Model Engine Maker

Help! => Machines, Tools and Fixtures => Topic started by: Brian Rupnow on January 08, 2022, 07:25:01 PM

Title: NYLON MILLING MACHINE GEARS
Post by: Brian Rupnow on January 08, 2022, 07:25:01 PM
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.
(https://imagizer.imageshack.com/img924/254/u7HCGJ.jpg)
(https://imagizer.imageshack.com/img922/2318/WcUdxZ.jpg)
(https://imagizer.imageshack.com/img924/6899/3Tbq0D.jpg)
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Brian Rupnow on January 08, 2022, 07:35:42 PM
And here you can see a 3D model of my milling machine with the knew "third hand" installed and a detail of the 3/4" thick third hand. The 1/2" diameter knurled steel pin screws thru the arm and is captured behind the sheet metal enclosure that houses the motor. This sheet metal housing is quite "beefy" and should easily be able to counteract any forces that try to shift the gear selector out of gear. To put the machine into it's normal gear, you just unscrew the threaded pin enough that it no longer is held captive behind the steel motor housing.
(https://imagizer.imageshack.com/img923/3954/I9TLC5.jpg)
(https://imagizer.imageshack.com/img923/1682/Rm1J74.jpg)
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Roger B on January 08, 2022, 09:11:57 PM
Is jumping out of gear the cause or result? Could you buy/cut some steel or bronze gears?
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Brian Rupnow on January 08, 2022, 09:34:55 PM
Roger--I tried to get metal gears from Busy Bee, but they didn't have them. I talked to the tech guys at Little Machine Shop, and they don't have them. I don't know for sure, but I think that these are metric gears. I have 24dp gear cutters, but they are not even close.
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Pete49 on January 09, 2022, 02:00:50 AM
Brian look for someone with a 3D printer as its possible to print nylon gears. All the printer needs is an stl file of the gear and the its a case of how many you want.most cad programs allow a drawing to save as (name).stl and your problem is cheap once the roll of filament is factored in if its needed to be purchased. Even most schools have them so maybe make a deal?
Pete
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Brian Rupnow on January 09, 2022, 04:25:43 PM
This is the shape of the nylon gear I currently have. The tooth form is an approximation
The gears are measured with a Vernier caliper.
(https://imagizer.imageshack.com/img922/1918/xtX4Lr.jpg)
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Jasonb on January 09, 2022, 05:07:49 PM
Most likely MOD1.5 20deg pa. Should be able to buy a couple of far eastern made ones quite cheaply and modify them to fit a boss.

Try a local gear/bearing/belt supplier. This is the type of thing from a UK source https://www.beltingonline.com/steel-c-366_367_375_519_388/56-tooth-15-mod-spur-gear-ss1556b-p-5569.html

Just bear in mind that with steal gears the machine may well be noisier and in the event of a jam or crash if the plastic gears can't fail then something else will have to give.
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Brian Rupnow on January 09, 2022, 05:15:32 PM
All right!!! You fellows have convinced me. Time to make a raid on the Rupnow Fortune and buy Three annular cutters, a 1", a 15/16" and a 7/8". These things come with a 3/4" shank, and I don't have any R8 collets that are big enough, so I will buy 3 dedicated R8 collets which will take a tool with a 3/4" shank. I will still go ahead and fabricate the aluminum arm which will prevent the mill from jumping out of gear when in low range under heavy load. Thank you for your help.---Brian
Title: Re: NYLON MILLING MACHINE GEARS
Post by: Roger B on January 09, 2022, 05:33:47 PM
Yup I agree MOD1.5 probably 20° PA.

Another UK suppliers catalogue:

https://www.hpcgears.com/pdf_c33/23.40-23.45.pdf

Does Mädler North America also deliver (sensibly) to Canada?

https://maedlernorthamerica.com/product-category/spur-gears-toothed-racks-internal-gears-ratchet-wheels/spur-gears-straight-tooth-system/spur-gears-steel-11smnpb30-c45-milled-teeth-module-0-5-to-10/spur-gears-steel-module-1-5/