# Putting a recess in a flywheel



## Bogstandard (Dec 10, 2007)

This is really a follow on from a post a fair time ago about making flywheels from plate material.
I am just at the moment about to start making three finger engines, two of them have recessed flywheels, and sometimes getting this recess can cause a beginner a few problems, I know it used to cause me a lot of heartache.
Now what I am going to be showing here will cause the purists amongst you to jump up and down, but it is my firm belief that there are no hard and fast rules with regards to grinding tooling, other than if it works, it is right, so what is the problem.

Away we go.

I recessed these two flywheels a couple of hours ago, the one on the right is a recycled one from my mine engine, just with a bigger recess put in. The recesses took less than five minutes per side.







This picture shows the tooling in question, which will be explained a little later.
I just can't get good close up shots otherwise I would have shown you the cutter in full profiles.






This next pic shows the tool in action (but you can't see it, but it does show how the flywheel should be mounted). Mine is mounted into soft jaws, but I would expect you to mount yours into your outside jaws that usually come with the chuck. Do not attempt this with the flywheel on a mandrel, it will not be able to withstand the cutting pressures involved.







Now to the profile of the tool I use, and please remember, this is how I do it, someone else might do it in a totally different way, this one works for me.






Using these rough dimensions (not critical) I can recess to about 250 thou deep, but on a 1/2" wide flywheel I will go a max of 200 thou each side.

There is no easy way to describe how to grind a tool so I am not even going to try, other than to say, keep the tool cool while grinding, grind a bit, quench, if it changes colour dramatically you have already softened the tool, and you will have trouble cutting harder materials.
This tool is designed just like a boring bar with a cutting edge on the right hand side as well, but stuck onto the end of a nice rigid bit of stock rather than on the end of a flimsy thin bar.

The angles shown on the sketch are slightly exaggerated to show where the angles should be to give you cutting clearances, somewhere around 5deg. for each one should be ok. The top face of the cutter should be totally level.

The way to use the tool is mount it very close into your holder, this will keep vibration to a minimum. At the same time square the face of the tool to the job, and get it bob on centre height or if you can't, just slightly below, on no account go higher.

I use a saddle stop for my in cutting, but you might have to lock your saddle and put the infeed in using your compound slide.

So, starting at the outside edge of your recess, minus about 10 thou, plunge straight in to your chosen depth minus about 5 thou, retract, move across just less than the width of the cutter and plunge in again. Keep doing this until you are about 10 thou from the size of your centre boss and retract.
Now you are going to do the finishing cut. 
Saddle still locked, bring the tool out to your outside edge of the recess, then wind in using the compound to your final depth, then wind across with your crosslide and carry on until you hit your size for the boss, then retract, bringing the boss to correct size.

If you have any slight chatter marks, these can easily be cleaned up with a bit of emery or wire wool.

My tool has made dozens of recesses in all sorts of materials, mainly non ferrous, but has done mild steel on occasions, and stainless just the once (which I don't want to repeat) and the tooling is still like new, just a slight stone up with an Arkansas stone before use keeps it razor sharp.

Keep the chips flying

John


----------



## shred (Dec 10, 2007)

Cool, thanks. This maybe answers a question I had.. I got a ton of lathe bits with one of my machine purchases and at least two of them are ground into a very similar shape.. I was wondering why somebody would want not one but two fat, short cut off tools.


----------



## jgarrett (Dec 10, 2007)

Thanks for the info. That process has been giving me fits. What you show is about the only tool shape that I have not tried.
Julian G.


----------



## cfellows (Dec 11, 2007)

John,

How long did it take you to grind that bit profile? Also, what kind of grinder did you use? Do you dip the bit in water a lot to keep it cool?

Chuck


----------



## tattoomike68 (Dec 11, 2007)

cfellows  said:
			
		

> John,
> 
> How long did it take you to grind that bit profile? Also, what kind of grinder did you use? Do you dip the bit in water a lot to keep it cool?
> 
> Chuck



I do know the trick to hand grinding is if the bit is too hot to hold dip it in water and cool it off. if you are so tough as to grind a bit blue with bare hands then you need to lay off the whisky.

If you cant hold it it is too hot, thats the key. I go slow myself and sneak up on +/- .001 of a size so its easy. when grinding a tool undersize is best anyway. you can always fudge an undersize tool but never fudge an oversize tool.


----------



## Bogstandard (Dec 11, 2007)

Chuck,
As far as I can remember, this tool was ground up from a previously shaped tool that I had done and not used for a while. But it is a fair time ago and can't be certain.
If it was being done from the solid it would most probably take about 15 minutes using my offhand grinder.
As Mike says, it has to be cooled very regularly, especially at the roughing down stage, this is the stage when people tend to go in and try to remove as much metal as possible, but if done as a grind, quick dip, grind, quick dip and don't allow the heat to build up the metal soon comes off. I have a little clip on the front of my grinder that takes a small linbin with water in it, so it is very close to where I am grinding, so no reaching for the quench, just a slight downwards movement and I'm into the wet stuff. When the time for final profiling comes it is just a touch on and dip. 
Also, I leave a rounded corner on one of my wheels if possible. This allows me to have a nice stress relieving radius for these small ended bits. 

But sometimes I get carried away and get a bit of light colour into the metal, usually when I am putting the stress relieving curve on. None of us are perfect, even though we think we are.
If I want super sharp corners and accuracy, like a grooving tool, I use my surface grinder, but that is another issue because most people don't have one.
As I have said before, I can only relay how I do it and what works for me, everyone has their own ways of doing things.

John


----------



## Bogstandard (Dec 11, 2007)

Just to show how easy it can be done, I made a quick vid about cutting a recess using my ground up tool.
You will notice that there is a bit of chatter, but I would expect that because of the heavy cutting and fairly high peripheral speed. It could be reduced maybe with a bit of lube and turning the speed down, but lazy as I am I tend to not change my cutting speeds unless really necessary. Just wack it in and cut it (beginners please ignore what I just said). 

Beginners, please refer to your reference tables for cutting speeds and feeds for the materials you are cutting.

About 3minutes from start to finish, except for a bit of polishing.

[youtube=425,350]kBgIFty8PgU[/youtube] 



John


----------



## rake60 (Dec 11, 2007)

Beautiful!

I've always done that with two tools.
A turning tool to cut in to the hub area, and a small boring bar to cut out to the rim.
Then I had to polish the blend line out.

Now I'm off to grind a tool.

Great video John!!!!

Rick


----------



## Bogstandard (Dec 11, 2007)

Thanks Rick,
I don't know if you noticed, but I will tell all anyway.
On the initial cut the lathe was in fact slowing down, as the vid shows, this wasn't caused by overloading but because the motor is way too small for the lathe, only half of what it should really be.
Maybe on some of the smaller lathes you wouldn't be able to compete with the speed of the plunge cutting, but a little slower RPM and a bit more care on the plunge and maybe a bit of lube and all should be ok. It does work a lot better on brass.

John


----------



## lugnut (Dec 11, 2007)

John, thanks for the Youtube link.. What rpm was you working at? The video seems like it's pretty fast. Not knowing much about turning I think mabe most of my turning is too slow.
Thanks 
Mel


----------



## Brass_Machine (Dec 11, 2007)

That's pretty darn cool!

Gotta love youtube (and the other vid sites) It makes it so much easier when you can actually see what people are trying to explain. The visual learning process!

Thanks
Eric


----------



## Bogstandard (Dec 11, 2007)

Thanks Lads,
That was running at just under 700rpm, but if you noticed my comments, it was a little too fast. Really it should have been down around 350 to 400 RPM.
The reason I did the vid was to make my attempt at the explanation of how to do it a lot easier to understand.

John


----------



## Cedge (Dec 12, 2007)

Excellent John
Now maybe I won't have to polish out the marks left by using both left and right cutters anymore.

Steve


----------



## jgarrett (Dec 14, 2007)

John, Where do you get/make your blanks??? Do you cut them from bar stock??? I have made a total of 3 trying to get one good one. I tried the first one by using a hole saw in the mill. Also tried cutting one with a RT, not so good. My biggest problem has been cutting the recess and this w/e I will make one of your tools.
Julian G.


----------



## Bogstandard (Dec 14, 2007)

Julian,

I did a write up here on how to make flywheels from plate material.

http://www.homemodelenginemachinist.com/index.php?topic=228.0

I hope this helps you over your problem.

John


----------



## jgarrett (Dec 14, 2007)

Now that's neater than a new puppy! Don't know how I missed that in a search.
Thanks for the link and good job of presenting.
Julian G.


----------



## Bogstandard (Dec 14, 2007)

Julian,
Glad it might help.
It does pay to open posts that you think of as not to your liking, because sometimes there are little snippets of good info that should really be in a post of their own.


John


----------



## DickDastardly40 (Dec 20, 2007)

John

Is that what some might call a trepanning tool?

When I get round to my flywheel , I was intending to cut the recesses in the mill with the rotary table offset. I may try this method but when I did it once before as an apprentice for a rotary lock, it all went a bit pear shaped first time through and put me off.

Al


----------



## Bogstandard (Dec 20, 2007)

Hi Al,
If it was a bit longer it could certainly be used as a trepanning tool, but as is it will only penetrate about 250 thou max. My trepanning tool had an angled cutting face rather than square, and was a lot longer, it was like that when I bought it so I expect it is that shape for a reason. But like all good spur of the moment purchases I have never used it and so don't know how it cuts. I must now try and find it and try it, just to put my mind to rest.
Thanks for reminding me about it, not.

As you can see from my vid, nothing spectacular, but it gets the job done. I still get a bit of chatter, but I would expect that anyway because of plunging cuts at such varying peripheral speeds across the full width of the recess. I can live with a bit of polishing up.


John


----------



## BobWarfield (Apr 17, 2008)

A nice trepanning tool too!

I needed such a tool not long ago to use to cut out a hole in some sheet metal. Not sure if this would've been exactly the best geometry, but it would of beat heck out of what I tried to use. My trouble was all I could find was pictures of ways to make holes in people's heads!  :big:

Anyone who's tried searching trepanning can see how unsatisfying those searches can be. I got it done, but I'll do better next time after seeing this. 

Good show on the video too!

Cheers,

BW


----------



## burkland (Dec 18, 2012)

As a beginner in the hobby, this thread looks to be exactly what I need to learn how to best turn the recess in a flywheel.  However, all the pictures seem to not load for me.  Am I doing something wrong or are the images really not available any more?  If not, does anyone know of a good alternative explanation for making a tool similar in design or purpose to the one mentioned in this thread?

Andy


----------



## mulac321 (Dec 18, 2012)

I am afraid the original poster bog standard has removed all his images from this site for reasons i will not go into. http://www.homemodelenginemachinist.com/f26/thinning-flywheel-web-16592/ this thread here is quite useful for what i think bogs meant by a recess on a flywheel (not being able to see the pictures i am only guessing) i used the information on the post above to sucsefuly make a very nice flywheel 

Calum


----------



## burkland (Dec 19, 2012)

Thanks, this is helpful.  Andy


----------



## reFlad (Dec 19, 2012)

You could also try http://www.modelenginemaker.com/index.php/topic,1150.msg14624.html#msg14624

Ronald


----------

