skate bearings yes or no?

[cvriv.charles]

I have plans to use 32 skatebearings for my homebuilt but 2 people already have mentioned that I shouldnt because skatebearings wont be able to handle the load?!?!

I know 4 skatebearings on a skateboard can hold up 180lbs. That just 4 of them. I have 16 of them just to hold up the gantry.

Am I missing something here?!?! How much force is generated while cutting?!?! To much for the bearings?!?!? I thought these bearing were widely used through the homebuilt cnc's?!?!

[dertsap]

they are commonly used for diy , it is scraping the bottom of the barrel in terms of linear slides but there are a number of us who have used them with great success , a guy just has to be reasonable in what he expects with using them

[cvriv.charles]

Originally Posted by dertsap they are commonly used for diy , it is scraping the bottom of the barrel in terms of linear slides but there are a number of us who have used them with great success , a guy just has to be reasonable in what he expects with using them

Scraping the bottom of the barrel? Really. So what would be a good bearing then? My machine is huge and VERY heavy. so I need a good amount of them. I wanted the 3/8" v grove bearings but I would need a minimum of 32 of them. At 10 a piece thats a lot of money just for bearings.

Whats the next stop up from skate bearings?!?!

[ger21]

5 years ago, skate bearings were used on 90+% of homebuilt machines. Back then, V bearings were $25 each. I'd say that V-Bearings are the next step up. But, I'm curious why you'd need so many. You shouldn't need more than 4 for each slide. So 16 total for a moving gantry, including the Z axis.

If your machine truly is Huge and Heavy, then $300 on bearings is not much at all.

[jalessi]

What do you mean by huge and heavy?

Can you post dimensions etc...

[dertsap]

v-groove is a good way to go if the gantry is big and heavy , If cost is a factor and if you have access to a lathe then its easy enough to make your own v bearings , i made up a bunch of them recently with skate bearings , to keep them solid with no play i pressed in two skate bearings per roller , cost me less than $20 to make a dozen
theres a pic here on my sons build http://www.cnczone.com/forums/showth...highlight=kydd

[cvriv.charles]

Originally Posted by ger21 5 years ago, skate bearings were used on 90+% of homebuilt machines. Back then, V bearings were $25 each. I'd say that V-Bearings are the next step up. But, I'm curious why you'd need so many. You shouldn't need more than 4 for each slide. So 16 total for a moving gantry, including the Z axis. If your machine truly is Huge and Heavy, then $300 on bearings is not much at all.

Well,... im designing the machine in a way that it technically has two gantry's. They are bolted together and once unbloted they roll away from each other so I can gain access to the spindle if I should ever have to remove the spindle. Each side needs needs 8. For the Y axis,... theres 6 of them on each side. The only reason for that is because the bearing centers are 10" apart. I could possible just go with 4 per side. Lastly there's 8 for the Z axis. So 32 - 36 bearings. Thats 64 to 72 skate bearings. I'm using a lot of 1/4" and 3/8" steel. Im estimating that teh machine is going to have a footprint of about 6' x 10'. Maybe 11'. not sure yet. Still in the design phase.

[cvriv.charles]

Originally Posted by jalessi What do you mean by huge and heavy? Can you post dimensions etc...

I have a worklog in the worklog section. I havent posted much because I keep changing the design due to problems that other members are informing me about. I'm going to post more recent pics tomorrow. MY gantry is going to be about 5.5ft long and the rail from v point to v point is 10". Made from 1.75" x1/4' angle iron held together as a pair with 3/8" thick steel ribs. heavy! Theres going to be two of those too. Sandwiching the spindle. Vibration and flexing should be minimal.

I guess I will suck it up and pay the money for the v-groove bearings I guess. Last thing I want is to have bearing grinding away on me. I need this machine operational at all times.

[ger21]

You should seriously consider building an enlarged Mechmate. Sounds like you may be in a little over your head. A proven design will be far cheaper in the long run.

[cvriv.charles]

Originally Posted by ger21 Sounds like you may be in a little over your head.

How so? I would rather try on my own. Building something like this from someone else plans is not satisfyling to me at all. It's cheating. I will build my own and it will be victorious.

I would prefer your advice instead of the your in over your head comments. I have recieved several already and it's getting to be quite annoying. It's an insult actually. I'm not trying to be nasty or mean back to you. I am just stating how I feel. I am one to try and figure things out for myself.

[harryn]

Hi - You are probably tired of hearing MHO by now, but I will give you my limited experience with bearings.

Standard skate bearings
- the nice thing about these is that they are cheap and made in large qtys.
- In theory, the higher ABEC numbers are more precise, and they are - when used in electric motors
- In practice - at least the VXB ones - have very little side load capability, and they don't remain concentric under load. In other words, if you roll one down a counter, the inner hole and outside don't stay concentric.

There are better skate bearings - look at the ones made by Swiss. They have side load capability, and they stay concentric. Not rocket science, but guess what - they do in fact make skaters go faster / smoother, etc. The skaters don't seem to understand exactly why, but they are happy.

Issue - price - these quality - "designed for real skating" bearings are not cheap, but you can make that decision on your own.

All that being said, I am planning to work with the Ahren trolleys (which have the VXB el cheapo bearings in them). Results - I am "hoping for " better, but will be happy with +/- 0.025 inch work.

[ger21]

Originally Posted by cvriv.charles How so? I would rather try on my own. Building something like this from someone else plans is not satisfyling to me at all. It's cheating. I will build my own and it will be victorious. I would prefer your advice instead of the your in over your head comments. I have recieved several already and it's getting to be quite annoying. It's an insult actually. I'm not trying to be nasty or mean back to you. I am just stating how I feel. I am one to try and figure things out for myself.

Over the years, I've seen several attempts at very large machines on tight budgets. None of them ever get finished. Imo, I gave you very good advice. Build a proven design. Sorry you don't see it the same way. Good luck.