Rotary Table Dividing Plates for Gears (Webster Engine)

[Danuzzo]

Haven't posted for a while on my Webster build. Been working on Connecting Rod. I plan to cut my own gears. I do have a Vertex 6" rotary table. I think I need dividing plates for gear making. I have found the vertex plates (3 plates) for the HV6. See link: https://easson-vertex.com/product/vertex-rotary-table-dividing-plates/. There are 3 plates.

Would any of those 3 plates work for the 48 and 24 tooth gears on the Webster. I obviously don't know how dividing plates work. The numbers for the hole on the link don't show 24 or 48.

 

[djc]

The two gears have 'nice' tooth numbers, so with some care, they could be made using the graduations on the RT rather than buying expensive plates (short version: you do not need to buy the plates).

360/48 = 7.5 degrees per tooth.
360/24 = 15 degrees per tooth.

The HV6 table has a 90:1 worm ratio. That means one turn of the handle is 4 degrees. The handle is graduated in degrees and will easily resolve to half a degree. You can use the graduations around the table to keep track of progress (or stick a hand drawn scale over the top of the engraved one).

There are also online division wheel producers, so you can print out a paper one with 48 (or 24) lines and stick onto the gear blank for further verification (https://www.cgtk.co.uk/metalwork/calculators/divider).

If you did want to use a dividing plate, 15 degrees table rotation is 3 3/4 handwheel rotations. 7 1/2 degrees table rotation is 1 7/8 handwheel rotations. Hence, a dividing plate with holes that have 8 as a factor (i.e. the 16 hole plate in the factory set) will work. Note that as you only actually need 8 holes (not 16), you could make the plate yourself on the rotary table as the plate holes will be at 45 degree increments.

Equally you could print out a paper one with eight lines on it, stick it to a piece of metal, draw a circle on it and drill 8 holes free hand at the intersection of the circle and radial lines. Any error in your setting out will be reduced by a factor of 90 when used on the RT.

I should also mention that it has been noted on the UK forums that the Vertex data sheet that accompanies the dividing plates had some errors so you are best to verify any calculations.

 

[Danuzzo]

Djc, that is great that I don't need to buy the plates. Thank you.

 

[timo_gross]

The simple (more expensive?) answer would have been: "A-Plate set to 16 holes." (end of anwer, but this is a Nerd forum)

Explanation:

• 90*16=1440 holes for a full revolution of the table
• 1440 holes / 48 divisions = 30 holes per division.
• Makes 1 full turn of the crank (16 holes) plus 14 holes.

So A-plate is what you "need" for both gears.

If it is whise to let the excuse to buy a new tool slip; is another question I come to the same conclusion as #2, do not buy plates (unless they are cheap and (or) you hate electronics), do not buy plates just for that one occasion you can go with below strategy based on djc advise. I add my 2Ct below.

• Next idea: slap a stepper motor on the rotary and make an electronic divider. You can find a complete instruction here somewhere on the forum. The cost? I guess: Arduino plus small bits 30$, motor driver 40$, motor 40$ plus some wires, power supply 30$ enclosure 20$, coupler to attach motor to table 20$. (ballpark numbers on the higher side)

• Next idea: Make a 16 hole plate? Should be easy to do it accurate, having a rotary table. (haha)
• Next idea: Just go with an 8 hole plate. ... (even easier)
  • Make dividing plate blank.
  • Mount dividing plate blank on table.
  • Drill (and ream) 8 holes using the dial 45° should be easy enough to adjust manually with care. (and possibly you have some 45° angle to sanity check)
  • Mount 8 hole plate on crank axis, you are ready to divide your gears 48 and 24 (and make a 16 hole plate)!
  • math 48 tooth gear:
    • 90 * 8 = 720 holes for full revolution.
    • 720 holes / 48 divisions = 15 holes per division
    • Advance one full crank turn 8 holes (15-8) plus remainder 7 holes
  • math 24 tooth gear:
    • 90 * 8 = 720 holes for full table revolution
    • 720 holes / 24 divisions = 30 holes per division
    • Advance 3 full turns (30-8-8-8=6) plus remainder 6 holes

Done!

I would look into the 1st idea, if I would not have done so already. That will be very useful in every workshop and is easier and (for me) fun to use.

p.s. I realize that there is quite some repetition in my post. Maybe I should have red #2 from djc before typing....

 

[djc]

p.s. I realize that there is quite some repetition in my post.

Different people think in different ways and the hole calculation can be a more intuitive method for them. To me it is not repetition, just an alternative route.

Should we say that "16 holes" is engineer's shorthand for "16 holes advancement from the one you are currently in"?

A third option could be to sellotape a change gear (Lego gear, Meccano gear) with a tooth number divisible by 8 to the shaft of the RT and use a plunger in the tooth spaces. It all boils down to the same thing - establishing a surefire way of turning the RT handle by 1/8 of a turn increments.

 

[timo_gross]

Different people think in different ways and the hole calculation can be a more intuitive method for them. To me it is not repetition, just an alternative route.

Should we say that "16 holes" is engineer's shorthand for "16 holes advancement from the one you are currently in"?

A third option could be to sellotape a change gear (Lego gear, Meccano gear) with a tooth number divisible by 8 to the shaft of the RT and use a plunger in the tooth spaces. It all boils down to the same thing - establishing a surefire way of turning the RT handle by 1/8 of a turn increments.

Yes, 16 holes means pull plunger and then start counting "one beeing the neighbor" . Which results in "one handwheel rotation" for a 16 hole plate. Same numbers really. Different memory hook. Expression "memory hook" reminds me on this hat.

Counting, without distraction, not bumping the sector arms! (now it is done by the electronics and I do not have to do it) Worst mistake is that I push the button twice.


The method with the gear actually works very well. Not a bad at all, specially for direct indexing.
The workpiece head of this Toolgrinder is using a gear and plunger for the divisions. I think it has 72 teeth allowing 5° degrees per step.

I make a bet that a 3d printed gear would do quite a decent job as well, not too small printed and with nice big teeth.
but then we have to replace "holes" by "teeth" and "plate" with "gear" when describing counting instructios. And if someone is using a lathe with change gears, will he find some gear that can be used? (maybe Danuzzo already has a gear that can be used)

 

[oldengineguy]

Use the scale on the rotary table to index for the gears. 48 teeth is (360 divided by 48=7.5 or 7degrees 30 minutes),24 teeth is(360 divided by 24=15 degrees) Make a list of degree positions of each gear 7.5 15 22.5 30 37.5 etc. and check off after each tooth so you don't get lost .Works for me!
Colin

 

[ShopShoe]

An auxiliary suggestion:

Whatever method you choose, make a practice run using a plastic material to work through the steps. That is what I did the first time I wanted to cut a gear and I found where the errors in the process can creep in. (I got the famous "half-tooth" due to losing my place due to an interruption.) Another trap for me is not having the blank tightly locked down and having it slip partway through the circle.

BTW, I bought the index plates with the rotary table I have, so that is the method I used. I later tried to make an electronic rotary table using a cheap table and found too many problems getting the motor mount sorted: Another "Round Tuit" project for the future.

There are now several options for purchasing ready-made electronic indexing tables that did not exist a few years ago. If I did not already have two rotary tables, I might go that route in today's world.

--ShopShoe

 

[Danuzzo]

Thanks for all the responses. As far as electronics are concerned, it isn't that I don't like them; it is that I don't understand them as far as wiring and set-up.
As djc said, "It all boils down to the same thing -establishing a surefire way of turning the RT handle by 1/8 of a turn increments". Lots of food for thought as far as getting there. That is my concern about making my own plate.

 

[timo_gross]

Instruction was here, read from start. I think it will be easy to judge for yourself if that is doable or away from what you consider fun.
https://www.homemodelenginemachinist.com/threads/arduino-rotary-table-for-dummies.26744/

A 8 hole dividing plate should be easier than to built any sort of engine .. I think the more complicated part are the sector arms and hand crank for it.

 

[Danuzzo]

Instruction was here, read from start. I think it will be easy to judge for yourself if that is doable or away from what you consider fun.
https://www.homemodelenginemachinist.com/threads/arduino-rotary-table-for-dummies.26744/

A 8 hole dividing plate should be easier than to built any sort of engine .. I think the more complicated part are the sector arms and hand crank for it.

Thanks Timo. Looks like a very good read. Maybe I'll learn something?