a Steel Box Section Build with SBR20 & Ballscrews Plus a few questions

[grain_r]

Well I thought I would keep my progress on here. Unfortunately It's not quick but going the right way.

I have made the frame sides and tacked the end screw plates on. Everything has been sanded down with a disc sander to give the best possible accuracy and then I have used my trusty Digital Vernier calliper although I have also made the screw holes larger diameter for a little fettling movment of about 1/2 mm Just in case.



The next step is to start drilling my holes for the Threads. I have chosen M5 allen screws and I have ordered a cobalt 4.2mm drill for the threads.
I just need to experiment getting the hole exactly centred for the thread holes to be as accurate as possible.

[Neale]

The next step is to start drilling my holes for the Threads. I have chosen M5 allen screws and I have ordered a cobalt 4.2mm drill for the threads.
I just need to experiment getting the hole exactly centred for the thread holes to be as accurate as possible.

Couple of tricks that you might not have come across. One is to start the hole using a clearance drill that nicely fits the hole in the mating part. Just drill lightly to give a centre mark then switch to the tapping size drill which, with a bit of luck, will follow the first mark. That doesn't guarantee that the hole is square to the work, though. I use a small steel block (turned from an odd scrap of steel) with a projection on one end that fits the clearance hole, and a hole up the centre that takes the tapping size drill. That helps a lot when you are using a hand-held drill in awkward places. Don't know if you have the facilities to make something like this (very easy lathe job) or perhaps know someone who can help? I find that I can go through in one pass with the 4.2mm drill, hand-held, but anything much bigger than that can do with a smaller pilot hole first (much easier going through steel) and then open up with the correct drill.

One other tip, if you're not doing it already - get the right taps! For through holes in steel, use a spiral-point tap. For blind holes, use a spiral-flute tap. Avoid using conventional hand taps (straight flutes) if you can. They are hard work and you find yourself going in a half-turn, then backing off to release the chips, then every so often bringing it right out to clear the flutes. The spiral-form taps are designed to push the swarf in front or bring it up the flutes, and you can tap in one pass without backing off all the time. They're cheap enough from China (I recently bought a couple each of M4/M5/M6 plus one M8, and the whole lot, including postage, was just over a tenner). Well worth while.

[cropwell]

Just an addition to the problem of zinc and welding :-
I use brick acid to take off the zinc. If you can't get self colour nuts then dip your nuts in brick acid Take them out when they stop fizzing and rinse them.

Happy holiday,

Rob

[grain_r]

Hey Rob

Thanks very much for that. I will have a look for brick acid. I haven't heard of that before I guess it is for cleaning mortar from bricks so I will have a look at the builders for it ? I saw a video recently that Ron covell uses some acid to do that too. I did look for the weld nuts in a larger size for the CNC feet but I think I will use the acid instead.

Thank you very much.

[cropwell]

http://www.wickes.co.uk/Wickes-Brick...er-5L/p/153779

Vicious stuff, keep it away from your skin.

[JAZZCNC]

http://www.wickes.co.uk/Wickes-Brick...er-5L/p/153779

Vicious stuff, keep it away from your skin.

That's Cat piss for brick acid it's only 5% active our Chip shop Vinagar is stronger than that. . . . . . Good Hydrochrolic brick Acid is 28% now that will make your tongue curl.!!

Oh and fumes from Hydro Acid are just bad if not worse than those from Galv so be careful.!!

[grain_r]

Wow It all sounds like an outside job then. and if I ever don't want fingerprints there's the stuff.