NYLON MILLING MACHINE GEARS

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

Drawfiler

Well-Known Member
Joined
Apr 7, 2020
Messages
56
Reaction score
18
Location
Uk
Brian, do I see a horribly chewed up plastic gear in the first photo?
Peter
 

Jasonb

Project of the Month Winner!!!
Project of the Month Winner
Joined
Mar 30, 2008
Messages
2,967
Reaction score
710
Location
Surrey, UK
Peter, look at the first page, first post of the thread and you will see the gear and the reason why it strips
 

Drawfiler

Well-Known Member
Joined
Apr 7, 2020
Messages
56
Reaction score
18
Location
Uk
I understand that, thats why I have made substitute gears in metal.
 

Brian Rupnow

Design Engineer
Project of the Month Winner
Joined
May 23, 2008
Messages
14,081
Reaction score
7,258
Location
Barrie, Ontario, Canada
I couldn't figure out why the correct R8 holder for these annular cutters cost $75, while a standard R8 holder for a 3/4" drill was only $31. Now that I have the parts here, I see that there is a spring and a snap ring inside the correct R8 holder that lets a centering-pin retract into the body of the holder as the annular cutter passes thru the plate you are cutting. The centering pin then becomes spring loaded and pushes the "slug" out of the annular cutter after your cut so you don't have to fish for it with a pair of pliers. You can see the end of the centering pin sticking out past the face of the cutter. You can also see a centering pin setting beside the cutter---I made that one .001" undersize, which normally wouldn't matter, but in this case the pointy end is cantilevered out so far from where it is held that with 0.001" undersize it wobbled all over the place---Not what you want for centering.
iw5M4y.jpg
 

Drawfiler

Well-Known Member
Joined
Apr 7, 2020
Messages
56
Reaction score
18
Location
Uk
These are made in plastic to deaden noise and vibration and work OK a until the day of the inevitable smash up when using a large cutter.
I have made replacements in both metal and Acetal (Delrin) with good results so message me if I can help
 

jumps4

Member
Joined
Nov 25, 2009
Messages
22
Reaction score
14
Hello Brian and others
Little machine shop (littlemachineshop.com) carries metal replacement gears and parts for many of these import lathes and mills.
It may be worth a look. You can call them by phone also.
I have been very happy over the years with their service.

Steve
 

terryd

Well-Known Member
Joined
Jun 15, 2010
Messages
351
Reaction score
184
Location
South Leicestershire, England
Peter, look at the first page, first post of the thread and you will see the gear and the reason why it strips
Hello Brian and others
Little machine shop (littlemachineshop.com) carries metal replacement gears and parts for many of these import lathes and mills.
It may be worth a look. You can call them by phone also.
I have been very happy over the years with their service.

Steve
Hi jason,

Be careful what you wish for when replacing plastic gears with metal. Plastic gears are often used to be sacrificial in the case of machine jamming to protect more expensive damage - rather like shear pins in shafts which are designed to fail before more serious damage is done to a device. Most manual lathes have some kind of shear pin in the final drive to the leadscrew so that for example in the case of the saddle jamming against the headstock when in automatic drive the pin will shear otherwise serious damage to the clasp nuts or leadscrew can occur, so a 50p shear pin could save many £££s and time in repair costs.

When I was involved in designing drive systems to large machines, conveyor systems etc we would always include such a sacrificial device. just in case. Just think, if that relatively inexpensive gear (which could easily be 3d printed at home) had not failed what other damage may have occured. On our conveyor systems if a shear pin failed a production line would stop but it was a simple matter to locate the problem, fix it and then replace the shear pin so production would be down for a relatively short time compared with what would happen with major damage.

Terry
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
822
Reaction score
122
Location
Minnesota
. Is there enough rom to use a wider gear, like stacking two gears?
These are made in plastic to deaden noise and vibration and work OK a until the day of the inevitable smash up when using a large cutter.
I have made replacements in both metal and Acetal (Delrin) with good results so message me if I can help
 

kvom

Well-Known Member
Joined
Jun 4, 2008
Messages
3,266
Reaction score
622
I suspect that the gear printed in Onyx fiber on my new Markforged printer would work well, as the material is about as strong as aluminum.
 

Jasonb

Project of the Month Winner!!!
Project of the Month Winner
Joined
Mar 30, 2008
Messages
2,967
Reaction score
710
Location
Surrey, UK
Terry you are posting to the wrong person, I often post that if someone replaces a plastic gear with metal they may find that the next time they crash or overload the machine the board or motor will be what fails not the shiny new metal gear. I've certainly not suggested it or wished for it here.

Also if you read again the failure of Brian's was not due to it being a failsafe but an issue with the gear selector lever meaning it was not correctly meshed.

Plastic gears on some of teh imported tools are also specified on grounds of cost and noise reduction.
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
822
Reaction score
122
Location
Minnesota
I suspect that the gear printed in Onyx fiber on my new Markforged printer would work well, as the material is about as strong as aluminum.
I looked up the onyx fiber spools snd material. It’s tough stuff if you can print it yourself it’s probably ok my as noted fixing one weak linnoften leads to another the motor and driver can be next and very difficult to replace the onyx is pretty good but if you have to have it done outside check prices it may be better to just keep a couple spare gears on hand .
 

Toymaker

Well-Known Member
Joined
Jan 26, 2022
Messages
177
Reaction score
72
Location
Thailand
I have a little story to tell. I have a CX601 milling machine from Busy Bee Tools and I love it. This milling machine does everything I want, except drill 1" holes in aluminum. I don't do that very often, but when I do, it's mostly ornamental holes thru flywheel webs. And this is the point where my mill lets me down. There is a nylon compound gear in the gear-head, and it lets you put the mill into the equivalent of "back-gear" on a lathe. About every two or three years, this compound nylon gear manages to strip all the teeth of one side. It costs around $70 for a new gear, and it's a royal pain to take the mill apart and replace the bad gear. It doesn't happen all at once. When it first decides to eat that gear, it jumps out of gear into neutral. If you can spare a hand to hold it in gear, it works just fine, but sometimes I run out of hands to do that. It doesn't take much force to hold it in gear, and I'm sure that if it was held firmly in gear so that it couldn't jump out, then it wouldn't wreck the gear. So, today I'm designing a third hand to hold the mill in "back gear" while I drill large holes. In the pictures, you will see a side view of my mill where the gear selector knob is, another picture that shows my "third hand" in position, and in the third picture you can see a bad nylon gear and it's replacement good nylon gear.


3Tbq0D.jpg

My "Mini Mill" uses similar plastic gears (below photo) and like your mill is also made in China. I was able to purchase a replacement set of metal gears thru AliExpress for $30, and replacement plastic gears were even cheaper.

Hopefully you can find metal replacement gears on either AliExpress or eBay.

1662348905132.png
 

a41capt

Well-Known Member
Joined
Jun 5, 2009
Messages
443
Reaction score
170
Location
Camp Verde, Arizona USA
I 3d printed “emergency” gears in PETG and they’ve performed admirably. Sure beats having your Mini Mill down awaiting replacements!

John W
 

Drawfiler

Well-Known Member
Joined
Apr 7, 2020
Messages
56
Reaction score
18
Location
Uk
if you are worried about metal gears being too strong to act as a safety device in case of a smash up, you could incorporate a small shear pin between the two gears, .062” dia would probably be big enough
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
822
Reaction score
122
Location
Minnesota
I just ran into a carbon fiber print material called onyx it’s supposed t be stronger yet quiet running as a gear material . Stronger but still be the saftey valve
I 3d printed “emergency” gears in PETG and they’ve performed admirably. Sure beats having your Mini Mill down awaiting replacements!

John W
 

a41capt

Well-Known Member
Joined
Jun 5, 2009
Messages
443
Reaction score
170
Location
Camp Verde, Arizona USA
I can’t quite get the nylon/carbon fiber material to run consistently. I’ve even had trouble with ABS, but with PETG, while a bit more difficult than PLA, I can achieve acceptable results. This is especially true when I don’t have large interior voids where stringing still becomes semi-problematic occasionally. I just utilize a “brim”, set my perimeters to 4 or 6 and use a 50% to 70% infill. As long as my fan speed is set relatively low, I can achieve some pretty awesome lateral strength.

Of course I still order the correct part, but my machine is only down 15 to 20 minutes while I change out the gear. I’m still hoping to scrape together the cash to change over to a belt drive!

John W
 

Bentwings

Well-Known Member
HMEM Supporting Member
Joined
Jun 18, 2020
Messages
822
Reaction score
122
Location
Minnesota
I like the belt drive idea maybe you could get fancy and make a step belt drive . You could machine your own pulleys if none are conveniently available .
I can’t quite get the nylon/carbon fiber material to run consistently. I’ve even had trouble with ABS, but with PETG, while a bit more difficult than PLA, I can achieve acceptable results. This is especially true when I don’t have large interior voids where stringing still becomes semi-problematic occasionally. I just utilize a “brim”, set my perimeters to 4 or 6 and use a 50% to 70% infill. As long as my fan speed is set relatively low, I can achieve some pretty awesome lateral strength.

Of course I still order the correct part, but my machine is only down 15 to 20 minutes while I change out the gear. I’m still hoping to scrape together the cash to change over to a belt drive!

John W
 
Top