"One Perfect Part at a Time"


…and a cast of thousands.

That’s a famous movie intro tag from when I was a kid. (Ben Hur, Moses and The Ten Commandments, etc.) In this case the “cast” is a bit different. No Charleston Heston. Yes, a pun.

The process here is casting pewter into a mold. Perhaps thousands could be made given enough time. What I find interesting is the use of a rubber mold. When I was much younger I remember toy soldiers cast in metal molds. (The metal ones are still available.)

The mold shown here looks like it was made with hot vulcanized rubber but hot metal casting process is also shown to work with RTV (Room Temperature Vulcanization) rubber. Of course metal and plaster molds can be used.

You will notice a few have short guns. The pour was a bit too cold and the flow didn’t get to the end of the rifle. Thin parts like that are tough to fill. I cast many more than shown here (just remelted them) before I got the process right.

All I did for the pictures was cut off the sprue while still hot and then file the flash from the bottom so each one would stand up. No clean up of the casting at this point.

My plan is not to make toy soldiers. This is just an inexpensive all-in-one kit I bought on sale to get the “hang” of casting pewter. I plan to make and cast my own mold designs and perhaps offer them for sale (the molds and what they make).

I choose pewter and this variety is lead free. There is so much concern about the “dangers” of lead, it is not a good idea to offer it to the public. Of course the other metals in pewter are not intended for… Continue reading

CNC Gun Part

A local person here in Frisco asked if I could duplicate this part (the black one). I don’t usually like to take on outside projects as I have enough of my own. This part looked interesting. It is part of a tripod bracket for an expensive, but what the owner called a “toy” gun. Actually is is a very sophisticated collector item.

As can be seen in the photo the bracket had the tab broken off. It is a very nice injection molded aluminum casting but the crystallization left it vulnerable to breaking where it did.

I was going to make a duplicate by manual milling. That’s the rotary table setup in an earlier post. I changed my mind and decided to do it with CNC milling.

I had to first very carefully measure the part in every detail then make a 3D drawing in Rhinoceros (Rhino) You can see the screen capture and a couple of output pictures.

I converted the drawing to two G-Code files with RhinoCAD, one for top and one for bottom.

I did a test run in oak then made the one in aluminum. I used my Taig CNC mill running mist cooling. Overall size of the part is rather small, about 1.5″ x 1.5″ x 3/8″

I’m not setup for doing anodizing and I have never done any. I have studied the process and it can be done in the home shop. The new part really needs to be anodized like the original, but that is not my “thing” right now. That’s all I need is another skill to master. 🙂

12 Inch Slip Roll

Finally, I found a high quality small slip roll.

This is the highest quality 12 inch slip roll you will ever see, use or own. I just unpacked this new sheet metal forming machine and will soon have a full report in The Hobbyist Machine Shop.

This product is so exquisite compared to the Chinese junk I once owned for a few days, I can hardly stop starring at it.  This picture barely does it any justice. The complete report will show a lot more close up pictures.

This is the model PR12W made by Accu Cutter. A definite high end machine tool. Well priced for the professional high quality US made tool that you see here.

I haven’t cleaned it up at all at this point. It still has a light coat of white grease which will be seen in all the “first look” photo’s taken. I will show how it was packed for shipping which was also first class double boxing.

UPDATE: Full writeup, more pictures in The Hobbyist Machine Shop – Under the “Workshop” tab.

Do You Need The Balls?

There is a common conception in the amateur machinist world that ball or roller bearings are always the preferred selection to bushing or solid surface bearings. That is not always the case. Machine engineers, of all people, should know it always depends on the application. There are many applications where ball bearings are contra indicated, meaning they should not be used. Some of those reason can be as simple as cost over performance, excessive noise or the possibility of bearing contamination in harsh environments.

The primary benefit of using a ball bearing over other types is the greatly reduced drag due to its small rolling surface contact point. Their use is preferred when low friction is a high priority and other factors like low noise is not. They will reduce power requirements, help reduce friction heat and provide long periods of operation. If they are properly sealed, they will reduce maintenance. The best, high quality ball bearings can reduce run out and take thrust loads. These are worthy goals but sometimes are higher goals than necessary.

To quickly get to my point, I’ll examine the bearing needs for the lead screws on all the axis of a small manual mini lathe. First, do radial ball bearings “increase machining (position) accuracy” on any of the calibrated axis including the Z axis main feed screw over a bushing type bearing? The answer is an absolutely no.

This is because the linear slide position accuracy is a function of axial (not radial) screw loads affecting the amount of compression/expansion of the lead screw, drive nut thread engagement, drive nut mounting rigidity, thrust surface material and screw shaft bearing end play. This as combined is commonly called backlash. Minor drive screw side play (run out) is not a factor.

 Radial bearing loads… Continue reading

Another Project Finished

Yes-sir, completely scratch built from raw ore. NO, not likely. Ha!

This is a little repair project my daughter gave me. It is a ball head for a camera (photography) mount. The bottom of this device screws down on a tripod or studio steady mount.

There is a quick release on the top that is attached to the camera.

The handle bolt is loosened to adjust the angle of the camera and that is where the problem was. There are internal splines in the original handle that were stripped out. It would no longer turn the locking bolt to secure the ball from moving.

I learned all about these spring loaded handles and also how the ball mount itself works in this little project. There are two main types of these handles. Most of us know the “pull the handle to adjust position” type. I have a lot of them on my machine tools. There is a second type called the “Safety” handle where the user must push in against the spring load to engage the handle. That is what I have here. The handle pops back out and drops to a safe position  when not engaged.

So the project was mostly selecting the correct replacement handle. However there was a catch. There is always a catch, right? The end of the original bolt was drilled out and a pin with a tapered cone inserted. It is this cone against an internal ramped surface that pushes up and locks the ball movement.

The machining chore was to drill out the end of the new handle bolt to fit this tapered cone pin. The challenge was to hold the bolt for drilling (without disassembling the handle) and drilling the hard end of the bolt deep enough for the pin to insert.… Continue reading

NOTE: Log in is for admin and members only, not required to post comments.