Reflection on Wheel Cut

The teeth gaps look pushed out rather than cut out. I think I`ve made a huge error as I aligned the cutter and wheel on the x-axis and then fed the wheel straight into the cutter on the Y-axis. Consequently, is this not simply pusing out the groove rather than using the cutting angle and cutting it out? I appreciate the tool may not be to correct size for module .8 cutter but in terms of the cutting angles and rake, the tool looks fine and is sharp. Thinking about it now, I`ve been "hitting" into the face of the brass with the face of the cutter rather than using the cuting edges, no?



Chris

Cutting my first wheel

I wouldn`t call it a complete disaster, I did end up with something that loosely resembles a clock wheel but I have a long way to go so before I start!

OK - so all the equipment was setup as shown in previous pictures. I also centered the cutter to the wheel centre and also leveled it square with the wheel blank.



The first issue arose as I started taking the second cut, I didn`t get a picture of it but the teeth seem bent and not straight! The first tooth to form looked more bent than the others so I don`t know why this happened! Perhaps my cutter is profiled at an angle and is therefore cutting wonky teeth? OR, and I could check this, is the cutters cutting area, i.e the cutter tooth, not at 90 deg to the arbor? I think this is most possible but will need to check it again tomorrow. This will explain why the teeth are at a little angle but not why the teeth look a little bent!

Well I know this wasn`t going to be used in my clock but I wanted to finish it to see what other problems arise:



Tooth form looks quite good so far!

Look at the first tooth and how bent it is ... obviously it is the furthest one away from the current cut in the next photo:



Then I finally got back to the start and that was just using 6 deg divisions on my RT, soon I`ll need to use a dividing plate and that should help a lot with spacing.



Next problem is the brass and how the cut is being taken. The brass is being bent rather than shaved or cut off. Notice how the teeth look a little convex ... not sure why this is happening BUT this is a scrap piece of brass and not the recommended CZ120 for clock wheels. Could this be the reason but look at the little bits that have been pushed forward and back instead of cut off. This is a major problem and needs sorting.



Notice the two teeth that a very close together at the top, this is where I made my final cut to come back around to the finish. I a dividing head will help here but I`m a little unsure why this happened as the error was not carried forward as I was simply cutting every 6 deg rather than adding up any errors...if that makes sense? Also the first tooth being bent doesn`t help the issue...



Then I had a brain wave, popped it back in the lathe to skim off these bits off the front of the teeth gap. What an idiot :bang: I caught the teeth tips with the cutting tool and stripped off the nice radius....[b]from now on in the pics the top of the tooth profile looks flat, that is my fault![/b]

Then it was time to strip off the wooden support. WOW the brass really had just been pushed back and not cut off! It was literally bent into the wood:



Then tidied it up a little more and now it looks like this:



Like I said, not a total failure, I learnt a lot but I have a lot of issues to sort out as this would be nowhere near good enough. I wonder if the brass type has a lot to do with it, maybe using the cz120 would cut rather than bend back? Have I used the cutter correctly feeding into the work on the Y-axis?

Some thinking time required.....

Wheel Blank Backing Plate

I need something to back the whole thing so that the brass teeth don`t bend under the force of the cutter. I have decided to back it with a piece of sacrificial wood. The cutter will follow through the brass into the wood and so will support the teeth from bending. I`ve seen this used in practice so I know it can work .... whether I can do it is a different story!

This is the wood I`m going to use with the wheel sat on top of it:


After some working on the wood (don`t like them damn brown flakes, they get everywhere!!) I got it down to size. I also used a thick brass sheet off-cut, turned it into a washer and mounted this at the front of the plate. This seemed to work really well, everything looks to be held down flush, running true and secure.



I then mounted the wheel blank in my RT and used a draw bolt to pull it through and clamp it down. Just need to change the chuck to my er32 collet chuck, mount the cutter and off I go .... in theory!



I also hardened the cutter this evening so tomorrow I really a ready to give it a whirl!

Chris

Wheel Blank Arbor

This is my first attempt at a wheel blank arbor. I`m sitting it straight into the 3MT of my Boxford headstock using a 2MT to 3MT sleeve. This will allow me to take it out of the lathe, remove the sleeve and transfer to my rotary table on my mill.

I first started out by cutting my wheel out in rought from brass sheet:



I used an open sleeve and my intention is to pull the arbor through with a long drawbar - unfortunately, I didn`t have anything long enough so for now I used live centre (probably not best as it was pushing on the bolt) but in actual fact, it was held solid and didn`t spin just in the MT alone.

..and then taken down to size. It looked to be running true using the live centre but should be more accurate when using the draw bar:



Hummm, then wondered how the hell I was going to get it all out! I went to have a look in the box that came with the boxford and found this lying next to the collet draw bar - just the job!



So this is what I have so far ... now need to harden and fine tune the cutter and then mount the wheel arbour directly in the rotary table 2MT centre

Wheel Cutter Arbor

I have been doing some reading on Arbors in general and realise that my attempt was quite crude. I have since produced a better version of an arbor for holding the cutter.

With the constant interrupted cut I decided I had room to fit a M3 screw off-centre so I have also included this in the new arbor. It makes it look more cluttered but in terms of functionality, at least there is no chance of the cutter slipping.

Making a Single Point Wheel Cutter

If I want to build a clock I need to understand wheels or gears! My plans specify the wheel Pitch circle diameter, number of teeth and module cutter to use. Consequently I`ll need to make the specific cutter determined by the "module", so I decided to try and make a 0.8 module cutter and find the measurements to make the cutter! I had some learning to do and this is what I found:



So the most important measurements as far as I can see are:
1. dedendum - the distance between the bottom of the tooth to the pitch circle diameter.2. addendum - distance between pitch circle diameter to the end of the tooth3. Distance between tooth = (normally) = width of tooth4. Radius of arc that forms the tooth.
Obviously this changed a little when your making the cutter as of course your cutting the gap and consequently forming half of two adjacent teeth.
I then found this site which has lots of formula for how the module relates to these dimensions. I can`t find a link to the site but I saved the image, here is the table:

So that kind of helped but now got me a bit hung up on this idea of module, as to me the minute you specified a module I expected that you were specifying or dictating a specific wheel (I thought this due to the link in the formula) needless to say I was wrong. It took me a while but I put together this spreadsheet which gave me examples of using the same module on two different sized wheels - so I used a module 0.5 cutter on a 1 pcd and 2 pcd wheel and then did the same calculations but using a 1 module cutter.
http://www.raynerd.co.uk/images/Gearing.xls

This proved in my head that in actual fact the module DOES dictate the tooth dimensions, simply if you’re using another sized wheel you are just adding teeth onto that wheel but with the same profile. Now I was happy that the module cutter is a specific cutter for a specific tooth form. I then calculated the dimensions for a 0.8 module cutter which is what I wanted to make - this is on the far right of the spreadsheet. There are currently no formula in the spreadsheet but I am working on adding this (that is what the notes page is for) and if I finish it, I`ll post it up. I used a pen and calc and simply used excel to tabulate the info.
OK, well now I have the dimensions for the 0.8 module cutter:Tooth arc diameter required would be 2.51968 mm (it was actually worked out as a radius for the arc but the way I`ll be forming it, described later will require the diameter). The addendum for this tooth profile is 0.0424 inches (1.07696 mm) and the dedendum is 0.0496 inches (1.25984 mm). Gap between teeth is 1.25mm
I have heard good things about John Shadle's wheel cutter as it is fully supported. The standard single point/tooth flycutter style is said to often brake and if it blunts during cutting, resharpening often changed the size. John's version is really clever as the forming tooth is fully supported by the body of the cutter:
http://onlineclockbuilding.com/DOWNLOADS/flycut.rtf
....... and sometimes I can do maths, but from here on in I am a novice. I`ll let the pictures do most of the talking:
My slither of apparently silver steel that I picked up from the scrappy. 2inc dia and about 8mm thick. Little bit of steel round stock to be used as the madrel:



Making the mandrel:

Mistake number one - I threaded the mandrel, I think M8 and tried to hold the steel blank. Whenever I hit something a bit tought it just spun the disk. When I tried to tighten the bolt I threaded it and it just spun! Why did I thread it and did I do something wrong?

Steel blank being drilled:

So I had to drill the mandrel fully through and bolt the steel blank on using a bolt pulling it all the way through. It worked a treat but wasn`t as neat as my original idea.......comments appreciated:

Then I used my parting off, grooving tool to cut the dedendum on each side to the correct depth and also gain the correct tooth gap or in this case, width of the tip of the cutter:

Then I needed to put the radius on which I did using a 2.5mm drill bit. I made a template by drilling a 2.5mm hole and cutting it in half. I was going to use that tool next to it but it was too hard to get it to size.

So I used an old 2.5mm drill and hand ground the radius on the end. I`m sure there must be a more accurate way but this is how John described doing it. I got it quite accurate and it seemed to fit the template well, it was just fiddly and very hard to mount in the tool post:

I then prodded the sides to add the addendum that would create the tooth tip profile:

Then dismanltled it all:

Then chopped it in half and started to give it some profile:

Then I drilled the off-set mounting hole and I think you can see the tip profile on this photo. I still have some sharpening and profiling to do but it is there! If you open the link I sent of John's article you will see that by mounting this off set hole in the arbor you automatically create relief below the cut.

So, there we go!
Will it cut a wheel? Is it silver steel (seems very soft, definitely needs hardening!)?
I`m not too sure but I feel good that I`ve made it! Next job is to harden it and I may even purchase some case hardening compound.
What is the best way to mount this on the arbor? I just think that if I thread a hole on a mandrel it will spin and not hold properly like when I tried mounting the original blank earlier in the post. I could do with a key way or perhaps bolt it in two places...hummm, I need a better arbour!

All the best.Chris

The Workshop

Some manditory pictures of the workshop where all the action happens:

Machines and Equipment

At the moment the machines and equipment I will be using are the Clarke cl300m lathe, a Boxford Model A lathe, a Chester Conquest mill and Vertex 4" Rotary table. I will have to purchase a dividing attachment shortly (they are currently out of stock everywhere!) but I`ll be able to cut most of my wheels using the rotary table for easy divisions.

Boxford Model A:

Chester Mill and Clarke lathe:

Colin Thorne's - Skeleton Timepiece

After much thought and contemplation, discussing on various forums and with specific individulas, I have decided on Colin Thorne's - Skeleton Timepiece. His design is elegant and more contempory than most and yet simple, or at least relatively.

Introduction & About Me

My ambition has always been to make my own clock and at the age of 18 I purchased a Unimat 3 lathe, tried to cut a wheel, failed, sold the lathe and that was the end of that. Now, nearly 10 years later I have return to model engineering and have spent the last few years gaining experience with metal working. I have built a few small steam engines, some useful tools and all this time I have built up a small home workshop at a very low cost. I`ve not touched a clock or the plans for a build in all this time but now feel that I am ready to begin my ambition of a clock build. I am not in engineering as a profession and therefore this is all a huge learning curve. If you have any tips or hints then please feel free to contact me or better still leave some comments.

I hope to post a log of all my experiences here as much for a log of my progress as anything else .... besides, I can`t see anyone reading it anyway!