Can this be repaired?

[deeferdog]

This morning my mill, an Optimum BF-20LV, (Grizzly G0704) started to make some funny noises. I assumed that one of the drive gears might have stripped a couple of teeth as they are plastic and apparently have a bit of a reputation for this. It was one of the gears, the main gear that meshes with the motor gear. The teeth were in good condition but the gear was skipping over the shaft key under load, hence the funny noise. I had a spare so all ended well, my question is this, is it possible to repair the damaged gear? I thought of boring out the gear centre and turning up a hub in brass, that would be easy enough. Is there any method or adhesive that would hold the new hub into the bored out gear? I would make a new one but the gear is helical and I don't know how to cut them. Not really trying to save money, although that always helps. Suggestions gratefully received. Cheers, Peter.

 

[SmithDoor]

I would not repair plastic gears. Plastic will let you down.
Since plastic you can make new gear out of aluminum or 12L14.
FYI since it is helical just make the mating too and will last a life time.
How many teeth is gear???

Dave

This morning my mill, an Optimum BF-20LV, (Grizzly G0704) started to make some funny noises. I assumed that one of the drive gears might have stripped a couple of teeth as they are plastic and apparently have a bit of a reputation for this. It was one of the gears, the main gear that meshes with the motor gear. The teeth were in good condition but the gear was skipping over the shaft key under load, hence the funny noise. I had a spare so all ended well, my question is this, is it possible to repair the damaged gear? I thought of boring out the gear centre and turning up a hub in brass, that would be easy enough. Is there any method or adhesive that would hold the new hub into the bored out gear? I would make a new one but the gear is helical and I don't know how to cut them. Not really trying to save money, although that always helps. Suggestions gratefully received. Cheers, Peter.View attachment 118628View attachment 118629View attachment 118630

 

[deeferdog]

37T. The OD is 49.5 mm. I think that it would be Mod 1.25 if it is a metric gear, I assume it is as the machine is metric. I only have Mod 1 cutters and I have never cut helical gears.

 

[SmithDoor]

I would not try making a helical it cost a lot for tooling.

Just make both gears it lower cost the 37 tooth can cut on most deciding head.

What is the number of teeth other gear???

Dave

37T. The OD is 49.5 mm. I think that it would be Mod 1.25 if it is a metric gear, I assume it is as the machine is metric. I only have Mod 1 cutters and I have never cut helical gears.

 

[deeferdog]

20T. Is your suggestion to cut two new gears, straight cut using Mod 1 cutters? I never thought of that.

 

[SmithDoor]

Both gears are easy to most on most dividing head.
I would use 12L14 on the gears
The gears will last for rest of your life.

Dave

20T. Is your suggestion to cut two new gears, straight cut using Mod 1 cutters? I never thought of that.View attachment 118633

 

[deeferdog]

Thanks Dave for your input, your suggestion to make two spur gears is the way I will go if there is another failure, however the question still remains, is it possible to repair the plastic gear? The reason is that I would like to have a temporary spare that I could slip into the machine if it fails again. This would allow me to finish whatever I was doing before going about repairing/modifying the mill. I have another milling machine, virtually identical to the Optimum that I have converted to belt drive and powered with a treadmill motor, the spare gear came from that conversion. I understand your aversion to plastic gears, I share you distaste, however that's what the machine comes with so we're stuck with it. I'm going to try to repair this and look forward to any other comments. Cheers, Peter.

 

[kiwi2]

Hi,
I made a 100/127 gear for my Boxford lathe out of delrin. I wanted a phosphor bronze bush for it so I used the method shown in the pictures. I brazed a 1/8" thick brass flange to a bush made from 5/8" phosphor bronze. The gear was drilled through to accept the bush and the hole was recessed to accept the flange. Three 4mm holes were drilled through the gears and tapped in the flange. The bushing/flange assembly was then attached using countersunk screws through the gears and into the flange. I've used the 100/127 gear without any trouble.
Regards,
Alan

 

[Apprentice707]

Doesn't your machine supplier (Grizzly???) carry the replacements in steel? Should be a part number on the assembly diagram.

Cheers

B

 

[SmithDoor]

The gear are helical and the gear is 37 tooth.

I would think you could buy a new plastic gear. But back to were started the plastic gear failed.

You will find some manufacture that will do this odd number for sales of parts or making the item obsolete.

So what you left with is making two gears that will live or since this on a motor it maybe able to use belts by extending the gear shaft. I have change over to belt in pass too.

Dave

Doesn't your machine supplier (Grizzly???) carry the replacements in steel? Should be a part number on the assembly diagram.

Cheers

B

 

[steveastrouk]

I don't think I've seen these guys mentioned, but their prices for gears are unbeatable, and though I am now US based after moving from the UK to head the R+D department for a company here, we buy gears from the UK and ship

Here's, specifically, their helical gear PDF
https://www.hpcgears.com/pdf_c33/24.24-24.27.pdf

 

[gjrepesh]

If this gear is still a good fit on its shaft, I would consider cutting the keyway deeper into the gear and making a new key to fit.

 

[SmithDoor]

That is good prices
But in UK we are in USA

Dave

I don't think I've seen these guys mentioned, but their prices for gears are unbeatable, and though I am now US based after moving from the UK to head the R+D department for a company here, we buy gears from the UK and ship

Here's, specifically, their helical gear PDF
https://www.hpcgears.com/pdf_c33/24.24-24.27.pdf

 

[steveastrouk]

Yes ,but I believe its possible to actually ship stuff across the Atlantic these days.

 

[deeferdog]

Thanks to everyone who commented, Kiwi2, Alan, has shown me the way and I will use his suggestion to repair the gear. I realise that I can buy a new one quite easily but this is only going to be used if the spare I installed yesterday fails and I need to complete whatever I was doing. I will probably now make a start on converting the machine to belt drive as this eliminates all the plastic gears and the mill runs a whole lot quieter, the equivalent Sieg mills are belt drive. My other machine has already been done, complete with a treadmill motor and it is vastly improved, (see pictures). Cheers, Peter.

 

[SmithDoor]

I have the page for later use
I have gone both way on shipping.
For 1 pound to my door and shipping from the USA over 50 Tons.
Even had to get parts from the UK

Dave

Yes ,but I believe its possible to actually ship stuff across the Atlantic these days.

 

[SmithDoor]

That looks great

No gears to go bad.

Dave

Thanks to everyone who commented, Kiwi2, Alan, has shown me the way and I will use his suggestion to repair the gear. I realise that I can buy a new one quite easily but this is only going to be used if the spare I installed yesterday fails and I need to complete whatever I was doing. I will probably now make a start on converting the machine to belt drive as this eliminates all the plastic gears and the mill runs a whole lot quieter, the equivalent Sieg mills are belt drive. My other machine has already been done, complete with a treadmill motor and it is vastly improved, (see pictures). Cheers, Peter.View attachment 118644View attachment 118645

 

[Johan Maritz]

Just my observation, the gears are plastic for a reason, similar to the Myford tufnol gears, If something went wrong it is suppose to act as a fuse to prevent other parts from damage.

 

[Lofty76]

If the gear teeth are ok, and the bore is ok, why not just recut the key way on the opposite side?

 

[goldstar31]

As far as I can see the 37T gear also fits the lathe.

The price of a replacement is about £65.

Yer pays yer and takes yer choice