Diamond Dresser

For Christmas a few months ago I made a diamond dressing tool for my brother in law.  He is a woodworker and uses his bench grinder for the initial sharpening of various wood working tools.

The tool is made up of 4 parts.  The body is a piece of steel with an angled lip (one on each side) that is used as a guide against the tool rest on the grinder.  It has a threaded hole for the diamond.  The diamond is an industrial diamond held in a steel rod – commonly used in surface grinding dressers, modified with threads along most of its length.  There is a lock nut and o-ring (to provide some cushion when tightening the nut down) and a handle nut to adjust the distance from the lip to the edge of the diamond.

The tool is useful for most sizes of standard bench grinders as the body has 2 different lip offsets.  The threaded diamond is also allows for generous positioning.

After giving him the tool I explained a few of the benefits of such a tool versus a traditional spur style tool:

  • The amount of grinding wheel material removed is easily controlled as the distance on the single point tool is adjustable.
  • A single point diamond tool does a better job at getting the wheel round in the first place.  This is because the forces involved are significantly less than traditional spur type tools, or even the newer T style diamond tools.  Forcing traditional tools up against the wheel isn’t a very steady process and the entire tool floats on the surface of the wheel.  In addition your hand can move back and forth with the high and low points on the wheel.  As such I’ve found single point tools create a wheel that is rounder, which helps with balancing.  (Grinder balancing always happens after a wheel has been dressed).
  • Unlike spur tools or the cheap T style dressers a properly used diamond tool lasts a long time on a bench grinder and also is very durable for various wheel materials.

After Christmas I finished up a tool for Max over at the Joy of Precision:

I made up a full set of drawings of the tool if you would like to make one yourself:

Body – (Rev 01) Diamond – (Rev 01) Handle Nut – (Rev 01) Lock Nut – (Rev 01) Dressing Tool – (Rev 01)

I’ve also had a fair bit of interest in people asking if they could buy one of these tools.  I’m making up a number of them for others so if you are interested send me an email: justin@thecogwheel.net.  I’ll be posting additional information shortly.

As usual I made up a video of making the tool and it also shows how I use it:

 

 

Vise Clamps and 1 Hour Red Rust Bluing

Let’s rewind to the summer when I purchased the Rong Fu milling machine for the shop.  The mill included an exceptionally well made French made Sagop milling machine vise that had a bit of wear but was very usable.  Up until this point I have never heard of Sagop before.

A quick search revealed a basic corporate webpage. It appears that Sagop is still in business and still manufactures a line of workholding products.  The vise that I purchased is the smallest of their precision CNC milling vises, a 100mm 800 series vise.  The construction of the Sagop is very similar to the Bison precision CNC milling vises.  I was also floored to learn the purchase price of this vise.  It is listed over 1000 euros with the swivel base – a number that is rather shocking when you consider that it is sitting on a Rong Fu milling machine!

The vise came with the swivel base – a very well made turntable base that allows for 360 degree rotation.  A very handy feature in some situations, but for most of the work that I do I usually just bolt the vise directly to the table.  This takes up less table space and is also more rigid.

Strangely the vise did not come with any way to mount it to the table.  Up until this point I had been using some of those standard import clamps that are sold everywhere.  This wasn’t the best solution as these clamps are quite bulky and don’t do the best job of holding in situations like this.  So set out and designed up some new clamps to be made.

But first I searched to see if I could find drawings of the vise and / or the swivel base, not only for this project but for future ones.  While not directly advertised on Sagop’s website, I managed to find the drawings for the vise and the swivel base:

Sagop 800 Series Vise Drawing  Sagop 800 Series Swivel Base

I modeled the clamp up in Fusion and made up a drawing of it based on the dimensions I found in the above pdfs.  Now some folks at this point say CAD is a waste of time for such simple projects, and it maybe for them.  But I’m actually quicker at modeling something up in CAD than I am drawing up a sketch on paper so for me I usually start with a 3D model.

The clamps are designed for 3/8 cap screws.  I then made up a shop drawing for the clamps:

Sago Vise Clamp – (Rev 01)

Making the clamps was a very straightforward process. The most interesting part was when I used the 4 jaw chuck in the lathe to counterbore for the cap screws – I haven’t invested in any counterbore tools yet for cap screws.  I need to quit being so cheap.

When they were finished I started to wonder about how I was going to prevent them from rusting.  Rust is a very real problem in home shops, and in particular my shop as I live in a climate that is somewhat humid and has significant temperature swings.  If you are willing to deal with plating shops you might be able to find a shop to do a zinc coating – but for small one off parts it is often impossible on a budget as most plating shops have a minimum charge that far exceeds what home shop machinists can afford.

I have considered cold bluing products in the past as a simple method to provide some rust protection on parts.  In Canada cold bluing is a bit harder to procure than south of the border, and is is also somewhat expensive.  So I started to read up on other processes.  Hot bluing looked interesting, but involves some nasty chemicals.  Rust bluing looked promising but it seemed like a long process – you had to wait around for the rust to happen.

I did some more reading and I recalled an experiment we did in high school chemistry involving a mixture of hydrogen peroxide and salt applied to steel wool. The hydrogen peroxide and salt rusted the steel wool so quickly that you could measure the temperature change. I then did some further searching and I found a fellow Canuck who beat me to the idea of quickly rusting parts using hydrogen peroxide and salt: https://mypeculiarnature.blogspot.ca/2014/08/quick-rust-bluing-back-in-black.html

The process is very simple:

  1. Thoroughly Clean parts using a good degreaser.  This step is very important!
  2. Etch parts in acetic acid (common household vinegar)
  3. Rust parts using a warm hydrogen peroxide salt mixture.  You can either fully immerse the parts or brush the mixture on.  I mixed it up about 1/4 cup peroxide and 2 tablespoons of salt.
  4. Fully submerse parts in boiling water and watch red rust turn to black oxide.
  5. Lightly wipe or wire brush parts.
  6. Repeat steps 2 through 5 until you are happy with the coating.
  7. Dry parts and oil

The final result is a nice black oxide coating that helps protect against rust and looks great:

I made a video of the process, including the making of clamps:

 

Cross Slide Screw Support

A few weeks ago I finished a project that I had on my mind for a number of months.  There was a lot of play in the cross slide feed screw on my import bench lathe.  This showed up as backlash in the feed screw – when you grabbed the toolpost and applied force in alternate directions you could see the entire cross slide move back and forth.  Some of it was from backlash in the feed nut itself, but most of it was between the feed dial and the support casting itself.

I tried tightening up the nuts themselves tor reduce the amount of clearance – but then it bound and you couldn’t turn the feedscrew at all.  This wasn’t the best design from the get go.

The first thing I did was modeled the entire assembly up in Fusion to get a clear picture of what was going on – and to give a good starting point for the modification: The nuts aren’t shown on the end of the feedscrew but you can see where the assembly is constrained for axial movement – at the right side on a shoulder machined into the feedscrew itself and on the left side the inner bushing of the dial.  These are just 2 plain bearing surfaces – and they weren’t machined the best to begin with.  No wonder it wasn’t the best!

I thought about doing what Stefan Gotteswinter did.  If this was my main lathe I would copy what Stefan did as it is the best solution by far.  Angular contact bearings are the way to go in this situation.  Since I’m keeping this lathe around primarily for cutting metric threads (the Standard Modern now in the shop doesn’t have a metric transposition gear) I decided to scale back the project and see if I could just stuff a deep groove axial bearing and a roller thrust washer into the space without having to modify the leadscrew, or make up a new dial.

Below is what I came up with:

I incorporated a deep groove ball bearing (6900-2RS) and a 10mm needle style thrust washer on the opposite side.  This required a new housing and the old cast iron bearing support to be shortened up.  The new housing was doweled to the cast iron block for location.  2 counter bored cap screws hold the entire assembly together.  The cross slide screw required minimal rework – a shoulder had to be turned for the bearing to sit against.  I also turned down the shoulder on the screw that previously was a bearing support.

The ball bearing is preloaded using the existing nuts.  Care needs to be taken not to overload the ball bearing as deep groove ball bearings aren’t primarily designed for axial load.  In retrospect I should have flipped the positioning of the deep groove ball bearing and thrust washer around when thinking about cutting forces as the cutting tool pushes away from the work piece.  If I have problems I can always make a new bearing housing.

The cross slide now is super smooth with no backlash due to the support.  There is a bit of backlash in the screw, but I don’t get too bothered by that on a manual machine.  It is significant improvement with not too much effort or time required.

I made a video of the entire project as well: