass, built from the finest woods and perfect details and construction. I've been making special truss rods and other metal hardware for his guitars and basses for over 20 years. He's an old friend, we've been mentors to each other over the years. He's now slowing down into a gradual retirement. These bridges are for the last 10 P55's that he's going to build.

After we go through these bridge sets, I have other parts projects lined up to show too. Lathe work, flat plates, shaped tailpieces, milled bridges with sliding saddles, etc. These DeTemple bridges are a good starting point to show the basics of metalworking.

 

[Bruce Johnson]

Sawing off bar stock into slugs:

Not very thrilling, but an important starting point for most bass hardware projects. When you are designing and planning out a custom part, think about making it from bar stock, a common size. 6061 aluminum bar stock is easily available in 1/8" increments in width and height up to 2", and 1/4" increments above that. Aluminum bar stock is cheap enough that I keep some common sizes in stock all the time, like 1/2" square, 1/2" x 1", 1/2" x 1 1/2", etc. I use it for all kinds of tooling and fixtures. I usually buy it in 6' lengths and saw it down to 2' lengths to fit in the metal rack under the Logan lathe.

These DeTemple bridges measured 1 3/4" x 5/8" which, unfortunately, isn't a standard bar stock size. I had to order 1 3/4" x 3/4" stock. The anchor blocks were simpler, 1/2" x 1".

When I'm cutting off a batch of slugs in smaller size bar stock, like this 1/2" square aluminum, I'll use the Small cutoff bandsaw. I've made a nice adjustable stop for the Small saw, which you can see in use here. It slides and clamps on that 1/2" round stainless rod, with an adjustable finger to touch the end of the bar stock. This is a big timesaver when cutting off a whole bunch of parts to the same length.

Note: Bandsawing barstock to length against a stop is not a high precision operation. The bandsaw blade can wander a little bit, and the sawn surface is kind of rough. I'd call the accuracy at +/- 0.020" in length. You need to allow for that in your stop setup. Cut them maybe 1/16" over length, and plan on doing a squaring/trim operation.

I could have cut the 3/4" x 1 3/4" bar stock for the DeTemple bridges in the Small saw, but it would have been kinda slow. The Big cutoff saw has a coarser tooth blade and three times the horsepower. It'll saw aluminum bar stock at about 5 X the speed of the Small saw.

The Big saw doesn't have a sliding stop (yet), so I used a ruler and a Sharpie to mark off the lengths, 1/16" oversize, right on the bar stock. The Big saw sliced them off quickly.

After the blocks are all sawn off, they get a quick trip to the Knife Belt Sander. All four edges of each end of each block gets touched for a second against the 180 belt to take off the flared-out burrs from sawing. This is really important. In the next step, these blocks will be clamped in a smooth-jaw mill vise. Those little burrs can interfere with the clamping and the accuracy. Don't skip the deburring step after almost all sawing drilling and milling operations.

 

[Flamingo21]

I'm intrigued by the Adjustable Finger. To me it looks as if (after loosening that bolt) you can turn it 360 degrees. Its slightly hooked end can then touch the slug near its middle, no matter the size of the stock.

But what does the Finger do? Stop the slug from falling?

 

[Bruce Johnson]

I'm intrigued by the Adjustable Finger. To me it looks as if (after loosening that bolt) you can turn it 360 degrees. Its slightly hooked end can then touch the slug near its middle, no matter the size of the stock.

But what does the Finger do? Stop the slug from falling?

The Finger is the actual stop. Before starting the saw, I loosen the vise and slide the bar stock over until it touches the finger, then tighten the vise. That sets the distance, the length of bar stock will be cut off. All during the cut, the bar stock is touching against the Finger.

The reason that the Finger is a separate part, with a bend in it, and a ground angle on the tip, is so that I can adjust where on the end of the bar stock it touches. When the saw breaks through the bottom of the bar stock, the sawn-off slug can get wedged between the still-moving saw blade and the stop. If you aren't careful where the Finger is touching the end of the slug, this wedging can kick with a lot of force, sending the slug flying. It can also jam hard enough against the finger to push it out of position. If you don't notice it, that can change the dimension of the next slug.

The way to minimize this wedging kick is to grind the tip of the Finger so it's a fairly small surface area, and bend it so it's angled back. Then position it so it's touching toward the forward upper edge of the bar. Then, when the saw breaks through, the slug will do a small roll and fall down.

Notice that I have a wooden tray built into the wooden stand that the saw is mounted to. The cutoff slugs and most of the aluminum sawdust fall down into it.

When I'm done sawing off the batch of slugs, I pull the tray out. Hold a plastic tray under the narrow end, push the slugs into it. Then pull the wooden tray out and dump the dust into a nearby trash can.

I built that wooden stand and tray for this saw in 1983. It's been working well for 40 years!

 

[MovinTarget]

Incredibly dumb question #2,635,744:

When working with aluminum (or other metals) is there somethin akin to a "grain"?
Or if you start with a cube, can you literally approach from any face as your starting point?

 

[T_Bone_TL]

Other than wrought iron (the real stuff, not mild steel pretending to be) metal is isotropic (same properties in all directions.) Wood, as you know, is anisotropic (different properties in different directions.)

As for jamming the stock against the stop, a fairly standard design to avoid that is to make the stop rotatable without longways motion. Flip it into position; set and clamp the stock; flip it out of position (stock is clamped, it's not gonna move); saw.

 

[Bruce Johnson]

Incredibly dumb question #2,635,744:

When working with aluminum (or other metals) is there somethin akin to a "grain"?
Or if you start with a cube, can you literally approach from any face as your starting point?

Like T_Bone says, generally no, metal is uniform internally in its properties. When you get into real high strength situations, and forged parts, then you do have to pay attention to the orientation of the internal structure. On parts that are being pushed to the limit. I used to build race car engines way back. We don't have much of that on electric basses.

On rolled aluminum bar stock, there are "mill marks". Little straight grooves and lines, along the length of the bar, which are lightly pressed and cut into the surface. Straight scratches, nothing structural. If you are making up a decorative part, and want to polish up one of those surfaces, you'll have to file and sand those scratches out. They are about like 220 grit scratches in wood.

 

[Bruce Johnson]

As for jamming the stock against the stop, a fairly standard design to avoid that is to make the stop rotatable without longways motion. Flip it into position; set and clamp the stock; flip it out of position (stock is clamped, it's not gonna move); saw.

Yeah I'll probably eventually add something like that to my stop. I've also seen some stops done with a spring-loaded pin, so it can snap back.

 

[Egg250]

When I did the cut I used a bit of WD40. I use WD40 for drilling and taping aluminum so I decided to use it here too.

My dad has used gojo waterless hand cleaner (no pumice, not the citrus type) for machining aluminum when he was doing production machine work.

 

[Bruce Johnson]

Vise Technique:

In metalworking, we have to apply a lot of cutting force to the part with the tool. Metal is like that. You can't just hold the part in one hand while you trim away the excess metal. You have to clamp the part in a vise. A strong vise that can clamp with hundreds or thousands of pounds of force on the part. Holding on to the part so it doesn't move when you apply hundreds or even thousands of pounds of cutting force to it.

The vise also plays an important part in accuracy, and in consistency in batches of identical parts. In Machine Drilling and Milling operations, the vise holds the part in a precise location in relation to the cutter. In a production operation (making more than one part) the vise is responsible for holding each part in the exact same position. In three axes. And allowing you to swap parts in a few seconds. To the exact same position. This is an important part of machine shop work. A little further down in this thread, we'll talk about Machine Drilling, where you use the vise as a quick-change part holder.

The technique here is to use Parallels and Stops. Accessories that go with the vise.

Parallels are strips or blocks of metal that go down inside the vise, between the jaws. They support the part from the underside and make sure it stays perpendicular to the machine spindle. The height of the parallels also sets the vertical position of the part in the vise, in relation to the top edge of the jaws.

The stop is an an adjustable rod or block that's usually mounted on the right side of the vise. You set the part in the vise, on top of the parallels, and slide it over until it solidly contacts the stop. Then tighten the vise.

Here's a typical parallel and stop setup in the big vise in the Kondia mill.

The parallels are two sections of 1/4" x 1 1/2" aluminum bar stock. The stop rod is adjusted to contact the lower right corner of the part.

I set a block of aluminum in there to show where the part would go. It's resting on top of the parallels, and is touching the stop on the right.

The vise is clamped shut, and I can fire up the mill and make a cut on the part. The block is held in there very tightly, at an exact location in 3 axes. Now it just takes a few seconds to change blocks. A half turn of the vise handle, lift the block out, set the new block in, slide it to the right against the stop, a half turn of the vise handle.

This is how you do production of batches of parts. Do one operation on all of the parts in the batch, swapping them quickly in the vise. Then adjust the machine for the next operation and do it again.

Setting up the parallels and stop is also very handy when making a one-off part. You frequently need to stop the mill, pull the part out, and check it with calipers. Then pop it back in the vise and continue. The parallels and stop make sure it goes back into the exact same location.

Here's what the stop holder looks like on the Kondia. It looks kinda crude, but it works well. The stop has to be quite solid mechanically. You don't want it slipping or deflecting if you slap a part against it. I've got a better design all thought out, but I haven't gotten around to making it yet.

Here's a typical parallel and stop setup in the vise of my green mill:

That is a single, narrow parallel sitting down in the vise, and the stop rod is adjusted to contact the right end of the part. This is the setup I'd use, for example, if I'm drilling holes in a long square piece of bar stock. This parallel already has two notches in it, for clearance when the drill bit breaks through the bottom of the part.

Here's the stop holder on that vise. It's very adjustable and works well. I screwed a small steel block onto the side of the vise's rear jaw. The aluminum bar has a slot in it, and a single 10-32 horizontal machine screw clamps it. The bar can be rotated or slid to any position and locked solidly. The rod is a piece of 3/16" stainless, the same as I make my truss rods from. I also have other rods of different lengths and special tooling that fits in where the rod goes.

The tip of the stop rod is ground to a slight dome shape. This to help prevent an oily chip from getting stuck on the end of the stop, and messing up the positioning of the next part.

Here's an example of Special Tooling! This is a custom size parallel with a built-in stop (the small step at the right) and a piece of stainless rod to locate it.

Here it is, set into the vise. It's machined to hold the part flush with the tops of the jaws, and the part is positioned accurately against the step on the right. The rod clamps into the normal stop holder. This holds the whole tool stationary in the vise. Also note the two holes for drill bit clearance.

And here's what it's used for: Accurately drilling the two jacking screw holes in one of my Scroll Bass bridges. This is the process called Machine Drilling, which I'll be explaining in more detail coming up. This particular bridge block is already drilled and tapped, but I stuck it in there to show how the special parallel/stop works.

Between batches of Scroll Bass bridges, the tool gets wiped off and stored in a box with the other bits of Scroll Bass Bridge Tooling.

Special bits of tooling like this don't take long to make up, and they save lots of time in the long run. They are an investment.

Coming up: More cool vise tricks.....but with drill presses!

 

[Bruce Johnson]

A quick note about the parallels:

One hidden feature of vises made for milling machines is that the bottom surface between the jaws is precision ground to be parallel to the bottom surface of the vise. To tight tolerances, like +/- 0.0005".

Real Machinists doing real precision machine work use parallels that are hardened and ground to within 0.0002". You can buy them in sets. That's what you use if you are machining your parts to 0.001" tolerance or better.

Here's a relatively cheap import set, for example. A top quality set can be a few hundred bucks.

https://www.amazon.com/HHIP-3900-30...064232&sprefix=parallels,aps,222&sr=8-11&th=1

For bass part work, I get along fine with my home made aluminum bar stock parallels. When I mill blocks with them, I'm usually +/- 0.002" in final thickness