Looking for linear guides for mill.

[WeaSiL]

I've been reading the forums quite a bit lately looking for information on linear guides. I've come to realize that most people regard THK as being excellent quality, however a less than excellent price (for those on a budget). I have also read good things about HIWIN and ABBA linear guides. However I have not been able to find pricing for either of those products. I am located in Canada and would really appreciate if someone could point me in the right direction.

Thanks in advance for your responses,
Scott

[Jarwalcot]

You might try here...

http://www.linear-bearings.net/

[svenakela]

The THK's are top quality, but I promise you they are 99 times out of 100 an overkill for any machine built. The forces your machine will put on the rails are far less than any linear guide handles. The reason why all "home maders" uses THK's and dito overkill guides is: they are the ones coming out on eBay regarly.
As long as you find guides without play, they are probably fine.

Good luck, and welcome to the cnczone!
Sven

[WeaSiL]

OK, I can see your point there Sven.

My next question then would be how do the round rod linear bearings compare to the square profile rails. I have some (1 axis worth) Thomson Super 12 bearings as well as some (other 2 axis worth) THK LM-20 linear bearings.

I couldn't really care less whether or not the linear motion system is round bar or square rail. My only concern is accuracy. I would like the machine to be within .001" across it's travel. It is going to be a small bench-top mill with 12"-X 12"-Y and 9"-Z so it's not like I will ever be able to overload it in concern to weight, but I want to be able to make small parts with a relatively high degree of repeatability.

So, am I wasting my money by going with the square profile rails or do I even have a choice in the matter?


Thanks again,
Scott

[Zumba]

I wouldn't say THK brand rails are overkill. However, I would say that the SIZE of THKs that most people buy are overkill.

For example, I recently scored some HSR35s on ebay. I could've gotten by with 15s but the 35s cost the same. Overkill? No doubt... instead of the 1700lb load rating, I got 17000lbs or something along those lines.

THK style square rails (or flatter wide rails like their HRW, SHW, etc), are the only rails I use. I'm not partial to the THK brand, Hiwins are just as good, but THKs are the ones that usually show up ebay. Abba... I'm not sure. Don't even know where to get em except from VXB.com, which only sells them in one size (and they cost more than Hiwins). I'd take the Hiwins any day.

Round rails? I hate em. Unsupported rails will flex like wet noodles. Supported Thomsons are more expensive than THKs. VXB... I tried em. Decent product but they don't sell drilled and tapped linear rail, nor do they sell rail supports. Making your own is one the biggest wastes of time ever, IMO. I tried. Gave up because it was so tedious to get the precision I wanted.

So yea... get THKs.

[blau_schuh]

Originally Posted by Zumba I wouldn't say THK brand rails are overkill. However, I would say that the SIZE of THKs that most people buy are overkill. For example, I recently scored some HSR35s on ebay. I could've gotten by with 15s but the 35s cost the same. Overkill? No doubt... instead of the 1700lb load rating, I got 17000lbs or something along those lines. THK style square rails (or flatter wide rails like their HRW, SHW, etc), are the only rails I use. I'm not partial to the THK brand, Hiwins are just as good, but THKs are the ones that usually show up ebay. Abba... I'm not sure. Don't even know where to get em except from VXB.com, which only sells them in one size (and they cost more than Hiwins). I'd take the Hiwins any day. Round rails? I hate em. Unsupported rails will flex like wet noodles. Supported Thomsons are more expensive than THKs. VXB... I tried em. Decent product but they don't sell drilled and tapped linear rail, nor do they sell rail supports. Making your own is one the biggest wastes of time ever, IMO. I tried. Gave up because it was so tedious to get the precision I wanted. So yea... get THKs.

I'll agree to this. I just got a pair of 25" THK25 LM rails with bearings off of ebay. Holy smokes. they are way, WAY overkill for my homemade machine, unless I decide to machine a 1000 pound slab of aluminum. 15's would have worked nicely...

[WeaSiL]

Cool .... I think I have decided to go with some Hiwin parts. Probably not for some time yet because I am currently unemployed and volunteering with a large construction project for the church that I am a member of.

Anyways, I am having a little trouble relating the Load Capacity ratings that are commonly given for linear guide rails into terms that I can understand. Everything is in N or kN or whatever and my lack of experience is hindering me.

Can anyone explain this a little further or more clearly for me.

Thanks,
Scott

[lgalla]

HI SCOTT,
Beleive what ZUMBA says.
Canadians&Americans can buy THK online direct fromTHK.www.tos-world.com.Be sitting down when looking at pricing.
HIWIN at www.automation4less.com.Reasionable prices
Abba at www.vbx.com.$250US for 60"rail and 2 20mm trucks.
Options,EEEEEE-BAAAAAY. If you have time to spare or wait thk is always on E-Bay at1/4 the price.
Round rail?Maybee 4 1 foot or so!
Hope this helps.Wish all companys would publish pricing.
Larry

[blau_schuh]

Originally Posted by WeaSiL Cool .... I think I have decided to go with some Hiwin parts. Probably not for some time yet because I am currently unemployed and volunteering with a large construction project for the church that I am a member of. Anyways, I am having a little trouble relating the Load Capacity ratings that are commonly given for linear guide rails into terms that I can understand. Everything is in N or kN or whatever and my lack of experience is hindering me. Can anyone explain this a little further or more clearly for me. Thanks, Scott

sure... N's are newtons.... kN are kilo-Newtons (1000's of Newtons) in order to get an idea of what kind of the poundage you're dealing with. you bascially divide the number of Newtons by 9.8, and then multiply by 2.2.

take the the THK SR30 blocks for example, the load ratings are
30kN (radial),
18.6kN (reverse radial), and
16.8kN (side).

so 30k = (30,000Newton*2.2)/9.8 = 6735 pounds
18.6 = (18600*2.2)/9.8 = 4175 pounds

as you can see, you could mount these sr30 rails on the ground, mount a platform on them, and them pull a car onto the platform and they wouldn't break a sweat.