Wednesday, January 18, 2017

Belt Speed Calculator

I get asked a lot about what speed a motor with a drive wheel and a ratio of pulley 1 and pulley 2. It's a lot of stuff to figure out especially if you factor in a VFD driving the whole lot.

Being shut out of the shop for another cold week where the temperatures were dipping to the -30°C (-22°F) mark. I put on my programming hat on and made a simple to use online belt speed calculator which covers a whole bunch of scenarios.




Hopefully you will find this useful if you are designing a belt grinder or working with different ratios to get belt speed to match the material that you are grinding or polishing. You will find some recommended belt speeds for different materials as well as some other useful information from Klingspor in their technical document.

Stay warm and happy grinding!

Sunday, December 18, 2016

The Dreaded Bevel Angle Calculation

Online Knife Bevel Angle Calculator

http://dcknives.com/public/grind_angle.php

It's been super cold the past two weeks and I haven't had a lot of quality time in the sub-zero garage working on knives. I have to keep busy, and warm, so I've been working inside on a tool that lets us set the bevel angle on a blade by the grind height and thickness.

To work this out we need to look at the thickness of the steel and the height of the grind and make a simple right triangle.











Here our steel is laying on the flat. Imagine we want bevels that look like 'A'.

Adding a horizontal center line will divide the steel in half.

Adding a vertical line at the grind stop will allow us to extract a right triangle. Voila! High School was finally useful!

 


In order to get from a right triangle to real world grinding angle, we need to assign the Adjacent (A) and opposite (O) values.


 



There is a mnemonic used to remember which trigonometric function to use when we need to find some missing part of a right triangle. This mnemonic is SOH CAH TOA. Okay... what the?

SOH CAH TOA helps us remember to use the Sine function when we know the Opposite and Hypotenuse, we use the Cosine when we know the Adjacent and the Hypotenuse and we use the Tangent when we know the Opposite and Adjacent values.

In our example for blade grinding we us TOA or Tangent for Opposite divide by Adjacent.

Let's put some real numbers in. Say our knife is going to be a hefty 0.25" thick. We take 1/2 of that to make the right triangle, so O is 0.125".  We'd like a grind height of 3/4" or 0.75".

Using the ATAN function on our calculator we can determine the angle in radians. But, radians is not degrees. We need to multiply radians by 180/pi to get the degrees.

Here's the link  for Imperial and this link is for the Metric Grind Angle Calculator.

I promise no more math for the rest of the year.

Merry Christmas,

Dan

Thursday, November 10, 2016

2x72 Grinder Wheel Set

2x72 Grinder Wheel Set

I am building another low-cost 2x72" grinder and I am super fortunate to have made a friend at Oregon Blade Maker.


Marinus at Oregon Blade Maker is offering some high performance, yet light-weight and durable grinder wheels for a low cost 2x72" DIY build.

These wheels are computer engineered, glass-filled nylon (durable composite plastic) with 1616RS bearings.

The wheels in this set are two 2-1/4" wide x 2" and one larger diameter crowned 2-1/4" wide x 3" which is designed to assist in belt tracking.

The wheels will mount with any 1/2" bolt. Plan for three 1/2" NC x 3" to 3-1/2" grade 8 bolts and suitable nylon lock nuts and washers.


These are low drag and spin freely.

Of course, the OBM glass-filled nylon wheels are not going to take over the aluminium premier wheel's top spot in roller Olympics, but these OBM nylon wheels offer value that cannot be denied.



Dan

November 10, 2016.


Tuesday, October 18, 2016

KN20-3 HONESUKI WA (WESTERN)



This is the first of the Christmas knives. A 150 mm Honesuki style with a western handle. It's made from AEB-L 0.130".

After shaping and some cleaning, I make a wire hanger and dip the blade in the stop-off paint.





The temperature of the furnace is targeted at 1060°C (1940 F).

Out of the fire and into the oil.








Although AEB-L is an air hardened steel, oil seems to result in a slightly harder steel. After hardening, it's tempering time. 185°C for two periods of two hours each.






Unlike some honesuki that have a left or right handed grind, this one will be symmetrical by request. I work each side with 60 grit ceramic belt cooling with water every pass or two. Once the primary bevels are close to 0.020", I move to a 120 grit ceramic belt.
This is a result of about 1 hour of grinding and polishing. For polishing I like the fine and very find conditioning belts, like Scotch-brite or Vortex. The "grain" runs longways. I feel that looks the best.








With the blade polished, the marks etched and cleaned with windex, the blade gets taped right up to the shoulder. Then the pieces of the handle stack get fitted. The most critical is the first piece as it has to fit well with no major gaps. For this I like to use a 3/32" bit and a flat needle file.




The block is desert ironwood. Here I am fitting and tracing the tang and screw against the block. This will give me an idea where the drilling needs to occur.

Once the pieces of the stack are complete and dry fitted, the epoxy comes out.






In this case, I am applying a small amount of pressure to keep the blade and handle in a straight line. I leave the clamp on for 12 hours.

After about 24 hours, the handle is ugly as hell, but ready to start shaping. The flat faces are ground first.







Then the rounding of the handle begins.
As the rounding gets closer to the finished shape, I like to run on the slack belt and rotate the handle to give is a nice uniform shape. A 60 grit belt is followed by a 120, then a 220, then a 400 and lastly a 600 grit aluminum oxide.




Then it is over to the buffing wheel. I used black compound then green compound. The ironwood is naturally very oily.
Here are some pictures of how the knife turned out. 

After taking the masking tape off and cleaning the blade with acetone to remove and extra epoxy and fingerprints etc.
 
















Thanks for stopping by!

Dan