Tufnol gears - 1967 Meddings drill refurb

[daxliniere]

In the processing of stripping and cleaning my new 1967 Meddings M4 mkII drill press, I've seen that one of the Tufnol drive gears is missing half of its teeth. Which half? The bottom half, thankfully, so it's serviceable as it is.

Does anyone have a technical drawing for this gear? I believe I would be able to recreate it in CAD and use my CNC to cut it from POM/acetal.


All the best,
Dax.

 

[Pete.]

That gear would last forever if you just turned it over, and make sure that you never change gear unless the spindle is stopped.

 

[daxliniere]

make sure that you never change gear unless the spindle is stopped.

Oh yes, absolutely. The drill was made in 1967 and I am definitely not the first owner!

That gear would last forever if you just turned it over

My concern is that only half of the gear has engagement. I'm certainly not going to be working this drill to the bone, but it seems like an easy fix with a CNC.

 

[Pete.]

If you're hell bent of having a new gear I've made several of them from Acetal, easy enough to make except right now I am solerly pressd for time - but I would not change THAT one.

 

[Agroshield]

The gear is still available from Meddings, so call them and price it up first to see if your time and materials are worth less than their selling price.

You can work out most of the information you need to make a new one from what you have. Count the number of teeth on the gear and measure the outside diameter. As a double and triple check, count the number of teeth and OD of the other three gears in the box and also measure the centre distance of the shafts.

There is a very good, free piece of software called geardxf that will get you 90% of the drawing you need if you feed it the correct numbers.

What sort of CNC do you have and how do you intend to cut the gear?

 

[Smouser]

Pete. made me a gear. It was a perfect match.

Thanks again Pete.

Photo of the old and new.

 

[Pete.]

Sadly I cannot cut the larger gear on my machine, it's limited to about 115-120mm diameter

 

[Brad93]

Over £100 from meddings.

Just run that gear as is, it will be fine.

 

[daxliniere]

If you're hell bent of having a new gear I've made several of them from Acetal, easy enough to make except right now I am solerly pressd for time - but I would not change THAT one.

Forgive me, Pete, I didn't know the clout you had around these parts. (I'm new here)

If you're the guy who makes replacements for the folks around here, you clearly know your stuff.

@Brad, I have read a few of your threads about your Meddings 'refurb journey' and I'm not at all surprised to hear Meddings went over £100 for this part. Thanks for the input.

 

[daxliniere]

u can work out most of the information you need to make a new one from what you have. Count the number of teeth on the gear and measure the outside diameter. As a double and triple check, count the number of teeth and OD of the other three gears in the box and also measure the centre distance of the shafts.

There is a very good, free piece of software called geardxf that will get you 90% of the drawing you need if you feed it the correct numbers.

What sort of CNC do you have and how do you intend to cut the gear?

@Agroshield, I've decided to take on the sage advice given here and run this gear to death, but the CNC option is definitely there for me. A 200x200x12mm piece of POM-C is under £30 delivered and though my CNC mill is small (max job 302x187x46), I've equipped it with a 1.5kW spindle, upgraded all the steppers and reinforced the frame (including 1/2" steel bed).
It would have no difficulty cutting this job and I noticed that the smallest radius ('trough' of the teeth) could be cut perfectly with a Ø2mm end mill.

For ****s n giggles, I might cut a mock up from a piece of nylon I have hanging around. Once I've gotten every thing else finished.

 

[daxliniere]

That gear would last forever if you just turned it over, and make sure that you never change gear unless the spindle is stopped.

@Pete., do you reckon it needs to be flipped? There would be the same amount of engagement either way (both gears are same thickness and line up at exactly the same height.

 

[Brad93]

@Agroshield, I've decided to take on the sage advice given here and run this gear to death, but the CNC option is definitely there for me. A 200x200x12mm piece of POM-C is under £30 delivered and though my CNC mill is small (max job 302x187x46), I've equipped it with a 1.5kW spindle, upgraded all the steppers and reinforced the frame (including 1/2" steel bed).
It would have no difficulty cutting this job and I noticed that the smallest radius ('trough' of the teeth) could be cut perfectly with a Ø2mm end mill.

For ****s n giggles, I might cut a mock up from a piece of nylon I have hanging around. Once I've gotten every thing else finished.

That gear will honestly last you decades before it wears out.

The sacrificial, and that's the key word, gear is there so if you have a crash the gear will shred instead of damage the steel gears, it's also there because of noise. The noise is actually the only real issue, as the belt will slip long before the gear eats itself.

These are a noisy drill at the best of times. I've replaced all the bearings in mine but have been too busy to get the input spindle remachined. One day when Pete has caught up with his many projects, I may get round to spraying it with a nice hard nickel powder and then kindly ask Pete to grind it for me.

 

[brewdexta]

I've had a Meddings gearbox on my bench to fix for quite a while, it came out of a Meddings radial arm drill I renovated a while ago, its an MF4 head. I had to get a donor drill as it was in a bad way, I found one with a broken casting but the gearbox worked, if a little noisy. The plan was to swap it out when I get chance to do this one up. Its not at the top of my todo list but I thought I would open it up to check the state of the gears.

One out of two aint' bad I guess

I doubt if there was any oil in the gearbox when they did it considering the evidence stuck to the casting wall

 

[Brad93]

They take about half a pint if I remember correctly. They loose oil down the spindle.

 

[Agroshield]

...It would have no difficulty cutting this job and I noticed that the smallest radius ('trough' of the teeth) could be cut perfectly with a Ø2mm end mill.

At the very least, have the drawing/specification for the gear stored away somewhere safe if you do need to make one. Right now, the machine is dismantled, the gear is clean and has all its teeth. You will curse when you have to rip the machine apart and try to measure a greasy one with stripped teeth.

It is not only the diameter of the end mill you need to consider: how thick is the gear? A 12mm cut with a 2mm end mill is 6 x diameter, so you need to find a tool that will do that and then be ever so gentle with it so it does not snap completely or deflect excessively. Chip clearance is also going to be an issue unless you have a vacuum or air blast.

 

[daxliniere]

I've had a Meddings gearbox on my bench to fix for quite a while, it came out of a Meddings radial arm drill I renovated a while ago, its an MF4 head. I had to get a donor drill as it was in a bad way, I found one with a broken casting but the gearbox worked, if a little noisy. The plan was to swap it out when I get chance to do this one up. Its not at the top of my todo list but I thought I would open it up to check the state of the gears.

One out of two aint' bad I guess

View attachment 347665

I doubt if there was any oil in the gearbox when they did it considering the evidence stuck to the casting wall

View attachment 347664

Oh man, that powder is sad to see.

Your large gear seems to be in better condition than mine. I don't suppose you'd mind taking an external diameter measurement, would you? I'm not sure I have a single diametrically opposed pair of unworn teeth on mine.

 

[daxliniere]

They take about half a pint if I remember correctly. They loose oil down the spindle.

1/2 to 2/3 pint is printed on the machine's lube plate, so for a complete rebuild, I'd recommend 2/3 pint.

As for losing oil down the spindle, I think of a 24mm seal is used rather than 25mm, this should be basically non-existent.

 

[Smouser]

I've had a Meddings gearbox on my bench to fix for quite a while, it came out of a Meddings radial arm drill I renovated a while ago, its an MF4 head. I had to get a donor drill as it was in a bad way, I found one with a broken casting but the gearbox worked, if a little noisy. The plan was to swap it out when I get chance to do this one up. Its not at the top of my todo list but I thought I would open it up to check the state of the gears.

One out of two aint' bad I guess

View attachment 347665

I doubt if there was any oil in the gearbox when they did it considering the evidence stuck to the casting wall

View attachment 347664

I can relate.

Here is the rest of my gear.

 

[Brad93]

1/2 to 2/3 pint is printed on the machine's lube plate, so for a complete rebuild, I'd recommend 2/3 pint.

As for losing oil down the spindle, I think of a 24mm seal is used rather than 25mm, this should be basically non-existent

It's an oil bath, it looses oil down the spindle even with seals. And I can tell you now it's a very odd size seal.

 

[not done it yet]

Is it 14 1/2 or 20 degree pressure angle? Likely imperial, not metric at that age? Diameter is easily calculated from DP (or MOD, if metric) and number of teeth.

Gear cutters are readily available, but easy, I suppose, once dialled in on a CNC machine. I would be making one a bit more slowly on my mill.