more questions

[Pete49]

I hope Im not wearing out my welcome but I have more questions
When the cutter arrive I will make a start on cutting the gears I need for my upshur farm engine but no realise that I don't have a 32 or 64 tooth gear for my Harold Hall dividing head and don't know enough to use my home made rotary table or have any dividing thingies with holes either. All ideas/suggestions welcome 
Pete

[Don1966]

Pete, do you have GHT'S (Workshop Techneques)? if you do, look under (Simple Indexing with worm wheel)  starting at page 130. You can do it with simple dividing calipers on a hole circle. The cordial length C= SIN 180/ N. where N is the number of teeth. CORDIAL length C is the diameter you set you dividing calipers to and walk them around the circle. You will have a small pit where the caliper mark, just center punch. You could use a protractor just as well. Hope this helps.

Don

[tel]

Pretty simple with the HH dividing head;

Mount a 40t gear on the spindle
Mesh it with a 25t gear that is coupled to a 20 t

For the 32t just index around one tooth space at a time til you fill up the blank.
For the 64 you will need the forked detent, and index every tooth and every space til you fill the blank.

[mklotz]

Pete, do you have GHT'S (Workshop Techneques)? if you do, look under (Simple Indexing with worm wheel)  starting at page 130. You can do it with simple dividing calipers on a hole circle. The cordial length C= SIN 180/ N. where N is the number of teeth. CORDIAL length C is the diameter you set you dividing calipers to and walk them around the circle. You will have a small pit where the caliper mark, just center punch. You could use a protractor just as well. Hope this helps.

Don

Ah, it's the CHORDAL length (a cordial is an apertif) and the formula is:

C = D * sin (180/N)

where D is the diameter of the circle.

If that's too much math for you, you can use the CHORD program on my site.

[tel]

With the greatest of cordial respect - you guys are not seriously suggesting he cut a 64t module .5 gear using choral layout are you???

[fcheslop]

Use a length of band saw blade I usually use 3x the number of teeth plus 20 for the overlap.Hard solder into a ring then turn a ply plug for it with a center bush to fit the indexing head. Make a simple click or detent from a bit of clock spring or packing case strap
A bit rough but its handy at times
cheers

[mklotz]

With the greatest of cordial respect - you guys are not seriously suggesting he cut a 64t module .5 gear using choral layout are you???

I'm not suggesting anything, Tel; just correcting the math and English.  BTW, is a "choral layout" a bunch of prostrate singers?

[steamer]

Make a disk out of plywood 3/8" thick...to 5.092" diameter on the lathe.   Arrange the disk to have a hub you can mount on your indexing spindle

Get a cheap tape measure and remove the tape.    Cut it on the diagonal at the 1" mark and the 33 " mark

When wrapped around the disk, the ends should just meet.   Carefully glue the tap to the OD.

Use the disk as a division plate with a clamp on arm and a small plastic pointer.   Indexing every half inch will give you 64 divisions, every inch 32 devisions, every quarter inch is 128 divisions.....ect.

the larger you make the disk, the smaller the error....so if you can make it twice that diameter (10.184" and 66" of tape) the more accurate you will be.

the tape is printed at +/- .002"    so the error is primarily the user.

Dave

[tel]

With the greatest of cordial respect - you guys are not seriously suggesting he cut a 64t module .5 gear using choral layout are you???

I'm not suggesting anything, Tel; just correcting the math and English.  BTW, is a "choral layout" a bunch of prostrate singers?

Yes - stranded on a cordial island somewhere! 

[Don1966]

Pete, do you have GHT'S (Workshop Techneques)? if you do, look under (Simple Indexing with worm wheel)  starting at page 130. You can do it with simple dividing calipers on a hole circle. The cordial length C= SIN 180/ N. where N is the number of teeth. CORDIAL length C is the diameter you set you dividing calipers to and walk them around the circle. You will have a small pit where the caliper mark, just center punch. You could use a protractor just as well. Hope this helps.

Don

Ah, it's the CHORDAL length (a cordial is an apertif) and the formula is:

C = D * sin (180/N)

where D is the diameter of the circle.

If that's too much math for you, you can use the CHORD program on my site.

Thanks Marv for the correction, my bad. Spelling was not my strongest attribute. I did forget to multiply by the diameter. I knew if anything was wrong, you would be the one to correct it.

The idea here was to make an index plate from this setup. Then cut the gear. Building the index plate this was would not generate that much of an error.


Don

[arnoldb]

Hi Pete

Do you have photos of your rotary table and your dividing head ? - That will allow us to think a bit more clearly on suggestions.

If your rotary table is graduated, it's fairly straight-forward to calculate the list of angles you need to set it to to cut the gears.  If it's not graduated, and you know the worm wheel ratio, it could still be possible to make an ad-hoc "division template" fairly easily to allow you to cut the gears.

Kind regards, Arnold

[tel]

Pete has a Harold Hall dividing head, which, with the compound gearing that I mentioned above, is more that adequate for the job.

These were cut on my HH DH

[Pete49]

I just looked through the gears I have on hand and no 25, 30 or 50t. Can I use a 60t and just index to every second one to make a 30t? failing that I'll use Steamers method. I guess it's all a learning curve.
Thanks Marv I have been to your site and downloaded programs to do with gears and the cutting as well. The only problem I have is with the gear program. I put in the numbers and then it disappears and I cant open the part that has the info in it.
Pete 

[steamer]

By the way....that method was described by none other than W.R. Smith  A Master Clockmaker.

Pete...if you use that method....I would use the indexer...to make an index plate with multiple circles of holes.

Make sure the arm that locks the indexer is rigid..and robust.

Make a reticle from a piece of clear plastic with a fine line on it and index to the same side of the tape line for every index position

All these things will reduce the chance of error.

Smith made index plates that made an award winning clock with this method....and it was written up in Home Shop Machinist.

If I can help .....let me know.

Dave   

[mklotz]

Thanks Marv I have been to your site and downloaded programs to do with gears and the cutting as well. The only problem I have is with the gear program. I put in the numbers and then it disappears and I cant open the part that has the info in it.

Well, fortunately, I've had my coffee and am in a forgiving mood (or what passes for one with me.)

I get this question literally hundreds of times in a year despite the fact that the answer is in the Introduction section on the site.  Please read it.

Maybe some of you can explain to me why you would go to a site like mine and not bother to read the Introduction at the very top of the page before jumping in and downloading programs.