Hi,

I'm wondering if any1 could tell me if
it would be strong enough for a tube with
1/16 wall to be tapped. It will be holding
a thk rail with a dozen CBored hole.
I got me a table, with 1" melamine( I plan on adding 3/4 MDF on top of it),
but the frame is 1-3/4 and 1/16 wall, it seems perfect, for my application.
I just need to put a lot of braces :).

Should I just use longer bolt then nuts,
the rail is not tapped, but needs M4 to get thru.

I've started my build with a footprint of 30"x30".
it will be used as an plexiglass cutter/engraver,
but will try to push it harder maybe cut 1/8 thick aluminum.(just maybe).

thanks.

M4 is small, what THK size is that?. With a M4 and even a fine .5 pitch would account for only about 3 threads, not enough at all. If you have access to the inside you could insert say a 6mm backup strip and then tap that.

Ken

1/16 wall what....aluminium...steel...?

either use an insert or a long bolt with a nut.

the rails 15mm HSR model I think, unfortunately there's no
access to the inside of the tube, The frame is made of steel
and it's probably softer than usual.
I have the frame drilled and tapped, I'm trying to rig up a
power supply for my el-cheapo usb camera so I could show you
what it looks like ,but could'nt find the darn driver for it.

what I'm thinking, maybe I should just drill all the way to the other side
of the tube and use a longer bolt with 4mm or 5mm DIA ( what's the closest
equivalent of this in inches?) I guess this is my only option, or trash it altogether
and start from scratch (chair) which would make my build time longer.

Even with a long screw, the tube will colapse!
You didn't say if you were a welder, but if you drill a 3/8 hole through both walls, and weld a solid pin from both ends and grind smooth, then you can drill and tap all you need! This would give 100% more strength and regidity, which will help in the long run!

Hope this helps!
Eric

25mm = 1 inch.....therefore.....3mm = approx 1/8 inch....5mm = slightly less than 2/8 inch

Here's a couple of pic I got just before I blew up a 7805 regulator.
I have it temporarily attached 4 screws holding each rails.
the X axis is surprisingly stiff. I think I'll sandwich the frame with 1/8"
flat bar, maybe it would work, I'm not sure what screw size I need
(preferably imperial) that has the right head size and has nut.


diarmaid:
thanks for the calculation, I'm hoping there's a imperial standard
screw that's almost the same size as M4, with head that would fit
on the CBOREd rail holes.

widgitmaster:
'am no welder but a friend who knows how to will be helping me
with the braces.

thanks.

8-32 or 8-36 will fit.

I have another question while I'm at it ( so I dont' have to start another thread)

the aluminum on my x axis is 4.5" high is it wide enough to split
the two rails, I mean it would only be 3.5" apart if I put the two rails in it.
the plate for my Z axis is 6"x10.875", I'm hoping to have atleast 2-3" of travel for it.

thanks.

Installing NutSerts in the tubing should work well for your application

is this the kind of nutsert?
seems like a good idea.

I'll try the 8-32. with the nutsert 'wonder if it's available locally.

thanks.

There may be a couple of downsides to those nutserts, I have used them and they work great, but.......
.
1) They take special tools to install.
2) The lip will not provide for the full flat surface of the THK rail to seat, this likely will cause the THK rail to rock and work loose over time and heavy loads.
There used to be countersunk nutserts, but 1/16" is not going to provide much surface area for the countersink.

Long bolts with a backup stiffener plate is looking better all the time :)

Ken Shea.....Oh, I agree with you on that.......but what about attaching a flat surface the rail onto a round tube.......geesch.....

Well Geesch :)
ViperTX, you must have read round tube the same place I assumed square or rectangular tubing.

Good one Ken Shea.....I just noticed that he mentioned rectangular.....

The "nutserts" I use are actually "AT series threaded inserts" They COULD be installed with a capscrew or bolt - some others need special tools for sure.
The THK mount rail can be spotfaced/counterbored to allow for the upper flange of insert to clear the base.
I am making these suggestions with DIY basment builder in mind and that fact that you WANT to use that tubing.

If it where me I would throw the tubing out and get a piece of "mans" tubing (oh oh oh oh oh (toolman)) or better yet 2" A36 plate stress relieved and ground - but thats just me.