Tufnol gears - 1967 Meddings drill refurb

[brewdexta]

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.

I was going to measure it tomorrow, but I see you probably have all the info you need now

 

[Smouser]

I contemplated getting my mate to print a gear with a 3D printer out of PLA.

I wonder how well it will hold up/if it all.

 

[Smouser]

Thanks.

I was just thinking PLA because that is what most 'home' 3D printers can print easily.

 

[Agroshield]

I contemplated getting my mate to print a gear with a 3D printer out of PLA.

I wonder how well it will hold up/if it all.

You will be able to improve the strength of it by paying close attention to how you model the roots of the teeth. At the very least, zoom in on your design and make sure there are no stress-rising sharp corners there. The very best way will be a radiused root as large as possible so it does not interfere with the tip of the mating gear.

There is some good information here: https://gearsolutions.com/features/gear-tooth-fillet-profile-optimization/ The important point to grasp is that 90% of gears are produced by subtractive machining methods and as such, the root profile is determined by the swept path of the cutting tool. When you use an additive process like 3DP, you can optimise the root even more than in the above article.

 

[daxliniere]

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.

Clive ("Workshopfriend" on Youtube) did the measurements/calculations and found it to be 20 degrees. And yes, it'll be Imperial, as all of the bolts are too.

 

[daxliniere]

Pressure angle 20 degrees - I thought it looked like it.
56 tooth would be 3.625“ (3 5/8”) diameter.
89 tooth would be 5.69” diameter. 89 is not a usual tooth count.

Knowing the tooth count of the other gear with the 56 tooth would allow the tooth count for the larger gear to be easily calculated (centre distance of the shafts are fixed, so only certain combinations are possible).

The mathematics of this is way over my head, but I can get the dimensions and tooth counts.

The larger Tufnol gear is definitely 89 teeth, I just counted them in my photos (though in my case closer to 88.5 teeth )

 

[daxliniere]

I contemplated getting my mate to print a gear with a 3D printer out of PLA.

I wonder how well it will hold up/if it all.

From my limited experience with 3D printing (I have a Mars 2 Pro resin printer), I would say that non-commercial grade 3D printers, FDM or resin, will give you disappointing results.
Consider that these gears can be cut from less than £30 of material (12mm POM-C) with a £5 end-mill (single flute, ø2mm, 15mm flute length).

If you, or anyone else needs one, let me know as I would be interested to try this out. POM-C is apparently the easiest of plastics to machine.

 

[Pete.]

If you're going to machine one make it from Delrin. I believe that is what you'll get from Meddings anyway.

The mathematics are easy.

Diameter (in inches) = tooth count +2 / DP. It's a 16DP gear so diameter = 89+2/16 = 91/16 = 5.586" or 144.46mm

 

[Brad93]

If you're going to machine one make it from Delrin. I believe that is what you'll get from Meddings anyway.

The mathematics are easy.

Diameter (in inches) = tooth count +2 / DP. It's a 16DP gear so diameter = 89+2/16 = 91/16 = 5.586" or 144.46mm

Meddings still supply their gears in tufnol

 

[Smouser]

Meddings still supply their gears in tufnol

Newest ones I have seen from Meddings was white Delrin (2022 purchase).

 

[Smouser]

From my limited experience with 3D printing (I have a Mars 2 Pro resin printer), I would say that non-commercial grade 3D printers, FDM or resin, will give you disappointing results.
Consider that these gears can be cut from less than £30 of material (12mm POM-C) with a £5 end-mill (single flute, ø2mm, 15mm flute length).

If you, or anyone else needs one, let me know as I would be interested to try this out. POM-C is apparently the easiest of plastics to machine.

Thank you for the offer. All my gears are intact, Pete. kindly made me a small gear from Delrin.

Next time I need a gear, I buy a machine so I can cut my own gears .

 

[daxliniere]

Alright, it's almost back together. Thank you so much to everyone who pitched in with advice.

One more question; since there's room, should I pack any more grease into these bearings? The front one has a grease nipple and a fairly large reservoir, but the rear one (input shaft/pulley) will be inaccessible once the pulley is back on.

 

[bricol]

Alright, it's almost back together. Thank you so much to everyone who pitched in with advice.

One more question; since there's room, should I pack any more grease into these bearings? The front one has a grease nipple and a fairly large reservoir, but the rear one (input shaft/pulley) will be inaccessible once the pulley is back on.

View attachment 347973 View attachment 347974 View attachment 347975

Already look to have too much for anything other than slow speed - usually a max of 1.2 to 2/3 of the free space in the bearing - worry is the grease simply pushes around with the race, rather in and around. In reality it's probably just push out as the bearing rotates and find a happy running quantity, especially I seem to remember discussion of oil somewhere?

 

[Seadog]

The top bearing on Elliotts is oil lubricated, daily, according to the blurb. Mine gets lubricated

Oh yes, whenever it gets stripped down

 

[Brad93]

Newest ones I have seen from Meddings was white Delrin (2022 purchase).

Ah mine was about 5 years ago

 

[Smouser]

Alright, it's almost back together. Thank you so much to everyone who pitched in with advice.

One more question; since there's room, should I pack any more grease into these bearings? The front one has a grease nipple and a fairly large reservoir, but the rear one (input shaft/pulley) will be inaccessible once the pulley is back on.

Oil might splash onto it lubricating it. To be fair they last ages anyway.

I have put some sealed bearings in one of the gearboxes I stripped down. In my opinion, the drill is not getting enough use for it to be a problem (DIY use).

 

[daxliniere]

Already look to have too much for anything other than slow speed - usually a max of 1.2 to 2/3 of the free space in the bearing - worry is the grease simply pushes around with the race, rather in and around. In reality it's probably just push out as the bearing rotates and find a happy running quantity, especially I seem to remember discussion of oil somewhere?

Thanks @bricol. Actually, it perfectly explains an issue I found when I put it back together. In the low belt, low gear (80 rpm), it runs beautifully, but low belt, high gear (310 rpm), it was spinning up, then the motor would audibly slow down to an almost stop, then come back up to speed, then slow down again. I used it at lowest settings for about 30 minutes and just now that I've come back to it to take a video, I managed to capture it happening only once and now it seems to be running fine. I guess the excess grease has been thrown out.

Should I still reopen the gearbox and dig out some of the grease?

Here's a video of the last time it did the weird slowing down thing. It was potentially doing it every 15 seconds or so.

 

[daxliniere]

So this was the first thing I did with my freshly reassembled drill.
Yes, I know that a drill is not a mill, but A) this uses angular contact bearings, B) I have neither space nor money for a real mill, C) I need a mill very rarely and D) I'm taking very light cuts.

The vice is the worst in the world and literally cost me £7 brand new (US$10 when on holiday) and the chuck is awful, too. I need to buy a reasonable machining vice and low run-out Jacob's style chuck when funds allow.
Using the MT2 arbour 50mm shell cutter with carbide inserts was much nicer as the runout is 0.045mm.

With all that said, I'm pretty happy with the results. I made the key I needed for the input spindle as it had been long lost.