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ZK worm parameters
5

ZK worm parameters

ZK worm parameters

(OP)
Hello,

I am working with an existing software application that generates dressing programs for different types of threads and worms and I have been asked to look into its support for ZK type worms.

I have been reading up the documentation we have on this (sadly some of it appears to have been lost when the company has moved offices over the years) and I've found some research papers on the internet which have given me some assistance so far, for example, "ZK-Type Dual-Lead Worm and Worm Gear Drives: Geometry" by B-W Bair and Professor C-B Tsay from the Transactions of the ASME journal in September 1998, along with a copy of the DIN 3975 standard that has helped and a few of the internal design notes.

The application I'm working with does ask for some standard values such as tip (OD) diameter, reference (pitch) circle diameter, root diameter, helix angle, whether it's a single- or dual-lead worm, whether it's right- or left-hand worm and the lead.

It does ask for some data about the generating tool: pressure angles, helix angle, tip & root fillet radii, tip width and tip diameter.

I was wondering if anyone would be able to guide me on what data would be provided on a schematic for a ZK worm please?

Many thanks,

Richard Watt

RE: ZK worm parameters

(OP)
I'd just like to add to my initial post since I've found some more information since then: we've received a sample drawing from a customer of a ZK worm part which now gives me an idea of one possible set of data that could be provided (I've put the DIN 3975 symbol after each item):

  • Number of teeth (z1)
  • Normal module (mn)
  • Normal pressure angle (αn)
  • Hand (left/right)
  • Lead angle (γ)
  • Reference diameter (dm1)
  • Tip diameter (da1)
  • Root diameter (df1)
  • Tip radius (ρa1)
  • Root radius (ρf1)
I can then calculate the following from the above:

  • Axial pressure angle (αx)
  • Axial pitch (px)
  • Axial module (mx)
  • Lead (pz1)
From my reading of the DIN 3975 standard, the minimum data required to "define the worm flank form beyond all doubt" are:

  • Milling/grinding cutter diameter (d0)
  • Worm parameters:
    • Number of teeth (z1)
    • Module (m)
    • Reference lead angle (γm)
  • Or:
    • Reference diameter (dm1)
    • Angle of generation (α0)
This standard also mentions that as the cutter diameter (d0) increases, then the ZK worm approximates more and more to the ZI form, which we already have working in our application, and as the value of d0 decreases, then the ZK worm approximates more and more to the ZN form, which we also have in our application: if I knew what the value of d0 where this changeover occurs was, I could then have our application use the ZI or ZN code according to the value of d0.

I would like to now calculate the (X,Y) coordinates for the set of points that define the ZK tool and worm profiles and was wondering if anyone knows how this would be done please?

RE: ZK worm parameters

All that you have written above seems to be right to me.

Quote (OP)

I would like to now calculate the (X,Y) coordinates...
apps.dtic.mil/dtic/tr/fulltext/u2/a239134.pdf
Page 324.
Might be reasonable to get a newer edition of this book.
I could calculate the profile coordinates based on your example numbers, so we could see if the results match.

RE: ZK worm parameters

Richard
typically worm gears have to be cut with a hob that has the same attributes of the worm. an a master worm is used to inspect pattern and center distance. the hob will be slightly larger than the worm.
typically a worm if single thread will be machined like a thread, if dual lead can then be machined as a helical gear. there are many ways to machine the worm, single point on a lathe, thread grind or hobbed.
if it is dual lead it can be inspected with 2 wires, a single lead requires three wires. important to under stand the mfg method used. a worm and worm gear must be machined as a set to control pattern and
center distance. here a short paper from gear technology.
https://www.geartechnology.com/issues/1013x/worm_g...

RE: ZK worm parameters

(OP)
Hi everyone,

Apologies for being away from the thread for a while: we've managed to find a ZK worm drawing submitted to us by a customer so I've been using that to help me.

spigor: what data would you need in order to calculate the profile coordinates please?

mfgenggear: I do have a number of papers and a copy of the book suggested by spigor, and I did save a copy of that article. Unfortunately, I am flying a little bit blind on this as my predecessor did include ZK worms but the documentation he left seems to be incomplete (and there have been at least 2 office moves since he was here), and we're trying to verify it.

I have been making some progress using the customer-provided drawing as test data - I'll dig it out and add the parameters it lists later on.

RE: ZK worm parameters

Usually:
-number of starts of the worm,
-reference diameter of the worm,
-lead angle on that reference diameter (or/and axial pitch/axial module - with the lead angle redundant but helpful for checking),
-axial tooth thickness on that reference diameter,
-major and minor diameters of the worm,
-profile angle (also called pressure angle),
-tool diameter.

RE: ZK worm parameters

Richard

I am a little confused so bare with me, what type of machine are you trying to program? why would you need the profile coordinates?
are you trying to mill these? Like I said in the previous post worms are single pointed cut with a standard tool.
like cutting a thread, based on the pitch held by the machine and the angle & geometry is on the tool, it chases the worm like 7 or more passes. it would help immensely
to know the manufacturing method and inspection method, for instance a CMM vs cnc gear checker. most gears are now done with a cnc gear checker.
is this a one only or low production, or a medium to high production. for a higher AGMA class a worm must be ground as a thread.
the worm profile is held by the tool. similar would be like cutting a rack. example would be 20 deg. pressure angle except straight sided.
a worm can be hobbed, but it's produced by the tool geometry also. so generally a grinding tool would be dressed but now a days it is pre programmed and
the pertinent data is imputed to the cnc controls. # teeth or starts, pressure angle, lead angle and so on. so what are the required inputs for your machine,
and does it have to be cad/cam post to get the machine code to generate the tool?

RE: ZK worm parameters

The method used to cut the worm, either a single point tool squared to the workpiece, single point tool tilted at the lead angle, milled, hobbed, or with a grinding wheel with the grinding wheel tilted at the lead angle will produce different profiles of the worm tooth. It's the "generating" action of the cut and the fact that the cutting tool has a different lead angle along the profile (tooth root to tooth tip). The grinding wheel diameter will make a difference in the profile of the tooth. The effect is more pronounced for larger lead angles.

You can produce a straight sided worm with a grinding wheel that has a not straight sided profile. I'd guess the OP is designing software to control the profile of the dressing of a grinding wheel or maybe maybe for a gear tooth profile measurement machine.

RE: ZK worm parameters

Brian
It is true, with cnc controls the dressing of the wheel is done automatically. And slight adjustments can be by tilting the wheel while dressing. I basically grew up with old style mechanical dressing where as engineering had to produce the data settings for the machinist to set up his or her machine. However the formulas were supplied by the manufacturer. With the new cnc dialog input all the data is easier. All they have to do is input the gear data. Or worm data. Bow a days there is software out there that can generate an exact gear profile. Within .0001 inch. Trying to recall a good book for that. Buckingham had good formulas, as well as vogel

RE: ZK worm parameters

In case of the ZK form some geometrical correlations tend to get more complex than for the ZN and ZI forms. I believe that the OP wants to calculate the grinding wheel's profile to grind the ZK form. The grinding wheel's diameter can be much different from the milling cutter's diameter. The profile of the wheel should compensate for that, as well as for the changes of the grinding wheel's diameter after each profiling. On the other hand, I haven't seen a tool diameter specified on a drawing. If no tool's diameter is specified on the drawing, ZI form could be used. Is it really necessary to use the ZK form? Is there the tool's diameter specified on the part drawing?

RE: ZK worm parameters

spigor

almost never is a wheel diameter called out on the drawing. sometimes the wheels have to be dress to remove interference. usually done with single point diamonds like an od grinder.
if that is the case OP needs the tooth space width, but correct me if I am incorrect a worm is like a rack straight sided. only pressure angle is required with the correct tooth space thickness.
it should be easily drawn with cad. and like autocad with a lisp command, I am not a solid works guy but I believe it has a rack and spur gear module. I know freecad does but I don't know how accurate it is.
what actually corrects the geometry is the machine when it interpolates the circular or axial pitch.

RE: ZK worm parameters

also as long as the worm and worm gear are cut with the same geometry and are made as a match set that is what is important, unless it is cross axis helicals.

RE: ZK worm parameters

mfgenggear

The ZI and ZK forms are not straight sided in no plane. In case of ZK the tool is disc shaped, in case of ZI it can also be thought of as a disc cutter with large diameter. That tool is tilted at a specific angle. That lead angle is specified on the reference diameter of the worm, but on every other diameter the angle of a helix is different from the lead angle. So e.g. at the tool tip the angle of the helix is different from the tool tilt angle. The tool will therefore cut outside the normal plane, as governed by the laws of conjugated surfaces. So in case of the ZK form the profile in the axial plane is dependent on the tool diameter. If this diameter is not called out on the drawing, ZI form could be assumed for safety. But in case of higher lead angles the difference between ZI and ZK as cut with a milling cutter could be big enough to cause manufacturing problems - uneven stock, long grinding times etc., and it doesn't look very professional. That might explain why the OP wants to calculate the ZK profile exactly. He could then calculate the profile corrections for the wheel to grind the exact shape no matter the wheel diameter.

RE: ZK worm parameters

(OP)
mfgenggear,

spigor is correct in that I wish to calculate the grinding wheel profile for a ZK worm as the application generates the NC dressing program to do that based on the worm data entered by the user.

Our application runs on a Siemens 840D sl machine's PCU and generates these dressing programs - it can also be run on a laptop or desktop PC.

Richard

RE: ZK worm parameters

(OP)
Hi spigor,

Thank you for getting back to me - I'm sorry I haven't been on the forum for a few days as I'm currently working on this flexible furlough rota and I'm not allowed to do any work on the days I'n off (the UK government is checking and has already taken a few people to court for breaking this law).

The worm parameters we have are as follows:

Number of starts: 2
Ref diameter: 18.2367 mm
Axial pitch: 7.6635 mm
Axial tooth thickness: we don't have the PLT for this worm, but we have the measuring wire diameter as 5.0000 mm and the size over the wires as 23.0000 mm
Major & minor diameters: the tip diameter is 23.0000 mm and the root diameter is 11.3.000 mm
Profile (pressure) angle: 15.0000 degrees
Tool diameter: we have a tool tip diameter of 200.0000 mm

The worm is a dual lead left-handed thread

Please let me know if you need any other details.

Best regards,

Richard

RE: ZK worm parameters

Hi Richard
I was under the impression that the idea is that you would calculate the profile coordinates first, what would possibly bring answers to many of your previous questions, and I double-check your results afterwards. But tables have turned, so for now I need to clarify as follows:
1. Should the x,y coordinates be calculated? That implies points on a plane - an axial plane, or a plane perpendicular to the axis?
2. Or maybe it is the tool's profile in its normal plane that should be found? If the tool tip diameter is 200 mm then what is the ZK form tool diameter? If it is also 200 mm, then this profile would simply be a straight sided reference profile with nothing to calculate.

RE: ZK worm parameters

(OP)
Hi spigor,

Sorry, that's my misunderstanding - I'm still working on the ZK profile calculation code we have as I can't get a full set of profile coordinates myself just yet.

  1. We calculate the X, Y coordinates for the worm profile on the axial plane.
  2. The application has a "tool tip diameter" parameter - I've been trying to work out if this refers to the actual tip diameter of the tool or the cutter diameter mentioned in the DIN 3975 standard but I've had no luck yet.
So I've tried to work out the tool (cutter) diameter as follows:

  • Worm tooth depth = 5.8500 mm
  • Worm tip-Worm ref = (23.0000 - 18.2367) = 4.7633 mm
  • Worm ref-Worm root = (18.2367 - 11.3000) = 6.9367 mm
  • Tool tip diameter = 200.0000 mm
  • Tool diameter (cutter diameter) = 193.0633 mm
I remembered I do have a set of profile coordinates already calculated and saved to a formatted text file: I'm having some issues attaching it from my work computer, so I'll have to attach it when I get home.

The code calculates the tool profile first and then uses coordinate transformations to calculate the worm profile from the tool profile, but the root point on the worm is about 0.5 mm higher on the Y axis (radius = 6.3912 mm) than where I think it should be (radius = 5.8500 mm).

It does add the tip and root fillet radii arcs in later once it's adjusted the profile to meet the 3-wire or caliper measurement criteria.

I was also wondering if anyone has used the MITcalc tool to help design a ZK worm (I do have a trial version at home that I can reinstall and put the parameters into to see what that provides)?

I apologize for drip-feeding information as I don't want to overload the thread with too much information (as sometimes I post stuff that isn't relevant to what I'm asking about).

Many thanks,
Richard

Edit 10/04/2021 18:59 BST: attached the ZK worm profile coordinates file I mentioned earlier for spigor's reference.

RE: ZK worm parameters

Guys I had to take dog to the vet,
So I not at home.

please provide the lead, diametral pitch
And helix angle.
Thanks

RE: ZK worm parameters

(OP)
Hi mfgenggear,

The lead is 15.3270 mm for both leads (since it's a dual lead worm) and the helix angle is 14.9770 degrees.

I had a little trouble with the diametral pitch as I googled the formula and I found one on Engineers' Edge (https://www.engineersedge.com/gears/worm_gear_form...), but the description and formula in their table is a little confusing:

The description says that you use Worm Lead = "3.1416 / Diametral Pitch * Number of Threads on Worm", but the formula is written as "Worm Lead = 3.1416 * Diametral Pitch Number of Threads on Worm".

I tried rearranging this to get the diametral pitch, but I was getting a value of around 0.4, which doesn't seem right to me.


I do, however, have the axial pitch, which is 7.6635 mm, if that helps?

Thanks,

Richard

RE: ZK worm parameters

2
Here's a fat read which may be of more general interest; no idea if it applies to ZK worms in particular, but it looks like good background info. https://core.ac.uk/download/pdf/153776393.pdf 191 pages.

RE: ZK worm parameters

3DDave
that is a great find. star for you my friend

excerpt from the white paper

Figure 1.4 Schematic of Cylindrical and Globoidal Worm Gear Pairs
ZA: straight sided axial profile
Convolute heiicoid ZN: straight sided normal profile (straight line generator) (slightly concave axial proflie)
ZI : Involute helicoid
ZK: milled helicoid
Single-enveloping (no straight lines anywhere. conical cutter with
(cylindrical) straight generators)
wormgear drives
ZC1: circular arc profile on
worm grinding wheel
ZC ZC2: circular arc profile in
(circular arc generator) worm normal section
ZC3: circular arc profile In
worm axial section
Typel: worm profile has straight generators(straight line blade)
Double-enveloping Typet: worm profile has straight generators(piane grinding wheel) [gioboidan
wormgear drives
Type3: worm Is generated with conical cutterigrinding wheel

RE: ZK worm parameters


RichardWattMatrix (Computer)(OP)11 May 21 07:16
Hi mfgenggear,

The lead is 15.3270 mm for both leads (since it's a dual lead worm) and the helix angle is 14.9770 degrees.

I had a little trouble with the diametral pitch as I googled the formula and I found one on Engineers' Edge (https://www.engineersedge.com/gears/worm_gear_form...), but the description and formula in their table is a little confusing:

The description says that you use Worm Lead = "3.1416 / Diametral Pitch * Number of Threads on Worm", but the formula is written as "Worm Lead = 3.1416 * Diametral Pitch Number of Threads on Worm".

I tried rearranging this to get the diametral pitch, but I was getting a value of around 0.4, which doesn't seem right to me.


I do, however, have the axial pitch, which is 7.6635 mm, if that helps?

Thanks,

RicharD

Hi Richard
is this in fact a ZK worm.
I have software that can create a DXF of the geometry.
Its old software created by a old barber coleman engineer,(software engineering service) he use to design the tool hobs & cutters.
I use to rely on these guys to design and build my custom hobs and cutters.
barber coleman was purchased by Gleason I believe.

yup that is correct
Pi/(DP*#Thds)= L correction oops
or
Pi/Cp = DP
I am forgetting critical data.

So Spigor thanks for that correction on the ZK worm I getting my wires crossed I was quoting ZA
which is straight sided. I gave you a star my friend.

edit so to add to that when I started when there were no computers, so we had to rely on contact pattern, between a master worm, and the worm wheel at a set center distance.
now with software it's easy, same with spiral and zerol bevels. little history but off topic. with the dxf file geometry
should be able to cad/cam post the XY machine code. or take actual XY measurements in cad.


RE: ZK worm parameters

(OP)
Hi mfgenggear,

Yes, it's definitely a ZK worm according to the drawing that we have (it was provided by a customer asking if our machines can grind ZK worms), so I'm not sure if I can share it for confidentiality reasons.

Richard

RE: ZK worm parameters

Richard
do you have center distance?

RE: ZK worm parameters

(OP)
mfgenggear - yes, the value I have for center distance is 105.65 mm.

RE: ZK worm parameters

Richard
ok let's start over my computations on my software are not calculating correct, some thing is wrong
give me all the data for both the worm and worm gear
My software are inputs are in normal, need # of teeth for both worm and gear
normal pressure angle , double check the gear wire and measurement over wires.
normal pressure angle

or give me the transverse data and I will pull my notes to calculate normal.
it should say on the drawing if it is normal or transverse data.
since my inputs are in inches I have to convert from mm to inch.

RE: ZK worm parameters

(OP)
mfgenggear,

The data I have from the drawing we were given is as follows (I only have a drawing for the worm gear itself and not the worm wheel):
  • Worm Type: ZK
  • Number of teeth (Z): 2
  • Normal module (mx): 2.3565
  • Normal pressure angle (αn: 15 degrees
  • Modification coefficient (x): --
  • Hand: left
  • Lead angle (γ): 14.9770 degrees
  • Reference diameter (d): 18.2367 mm
  • Tip diameter (da): 23 mm
  • Root diameter (df): 11.3 mm
  • Tip radius (ρa): 0.25 - 0.45 mm
  • Root radius (ρf): 0.5 - 0.9 mm
  • Dimension over pins (Mdk): 23/683 +- 0.015 mm
  • Best pin (DM): 5.0 mm
The only other information on the drawing are the accuracy and technical requirements, but I don't think they're relevant here.

I'm also going to try using MITCalc on my computer at home to see if I can come up with anything.

Many thanks,
Richard

RE: ZK worm parameters

I have checked the worm data you have provided in the messages above and made some calculations of the macrogeometry, so let's let the numbers speak.

The data in your last message is consistent except for:
-The lead angle should be 14.9772 degrees - just for the record as this has no real life meaning.
-The dimension over Ø5 pins was specified as 23.000 and 23/683. In such case the tips would get pointed way before the Ø23. I suspect that Ø5 is incorrect, as it should be approx. Ø3.85. Please check it and let know what the pin diameter should really be, and what the dimension over pins is - 23.000 or 23.683?

RE: ZK worm parameters

Hi Guys
I am getting the same results as spigor, I have the same questions

MOW
lead angle

My programs were calculating closer but I got funky results on the actual worm geometry.

the Major diameter and the MOW are the same size. the mow measurement will have interference from the gear tip diameter.
I believe the worm addendum and dedendum are incorrect? the whole depth ?
I would recommend to check design with MIT with both worm & gear worm.

Richard please advise if this is a new design from the customer? they may possibly have errors
if not get a sample part if possible to review.

here is a good read on mfg of worms wheel hobs, & worm & worm gears
http://www.tokugawa-gears.com/Hobs%20technology/Wo...
and
https://www.geartechnology.com/issues/1013x/worm_g...

RE: ZK worm parameters

So the results are in Inch
Normal Circular Tooth Thickness = .085185 (based on 23MM ) If posted mow is incorrect, I can input correct mow if necessary.
Ref Diameter (Pitch Diameter) =.7179904
Ref Base Diameter = .4984344
lead = .6034248
root dia. clears the gear wire by .0335
except I did not get pointed teeth I calculated Normal Tooth Thickness at major diameter =.038287 INCH
best wire in english is .178129

RE: ZK worm parameters

I have not run numbers on worm in while.
A standard tooth thickness is .157 inch.
.085 is way to thin, when I get chance I will calculate an mow for this worm.
Now make sure the customer is not given
A measurement over one wire.
We need to calculate over two wires for
Two threads. Even thou it would be preferred with one wire measurement for inspection.

RE: ZK worm parameters

(OP)
Hi mfgenggear and spigor,

Thank you so much for running those parameters through for me: I'm off work today and tomorrow due to the flexible furlough scheme my employer's using, so I've just logged on quickly.

This drawing was submitted to us by a customer making an enquiry (I think as part of a tender/quote request) to see if our machines & software could grind the ZK worm part and it's possible that the drawing is incorrect, like you've said (some of my colleagues have mentioned this as well).

Unfortunately, I don't have any more information on the drawing to hand as I'm at home as I type this so will have to look for some more details (if we have them) when I'm back in the office on Monday.

Richard

RE: ZK worm parameters

How about assuming a realistic tooth thickness and moving forward?

RE: ZK worm parameters

I have taken worm data as follows:
  • Worm Type: ZK
  • Number of teeth (Z): 2
  • Normal module (mx): 2.3565
  • Normal pressure angle (αn: 15 degrees
  • Modification coefficient (x): --
  • Hand: left
  • Lead angle (γ): 14.9772 degrees
  • Reference diameter (d): 18.2367 mm
  • Tip diameter (da): 23 mm
  • Root diameter (df): 11.3 mm
  • Axial tooth thickness on reference diameter: 3.83175 mm
I calculated the worm profiles on the axial plane, as requested - ZN, ZK/D0=200 mm and ZI forms for your reference:

ZN:
x; y; z
0.992899; 5.655016; 0
1.068107; 5.934158; 0
1.143036; 6.213308; 0
1.217723; 6.492466; 0
1.292197; 6.77163; 0
1.366483; 7.0508; 0
1.440604; 7.329976; 0
1.514576; 7.609156; 0
1.588417; 7.88834; 0
1.662139; 8.167528; 0
1.735755; 8.446719; 0
1.809274; 8.725914; 0
1.882705; 9.005111; 0
1.956057; 9.28431; 0
2.029336; 9.563512; 0
2.102548; 9.842716; 0
2.1757; 10.12192; 0
2.248796; 10.40113; 0
2.32184; 10.68034; 0
2.394836; 10.95955; 0
2.467788; 11.23876; 0

ZI
x; y; z
1.362954; 6.566138; 0
1.375764; 6.679398; 0
1.393514; 6.812788; 0
1.416659; 6.965151; 0
1.445503; 7.135273; 0
1.480212; 7.321916; 0
1.520836; 7.523851; 0
1.567323; 7.739881; 0
1.619545; 7.96886; 0
1.677317; 8.209706; 0
1.740409; 8.461405; 0
1.808567; 8.723017; 0
1.881519; 8.993678; 0
1.958988; 9.272596; 0
2.040698; 9.559048; 0
2.126376; 9.852376; 0
2.215762; 10.15199; 0
2.308606; 10.45734; 0
2.40467; 10.76794; 0
2.503733; 11.08335; 0
2.605586; 11.40318; 0

ZK D0=200
x; y; z
1.341905; 6.493639; 0
1.357162; 6.619352; 0
1.377517; 6.763952; 0
1.403314; 6.926276; 0
1.434753; 7.105117; 0
1.471912; 7.299268; 0
1.514763; 7.507547; 0
1.563194; 7.728817; 0
1.617032; 7.961999; 0
1.676055; 8.206084; 0
1.74001; 8.46013; 0
1.808629; 8.72327; 0
1.881631; 8.994709; 0
1.958736; 9.273719; 0
2.039669; 9.55964; 0
2.124162; 9.85187; 0
2.211961; 10.14986; 0
2.302822; 10.45313; 0
2.396517; 10.76122; 0
2.492831; 11.07374; 0
2.591565; 11.39031; 0

I also attach a dxf file with the profiles.
Between the lowest point generated by the cutter and the root diameter there will be a transition curve, dependent on the tool tip radius.

RE: ZK worm parameters

(OP)
Hi spigor,

Going back to your question about the MOW, it's definitely 23.683 mm from the drawing (I just realised I'd entered as 23.0000 in our application, so I've changed that, but it's still giving me some errors that I need to look into).

I'd have to ask if we'd be able to get a sample part from the customer - we usually just get a drawing at quote/tender stage and then they supply parts for acceptance testing if they place an order.

Many thanks to everyone so far,
Richard

RE: ZK worm parameters

Then the wire diameter must be wrong, is it not Ø4?

RE: ZK worm parameters

(OP)
The wire diameter is given as "Best Pin DM 5.0 diameter" on the drawing, but it could still be wrong and could be 3.85 as was suggested earlier.

The lead that mfgenggear calculated in inches works out as around 15.3270 mm to 4 decimal places, which is what I calculated myself.

RE: ZK worm parameters

Richard
Based on the previous attachment provided :
Quote: Flank form K (worm ZK)
This is obtained with a grinding wheel or with a large diameter milling cutter with straight-sided
flanks inclined by an average angle Ym (figure N°4). The flanks that are obtained are slightly
convex and the amount of this convexity is determined according to the helix of the thread and to
the diameter of the tool. The smaller the tool’s diameter is, the closer this type of profile will be to N
type. Unquote

Based on the above, to obtain the correct geometry the wheel will be dressed straight sided. inclined at Ym
an operator will rough feed in with the Hold Depth and back off for roughing, the Measurement Over Wires/Balls (M.O.W.)
will be for roughing. taking an actual measurement the operator will then feed in to the required finish M.O.W.
a setup part (1st Run) The operator should verify the roughing and the Involute should be within .0254 MM or less
this will verify the correct involute.
what is critical is obtaining the correct roughing and finishing M.O.W. for the operator. (old school)
many new CNC controllers have measuring compensation which can do it automatically.
Turn an aluminum blank and run 2 parts to verify the above. Just run with it, Then check it on a CNC Gear checker for the correct Involute.
this is the best way to verify the results, in order to get the correct Involute the Module and Pressure Angle has to be correct.
the M.O.W. to to obtain the correct circular Tooth Thickness. which maintains the correct center distance. Piece of cake.
a sample part will be the master to verify results with M.O.W and Involute Check, that is a plus.
Have the estimator to allow for the extra cost of these setups, I believe you will be fine, with the thread grinder.
I had operators do many of these in the past. I ran this with my program I wrote many years ago, and Purchased software.

let:
2 T
Normal Module 2.3565 (10.77869722 NDP)
Normal Pressure Angle 15 Deg.
Lead Angle 14.9770 Deg.
Pin/Ball Dimeter 5 mm (.19685039 inch)
Dimension over 2 Wires/Balls
23.698/23.668 mm (.932992/931811 Inch)
normal CTT = 2.3515/2.34340 mm (.09258/.09226 Inch)
Transverse CTT =9.1000/9.06805 mm(.35827/.35701 Inch)
The Pin or Ball Clears the Tip Dia by .34798 mm(.0137 Inch)
The Pin or Ball Clears the Root by 1.18364 mm (.0466 Inch)


RE: ZK worm parameters

Could you please now make an axial cutout of the worm to get its axial profile and compare it with mine? I would be interested to see the differences.

RE: ZK worm parameters

(OP)
mfgenggear - thank you for creating that for me, I'll download that when I'm back at home as I can't get the download links to work from the office.

spigor - I'm having some issues with the code that creates the axial worm profile from the cutter/tool profile as it's making the worm tooth depth about 0.5 mm shorter than it should be, so I'll have to fix that before I can provide the full axial profile, however, I do have an intermediate stage one I could share if that would do in the meantime?

RE: ZK worm parameters

Richard - it would be nice if you would calculate your axial profile of the worm (as soon as you get the code fixed), compare it with mine and let us see the results.

RE: ZK worm parameters

Richard
I drew the normal view in AutoCAD, I use to do this to cheat for worms
saved as an stp file, Import this as a cad file and zoom up, there is an involute also next to the straight sided
this is the min and max wheel with require to be held by the operator should be approximately 20 inch Diameter wheel.
let me know if it was helpful.
edit: oops wrong file

RE: ZK worm parameters

(OP)
spigor - no problem, I do have an intermediate stage profile I could post up that is just the flanks if that would be any use?

I'll download the files you and mfgenggear created and posted as soon as I can - I'm juggling 2 projects at the moment so finding time for both as I can :)

RE: ZK worm parameters

You have my profile calculation results above. If you ever choose to compare them with yours and let us know about that, it would be great.

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