By Rob, on August 29th, 2009
Here are a couple of calculators that you can use to determine the weight of a piece of metal. You just have to tell them the kind of metal, its shape (round, square, tube, plate, etc.) and its dimensions. The first is a downloadable calculator that will run on a PC. The second is an online calculator you can access from a web browser. Both calculators will accept dimensions in either English or Metric units, but for some strange reason they only give the results in pounds.
I used one of them to see if I paid a good price for some of the cutoffs I bought yesterday at a surplus metal store. I paid $8/pound for a piece of brass that was 1.625-inches in diameter and 12.5-inches long. I determined by using one of the calculators that Enco charges $6.02/pound. But I would have had to purchase a 6-foot long piece for $270.89, even though I need a piece less than 2-inches long for the project I’m making.
Yesterday I thought that was an acceptable price, but today I am kicking myself really hard. I just checked Smallparts.com and discovered that I could have bought a slightly smaller piece (1.5 x 12-inches) for $17.76, which works out to $2.17/pound. Ouch, ouch, ouch.
By Rob, on August 27th, 2009
LittleMachineShop.com has the Ron Steele belt drive conversion kit for the mini-mill on sale for just one week, until Tuesday, September 1, 2009. It’s $109.95, which is $20 (15%) off the normal price of $129.95.
I’m going to order one. It is one of the most popular modifications for the X2 mini-mill, I was going to eventually buy it anyways, and I’ve never seen it on sale before.
Advantages
- The kit eliminates a couple of drive gears, including a plastic one that can break easily if your cutter jams.
- It increases your maximum spindle speed from about 2500 rpm to about 4300 rpm, which is important if you use very small end mills or drills.
- Your mill will run much quieter.
The conversion kit is very easy to install and it will probably take only about 25 minutes.
But don’t take my word for it. Richard Bradshaw made an excellent 8-minute YouTube video that will show you how quick and easy it is to install the kit, and how much faster and quieter your mill will run.
By Rob, on August 11th, 2009
Here is a list of the materials you will need to build Jan Ridders‘ new simple low temperature differential Stirling Engine. You can download the plans here (PDF).
I was going to build his Coffee Cup Stirling but I have started building this one instead because it will take a lot less time. I have not been able to spend much time in my workshop lately, which is typical during the warm weather months, and I would like start a project I can finish within a reasonable amount of time.
I know I get a lot of visitors looking for information about Jan’s Stirling engines, so I am posting this with the hope that someone will find it useful. I usually hate studying plans to determine what materials and tooling I’ll need to buy. I’m always worried I’m going to miss something and the project will grind to a halt while I place an order and pay a huge shipping fee for just one item. I’m not too fond of ordering stuff either.
Fortunately, I already have almost everything I will need. I just have to buy the graphite, a glass tube for the power piston cylinder and a suitable plastic tube for the displacement cylinder. I did some checking last week and I think the glass and graphite will be easy to obtain. Finding a 4-inch clear plastic tube has been a problem. You really can’t make the top and bottom plates until you know dimensions of your tube.
Jan’s plans are in Metric units and I’m in the US, so I am going to have to convert them to English units. I have not built this engine yet, so consider the fractional English sizes I listed to be just suggestions for now. Stayed tuned because I’ll start posting some construction photos and notes soon.
Aluminum
- 18 mm [.70 ~ 11/16-inch] round – Countra weight (Counterweight) – Sheet 6
- 20 mm [.78 ~ 3/4-inch] round – Displacer kernel (Hub) – Sheet 5
- 32 mm [1.26 ~ 1-1/4-inch] round – CD kernal (Hub) – Sheet 6
- Material to make two 112 mm [4.41-inch] diameter disks for the top and bottom plates of the displacement cylinder. One needs to be 5 mm [.20-inch] thick and the other 8 mm [.31-inch] thick.
You have a couple of options here. One is to start with a couple of disks cut from a 112 mm or bigger round bar. This could be very expensive if you have to buy a length of it.
A cheaper alternative is to make them out of a flat plate by following Bogstandard’s excellent tutorial. You also have some choices if you do it this way. You can buy your aluminum plates in the two thicknesses you’ll need or use the same thickness for both cylinder plates, which should look and work fine. You can also mill the metal down to the thicknesses you’ll need.
Brass
- 5 mm [.20 ~ 3/16-inch] round – Fork (2) – Sheets 5 & 6
- 11 mm [.43 ~ 7/16-inch] round – Crank webs (4) – Sheet 7
- 1 mm thick x 6 mm wide flat stock [.04 x .24 ~ 1/32 x 1/4-inch] – Displacer & Piston Rods – Sheets 5 & 6
Continue reading → Materials List for Jan Ridders’ Simple LTD Stirling Engine
By Rob, on August 3rd, 2009
This is a review of the Drill Doctor model 750 drill bit sharpener. Not that long ago the 750 was Drill Doctor’s top of the line model until it was replaced by the 750X, which you can buy new for about $140. I’ve seen videos of the 750X in operation and although it looks different, I believe it works in the same way, so you may find this review useful if you are thinking about buying the newer model.
You may also find this review useful if you are considering a Drill Doctor 500X or a used model 500, which was its predecessor. The main difference is that the 750X and 750 come with an extra chuck that allows you to sharpen bits up to .75-inches in diameter. The 500X/500 can only sharpen drill bits up to .50-inches in diameter unless you buy the larger chuck separately as an accessory for about $40.
The 750X and 700 are also the only models that come with a carrying case, although you can buy one for the other models as an accessory.
I have heard that a good machinist should know how to sharpen a drill bit by hand, without a jig or fixture of any kind. That’s probably true, but I am a mostly self-taught home machinist with no one who can show me how to do it. I have tried it a few times but each attempt was a complete failure and I would have been better off continuing to use the dull bit.
I have also heard that even if you can hand grind a bit, it is hard to grind both flutes evenly so they will drill a round, exact-sized and straight hole. Putting a split point on a drill bit is suppose to be even harder and requires a grinding wheel with a sharp, not rounded, edge.
So for me, sharpening drill bits by freehand grinding was not an option. That left me with the following choices for dealing with my dull drill bits:
- Send them out for sharpening – I’ve heard it costs between $1 and $2.50 per drill to have them professionally sharpened. I am not going to spend that kind of money to sharpen inexpensive HF drills, although I might if I had a nice set of cobalt bits or if I used larger diameter bits (5/8-inch or bigger).
- Buy some kind of sharpening machine or jig – I can’t afford even a used commercial quality tool grinder like a Darex. That left either buying or making some kind of device for holding a drill at the proper angle against a grinding wheel, or buying a Drill Doctor or some other drill bit sharpener that is affordable enough for a home/hobbyist machinist.
I decided I wanted a Drill Doctor because they got great customer reviews on Amazon.com. When someone did badmouth it, it often seemed like it might be because they hadn’t learned to use it properly by reading the instructions or watching the video that came with it.
Cost was an issue for me. A new 750X costs about $140 and the 500X is about $30 less. That’s a lot of money to spend just to sharpen some drill bits. Especially if you have a limited budget and there are more important things your workshop could use. In my case, that would be a rotary table.
So I waited patiently for more than a year for a Drill Doctor in very good or better condition to show up on Craigslist. I finally bought a model 700 in excellent condition for $65.
Continue reading → Review: Drill Doctor 750
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