Is a 8 arc minute Gearbox tight enough for Plasma/oxy?

[WSS]

My current system is between 3 and 6 arc minutes (apex, nema 23), I can't really detect/feel any backlash in them. I am looking at some nema 34 boxes that have 8 arc minutes. Any ideas???

WSS

[scrambled]

wss-
i sent you a p.m.


steve

[WSS]

Steve, sent you a PM too.

Tommy

[millman52]

Tommy if my understanding of "arc minute" is correct, you are talking 2/15 of 1 degree or 8/21,600 of a circle. I don't think you'd notice the differance between what you have now & what you are looking at.

Someone else please correct me if I am wrong.

[WSS]

I am not sure if that is what it means. I know that I was told that under 6 was good. Some of the better ($$) gearboxes have 10arc mins. I can get some cheap boxes that have 5, but can I rely on them? The Thompson, Parker/Bayside and Minarik boxes are in the 500 to a grand range but the keling is $240 and a midrange box from moitiontek is $350. Both Keling and motiontek are advertisers here on the Zone, so I will probably give one of them a try (and save some money).

WSS

[millman52]

Well there's no shock load on the gearbox running a plasma table. Like there would be on say a 3 HP knee mill swinging a fairly large indexable end or face mill.

Personally I've had really good luck with China pillow block bearings & other imports I was actually afraid of the quality till I used them.

I'd want to hold backlash to a minimum even if that cost me a few extra bucks.

I also took a stab at calculating just how much backlash or error 8 arc min would be on a 1" pinion. If I'm in the ballpark there it's about .0001"

[WSS]

.0001" is acceptable if I have too, LOL. In use, the closest tolerance I get know is <.010", way outside of the gearbox capabilities. Often .030" is acceptable.

That said, I did buy three 12:1 boxes today from global motion tech/motiontek.ca today. The fit will not be excactly a drop in as the shaft is metric, 15mm so I will have to get some pinions with that bore made. The pinion is a 1" DP. I think I will have to go to a 1.25" dp to get a hub large enough to broach a keyway in. I did a custom build on rushgear.com and got a quote of $1200 ea for 1 or $120 ea for a quantity of 10. Go figure. Anybody know a good place to get pinions in a 24 pitch, 14.5deg build?

I also received the float head Z from K2 yesterday, it is better made than I expected, nice design. It has four 20mm round bearings and two float and two support the main and hold the switch. Very solid. I was worried about the acme leadscrew but it has a natural preload due to its vertical position and the motion is so fluid that it rides on the thread with gravity pulling the slide down. It will be even better once the mount and torch is on it.

WSS

[scrambled]

Tommy-
There is a pinion called a stem pinion made by boston gear, where the teeth are special cut, and you can get smaller than 1 inch.

If you want I can take a picture of how I made a hub and installed the pinions on my first set of pinions.


Steve

[WSS]

Steve, That would be great. Is it an adapter? The hub on my pinion is just over .80" and the bore needs to be .59 (15mm). That does not leave much room.

Thanks,
Tommy

[WSS]

Steve, I just googled it and they don't go to 24pitch, 20, tops. I have a strange set-up I am finding. Looks like you could couple it to an end of a shaft easily enough. Does yours work good?

Tommy

[scrambled]

Tommy-

My rack and pinion is working great! It is just the rest of the table that sucks.


I will get the pictures tonight when I goto the shop



Steve

[WSS]

Steve, Whats up with your table? I remember the gearbox retro but thought it was all worked out.

Tommy