Joining 2 THK HSR 35 rails seamless?

[rodjava]

Hi,
I have sent this same question to THK and just waiting for a reply........

I have a application where I need to join 2 THK HSR 35 rails, butt to butt, to make 1 long rail.

The joint should be as seamless as possible. Is there some type of THK "bridge"? Or just cut the rails at 45 as accurately as possible and butt them up.

The whole lenght of the rail is used for cutting, so the joint can't be located in a non critical cutting portion of the rail.

Any suggestions?

Thanks in advance,

Rod

[rodjava]

Here is a very quick response to my question to Technico.

BTW, from the President.......

Hello Rod,
For jointing, we Grind or Mill the ends, depending on customer
tolerance eeded.
We do this at Technico everyday.
Contact me if you need more info.
Best Regards,
Steve Lussier
President
Technico Inc

[Zumba]

Chop at 45 degrees like a scarf joint? I don't think that's the way to do it with THKs. Chop/grind at 90 and butt them together, just like the gap in a gap bed lathe. If they're not perfectly square and ground to a smooth finish, you won't get the smooth, seamless sliding action that you seek.

Also, the flatter and smoother your mounting surface, the easier it will be to align the rails vertically. Bolts should be torqued evenly as well. For horizontal alignment, set screws are the way to go.

It's pretty simple, really. It just requires very accurate machining. That's one of the reasons why big commercial CNCs are so expensive. There are no shortcuts. This may discourage a lot of DIYers but it doesn't change reality.

[rodjava]

Zuma,
Thanks for the suggestion. I'm now planning to have the ends cut and then ground square with whom ever I buy the Thk rails from.

Rod

[Zumba]

See if they can cut them to an exact length, +/- .002 or so. It'll be much easier for you if the 80mm hole spacing is maintained.

[walter]

I have a few factory "originals". Nothing fancy but the cut is pretty straight. Almost seamless.

Hole spacing is 'not' maintained.

[rodjava]

Zuma,
That's exactaly what I planned doing.
Here is a quote from Technico:

Rod,
We charge $25 per Jointed End for Sizes 25 and Under.
We charge $50 per Jointed End for Sizes 30 thru 55.
We charge $75 per Jointed End for Size 65.
Anything larger than the 65 Size needs to be done by THK.
Best Regards,
Steve Lussier

[Perp]

Can you have them drilled for alignment dowels at the factory to make alignment faster/easier?

[Zumba]

Dowels are useless when you're seeking tenths precision.

[Perp]

I would have thought they were good, but I learned something new today.