New guy from Norway, planning a Bonelle grinder

Thanks, that's good advice. The drawings aren't checked for errors yet, and they will be "metrified" before construction. So plenty of time to add my own errors

Nice drawing - essentially a Quorn type I think? The Quorn has an 8mm taper that matches a standard watchmaking type of collet I think - these collets are quite hard to find and expensive. You can of course just use a plain tapered mandrel but if you were thinking of fitting collets as well maybe consider an ER16 nose? You could use it with a drawbar for wheel mandrels and have the option of collets.

Wow, this turned out better than I could have hoped for. Got a call today from a nice member of this forum that had ductile iron for me. He could even cut it to the rough shape for me.

Guess I'm all out of excuses now

I'm a bit stumped now. I've been working on the wheelhead and something doesn't add up right:

The wheelhead guide (Drg 11, Det 1) does not line up with the jack screw (C10 Det1) and the square guide rod (C11, Det 2). I've double and triple checked the drawings and I can't find any mistakes. Also the guide collides with the mounting bolts for the wheelhead arm (C3 Det 1). I've checked both Don Williams original PDF and this metric one: http://www.mosoft.nl/slijpmachine/A0%20Bonelle%20TCG%20drawings%20Metric.pdf

I found that I had to redrill the threaded holes in the wheelhead arms in order to attach the guide block when building my Bonelle - It seems that there are various cumulative errors that eventually don't quite add up! I had real trouble trying to find out why the thing didn't fit!! Additionally I had the problem that my 2" square iron bar for the wheelhead block (C4) was metric i.e. 50 mm square (rather than 2" or 50.8mm) and had also been cleaned up on all four sides making the actual dimensions even less by a few thou all round. Not really surprising that it did not fit off the drawings.

So far this is the only part that has not fitted after being machined straight from the drawings. I am currently building the toolholder and have worked through the drawing in more or less the order that they are set-out.

The only modification I have done is with the bellows and their attachments. I will be using commercial rubber bellows and have designed and machined a set of attachments to allow the bellows to rotate as the front bar is rotated - otherwise the bellows would twist and prevent free movement of the bar.

Just to add - Don't alter the guide block.  Just reposition the threaded holes used to secure it.  You will have problems if you alter the block.  There are two positions for the leadscrew in the wheelhead guide (C8) that can be used and both will fit if you simply reposition the holes for the block.

Edited By Bizibilder on 03/04/2023 15:35:17

Welcome to the world of Model Engineering! You will find things don’t line up, bits are drawn wrong, 26 tpi threads are supposed to fit in 40 tpi holes, the list goes on. Although all these drawings, steam loco, traction engine and workshop tooling have been around for years the drawings are never updated, the pathetic excuse from all the sellers of castings and drawings is copyright issues, this is just a lame excuse, all that is needed is a sheet of corrections sent out with each set of drawings, please watch out for missing holes here, wrong size hole there etc. Rant over, I wish you luck with the Bonelle, not many finished ones exhibited unfortunately. Please keep us all updated on your progress.

Ok, you've calmed me down a bit. I just figured all the bugs world be fixed after all these years. It's an easy fix, I just had to make sure it wasn't one of my stupid mistakes.

I'll reposition the holes and reduce the height of the guide so it doesn't interfere with the mounting bolts. This is why I model everything in 3D before building.

BTW, I came across this yesterday: hexagonal paper bellows

https://www.youtube.com/watch?v=ldmCQayLieI

Plain office paper covered in packing tape works like a charm, I just printed the template and scored the paper with a ball point pen. The pattern is easy to make, the width of the vertical lines is 3.46 (2*tan(60)) times the height.