Gear Tooth Count Calculation?

Uglydog

Uglydog

Active User
H-M Supporter Gold Member
Joined
Dec 6, 2012
Messages
2,677
There were two gears stripped off inside the column of my Van Norman 22LU.
I found a used one Ebay at a price I was willing to pay.
The gear is cast brass.
The teeth were completely sheared off.
As you can see I've brazed over the broken teeth.

Without a complete gear how do I calculate the spacing for my DH?
As you can see by the gear gage she appears to be a 16tooth.

Suggestions?

Thank you!!
Daryl
MN

IMG_0104.JPG IMG_0106.JPG
 
If I understand your problem correctly... Measure the pitch diameter first, looks like you will need to measure the pitch radius and double it. You can probably measure it close enough with a 1/100" increment ruler. Use Machinery's Handbook, Spur Gearing, table 11 in my 22nd edition, "Pitch Diameters of Diametral Pitch Gears." You know the DP to be 16. Go down the chart until you find your measured, fudged, and calculated pitch diameter. If you come up with a pitch diameter that is not quite close to the chart value for one of the tooth counts, start over. Once you know how many teeth your gear would have if it was a complete gear, and not just a segment, use that tooth count to set up your dividing head. Off the top of my head that's how I would go after it...

edit: diametral, not diametrical
 
Last edited:
You've got 5 good teeth Daryl. Measure the angle between them from the centre of the bore, (say 20 deg). Divide the angle by 4 to get the individual tooth angle, (20/4=5 deg). Divide 360 by that, (360/5= 72) to get the tooth count if it was a full; gear.

Greg
 
Measure the dendum, this will be the clearance cut with working depth, your picture looks like the gear is round. If it is cam shaped it will not work. If it is a 16DP you can get the Whole Depth by looking up a 16DP gear and add that to your dendum to come up with the addendum and have the outside dia. With the outside diameter of the gear and DP you can calculate the number of teeth and set your DH to match. Hopefully I explained this correctly.
 
I'm finding this thread is very interesting as I'm trying to make a small thread counter gear but didn't know where to go for things like the tooth profile or for info on milling profiles /cutting wheels .
I've seen the machinery hand book mentioned several time WRT gears .
Can anyone give me the ISBN code for one please or a link to PDF with such info in it.
 
In addition to the standard print size, I've got a large print edition.
If you are going to get your first MH.
Think about the machines and tooling you have and are using.
The newer editions add information appropriate to newer machines, vintage editions cover content for vintage machines and tooling.
Both cover content about trig, gear cutters, taps, etc.

Daryl
MN
 
Round in circles said:
I'm finding this thread is very interesting as I'm trying to make a small thread counter gear but didn't know where to go for things like the tooth profile or for info on milling profiles /cutting wheels .
I've seen the machinery hand book mentioned several time WRT gears .
Can anyone give me the ISBN code for one please or a link to PDF with such info in it.
Click to expand...

Here is what I have, will this help you?
Machinery’s
Handbook
28th Edition
BY ERIK OBERG, FRANKLIN D. JONES,
HOLBROOK L. HORTON, AND HENRY H. RYFFEL
CHRISTOPHER J. MCCAULEY, SENIOR EDITOR
RICCARDO M. HEALD, ASSOCIATE EDITOR
MUHAMMED IQBAL HUSSAIN, ASSOCIATE EDITOR
2008
INDUSTRIAL PRESS
NEW YORK
ISBN 978-0-8311-2800-5 (Toolbox Thumb Indexed 11.7 x 17.8 cm)
ISBN 978-0-8311-2801-2 (Large Print Thumb Indexed 17.8 x 25.4 cm)
ISBN 978-0-8311-2888-3 (CD-ROM)
ISBN 978-0-8311-2828-9 (Toolbox Thumb Indexed / CD-ROM Combo 11.7 x 17.8 cm)
ISBN 978-0-8311-2838-8 (Large Print Thumb Indexed / CD-ROM Combo 17.8 x 25.4 cm)
LC card number 72-622276
All rights reserved. This book or parts thereof may not be reproduced, stored in a
retrieval system, or transmitted in any form without permission of the publishers.
INDUSTRIAL PRESS, INC.
989 Avenue of the Americas
New York, New York 10018
MACHINERY'S HANDBOOK
28TH EDITION
 
Got this one done!!
Seems to engage well enough. But she isn't powered up so it's difficult to know.
Spent about 6hours measuring her and doing trigonometry. The degree suggestion above was very helpful, as while not super absolutely accurate. It provided a great double check of all my calculations.

Well, knee is together. Now on to making parts for the headstock transmission!
I'm most nervous about the electrical. She came with a single quick disconnect (on/off switch). I think I want to add three magnetic starters, one on/off for the PF, and one off/fw/rev for the drive motor, one for the coolant pump, and a 220v/120v transformer.

Electrical opinions?
Perhaps I should post in the electrical questions forum...

Daryl
MN

IMG_0219.JPG IMG_0215.JPG IMG_0217.JPG IMG_0211.JPG
 
You must log in or register to reply here.
Back
Top