Member postings for Mark Davies

Nigel, thanks, some good info there I will work through, currently tramming the bed. Con rod is from a Lycoming Aircraft engine, I'm an aircraft engineer and have also been overhauling these engines for 10 years, but I always subcontracted this bush replacement job out to another engine shop, I now want to be able to do this myself.

Andy, thanks for your suggestions too, it does look like head has some nod.

Bruce, I agree, normally .001'' is a good margin, but I have a finished tolerance of .0008'' to work to.

Hopper, test bores sound a good idea once I've trammed and shimmed as best I can.

I also have a Roller burnisher that I can use for final sizing if I can get bore size close to final.

Will try the check Rob suggests next.

Ian, X and Y both locked.

DC, bushes are in the con rods, Rods clamping to parrallel bars. I think Y axis is the problem as when I make several passes without making any boring head adjustments, the Y axis Dia keeps getting bigger but X stay pretty constant. Bushes are a split bush, pressed into place, wall thickness before working is 0.035''.

But I'm here to learn, thanks.

Locked Quill and lowering whole head.

Hi All, I bought a Sieg SX3 mill a few months ago and am teaching myself milling. I'm currently boring bronze bushes on Con Rod small ends for an engine. The bushes are 1.5’ deep and finished diameter is 1.1254’’ to 1.1262’’ (they start off at 1.1115’&rsquo. First found the holes were not round or parallel ( they were bigger as they got deeper) but have improved this a lot now since I found the head rotation when set to Zero was slightly out. I’m pretty happy the hole is nearly parallel on the X axis, but the diameter on the Y axis is always slightly larger by about .001’’ to .002’’ giving me a slightly elliptical hole. Any idea what may cause this, do I need to adjust the alignment of the head vertically over the Y axis too?

If I can get the hole Diameter the same on X and Y axis this would be a huge improvement.

Thanks