Need Help!- Mounting THK rail to 80/20

[Drools]

Before I try to come up with a solution I was thinking someone on the zone must have done this. I want to mount 25mm (almost 1") rails to my 80/20 1530 series. Please share your methods, thanks for the help.

[stevespo]

With the 8020, you can order 36" long lengths of undrilled nut stock (part number 8900 for 15 series, I believe). You can then drill/tap and it makes installing the rails faster and easier than individual nuts. 8020 will also provide this as a service, but you'd have to send them a drawing for a quote.

There was a discussion a while back about mounting rails. Check out this thread:

http://www.cnczone.com/forums/showth...968#post692968

With my 15mm rails, they don't quite span the angled part of the slot, so it makes alignment a little tricky. The 25mm rails might sit on the flats nicely. In any case, one suggestion is to have a shallow dado milled above the slot to act as a registration for the rails. That would ensure they were parallel and compensate for any inaccuracy in the extruded 8020.

Steve

[Drools]

Thanks Steve, I really appreciate the help. I guess having a shallow groove milled into the 8020 is an option. Is the long side of the 80/20 flat or is there a slight angle closer to the center? I can't recall if I had read some where about a 2 degree angle on the long side of the 80/20.

[stevespo]

I think the 2 degree angle is on the area that overhangs the t-slot. It provides that "sprung" resistance to vibration when the parts are clamped tightly.

Your 25mm rails might just span this area, but I don't have any 8020 in front of me to measure. Another option is to use a flat plate (steel, aluminum) and mount the rails to that, and then mount the plate to the 8020, but that seems like a fair amount of extra work.

If you don't have access to a machine shop with a big milling machine, I think a hand held router and fence could be enough to cut the shallow slot. It wouldn't have VMC accuracy, but would be reasonably straight and as flat as the 8020. I sure wish I had done this, because alignment was tough without it (getting everything straight, parallel and without any twist).

Steve

[Drools]

yes the 25mm = .984inch
Which will span the gap easily. This is a large rail, the bearing blocks are huge. I did not realize just how big they are until I got one. The bearing block weighs 1lb 10oz each for the regular length bearings (SHS25C).

[wendtmk]

I ended up buying a length of 1/2" thick aluminum the width the the 8020 piece I was mounting the rail on and mounted the rail to that. Two rows of holes on either side of the rail the width apart of the slots on the 8020 piece and it was good to go. Made aligning the rails pretty simple too.

Mark

[Drools]

Thanks Mark. That is probably the route I will end up going. The other thread that Steve posted basically said the same thing but using steel. I was thinking the 1/4 steel milled out with a shallow groove to fit the rail. If they are going to mill the grove I might as well have them drill the mounting holes for the rail and the 80/20. It looks like I will be doing a CAD drawing and spending even more money.
I would really like to see pictures of the mounts and what you have done to protect the bearings from debris.
Thanks for the help!

[wendtmk]

Here's a link to the build log on another site: http://clarksclassicflyrodforum.yuku...l#reply-168178 I haven't gotten to the point yet where I've figured out the debris covers.

There's also other pics of the build process prior to that and another fella's machine that's pretty neat too that uses 8020 stuff.

Mark

[Drools]

Wow that is fantastic workmanship Mark!
My machine is much more modest that the monster you are building. I know the 25mm rails are quite large for my little machine where the 15mm rails would have done nicely but I got the 25mm stuff for quite a nice price. The dimensions of my machine are only X30xY20xZ6 inches. This has me thinking, maybe I should save my 48" rails for the Y-axiz of a new machine and use some of the carriages from Ahren for this machine. I was going down this route originally until I got a deal on this THK 25mm stuff.