Cutting a small flywheel

[Chris333]

Hello,

I'd like to make a "Huff n' Puff" small engine and now I have the plans and instructions. The one item not explained is the flywheel (probably because this is a simple part?) I understand how to turn it on the lathe and drill the holes, but I can not figure out how I would make the 1/16" insets on each side. I don't have a tool bit that small to use a lathe. My only other thought were to use a rotary table on the mill (I don't have a rotary yet)


How do I cut these insets?

Thanks
Chris

 

[hobby]

You have a lathe, but not a small enough toolbit?

I would try a 1/8" endmill for a tool bit, feed it very slow, to see if it could be used.

You might have to modify it, but something like that might work, Or grind a 1/8" tool steel rod, to make a round toolbit.

Just a few suggestions to get the ball rolling...

 

[mklotz]

When I did mine I ground a trepanning tool for this job. Sorry, no photo; the tool is long gone. It looked like a miniature cutoff tool with extra side relief and tiny radii on the two edges.

The trepanned section is not necessary to the operation of the flywheel. You can use a solid flywheel or, if ambitious, make up a spoked flywheel from separate parts.

 

[jodhner]

Use the pointy V shaped bit. You'll have to do half the pocket, then reorient the bit, and do the second half of the pocket.

Wear your safety glasses.

 

[Chris333]

Sounds like I need to learn how to shape too bits...

I found this when I searched "trepanning tool"
http://www.micromanufacturing.com/showthread.php?p=485

I have some old bits laying around to practice with.

I don't think I could make a spoked flywheel. I wish it was this easy:
[ame]http://www.youtube.com/watch?v=p2KrukXzCx0[/ame]

Thanks for the replies.

 

[Noitoen]

9 axis??? That's some serious programming to get a single part.

 

[mklotz]

I wish it was this easy:

If it were that easy, I wouldn't want to do it.

 

[Chris333]

OK I took a 1/8" tool bit and ground a radius to one side. That seems to give a good side cut, but the face of the bit is skipping. So I ground a relief under the tip of the tool and no luck it is still skipping at any speed.

Here is a scrap of brass to try it out:

A little over exposed, but you can still see the skipping.

Here is a profile of the front of the tool:

And this would be the side:

What am I doing wrong here? I have never shaped a tool bit before. :-[

 

[mu38&Bg#]

You can make it the cutting face more narrow. Or make the tool from larger stock with a short cutting tip to stiffen it. I would not attempt to cut the whole width of the face groove with the tool.

 

[Ed T]

A bit hard to tell from the pic, but it looks like the tool is sticking out of the holder a lot further than it needs to for such a shallow cut. This causes the tool to deflect when you try to make the cut giving you the chatter marks . There are a million ways to make this part, but the small size makes it more interesting. I think I might try a round ended tool about 1/8" wide. Use that to remove most of the metal with a plunge cut then go back in with a sharp corner tool to clean up the corners. A corner tool that looks like a dovetail from the top could do both inside and outside corners with out a new set-up, but not both corners at once. The whole process is worth testing out on a scrap before you commit to the real part. Good luck!

 

[Blogwitch]

This might help you, an old article from ages ago

http://www.homemodelenginemachinist.com/index.php?topic=844.0

Blogs

 

[Chris333]

Thank you for the ideas. I just ground down the tip till it was about 1/32" wide and it looked good. The second it touched the tip popped right off like it was plastic.

I'll keep trying...

 

[ksouers]

Chris,
When grinding a thin tool like that it's really easy to overheat the metal. You really have to keep it cool. Getting it hot will lose the temper. As you found out it can get really brittle and break off, or lose the heat treat altogether and not hold an edge.

The smaller the edge or tip gets dunk it more and grind on it less. You'll get to a point where you're just touching the tool to the wheel and dunking it. It takes practice, keep at it, you'll get there.

Watch the color of the tool. If it's red, it's way too hot. You've already lost the heat treat.

If it's blue or black you just lost the temper. Dunk it and let it cool then clean it up. If you were to look at it under a microscope you'll see lots of little cracks.

If it's yellow you are getting close to losing the temper. Dunk it and let it cool. Keep at it but don't let it get so hot.

 

[Chris333]

I tried a second time trying not to take off so much. I didn't think the front needed rounding so I just tapered it slightly and rounded the one side. It worked with no chatter!!!

Here are the pics. Keep in mine this bar is 1/8" square:

My practice was with cutting brass. I need to make this flywheel out of steel. So I may still have problems.

 

[GailInNM]

Chris,
If you have or can get some 12L14 steel it will cut as easy as the brass. Even less tendency to chatter.
Gail in NM

 

[starbolin]

Those square nose bits such as used for trepanning, cutoff, slotting and etc need to have either some top rake or a top U channel to provide chip control and help with the chatter. As Ed T says the tool is sticking out way too far. If it sticks out from the tool holder any farther that one bit width then one has to somehow provide a thicker/deeper shank.

On trepanning bits in brass I use quite a bit of back rake. On slotting and cuttoff bits I grind a U channel along the bit axis with a small rotary stone.

 

[PaulG]

Chris, Repeat advice of Ed T & Starbolin!!! Also replace the round packing under your bit with another bit or raise the holder if you can. Paul

 

[Chris333]

Thanks.
I guess this topic should have been "How do I shape a bit", but either way I still learned a lot.

Once my mill shows up one of the first things I plan is to cut a slot for a 1/8" bit on the other side of the tool holder.

 

[gerd niephaus]

Hello,

I am fascinated by the "Huff 'n Puff" engine by Philip Duclos and I would like to build this engine. As I am living in Germany, it is not so easy for me to get hold of an old issue of the magazine "Projects in Metal". I know that the magazine article is reprinted in a book but this is quite expensive over here. Any idea where I can get hold of the plan for this engine?

Regards
Gerd Niephaus