Cutting a flat spiral gear / grinder pattern.

[NeoTech]

So, this is just for being able to cut more complex things.
As a manual machinist im facing a problem down the road, i need to cut spiral pattern on a flat pice of stock, similar to a spiral bevel gear but no bevel.

This would work if i could synchronize my linear travel of the table with the rotation of a roundtable. This could prob be solved in two ways. either slaving the roundtable somehow to the tables "turning" mechanism, through some gearing or shaft.. Or electronicaly with a positionining device and a stepper motor im guessing..

Anyone done this type of cuts before?  (this type of gear is common in rear axles for the differential drive).

[awemawson]

Conventional way was to gear a dividing head to the travel of a milling machine. Cincinnati published a very nice blue bound book described the hows and what's of the  process

Andrew

[John Stevenson]

Be very afraid.

The gearing of the table to the rotary axis is only part of it.
The tools uses and the way they are applied is a far greater problem.

Do a search on Youtube for Gleason Spiral bevel to see what you are faced with

[NeoTech]

John Stevenson, checked the tube for what you suggested, and thats a modern way of making a spiral bevel gear. Now lets step back, i want to cut each groove, one at a time by the means of a single point tool or an endmill. =)

The old way of gearing the round table to the travel of the mill table is a bit trickier. I have seen some weird ass badly illustratated instructions for it in a photocopy for my aciera milling machine. But it made use of a custom gearbox and alot of other hassle. The same technique is actually used for cutting a spiral on a piece of round stock as well.

The math of spiral interpolation on a flat surface suggests that the linear travel synchronized with the turning of the round table would create  radius rather than a straight line. When cutting that with a end mill you would end up with a groove, offset the workpiece a set amount, return to zero and then cut the next groove..

*googling cincinnati blue bound books now* =)

[NeoTech]

this is what i wanna acomplish, but not using a cnc .. =)

And this is the principle.. just trying to figure out how i do that with a round table. ;)

[awemawson]

Here you go:


https://archive.org/details/treatiseonmilli00cinc

Gave my copy to the SM&EE library years ago

Andrew

[NeoTech]

Awesome site.. what is that.. *reading up*

[Manxmodder]

Hi there NeoTech, I'm new to this forum and this is my first post.

Regarding your problem with driving a rotary table from the leadscrew I think this could be quite simply achieved by using a toothed timing belt and and 2 idler pulleys to enable you to change the plane of drive from horizontal to vertical.

This setup enables you to turn/twist the belts through 90degs and changes the plane of the drive.

I have seen this method used to drive induction disc valves on competition 2 stroke motors where the drive is taken from the crankshaft end and changes plane to propel the disc valve which is on the intake face of the cylinder and 90 deg out of plane with the crank.

Hope you can get a picture of the setup from my description, if I can find a pic anywhere I'll link it for you.....Bye for now, OZ.

[Manxmodder]

NeoTech, check out this photo of the disc valve Konig 500 GP motorcycle engine and you can see the belt path
 I am trying to explain in my earlier post.

I have seen better examples of this type of drive on other disc valve engines,such as Helmut Fath's flat four 2 stroke,though I'm not yet seeing a decent photo of that arrangement.

The flat or face spiral cutting setup you're trying to achieve  would be really useful for cutting a scroll plate for a 3 jaw chuck.....OZ

http://www.odd-bike.com/2013/04/konig-500-gp-outboard-powered-underdog.html

[NeoTech]

thats one odd belt setup... damn

and yeah what im trying todo could be used cutting a scroll plate aswell.

[Manxmodder]

Neo,it is an odd looking setup and the first time I ever saw it used was on an experimental TZ 700 Yamaha sidecar engine built by well known sidecar builder and racer Trevor Ireson showed me in the early 80's.
He had a very trick design that used one rotating disc valve at the cylinder manifold interface to control the inlet opening/closing times of 2 adjacent cylinders(the disc mounted on an shaft at a point between the 2 cylinders).

Originally he started with just the 2 discs mounted on 2 seperate shafts controlling all 4 inlet ports.

Later he improved by employing a design of Helmut Fath's another famous sidecar builder and vastly talented engineer who scratch designed and built world beating 2 stroke and 4 stroke race motors,Google URS engine for more on that.

Fath's design employed 2 coaxial contra rotating disc valves on the same shaft which effectively doubled the port opening/closing speed hence allowing for greater degrees of opening dwell in relation to piston travel/crank rotation and controlling port timing very accurately.

Ireson's later improved design merely added another 2 discs coaxial with the first pair and a second drive belt from the opposite end of the crank took care of the contra rotation bit.

The net result was greater torque and flexibility of power band with port timings which gave big horse power higher up the rev range.

Do you think you might consider using this type of belt drive to achieve your requirement?

Keep me posted on any further developments re powered rotary table project.

Hope that didn't bore you too much, Bye for now.....OZ.

[NeoTech]

Well my approach was to mount a gear on the turn handle axle out of the table, having a idlear gear that mesh with somekind of worm gear box, a shaft that connects to the turn table.. and the turning motion would be calculated through gearing.. But belting would work as well i guess. And belting requires less.. hassle..

[Manxmodder]

Yeah,the toothed belts are available in a wide variety of widths and pitches and they are pretty inexpensive to buy.

The pulleys are also readily available  from a lot of suppliers,but you may want to consider machining your own large toothed pulley that would drive the rotary table.

There are a couple of videos on youtube showing how to cut your own toothed pulleys using a fly cutter in the milling machine.

The other good thing with the belt method is you won't have any backlash like you would with gears.

Maybe you could get a couple of camshaft pulleys from the vehicle breakers just to experiment with......OZ.