Wheel Shop

Funnily enough, I got my first instances of wheels going like swashplates today, even when I was taking care to press them on square. I was experimenting with the amount of interference on the push fit and had increased it by lessening the penetration of the taper reamer. That must have been caused by the resin releasing some stresses after the push fit. I think there is a reaction to the push fit since there is a combination of displacement and cutting by the square edge of the axle. If I get another set of axles made I think I might investigate getting the corner of the axle end rounded so that the push fit only displaces. I did get over today's problem by restoring the previous depth of penetration of the reamer and I also increased the diameters in the printed hole in the printed centres to cut down the amount of material removed by the reamer.

Jim.

 

There is a temporary halt to the proceedings. I was getting too much variation in TIR which was out of spec - not too far out, but enough to cause problems. I did a sample check on assembled centres in tyres. I set the wheel assemblies in the ring collet mounted in the four-jaw and got the tyres running with zero run out. The hole was carefully reamed out to accept an axle and I then put a an axle in the hole and found that the TIR was 0.001", so pretty good.



My attention then turned to the small pillar drill and I reckoned that the problem was the Jacobs chuck. I had suspected all along that I was pushing my luck since Jacobs chucks rarely have the same accuracy as a collet chuck and I was really looking for zero runout from mine. In my first production run I must have got things pretty well spot on by accident and in subsequent runs I was not so lucky. So my small pillar drill...



... is going to be replaced by this...



...my Centec mill out in the garage workshop. No comparison. The mill probably wasn't initially considered because the pillar drill is in the house and the Centec is out in the garage workshop and the approaching winter probably had an influence. I have to get an ER25 collet holder for the Centec so that I can use my ER25 collets and I will re-visit the attachments to hold the wheels in the Centec.

The Centec is returning to making parts for a model railway society. It was last used for this purpose in the 1990s for the Scale7 Society by Dick Ganderton.

Jim.