Elegent Scroll Frame Skeleton Clock

[Kim]

Thanks Bent! 
Yes, I'm pleased with the results.  It's taken me a while, and I'm still plugging away at the various gears, but I'm getting there.  And having fun in the process.

I learn so much more by posting all my warts, as you call them  .  That way, other people can offer suggestions about ways that have worked for them, or things I might tweak in my process to get better outcomes.  And, hopefully, others can get some value from my learning, too!

Kim

[Kim]

Over the weekend, I made the maintaining ratchet.  This wheel had 120 little ratchet teeth.  I used the same 60^o cutter that I’ve used on all the other ratchet wheels.


Here’s the completed ratchet wheel.  Well, not completed.  It still has to be crossed out and all, but you know… done up to this point anyway.


My final wheel is the escape wheel.  This one requires a different cutter.  John Wilding shows the cutter shape as an arc from a 1 5/8” diameter circle.  So I tried making a little pattern for me when shaping the cutter.  I started by using a 1 5/8” circle cutter on some 1/16” aluminum plate.


Then cut it out on my predetermined lines and glued a straight edge to it (another piece of 1/16” aluminum).


And here’s my gauge for shaping the escape tooth cutter.  It’s shown on top of the diagram John provides for making the cutter.


After shaping my cutter.  It’s not an ‘exact’ match, but pretty close.  Hopefully close enough.  (But then, my shape gauge isn’t an exact match either, so maybe my errors cancel out, right?  )


Next, I cut the teeth:


And heat-treated.  I did the hardening using the torch. But for tempering, I used my new oven.  This is pretty cool, I’ll have to say!  The oven doesn’t have a permanent home yet.  It’s just sitting on the floor next to my lathe.  It shares the power outlet with the lathe or the mill


Unfortunately, cutting the escape wheel didn’t go as smoothly as I’d hoped.  I was a little worried about those long, skinny teeth, and my worries proved to be well founded.  I got maybe 10 teeth in and decided that the teeth were NOT looking the way I wanted them to.  They were bending backwards radially and to the side due to the force of the cutter.  I think I started out cutting the teeth in the wrong direction (I was going counterclockwise, as I’ve done for all of the gears so far).  But here you can see that even after cleaning up the side burrs, the tips of all the teeth on the left didn’t get touched. That’s because they are bent downward, out of the plane of the wheel, by the force of the cutter.  So I did some experimenting with cutting the teeth in the other direction (progressing clockwise to the next tooth) and that helped a lot.


Here’s a close up of the teeth.   The red section is the first part I did, progressing counterclockwise.  You can see that each tooth bent backwards, radially, into the opening left by the previous cut.  The right edge of the tooth should be straight, but it tips clockwise.  In the blue section, I moved clockwise for each tooth.  The higher cutting force is around the curved part of the tooth.  And when progressing clockwise, the curved part of the tooth is supported by the rest of the wheel, and the straight part (less cutting forces) is only supported by the narrow tooth.  This worked much better, but the tip of those teeth got curved clockwise a bit.  I believe this is because I was cutting the teeth a little too deep and the tip of the tooth was hitting the cutter arbor.  For the green section, I continued progressing clockwise, but I backed off on the tooth depth by about 20 thou. That seemed to help decrease the hook in the tip of the tooth.


So, my plan now is to cut the teeth a little shallower, to progress clockwise around the wheel, AND to have bigger support disks for the wheel.  As you could see in the previous pic (2 pictures back, I think), the support disks I made only extended out to the root of the tooth, so they didn’t provide any support for the tooth itself.  This time, I made support disks from 12L14 that are the same size as the wheel.  And I superglued the support disks to the wheel (all the way out to the edges) in hopes that his will provide a little extra support for the teeth while they are being cut.

Here's the new escape wheel blank, all prepped, sized, and ready to go.  But I’m going to wait till tomorrow to start this.  I want to be fresh when I start this wheel.


We’ll see how tomorrow goes!
Kim

[crueby]

Here's hoping the support discs do the job! On each tooth, is it taking out the whole valley in one pass, or is it multiple passes goiing deeper on each? With the 12L14 discs, it may start accumulating heat, don't want the cutter getting hot and ruining the temper.   

[cnr6400]

  The support disks should help I think Kim. Good luck tomorrow! 

[Kim]

Thanks Chris and CNR!

On each tooth, is it taking out the whole valley in one pass, or is it multiple passes goiing deeper on each? With the 12L14 discs, it may start accumulating heat, don't want the cutter getting hot and ruining the temper.

Yeah, I was taking many small passes to get the full depth on those teeth.  Seems like one full depth pass would be rather problematic.

Kim

[wagnmkr]

I was also going to suggest some sort of support disk to help stop the teeth deforming. That will be a tricky one to do for sure and I have often wondered how the were made so well in the "olde" days. Fingers crossed for a good outcome Kim.

 

Tom

[PaulR]

When you've mastered those teeth can you sort mine out please, my dentist always looks clueless when I open wide 

 

[Kim]

That will be a tricky one to do for sure and I have often wondered how they were made so well in the "olde" days. Fingers crossed for a good outcome Kim.

Thanks Tom.  I'm wondering that myself now too! 

When you've mastered those teeth can you sort mine out please, my dentist always looks clueless when I open wide 

Yeah, I'm pretty sure you don't want me fiddling around inside your mouth!  Oops, broke another one.  Let's try again! 

Kim

[Kim]

So today I set out to cut the escape wheel using all my newfound knowledge and tricks. It seemed to be going ‘pretty’ well, but I could tell that the teeth were still bending up at the tip.  Not what I wanted   But I decided to go ahead and finish up all the teeth anyway. Took about 2 1/2 hours to cut all 32 teeth.


Clearly, the teeth had turned up a burr along the pointy end, too, so I tried just a light clean-up on the lathe to take that burr off.  It seemed to work pretty well, and the teeth looked much better at this point.  Though I could still see that the tips were bent a little.  I was thinking maybe I could file that lip off the ends of the teeth.


However, after I took the gear out from between the stiffeners, I noticed that not only did all the teeth have little bent tip at the end, but the last tooth was WAY out of whack.  I had taken REALLY light cuts for this last tooth, in hopes that it would help it not bend into the opening of the adjacent tooth, but no such luck.  It had bent down, and because of this, the tooth was much wider than the others.  I figured I could file the tooth down to size, but it needed to be bent back into position.  As I was trying to bend it down a little, it just cracked right off.  I was none too pleased.  (Note the missing tooth at the top)


I should have taken a picture of it beforehand, but I wasn’t that smart.  But I did find that you can see the same effect on one of the stiffeners.  I positioned that spot right at the top here.   See how the space is wider?  The side of the tooth on the left should be straight, and the side of the tooth on the right should be curved.  But it actually looks straight because it bent so much over into the space on the right.  You can’t tell it in this picture, but the tooth is actually wider.  I think the burr is hiding this (I didn’t debur the stiffeners).  But it was very apparent on the escape wheel.


So, now I’m unsure what to do next.

Some thoughts I’ve had are:
1) Form the teeth some other way.  Like use a slitting saw to form the straight edge, then file or grind out the curved shape of the tooth.
2) Make the form tool for the tooth a little narrower, such that the teeth won’t come to such a point, and give them a little more meat.
3) Add some relief to the ‘flat’ on my tooth-cutting tool.  Right now, the flat part is just flat.  But it seems to be rubbing on the flat part of the back of the tooth enough to make it bend up, for some reason.  Guess that’s why most tools have some relief on them.  This one doesn’t.  So that might help.
4) Admit defeat, and use brass for this.

I’m not ready for #4 yet.  I’m frustrated, but not ready to give up.  This must be possible.

I’m afraid that if I try shaping the teeth by hand (as in #1), they won’t come out very uniform.  So I’m reluctant to do that.

I could try a combo of #2 and #3 together.  That might be my best bet. But I’m afraid I’d still end up with the last tooth bending.  So, I’d either have to cut the last tooth in a different way (as in #1), OR, find a better way to straighten the tooth.  Maybe if I’d annealed it before trying to bend it?  Or tried to bend it while it was red-hot?  That doesn’t sound supper easy to do though.

If I could make a plug that was the right shape, maybe I could fit a plug in between the space behind the last tooth so that it wouldn’t bend. But this seems like fanciful thinking.

Oh, I just had another thought:
5) Make a longer piece of stock the correct diameter and just cut the teeth into it for 1/4" or so. The bar would provide additional support for the teeth – especially the last one.  The outside edge would probably still deform some, but it seems like the closer you get to the parent stock, the less deformation you’d get?  Then I could face it off and cut off a little chunk for the actual escape wheel. This is the method I've seen used by some people for pinions.  Maybe it would work here?

Maybe add #5 to my #2 & 3 above?

Hmm…  I’m open to all suggestions or ideas!

Thanks,
Kim

[cnr6400]

Sorry to hear the wheel didn't go well today. One thing I know would work perfectly to form the teeth in stainless would be wire EDM, as used for tool and die work. It is expensive compared to milling, but if there's no alternative it would work for your stainless wheel and the precision will amaze you. It is a zero force electrical cutting technology so there will be no tooth bending. If you are interested in getting a quote for this method, check with local suppliers to the metal stamping industry in your area. Hopefully there will be a job shop that does dies and punches for sheetmetal production shops in your area. If there is nothing local I can put you in touch with wire EDM service firms in my area or in the Detroit area. Hope this helps Kim.

[crueby]

Not having the relief in the cutter was a lot of the problem in earlier gears, and adding it helped a lot didn't  it? I would check that out further. This cutter doesnt have relief on either face, straight or curved, does it? Without telief its going to hammer the cut edge back. All milling cutters should have it.




Option 6, have it cnc cut at one of the online services. Option 7, send me the cutter and plan and I'll  cut it in brass, I  have c353 sheet stock.

[crueby]

Okay, the more I think about this the more I am convinced that relief on the cutter is the issue. You need both the curved and the straight side of the cutting edge to have relief behind it, at least a few degrees, or all you are doing is rubbing the sides of the cutter on the stock as its trying to advance in on each cut. Thousands and thousands of little glancing blows with a hammer beating back the teeth you are trying to cut into the wheel. Think about what it would take to bend those teeth back with pliers - it would take a lot of force. With relieved cutter edges, it would be shearing off chips. With square edges on the cutter, the cutter cannot advance in and bounces off. Imagine grinding a parting tool with no side relief, AND having an end shape that sticks out and matches the radius of the round bar you are trying to cut. It wouldn't go anywhere well, generate a lot of heat, and bend the bar into pretzel shapes. Thats an extreme example, I know, but its the same effect. You had the same problem on the gear teeth cutters till you relieved the cutting edges on all sides.

Sorry for the long winded rant! But I hope the point is in there...
Chris

[Kim]

Thanks CNR and Chris,

Wire EDM is an interesting idea. I might look into that.

And you're right, Chris, having some relief would probably help a LOT.  I was thinking about how to do the cutter with some relief.  I have that jig I used to make a 4 tooth cutter with relief, but the problem with that is I have to be able to create the cutting edges repeatably.  And using my 'file' method, that just won't work.  I'd have to come up with another way to make the shape, which I could do.

Or, maybe I'll just grind a single point cutter and try that method. I seriously considered that for the escape wheel, but came up with this idea.  And these cutters had worked so well for the other gears (as long as I kept them sharp!).  But it would be much easier to make a single point cutter, with relief. I'd just have to make an arbor for the single point cutter.   But that might be my best shot...  unless I want to farm it out for CNC or Wire EDM.

Kim

[crueby]

On the clocks I made, with brass escape wheels, they were all done with a single point fly cutter. Lots easier to keep it sharp with brass than it would be with steel wheels  though.

[Kim]

Thanks, Chris!  So that's going to be my next attempt. 

I ground a new tool for single-point-fly-cuting the escape wheel teeth.  Here’s an out-of-focus picture of the tool.  It’s a 1/4" tool blank (short piece).  I ground a 6-7^o relief on all sides of the cutting edges, and I tried  to cut the straight edge back a little from the tip.  That’s what this picture was supposed to show.


I cut one end off of a foot long boring bar that already had a 1/4" square hole in it, with a set screw, to use to hold the fly cutter.  I set that up in the mill and used one of my rejected escape wheel blanks to do some new test cuts.


It seemed to go quite well.  The burr on the edge was a much more typical burr.  More of a thin shaving that curled over, rather than the pile of metal that I’ve been getting.  So I’d say our cutting is much more effective with this setup.


Here’s a shot after filing the burrs off.  I did 3 spaces going Counterclockwise (in green), where the straight edge of the tooth is exposed while cutting the long curve of the tooth (the part I thought would have more forces from cutting). Then I went back and did three teeth going clockwise (in red) where the curved edge of the tooth is exposed while cutting the flat part – the part I’d postulated had less cutting forces exerted on it. Interestingly, the counterclockwise direction seemed to work better, which is the opposite of what I’d expected.  The clockwise direction resulted in the tips of the teeth bending up.


This didn’t fit my theory.  But looking at the tool, I think that I may not have provided enough (if any?) relief behind the tip of the tool.  I think I may still be getting a lot of rubbing from that long straight part of the tool.  Maybe chips get in there and cause the tooth to bend up.  But when going counterclockwise, the rest of the wheel is providing enough support that it stayed straight.

Also, the teeth didn’t bend very much laterally (out of the plane of the wheel, that is).  They moved a bit for the ones cut counterclockwise, which is what I expected. But not very much.  You can see the two teeth on the left didn’t get touched by the sanding during deburring.  It’s just a touch, but they did bend.  That bending could easily be fixed with a gentle squeeze in the vice.

So, I increased my relief behind the tip of the tool along the straight side, as shown in this picture.  Please note, that the wheel is shown upside down from the other picture.  Also, I had gently straightened the three teeth that had their teeth bent.  So I CAN do that.  Which is good to know, because I will always have ONE tooth that has to be cut with no support.


I’ve prepared another escape wheel blank.  This time I set it up with a large stiffener on the back side (the direction of the force) to hopefully keep the teeth from bending away from the surface of the wheel.  And I plan to cut the teeth counterclockwise, since that seemed to make MUCH better teeth, even though it is contrary to my original theory.

So that’s where I’ll pick up next time.

Thanks for looking in.
Kim

PS  Oh yeah, I also meant to say that I'm certain that part of the problem I'm experiencing with making the escape wheel is the tooth profile.  I believe my first escape wheel tool was too wide.  I did a bunch of calculations and determined that with the tool profile John Wilding shows, at 3/16" deep (his specified depth), the cut would be 0.174" wide.  And with 32 teeth, and the offset he specifies (0.080"), each tooth would have 0.154" width at its max opening.  Those two numbers don't fit.  If I only have 0.154" per tooth, and I want a non-zero width at the tip of the tooth, my max width of the cutter has to be less than 0.154".  John's cutter profile doesn't fit.    So, for my new single-point tool, I was aiming for ~0.140" at 3/16" depth.  And that gives me a tooth profile that looks about right.