Cutting inside edge and hub of a flywheel

[Garyg]

I finally got my new 10 x 22 lathe fired up for the first time. I have made things on my wood lathe but this is the first time with a metal lathe.
My first project will be a wobbler. I wanted to make a 1.5 inch flywheel out of a piece of steel but ran into a problem cutting the middle out.
I wanted to create a rim and hub. I had bought a set 8 10mm HSS cutters with the common profiles. I can't figure out how to do this. The bottom of the cutters rub on the inside edge of the rim ruining the square edge. I could only get about 20 thousand in before this happens. Could not get square edges on the rim . Do I need to custom grind a bit ? Do you need 2 bits ,one for the hub and one for the rim.


I would like to make a flywheel like this but deeper profile.

 

[f350ca]

Gary, sounds like you need to grind a higher clearance angle on the cutting edge of your tool to get out to the rim, raising the tool above centre will help but isn't the best solution. Once you've raised it the your cutting angle at the top of the tool will be wrong. This trick helps some times with a boring bar though. Yes you'll need right and left hand cutters to cut to the rim and the other to cut towards the hub. That one won't need the extra clearance angle.
Hope this helps.
Congratulations on the metal lathe.
Greg

 

[T Bredehoft]

Yes, you undercut the bottom of the cutter, below the cutting edge. If you are using brazed Carbide cutters this may be a bit difficult. I recommend HSS cutters for this cut. With HSS cutters, keep the RPM below 200, this will give you an approximate 80 Feed Per Second surface speed past the cutter. Too much more than this will overheat the cutter, causing the cutting edge to smear.

The radius of the relief should be a smaller radius than the finish cut, but only enough to clear.

You'll get onto lathe operations in a hurry, just keep an eye on what actually is happening between the cutter and the work.

One more thing, don't be afraid to change the original shape of the HHS cutters, experiment and see what works best. Remember to hone the vertical edge of the cutter after grinding with a hand stone.

 

[Wreck™Wreck]

It's a bore, use a boring bar.

 

[kd4gij]

Can you post a pic of the tool bit set.

 

[mekanix48]

Hi Gary
As mentioned.. it's actually a boring exercise, use the smallest boring bar you have, it will already have the relief on the underside, so give yourself a drilled centre to start off with even if it's just the depth of the 118* drill point angle... well actually, :thinking: you have the bore already done to start off with...

George

p.s. I have made one of the wobblers shown in the pic, but with a plain flywheel ...



George.

 

[Garyg]

My bit set I bought had a boring tool but it is ground from a 10mm square hss and its to big for the radius I want to cut. I don't want to grind it till its dull (its too nicely cut)
I had bought these also to get an example of the proper angles on different bits.
I am going to pick up a small set of 3/8" boring bars with holder and some 3/8 and 1/2 hss blanks.

 

[mekanix48]

My bit set I bought had a boring tool but it is ground from a 10mm square hss and its to big for the radius I want to cut. I don't want to grind it till its dull (its too nicely cut)
I had bought these also to get an example of the proper angles on different bits.
I am going to pick up a small set of 3/8" boring bars with holder and some 3/8 and 1/2 hss blanks.

If you can afford it try & get a 6 mm insert type boring bar this will allow you to get in to smaller areas, or have a look on flea bay for offers, there are smaller ones around. with respect you're not doing yourself any favours by limiting tools to 10/12 mm (3/8" - 1/2") If you're concerned about freehand grinding don't be e.g. if you have a broken 6mm tap (or even smaller) find the last full tooth, grind the end flat, with a small angle tapering back from the tooth root (leaving the full tooth ) then freehand grind the remaining teeth behind that tooth away leaving you with a boring bar, the radius of the tooth will give you enough clearance to cut quite well, that's what I did to get my smaller boring bars, 3 are made from broken taps, see pic...

Some of my boring bars...




George.

 

[Bill C.]

I finally got my new 10 x 22 lathe fired up for the first time. I have made things on my wood lathe but this is the first time with a metal lathe.
My first project will be a wobbler. I wanted to make a 1.5 inch flywheel out of a piece of steel but ran into a problem cutting the middle out.
I wanted to create a rim and hub. I had bought a set 8 10mm HSS cutters with the common profiles. I can't figure out how to do this. The bottom of the cutters rub on the inside edge of the rim ruining the square edge. I could only get about 20 thousand in before this happens. Could not get square edges on the rim . Do I need to custom grind a bit ? Do you need 2 bits ,one for the hub and one for the rim.

View attachment 94023
I would like to make a flywheel like this but deeper profile.

I have made shoulder cuts before. Depending how deep the shoulder is I usually rough out the material using HSS bit. Then I change HSS bits, the one I like has a lot of relief on its side but the face was just enough clearance not to rub. I plunge cut edge of the rim until the tool touches the shoulder. On the face cut I turn the compound rest 90 degrees to the cross-feed. The final cut I hand feed the compound until the tool reaches the shoulder.

Good luck with your project.

 

[Wreck™Wreck]

My bit set I bought had a boring tool but it is ground from a 10mm square hss and its to big for the radius I want to cut. I don't want to grind it till its dull (its too nicely cut)
I had bought these also to get an example of the proper angles on different bits.
I am going to pick up a small set of 3/8" boring bars with holder and some 3/8 and 1/2 hss blanks.

Grind it until it works, this is what it is all about as a hobbyist, this will teach you how the tools actually work in use (you will not learn anything otherwise), it will be an experience that you will remember.