Newbie- Thrust bearings and drive mounting...

[JD_Mortal]

I am at the point where I have all aspects of assembly nearly complete, in my design... except for the thrust bearings.

I can visualize it, but it is cloudy in my head... (I am unsure if what I am visualizing will actually work.)

There are two plans in my head. One is for a true drive-screw, the other is for an all-thread, until I can afford a true drive-screw.

I know I will have to turn-down the true drive-screw, and either tap-threads for a nut, or use a key-slotted mount. However, for the all-thread, which will be about 3/4" 10, or 5/8" 11, I should just use two nuts locked against a washer, against the thrust-bearing, against the mount... Reverse for the opposite side, still at the motor-end. (Followed by a spring-tensioned "pulling" setup on the free-floating end, away from the motor.)

Eg... (More ASCII art...)

MOTOR SIDE
//////[nut][nut]{wash}(BEAR)|#FRAME#|(BEAR){wash}[nut][nut]//////...

FREE END
...//////|#FRAME#|\SPRING\{wash}(BEAR){wash}[nut][nut]/////

The spring is only acting as a pre-load tension, to help reduce vibration. The frame mount will have a normal bearing, also to help reduce vibration. However, the tension/stress will all be put on the double-bearing setup close to the motor/love-joy.

I keep finding two types of bearings, ball and pin. The ball also has two variations, flat-washer with the bearings in a nylon-cage, or deep-groove washers with bearings in a classic metal-cage. The pin bearings are all metal, on flat washers, but indicates they are for breaking. (Which seems logical since they use untapered bearings which will cause friction as they roll on the two separate radius surfaces.)

(I am use to seeing "V" shaped, tapered-mount thrust bearings, like you find in a car, or heavy machinery, or old bike handle-bars. I don't know the reliability of the round bearings, which will be working against centrifugal forces in these setups I see on the net.)

Any input?

[ahren]

How big of a machine are you building? If it is under 4' of travel, you can use 1/2-10 ACME, which is a popular choice, and supported by the components we sell. You can see a helpful diagram of components used for this on our website:

CNCRouterParts

If you are going larger than this, I would highly recommend rack and pinion drive over a screw, especially all-thread. This type of thread is really a poor choice for cnc applications, both in terms of efficiency and accuracy.

Best regards,

Ahren
CNCRouterParts

[JD_Mortal]

The machine travel will be 2' which covers a 4' length, but the thread will only be 3'. The all-thread is just until I can get funds and pieces made, by this machine, for this machine. It's first task is to upgrade itself.

If I don't go with a screw-drive, I will go with rack and pinion, or a dual chain-drive on a pulley setup.

The base is a 2'x2' platform, with a 1' all-thread mount (Spans 1', but the nuts are at each end of the 1' mount.) The travel is only 2', but I am using 3' of all-thread to get that travel, giving a 2x2 work area that consumes 2x4 glide space.

EG...
__________________________________
|=============================|------------------------------------|
[Motor]///[Nut-----------Nut]/////////////////////|/////////////////////[END]

So the needle-bearings are ok to use?

[DeadTom]

JD,
Try Miniature Bearings,Miniature Bearing,Bearings,Ball Bearings, they have alot of different bearings at a reasonable cost.
Tom

[JD_Mortal]

Thank-you, both of you, for your reply.

Parts are now ordered, and hopefully I got what I need. This is my experimental creation, so it is purely a learning device. Hopefully, I will be able to get it working well enough to upgrade itself, and have it make the next version too.

I am glad that I wasn't too far off in my plans. Given that I could not actually see that component, and had no idea what exactly to search for. Heck, I couldn't even find assembled units. Now I have access to all the goodies!

Time to start grinding metal and cutting MDF.