[tonebag]

I recently noticed some inconsistencies with the accuracy of my Chinese CNC router so I checked for backlash and then checked to see the wear on the pinion gears. Sure enough the pinion gears need replacing but I am having difficulty finding a replacement gear. To make matters worse is the fact that the pinion appears to have been press fit as is there is no set screw to assist in removal. There is a belt drive attached but I can't seem to get that apart either.

The pinion gear has 20 teeth and measures 27.52mm OD and is 15.24mm thick. There is no hub or set screw but it is press fit on a shaft measuring 18mm in diameter.

Does anyone have any experience with these types of machines that they could offer some suggestions? Any help would be appreciated.

[Torchhead]

There are two important factors on a spur(pinion gear) it has to has to have the same PITCH (tooth spacing as the rack and the same pressure angle. I don't know about China but there are two predominate pressure angles :20 deg and 14 1/2 deg. Once you know the pitch you get the diamter by counting the teeth The DP is the diamter of the pinion at the root of the teeth (somewhat less than the overall diameter. The pitch is the DP times PI divided by the number of teeth. YOu can measure it on the rack by using the valleys per MM. So a 27mm diamter is an 84.9 mm circumference so to pitch is somewhere around 4/25mm Seems kinda weird numbers

[ger21]

It could also be metric R&P.
MOD 1, MOD1.5, MOD2, .....

[Jim Dawson]

It looks like that gear is part of the shaft or in other words, the gear and shaft are all one piece.

It looks like the bearing is pressed into the housing from the back, so to remove the cover, tap on the end of the gear and drive it towards the back. Once you get the ''box'' removed, then you should be able to get to the set screws for the belt drive pulley.

I would try to find a proper gear and just fit it to a new shaft. Maybe you can match the size and tooth form here https://www.ametric.com/s-461-gearsspur.aspx

EDIT: After looking at the pictures again, it could be that the bearing goes out the front. In that case the back end of the shaft would be pressed into a bearing in the cover. Might take a little pry bar action to separate the halves.

[Sterob]

As Gerry says, I would guess its a metric pinion, seeing as its Chinese.
All I can suggest is to pull the unit gently apart to try and determine IF the pinion CAN be removed.....
It may be part of teh shaft, as someone has suggested, or maybe its on a taper or retained by an internal bolt??
Just take it slowly.....good luck.

[tonebag]

Thank you everyone for your suggestions. They were very helpful. The gear is MOD 1.25 and is attached to the shaft. The back end is pressed into a bearing in the cover. I managed to find what I believe to be is a replacement here. The only issue that remains is how to remove the old one and install the new one. Thanks again for all your help. I will keep you posted on my progress.

[Sterob]

Good stuff....Your on it!

[tonebag]

Upon closer inspection I noticed the racks were also showing wear. I'm assuming i should replace those as well and she should be good as new. Found a supplier in China but the shipping will cost more than the racks themselves. Can anyone suggest a local supplier? I am in Ontario Canada. I tried Motiontek but they only carry MOD 1 and 1.5.