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Replacement Gear for Craftex CT089 13x24 Lathe

Xyphota

Xyphota

Ultra Member
Hello All,

I have sheared some teeth off this plastic gear in the drivetrain of my craftex CT089 lathe. All the gears in the lathe are metal, except for this gear which is the one responsible for driving the spindle. Fortunately it performed its job adequately and gave up the dust before damaging the spindle I suppose lol. Additionally, it looks like the gear stalled and the keyed shaft its mated to just started line boring out the bore lol.

I have emailed busy bee and am eagerly awaiting a response for a replacement, but I have also been looking elsewhere for a replacement as I would like to get this lathe repaired quickly. I have not dealt with busy bee customer support before so I do not know what to expect for timing.

The gear looks to be a 1.5 module, 56 tooth gear. 15mm face width, 10 mm hub projection for a total width of 25mm. 20mm bore diameter with a 5mm keyway slot. Visually the pressure angle appears to be 20 degrees, but I am honestly not sure. KHKgears, SDP/SI have configuartions of this gear, but nothing readily availble. For fun I contacted rushgear and they could make me one in two weeks for $2800 USD lol. I have access to a second lathe I can use to increase the bore size or reduce the shoulder projection if I can find something close atleast.

Does anyone have any recommendations as to where else to look for a replacement? And, if I am unable to find a plastic replacement gear, would I be stupid to install a steel gear?

Broken Gear 1.jpg

Broken Gear 2.JPG
 
Is there an equivalent Grizzly lathe? If there is then the gear may be available from Grizzly.
 
That gear almost looked like it was machined. I’m referring to the side away from the hub.

I don’t know about plastic but Boston Gear comes to mind. I picked up some change gears for my Myford from them, off the shelf via BDI.

For plastic it might be interesting to troll around Aliexpress a bit too.

D :cool:
 
Tecnico said:
That gear almost looked like it was machined. I’m referring to the side away from the hub.

I don’t know about plastic but Boston Gear comes to mind. I picked up some change gears for my Myford from them, off the shelf via BDI.

For plastic it might be interesting to troll around Aliexpress a bit too.

D :cool:
Click to expand...
The side away from the hub is the original surface. The Hub side is the side that was bored out from the Key when the gear stalled by the axle kept turning lol.
 
Xyphota said:
The gear looks to be a 1.5 module, 56 tooth gear. 15mm face width, 10 mm hub projection for a total width of 25mm. 20mm bore diameter with a 5mm keyway slot. Visually the pressure angle appears to be 20 degrees, but I am honestly not sure.
Click to expand...

I recently ordered a full set of modulus 1.25, 20 degree gear cutters from Ali. Everyone says it's easy to use paper based comparison tooth profiles to identify the modulus and pressure angle. I didn't find it easy at all.

The best method I found to identify the pressure angle was to lay an angle gauge inside a pair of adjacent gear teeth. It suddenly becomes obvious which angle it is cuz the other one isn't right.

For the modulus, I think it's better to do the math. But some of the metric and Imperial ones are awful close. I chose metric cuz it was the closest and its an Asian lathe......
 
Xyphota said:
The side away from the hub is the original surface. The Hub side is the side that was bored out from the Key when the gear stalled by the axle kept turning lol.
Click to expand...
I‘m not sure we’re looking at the same thing. I’m looking at the surface between the OD of the hub and the OD of the gear. To me it looks like tool marks or perhaps the gear was rubbing on something.

@Susquatch could be right, the fastest way to get the machine going again might be to roll your own replacement.

D :cool:
 
If you have access to a 3d printer you can do a search for lathe gear on thingaverse and print your own.
You maybe able to modify an existing 52 tooth gear to get the correct size and bore. Just an example

www.thingiverse.com

Grizzly G4016, Birmingham YCL1340GH, Jet 13x40, Threading Change gears. by Ken226

My Birmingham YCL1340GH came with a 30t, 40t, and a 127/120 double gear, which allow most common inch and metric thread pitches. These additional change gears will allow you to cut nearly any pitch that exists. For example, The stock gears don't allow for 1.25mm, 2.5mm or 5mm threads...
www.thingiverse.com www.thingiverse.com
 
I had the same lathe as my first lathe since new and I do not recall any plastic gears in it.

Why don't you cut a new gear as a project? Do you have access to a milling machine?

A new cutter from aliexpress will take about 3 to 4 weeks to arrive and set you back about 15 CAD.

I think I have Mod 1.5 but in 26 teeth configuration not 56.
 
Tecnico said:
I‘m not sure we’re looking at the same thing. I’m looking at the surface between the OD of the hub and the OD of the gear. To me it looks like tool marks or perhaps the gear was rubbing on something.
Click to expand...
Ahh I think those are just leftover machining marks from when the gear was made.

combustable herbage said:
If you have access to a 3d printer you can do a search for lathe gear on thingaverse and print your own.
Click to expand...
I've had success printing change gears before, but as this gear transmits power directly to the spindle, I think a 3D printed gear would detonate pretty quick lol. For how much work it was to get the thing out, I'll put the proper thing in there.

Tom Kitta said:
Why don't you cut a new gear as a project? Do you have access to a milling machine?
Click to expand...
Long term plan is to get a dividing head and some gear cutters! For now I just want to get something that will work.

I found a steel gear on KHK gears for $45 USD that should work with a bit of rework, so I think I'll go that route unless busy bee gets back to me tomorrow. Fortunately I have access to a second lathe so I can rework the gear on that one.
 
Xyphota said:
Ahh I think those are just leftover machining marks from when the gear was made
Click to expand...

Yep, we're on the same page now. That leads directly into the discussion about making a new (plastic) one. If they can do it........;)

Xyphota said:
.I found a steel gear on KHK gears for $45 USD that should work with a bit of rework, so I think I'll go that route unless busy bee gets back to me tomorrow. Fortunately I have access to a second lathe so I can rework the gear on that one.
Click to expand...

Just thinking out loud here but I wonder if an annealed aluminum or even plastic key would give you the "circuit breaker" function that the plastic gear did originally and protect the rest of the gear train?

D :cool:
 
Tom Kitta said:
I had the same lathe as my first lathe since new and I do not recall any plastic gears in it.
Click to expand...

@Xyphota - I confess that my brain is misfiring over your plastic gears.

When I was first shopping for a mill, the salesman at BB actually told me to avoid them. What a bummer that was. The good news is that I ended up getting my Hartford as a result.

My heart burn is over why they do it. It doesn't make sense to me to use a plastic gear in the final drive of a machine.

Why not steel with a shear pin?

Why do others use steel while BB uses plastic.

What is the rationale?

A huge part of me thinks this is all just a BB brain fart. It's just what they always did. Or some dumb engineer (or manager) has a bee in his bonnet about it. Or some character doesn't want to admit he was wrong? Or or or

Another part of me thinks its to reduce noise. But I'll take a little noise to improve durability all day any day. So I doubt this one.

I did a crap load of research just now. I found absolutely no justification for plastic that held water. I even found comments where BB themselves told users to replace it with metal if they had the means.

That's definitely the way I'm leaning myself.... If it were mine, I'd cut a new steel gear and be done with it. If I had any reason to be concerned, I'd drill it for a brass or steel shear pin sized to be equal to the shear strength of a plastic gear tooth.
 
@Susquatch Yeah I'm not sure, seems a bit out of place to me too. Its the only plastic gear in the lathe, all the change gears are steel too.

I just got a response back from busybee this morning and they confirmed they do not have this part as a replacement anymore, so steel gear it is!
 
 
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