Need help understanding how to measure a gear, and locating a source of supply

[lionelt]

Sorry it's a long post.

The pinion on my Myford is badly worn, so bad it’s impossible to measure accurately

It has 16 teeth.

Gear is about .998” or 24.4mm diameter
Width of gear .515” or 13mm
Length of shaft including gear 3.900” or 99mm
Diameter .550” or 14mm


It meshes with the larger gear on the Rack Pinion Assembly.

I am told by Myford the gears have a pressure angle of 14.5°, and are normally 20DP.

The large gear on the Rack & Pinion Assembly appears to be 18DP As the O.D. for DP 18 is close to what the gear measures, 2.766” Diameter. At 20DP is come out at 2.500”

Never needed to make any gears in the past so used Google to try and understand how gears are measured, hopefully I have got this correct.


These are what I have found.


48 Teeth and 2.766” diameter

Measure across 5 teeth is 0.771”
Measure across 4 teeth is 0.610”

So is the pitch 0.161”?

For 18DP Gear I get these results.

PCD. Teeth Divided by DP = 2.666” For 20DP 2.400”
OD. Teeth +2 Divided by DP = 2.777” For 20 DP 2.500”
Module. 25.4 Divided by DP / 25.4 divided by 18 = 1.41 For 20DP 1.27
No of Teeth PCD x DP - 2.666” x DP18 = 47.98 For 20DP 48


This leads me to believe that the DP is 18.


Therefore I need to find a 16 tooth 18DP Spur Gear either on a shaft, or a gear that can be pinned to a new shaft.

I’ve looked at HPC Gears, they do pinion gears on shafts but not one long enough.

Emailed Myford and they do not have this part.

Contacted Lathe Parts but not yet had a reply.

Anyone able to suggest where I can obtain a suitable part or get one made?


Thanks




Photo 1

Shows the Pinion next to the gear it meshes with, I have used this gear for my calculations as it is a new gear.

Photo 2

Shows where the gear locates, it’s not pushed all the way in it sits under the larger gear at about 4 o’clock.
All the four gears at the top of the apron are new, unfortunately Myford no longer stock the pinion with the small gear.


Photo 3

Pinion is part number 45 in the diagram.

 

[Peter Colman]

Contactme and I will make you one,I also am in the UK
Peter

 

[lionelt]

Contactme and I will make you one,I also am in the UK
Peter

PM sent.

Thank You

 

[timvercoe]

If you cleaned up the gear and then cut it off the shaft and reattached it to the shaft flipped over, so the unused part of the gear runs in the matching gear would this suffice to make your machine operational why one was being made? Did this on our chinaman lathe to keep it serviceable. Just a thought.................

Tim

 

[lionelt]

If you cleaned up the gear and then cut it off the shaft and reattached it to the shaft flipped over, so the unused part of the gear runs in the matching gear would this suffice to make your machine operational why one was being made? Did this on our chinaman lathe to keep it serviceable. Just a thought.................

Tim

Unfortunately the gear is too far gone.

Was considering purchasing a gear and turning the old one off leaving a shoulder.

Push on the new gear tight and drill across the joint and pin it.

All the gear catalogues I looked at so far do 20 degree gears, and I this one is 14.5 degrees.

 

[timvercoe]

Unfortunately the gear is too far gone.

Was considering purchasing a gear and turning the old one off leaving a shoulder.

Push on the new gear tight and drill across the joint and pin it.

All the gear catalogues I looked at so far do 20 degree gears, and I this one is 14.5 degrees.

View attachment 132246

Have you tried Boston Gear Co? Try this link: http://www.bostongear.com/pdf/gear_theory.pdf Lots of engenering data.....

Tim

 

[jim rozen]

Hmm.

OD = N + 2 / DP

For a 16 tooth gear, if it were 18 diametral pitch, this means the outside diameter
would be one inch, which is close to what you are measuring.

If you had a dividing head, the next course of action would be to purchase a 14-1/2 degree
pressure angle involute cutter, in the range of 16 teeth, that is 18 DP. Then either
make the pinion and silver solder it on to the shaft (if the shaft's not too worn) after
turning off the old one. Or make the entire shaft and gear from scratch.

I'd probably just go with 1018 steel for this.

 

[stephen thomas]

Do you have a mill and dividing head?
It's pretty simple to make spur gears and pinions.

Ivan Law's book is a good practical compendium, but for goodness sakes, buy your cutters, don't get lost in the rabbit hole of making them with 2 button cutters, relieving attachments, Quorn grinders and mining your own ore to start!

954 Al bronze.

steel spur gear for tumbler in SB gearbox.

In this case the smaller gear with the integral keys could be turned around to present new teeth surfaces. It contacts no other gears, power is trasmitted through a shaft and the keys.

smt

 

[lionelt]

Thanks Jim & Stephen,

For now will accept Peter's offer in post 2.

Yes have a Bridgeport, but no dividing head, but having watched some YouTube video's the process looks straight forward so will lookout for a dividing had and give it a go when I get some free time.

I think I can work out the calculations now I've spent a few evening reading up on it.


If I did make a new shaft, I was thinking of using Silver Steel, so it could be hardened, what do,you think?

The old Gear is blue at the gear end of the shaft so looks like it was hardened.

Although the replacement gears that I bought from Myford did not look like they were hardened, but maybe done in inert atmosphere so showing no heat treatment colouring?