pinion cutters

[tk_highlife]

hello, so we just decided to add wheel and pinion cutting accessories to our workshop and we have ordered the sherline tools but we were looking at the cutters in merritts and I like how they recommend modules for different clocks but I realized that they do not offer a 7 'tooth' pinion cutter which I think is really odd as 7 leaf pinions are one of the most common. So I was wondering if anyone knew where I should buy a 7 leaf cutter other than straight from Thornton's and if you could recommend a module for American and English long case clocks. We can order different cutters in the future, we are just looking to start a base at a good price and not break the bank on just one cutter.

Oh I was also considering the reliability of the single tooth cutters and wondering if they come in pinion cutters.

any help would be much appreciated thank you

 

[Max Phillips]

I'm afraid I can't be of much help, but I would like to mention that fly cutting pinions isn't generally recommended (though I'm sure you could make it work with the right setup). There are some multi-tooth cutter styles that aren't too difficult to make in the home workshop, so perhaps that would be an option for the pinion cutter you need. If you haven't a copy of "Wheel & Pinion Cutting in Horology", I highly recommend picking it up, it should set you up to be able to make your own cutters of various types, as needed.

 

[Jerry Kieffer]

I'm afraid I can't be of much help, but I would like to mention that fly cutting pinions isn't generally recommended (though I'm sure you could make it work with the right setup). There are some multi-tooth cutter styles that aren't too difficult to make in the home workshop, so perhaps that would be an option for the pinion cutter you need. If you haven't a copy of "Wheel & Pinion Cutting in Horology", I highly recommend picking it up, it should set you up to be able to make your own cutters of various types, as needed.

Max
Actually, (No disrespect) I can think of no reason not to use home shop constructed single point cutters of practical design for either wheels or pinions. On the other hand, I can think of several reasons not to use home shop constructed multi- tooth cutters on either.

First, in the home shop it is generally not practical to duplicate the HSS alloy`s/hardening/tempering/cutting ability/toughness achieved by manufacturing techniques. However, this in part can be off set with properly designed single point cutters that can be quickly/easily sharpened razor sharp before each use.
Sharpening multi-tooth cutters so that all teeth cut equally requires expensive grinding equipment not normally part of a home shop. It is doubtful that common quick grinding setups will achieve required accuracy rendering a multi-tooth cutter into a single tooth cutter. Or at least not in my experience.

In addition, multi-tooth cutters are very time consuming to make compared to the 15-20 minutes of a single tooth cutter on a milling machine.

Commercial multi tooth cutters are very efficient when used in a commercial manufacturing setting under flood coolant requiring far fewer time consuming setups for replacement.

Steel Pinions are of course far tougher to cut than brass wheels. When using constructed single point cutters for this application, I generally machine about 80-85 percent of the cavity before using the cutter as a final form tool. This is easily and quickly done with an Endmill or slitting cutter in a Mill since the number of pinion leafs is minimal. For this type work, a properly designed quality rotary table is far more accurate and efficient than index plates.

Jerry Kieffer

 

[Max Phillips]

Max
Actually, (No disrespect)

None taken - we're all in this together, as they say. As a hobbyist, I'll often have a much different (and frankly, often much less valuable to any of the professionals on here) perspective on things. My usual choice is "make it or do without", whereas if I was doing this for a living I would make monetary investments to save my time.

I can think of no reason not to use home shop constructed single point cutters of practical design for either wheels or pinions.

I think it would work fine with correct set up as well, my point was simply that it isn't generally recommended. Most of the literature I have read has advised multi-tooth cutters for steel pinions. Personally I only put so much stock in theory and academics. I take such recommendations into consideration, and then typically set out to test them myself. I've done enough fly cutting to feel that I understand the caveats given, and I do believe they're completely manageable if the operator is aware of them.

Sharpening multi-tooth cutters so that all teeth cut equally requires expensive grinding equipment not normally part of a home shop. It is doubtful that common quick grinding setups will achieve required accuracy rendering a multi-tooth cutter into a single tooth cutter. Or at least not in my experience.

I have made "quick and dirty" (plain relief, rather than form relief) multi tooth cutters that I agree would be pointless trying to sharpen, and would even be pointless to spend time making when a single point fly cutter would suffice.

With a form-relieved cutter, providing that the teeth are all sharpened evenly, it should be fine though. But as you say the trick is ensuring that they are sharpened evenly. It would be my own personal inclination to make a simple fixture for sharpening by machine. Part of the thrill of all this, for me, is learning simpler, traditional techniques for producing accurate precision work, without the use of expensive tooling and equipment, and learning how to make a lot of your own tooling at the same time. That is my amateur hobbyist perspective coming through. To me this type of cutter seems like the approach to use if you want to make a nice cutter that you'll use often. But perhaps future experience will lead me to conclude otherwise.

In addition, multi-tooth cutters are very time consuming to make compared to the 15-20 minutes of a single tooth cutter on a milling machine.

Very true, I suppose it's up to the individual to determine whether the trade-off is worthwhile. If I'm having to feed by hand (for example, I have no power feed on my mill yet, whereas my lathe has power feed on both axes), I certainly prefer using multi tooth cutters for any task (not just gear cutting). Those rare occasions that I've been able to set up a single point fly cutting task on my lathe, the power feed makes it a worry-free operation (well, almost worry-free).

Steel Pinions are of course far tougher to cut than brass wheels. When using constructed single point cutters for this application, I generally machine about 80-85 percent of the cavity before using the cutter as a final form tool. This is easily and quickly done with an Endmill or slitting cutter in a Mill since the number of pinion leafs is minimal. For this type work, a properly designed quality rotary table is far more accurate and efficient than index plates.

That's an excellent idea, about pre-machining the profile. According to what I've read so far, many of the caveats with fly-cutting steel pinions are work piece flex, and smoothness of cut. The former can be corrected, if nothing else, by extra support being given to the work (one example in the book I've mentioned actually shows supporting the pinion being cut with a tiny screw jack from underneath). A little ingenuity is really all that's needed there, I suppose. The latter isn't really much of an issue in my opinion, especially if you can use power feed.

 

[Jerry Kieffer]

None taken - we're all in this together, as they say. As a hobbyist, I'll often have a much different (and frankly, often much less valuable to any of the professionals on here) perspective on things. My usual choice is "make it or do without", whereas if I was doing this for a living I would make monetary investments to save my time.



I think it would work fine with correct set up as well, my point was simply that it isn't generally recommended. Most of the literature I have read has advised multi-tooth cutters for steel pinions. Personally I only put so much stock in theory and academics. I take such recommendations into consideration, and then typically set out to test them myself. I've done enough fly cutting to feel that I understand the caveats given, and I do believe they're completely manageable if the operator is aware of them.



I have made "quick and dirty" (plain relief, rather than form relief) multi tooth cutters that I agree would be pointless trying to sharpen, and would even be pointless to spend time making when a single point fly cutter would suffice.

With a form-relieved cutter, providing that the teeth are all sharpened evenly, it should be fine though. But as you say the trick is ensuring that they are sharpened evenly. It would be my own personal inclination to make a simple fixture for sharpening by machine. Part of the thrill of all this, for me, is learning simpler, traditional techniques for producing accurate precision work, without the use of expensive tooling and equipment, and learning how to make a lot of your own tooling at the same time. That is my amateur hobbyist perspective coming through. To me this type of cutter seems like the approach to use if you want to make a nice cutter that you'll use often. But perhaps future experience will lead me to conclude otherwise.



Very true, I suppose it's up to the individual to determine whether the trade-off is worthwhile. If I'm having to feed by hand (for example, I have no power feed on my mill yet, whereas my lathe has power feed on both axes), I certainly prefer using multi tooth cutters for any task (not just gear cutting). Those rare occasions that I've been able to set up a single point fly cutting task on my lathe, the power feed makes it a worry-free operation (well, almost worry-free).



That's an excellent idea, about pre-machining the profile. According to what I've read so far, many of the caveats with fly-cutting steel pinions are work piece flex, and smoothness of cut. The former can be corrected, if nothing else, by extra support being given to the work (one example in the book I've mentioned actually shows supporting the pinion being cut with a tiny screw jack from underneath). A little ingenuity is really all that's needed there, I suppose. The latter isn't really much of an issue in my opinion, especially if you can use power feed.

Max
For the benefit of those less experienced, I would like to further explain even though this discussion is only scratching the surface


In the NAWCC Wheel and pinion workshop, students are required to machine a single point cutter , harden it, sharpen it and cut both a wheel and pinion. Upon completion, tooth form quality and finish are compared to teeth that are cut with commercial multi tooth cutters during demonstrations. Rarely will the single point cutter not equal or exceed the surface finish/tooth form quality of the commercial cutters. No special supports or power feeds are used nor would they benefit the machining of the cutter or cutting of a wheel or pinion. Of course the use of CNC for either is separate discussion.

If one is building a movement or mechanical devise from bar stock, one would normally purchase matching commercial wheel/gear/pinion cutters normally multi-tooth from the same manufacturer assuring proper friction free operation.

However in the repair of Horology, it is very rarely that simple.
For any given calculated module, there will be dozens of various tooth forms. When cutting a replacement wheel or pinion with commercial cutters, it would be rare if the tooth form matched the tooth form of an existing horological wheel or pinion. Fortunately, in many cases even though slightly different, they will function but not always. However in most cases, the different tooth forms are readily visible. While of no concern in an inexpensive movement, they may be unexceptable in a collectable movement.

As covered in class, single point cutters are machined to match the tooth profile of the wheel or pinion to be replaced. Since the exact profile/module may or may not ever be encountered again, a successful repair person cannot afford to spend extra time on a more complicated cutter with no advantage.



As I have mentioned before, this sort of thing must be experienced to be understood and evaluated.

Jerry Kieffer

 

[Max Phillips]

Great info as usual, Jerry!

 

[karlmansson]

I'm trying to plan my next steps in tool acquisition and such and this is a great read! My biggest fear so far has been pinion cutting as the cutters are pretty pricey to say the least.
I've read what Daniels has to say on the subject in Watchmaking and I'm getting Wheel and Pinion cutting in a forseeable future. The problem as I gather it is flex in the workpiece, as you say Max, but also limited room for a flycutter to get down between the centers that are required to hold the pinion blank in place. Daniels has a design for an impromptu dividing head for pinion blanks that seems to leave a little bit more room.

Do you think the same results could be achieved cutting steel pinions for watches, as well as clocks as I understood the initial discussion was about?

Best

/Karl

 

[Jerry Kieffer]

I'm trying to plan my next steps in tool acquisition and such and this is a great read! My biggest fear so far has been pinion cutting as the cutters are pretty pricey to say the least.
I've read what Daniels has to say on the subject in Watchmaking and I'm getting Wheel and Pinion cutting in a forseeable future. The problem as I gather it is flex in the workpiece, as you say Max, but also limited room for a flycutter to get down between the centers that are required to hold the pinion blank in place. Daniels has a design for an impromptu dividing head for pinion blanks that seems to leave a little bit more room.

Do you think the same results could be achieved cutting steel pinions for watches, as well as clocks as I understood the initial discussion was about?

Best

/Karl

Karl
In regard to cutting watch pinions.

Personally, I have found mounting watch parts in tiny centers to be unstable and inaccurate where the stresses of machining are required. Not to mention tension effects and possible alignment inaccuracy.
The most critical things that I have found for this type of work is work piece strength for the machining process and clear optical observation of the machining process

Again personally, my method of cutting watch size pinions covers these concerns as follows.


(1) The work piece is setup mounted in a rotary table facing forward in a milling machine per first attached photo.

(2) The pinion OD and length is machined on the tapered end of a .375" diameter work piece and mounted in the rotary table per the second photo. This provides maximum strength possible while machining the pinion leafs without the effects of center tension and other effects on accuracy.

(3)This mounting method also provides single point cutter clearances without issue. Mounted cutter third photo.

(4) Forward mounting of the work piece provides a very clear unobstructed optical vision of the machining process with Machine mounted Microscope per fourth photo.

(5) Once the pinion has been cut , then the length of the arbor is machined in the mill the same diameter as the pinion before parting off. This is done by rotating the R/T and moving a Endmill over the length of the arbor using the "Z" axis to control diameter.

(6) Once the arbor has been cut to length, it is then moved to the lathe for final machining to size. Again it is not placed on centers that avoids a lot of issues. When transferring a machined part from where ever to lathe centers, you now have center/mounting/spindle inaccuracy with little course of correction. However, if the work piece is mounted in a WW collet with the spindle collet position pin removed, corrections are easily and quickly dealt with. With the pin removed, you can rotate the work piece in the collet and rotate the collet in the spindle until inaccuracy off sets its self providing a greater level of accuracy.

Please note that in this discussion the use of centers is in reference to watch size parts. For much large work, the use of centers has proven to be highly effective.


Jerry Kieffer

 

[Jim DuBois]

What one may conclude in reading Jerry's detailed note (thanks again Jerry) is that cutting very small pinions successfully is (in my opinion at least) substantially more difficult than cutting larger pinions. Much harder to see what is happening even with a stereo microscope, machine tolerances come more into play, there are limited options on how to hold the material/how to finish the material etc. as well as one will need an optical comparator to effectively evaluate finished tooth profiles and the like. Since I never got into watches I seldom cut really small pinions but I have cut some as small as .050" and I would rather cut several tower clock pinions at 1" or more in diameter than another pinion at .050". .......those at .025" and smaller amaze me, particularity when finished with a high polish etc......

 

[Jerry Kieffer]

What one may conclude in reading Jerry's detailed note (thanks again Jerry) is that cutting very small pinions successfully is (in my opinion at least) substantially more difficult than cutting larger pinions. Much harder to see what is happening even with a stereo microscope, machine tolerances come more into play, there are limited options on how to hold the material/how to finish the material etc. as well as one will need an optical comparator to effectively evaluate finished tooth profiles and the like. Since I never got into watches I seldom cut really small pinions but I have cut some as small as .050" and I would rather cut several tower clock pinions at 1" or more in diameter than another pinion at .050". .......those at .025" and smaller amaze me, particularity when finished with a high polish etc......

Jim
Actually Micro machining is not difficult if a few key things are kept in mind.

(1) You must be able to think for yourself. If a procedure or setup does not make sense, its probably not effective regardless of by who or how long it has been used.

(2) You must Have equipment of quality and versatility capable of placing you at the greatest advantage regardless of what needs to be done. You need to understand that Horological machining is done the same way everything else in the world is machined. Concentrate on what needs to be done regardless of where useful info may come from.

(3) You must have quality Optics with setups that allow clear observation of the machining process. In the case shown in my last post, the Microscope is tool mounted and rotates 120 degrees while remaining in focus at all times. This allows one to view at various angles hands free during the machining process giving far greater advantage than non tool mounted.
Quality Optics will allow you to visually position cutting tools far more accurately than by measurement on micro work pieces. In addition, if you make a pinion look like it is one inch in diameter, it will be no more difficult to machine than an actual one inch pinion.

(4) You never strain your back and you have fewer chips to clean up.

Jerry Kieffer

 

[karlmansson]

Nice!
As you might recall Jerry, I've seen your setup before and we've had a similar discussion but with wheels . Good to hear the same principles apply! I'm inspired by your setup and will try to construct something similar when I get the chance. Sherline just so happens to have an agent in Sweden but the prices are a little out of my league at the moment. I see that you have their rotary table with the stepping motor attachment. Does that provide any advantage when performing a task like this?

I also noticed that the shank of the cutting tool is protruding a bit on the other side but judging from the other pictures I assume this was just put together for demonstrational purposes?

The method of using much larger diameter stock to produce the taper to hold the piece seems like something of a waste of material but maybe that is necessary? The number of parts produced in this way won't be great so maybe that's of lesser concern?

Best

/Karl

 

[Jerry Kieffer]

Nice!
As you might recall Jerry, I've seen your setup before and we've had a similar discussion but with wheels . Good to hear the same principles apply! I'm inspired by your setup and will try to construct something similar when I get the chance. Sherline just so happens to have an agent in Sweden but the prices are a little out of my league at the moment. I see that you have their rotary table with the stepping motor attachment. Does that provide any advantage when performing a task like this?

I also noticed that the shank of the cutting tool is protruding a bit on the other side but judging from the other pictures I assume this was just put together for demonstrational purposes?

The method of using much larger diameter stock to produce the taper to hold the piece seems like something of a waste of material but maybe that is necessary? The number of parts produced in this way won't be great so maybe that's of lesser concern?

Best

/Karl

Karl
You are correct in that the Mill and other items were handy on the bench so the quickie photo`s were for illustration purposes.

The Rotary table is the stand alone Sherline CNC unit that is very helpful. However in this case, the manual unit would do the same job.

3/8" diameter drill rod about 1.5" long costs about .30 cents or almost nothing. However if it were a 100 times that cost, it would still be a great bargain to have the part come out right the first time.

Jerry Kieffer

 

[karlmansson]

Alright! Thanks again Jerry!

I didn't mean to point out any errors or anything about the tool holder, I'm just trying to work out how to make my own. I've been looking to make something I think I found online which is an arbor with a plate that screws in from beneath to clamp the tool bit in place. That one had two tool slots though, one centered and one offset, and was intended to be used together with a button form tool. Yours looks simpler and sturdier. Think I'm going to go with something similar!

I was just curious as to why you would have the rotary table CNC equipped but not the X-Y.

Good point!

/Karl

 

[Jerry Kieffer]

Alright! Thanks again Jerry!

I didn't mean to point out any errors or anything about the tool holder, I'm just trying to work out how to make my own. I've been looking to make something I think I found online which is an arbor with a plate that screws in from beneath to clamp the tool bit in place. That one had two tool slots though, one centered and one offset, and was intended to be used together with a button form tool. Yours looks simpler and sturdier. Think I'm going to go with something similar!

I was just curious as to why you would have the rotary table CNC equipped but not the X-Y.

Good point!

/Karl

Karl
You did not point out an error, but pointed a logical constructive concern that I should have explained.

Jerry Kieffer

 

[John MacArthur]

(2) The pinion OD and length is machined on the tapered end of a .375" diameter work piece and mounted in the rotary table per the second photo. This provides maximum strength possible while machining the pinion leafs without the effects of center tension and other effects on accuracy.

Jerry Kieffer

Hi Jerry -- I guess I must be missing something pretty simple. What is holding the 3/8" rod in the center hole of the rotary table? I have a setup like that, and have always made little fixtures to hold stuff. This looks good and solid, but I can't see what is holding the rod in place. It also looks like you might have a little piece of feeler gage stock wrapped around it, to center it? jamb it in?

Thanks for all your explanations.

Johnny

 

[karlmansson]

If I remember correctly, Jerry threads his stock to fit the center thread of the rotary table.

 

[Jerry Kieffer]

Hi Jerry -- I guess I must be missing something pretty simple. What is holding the 3/8" rod in the center hole of the rotary table? I have a setup like that, and have always made little fixtures to hold stuff. This looks good and solid, but I can't see what is holding the rod in place. It also looks like you might have a little piece of feeler gage stock wrapped around it, to center it? jamb it in?

Thanks for all your explanations.

Johnny

John
Actually a very good question. One of the first things that should be considered when purchasing equipment/accessories is how work pieces will be mounted. If it is difficult to mount work pieces, equipment and accessories are of little use.

In this case the rotary table has a threaded center hole and centering register for mounting a chuck adaptor.
This makes mounting various work holding items such as a arbor/pinion stud very easy and simple.
While the centering register generally exceeds accuracy required for clock work, it generally is not accurate enough for watch work or micro machining. In this case the pinion blank is machined center to the R/T rotation by machining its final diameter after fitted to the R/T using a Endmill as described.

Jerry Kieffer

 

[karlmansson]

I'm trying to wrap my head around this... The milling for truth, is that performed with the rotary table in the place it is intended to be in when milling the pinion teeth or with the RT place flat on the cross slide so that the stock is parallel with the endmills length?

If the endmill is at 90 degrees with the stock, I'm thinking milling it in the round would be pretty complex, getting an even surface when having to rotate the RT and mill in the Y-axis at the same time. Maybe I'm missing something.

Best

/Karl

 

[Jerry Kieffer]

I'm trying to wrap my head around this... The milling for truth, is that performed with the rotary table in the place it is intended to be in when milling the pinion teeth or with the RT place flat on the cross slide so that the stock is parallel with the endmills length?

If the endmill is at 90 degrees with the stock, I'm thinking milling it in the round would be pretty complex, getting an even surface when having to rotate the RT and mill in the Y-axis at the same time. Maybe I'm missing something.

Best

/Karl

Karl

If I understand your question, the end mill is 90 degrees and centered to the work piece per the attached sketch.
Both the end mill and work piece rotate at the same time. ID is controlled by end mill depth per the "Z" axis. Length of the ID cut is controlled by moving the end mill the length of the work piece or the "Y" axis.

In CNC mode the R/T is set to rotate in continuos motion. In manual mode, the end mill is set to take a "Y" axis cut and then the R/T is rotated 360 degrees. This is repeated until the desired length of cut is achieved. Or whatever way works best.

Jerry Kieffer

 

[karlmansson]

Aah, now I get it. For some reason I was picturing the endmill being smaller and the side face of it being used. Thanks for the explanation!

Best

/Karl

 

[dshumans]

I have been able to make steel watch pinions on an antique Geneva style lathe with an index plate and a pinion cutter blade mounted on a simple milling attachment to my cross slide. Pictures are of a 32mm steel rod being cut first, then machined after cutting to make pinions or center hole. Correct cutting speed, oil and slow movement of the cross slide are important to getting a smooth leaf finish. The antique pinion cutters were from a Waltham shop and they cut the profile of one side of two leafs at once. Selection of the cutter size is critical to the pinion size and leaf count.

Doug