THK linear rails/guides

[LUCKY13]

I am going ot be building a machine much like Leeways build. 80/20 mill build

I want to use the THK linear guides and I needing to know what size I can get by with. I believe Leeway used 25 series blocks but that may be because of a deal he got on some off of Ebay. I am finding many differnt sizes on Ebay but there are a lot of deals on the 15 series blocks. I know there are other things that come into play with the type rail and such as far as what type loads they are designed for.


I dont know how to figure what loads will be handled on the machine, but I will need to be able to cut alunimum and steel even if I have to go slow with the steel cutting. The machine will have a X2 spindle box with a upgraded motor so it will have the power to cut steel. I am only talking probably small brackets when it comes to steel, mostly I will be cutting alunimum.


I expect maybe different sizes could be used on the table compared to the Z axes. Any idea what would be the smallest, and then the recomended size for the Z axes, and then the table (X & Y). I need to start buying these and what kinda deals I get on these will kinda guide what size I build the machine to. Ofcourse if I can find the 25 series blocks that should work as it has proven to work good for Leeway, but was it needed. What blocks and lenth rails I find will have a lot of input on the machine build because I cant afford to just buy new ones. I seem to be finding more 15 and 35 series rails and blocks in lenths that I can use.


Thanks Jess


Jess

[cyclestart]

A bit of advice on selecting rails at 5bears
http://www.5bears.com/cnc02.htm

In fact the whole site is a good read.

[widgitmaster]

Hi Jess,
I have just purchased 3 pairs of THK rails for my big router, after plenty of research I found that not all rails can take force in all directions (something that is required in milling) ! The other thing I learned is that not all trucks are sealed all the way around, to keep dust an swarf out of the bearings!

Here is a PDF file of THK's HSR series rails with specifications.

Hope this helps!

WidgitMaster

[LeeWay]

That particular PDF and my experience with smaller THK rails and trucks lead me to search for the 25's. The smaller ones are on the Z axis of my router. They are 12's. Quite small, but prove to be pretty bold in such a small package.
15's might be a little small, but may still work fine if they are the HSR type.
The two I would choose to look for though are HSR 20's and 25's. Also low profile wide trucks would be better. I did get a couple on a rails for my lathe that were narrower, longer and taller trucks. Probably still usable, but I never intended to use those two. I had extra blocks from the lot of 10 I picked up.

While what will work is a large venue, what is best gets smaller. I think 15's are a little on the small side and 30's are too big unless using just one truck per rail.

Also consider looking for the HRW type. These are wide rails and low profile.
That's what I used on the Y axis. They were HRW 27's. I bought another set of those to use on my lathe cross slide. They seem at least as beefy as the 25's HSR type, but save a little space and would yield more travels.

The HSR 25's and the HRW 27's worked so well on my mill that I bought the same for my lathe. Good deals were had again on Ebay, so they do appear often. Now that I'm not biding on them, you have an even better chance of getting them.

[LUCKY13]

Thanks for the replies guys.



Leeway, do you have extra 25's, low block's that you wish to get rid of. LOL, if your like me I like to keep thinks like that around anyway for later prodjects. I will start watching for them on the auctions but sometimes I see one rail set with two blocks that is long enough I could cut and make two rails if I had extra blocks.
I havnt bought any thing yet though , but I have a lot of setups I am watching to see what they do.

If you do wish to get rid of any of the 25's you can PM me and let me know what where talking about.

Thanks Jess

[LeeWay]

I don't have any extra's. I do, but they are planned for. The only extra's I have are the two narrow and taller trucks.
I did look again on Ebay, and find only very few listings for the HSR 25's in THK brand.
They don't have to be THK though to work well.
I did see many listings that I would have been interested in for a small mill like mine.
Just search for "Linear rails." There are currently at least a dozen listings in a good price range. Some more affordable than others, but many that might handle your project.

Another option would be to buy new Hiwin's. A little more cost maybe, but then you could request exactly what you wanted.

I saw one listing on Ebay in particular that looked kinda neat.
A big HRW 60.
That is a whole axis right there.

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=016

Of course the screw would have to go off to one side, so that might work better in a lathe format or a Z axis.

[Jason3]

Originally Posted by LeeWay I saw one listing on Ebay in particular that looked kinda neat. A big HRW 60. That is a whole axis right there. http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=016 Of course the screw would have to go off to one side, so that might work better in a lathe format or a Z axis.

I saw that too! - I would absolutely be going for it, but the seller won't ship outside the US. Would somebody ship that to me in New Zealand if I bought it

Best regards,

Jason

Ps - I'd swap a brand new set of 4 blocks/2 rails for it...! HRW21, HRW27, HSR35, you name it

Edited: Very many thanks to the great people on the Zone - I have accepted a kind offer to help me get my mitts on the beast, and thank you too the other person who also offered. This is a great community, there are some very good people here.

[Jason3]

Jess, sorry I think I almost hijacked your thread...

I'm not sure what's on Ebay right now, but you wouldn't usually have to wait very long to get HSR25 blocks/rails. As you said, often a single rail and a couple of blocks can be had for lots less than half what a pair with 4 blocks would fetch. You'll find blocks on their own regularly too.

Also, I wouldn't discount the 30's and 35's too soon - I've used them, they are heavy for sure but overbuilt doesn't usually hurt at all in this game. If they'll physically fit in your design, why not? That said, if your axis motors are marginal for power, or inertia is likely to be a big consideration (for instance, if you have very coarse pitch direct drive ballscrews, and high speeds) then the smaller sizes might be a better choice. Also as Lee said, the THK HRW series can be used too. NSK is another excellent brand, very high quality.

Best regards,

Jason