Wobblycogs CNC Mk1

[JAZZCNC]

Martins right what you want is etching primer with synthetic brush on coach paint available from any motor paint factors. . . Lasts for years and easily applied.!

[martin54]

Jazz I joined the Royal Navy as a stoker, I know all about painting stuff lol

[Wobblycogs]

Thought it was time to put in an update as a little bit of progress has been made.

Thanks for the advice about painting metal. In the end I went with CombiColor in bright yellow:

It's great stuff, goes on smoothly with very little odour and the coverage is pretty good considering the colour. That lot you see there was covered using <100ml of paint. It needs another coat but the 2 litre tin I've got should be more than enough to do the whole frame. Also, I think it's bright enough even for me I can practically see the frame in the dark :-)

Not having worked in metal before I thought it wise to perhaps have a go at drilling and tapping for brackets before launching into the frame construction properly and lets just say I'm really glad I did. I won't bore you with all the gory details but here's a shot of attempts 1 and 4.

On attempt 1 I chose a dopey hole pattern, the back holes are too close to the corner of the angle and all the holes are too close to the edge for my liking. At this point I didn't have a vice for the pillar drill, transfer punches or centre drills and I ended up having to make the holes in the bracket 8mm in order to get my M6 bolts in and there was no play in the bracket.

By attempt 4 I'd watched a couple of YouTube videos and had a drill vice, centre drills and transfer punches. The holes in the bracket are 7mm and after fitting the bolts I get about 1mm play in both directions (as you would expect). Phew, I was worried for a while that I couldn't achieve the accuracy needed.

As a final trial run I've drilled some new holes in the angle at 6mm and transferred those to the box section and the bolts go in fine. I reckon I can't be more than 0.1mm out now and probably quite a bit less.

I've got a couple of questions though...

In my design I've used M8 bolts to hold the brackets on as per this build. I did a bit of experimenting with my steel though and I think M6 is a better choice. The box section I'm bolting to here has a 3mm wall and while an M8 bolt will hold the M6 feels much better as the pieces is bolted up. In terms of strength I think the M6 is more than enough, I've used my test piece as a pogo stick to see how strong it was to no ill effect. I wouldn't mind hearing the thoughts of anyone with more steel working experience though.

The other question is regarding the holes in the angle brackets, what size would you drill them? Assuming I use M6 bolts if I drill them at 7mm then I've got a little bit of play to adjust things if the alignment of the frame isn't perfect. Does this sound like a good or bad idea? There's a little voice telling me that I'll end up with a wobbly frame that I can never get properly aligned.

Cheers and Merry Christmas :-)

[wilfy]

to quote jazz from a pm he sent me...

Tip use M5 bolts @100mm centres has the finer pitch means they have more thread engaged and small centres mean lots of support.

[JAZZCNC]

Thanks for the advice about painting metal. In the end I went with CombiColor in bright yellow:

It's great stuff, goes on smoothly with very little odour and the coverage is pretty good considering the colour. That lot you see there was covered using <100ml of paint. It needs another coat but the 2 litre tin I've got should be more than enough to do the whole frame. Also, I think it's bright enough even for me I can practically see the frame in the dark :-)

Sure I've seen that paint on an episode of "Only fools and horse's" the one where they painted the Chinese restaurant. . Lol

[wilfy]

one thing i wanna know whilst people are talking powdercoat and paint... is it better to paint/powdercoat the surface you are going to mount the rails on or leave them bare metal?

[Wobblycogs]

You nailed the colour in one Jazz, l knew I'd seen it somewhere before :-)

I'll give the M5 bolts a try. I have to admit I'm using M6 because that's what I've got to hand and it looked ok. I'm guessing the advice was originally for mounting rails.

I'm going to paint the steel before mounting the rail. A paint layer is quite thin and should be fairly uniform. I'd guess the errors in the steel swamp any additional errors the paint might cause.

[martin54]

Probably to late now but if you have a lot of bits to join together & making a lot of brackets then you are best off making yourself a little jig to ensure all the holes are marked in the same place on each bracket & each length of framing.

[Wobblycogs]

Not to late and exactly what I am planning on doing, at least for the brackets. I'm going to clamp the drill vice to the table and then clamp in a stop so that, for example, the top left hole in every bracket is in exactly the same position. Then I'll move the vice and drill all the bottom left holes etc etc. I'll always reference off the same side of the bracket so I should end up with all of them exactly the same.

For the framing I'll certainly batch them up and mark them together, I'll have a think about how I might make a hole transfer jig though as that could really speed the process up.

[martin54]

It's not just a case of speeding up the process, yes it will do this but more importantly if you ensure all the holes are in the correct place it makes squaring the whole frame up much easier & having a square frame is essential. Once you have made the brackets you could probably use one of the brackets as a jig for the framing.