The 3 jaw chuck for my Harrison M300 lathe is missing the outside jaws, and this has proved to be an inconvenience over time.
I try to obtain bits and pieces for the lathe when I can find them at advantageous prices. Consequently early on in my ownership, I picked up an 8" D1-4 backplate for next to nothing because it might come in handy one day. That day came along about 6 months ago. On our favourite online auction site I got a 6 Buck 6 jaw Tru-Grip chuck that had been badly advertised (for a Hardinge lathe) so I was the only bidder. It had hardly any use in its previous ownership, but it did need a backplate.
All fitting information was available from the Buck website and it soon became clear that the chuck would not fit directly to my spare backplate. Hmm. Good money wasted? Not a bit of it. In the metal stock pile I found a slice of 8 Ali that was just waiting to be used as an adapter for the backplate. Normally I would have preferred to use steel or cast iron, but needs must...
The first job was to whittle away the diameter to get it down to about 6-1/4 diameter. The backplate was thinned down until the locating screws were just still buried (about 1/8 removed), this in order to reduce the total overhang of the chuck when finally fitted. A register was put on the front in order to locate the adapter.
[/URL]
Next, the slice of Ali had a recess machined to make it to a push fit onto the backplate and a 1 hole was put in the centre.
The Ali disc was reversed and rough machined down to leave the boss against which the Tru-Grip pads would bear. The thickness of the main body ended up at about 1/4.
Then it was off with the 4 Jaw and on with the backplate again and the embryo adapter pushed on to it. To ensure it stayed in place I put a threaded rod through the spindle with a thick washer on the adapter and a suitable plug at the other end of the spindle. This allowed me to finish machine the boss for the Tru-Grip adjusters. I briefly considered gluing the Ali to the backplate, but didnt want to take any chance that it could be distorted when the heat was applied to separate them.
I was now able to match the outer diameters of the backplate and adapter. This pair would be reduced to the correct diameter once the chuck was mounted.
There was now a wait while I looked for suitable length cap screws to go through chuck and backplate. I then realised after receiving them that I didnt have the correct tap for the (1/4 BSW) screws that arrived. Tap ordered. Then, the VFD decided to throw in the towel so there was another months wait seeing if it was economic to repair the VFD or get a new one. Got a new one from Newton Tesla but my old remote controller didnt match up with their device. Presently, I am running the lathe directly through the VFD until I can work out the new wiring scheme.
In the meantime, I temporarily fitted the chuck, holding it to the backplate combo by the Tru-Grip adjusters. This allowed me to mark out the bolt hole positions using a specially made centre punch that just slid down the holes in the chuck. The bolt holes drilled and tapped. Before removing the assembly from the spindle, I secured the two parts together with 3 toolmakers clamps. Because I could not fit the backplate to my rotary table, the assembly was clamped to the mill table on parallels and the punch marks were located using a sticky pin and DTI. Sorry, forgot to take any pics here.
Got to get this job finished. Lathe now operational, new backplate mounted on the spindle and started to reduce the diameter to perfectly match the chuck. When the diameter was getting close to what was required, I removed the chuck but didnt realise I had machined away the register!
Oops! Fortunately, the adapter was tapped as well as the backplate, so it was a question of matching up the screw threads to finally reduce the diameter to what was required. (Because both parts were threaded, there was only one possible orientation). With all 6 screws in place and tight, there was no runout between the two parts. A felt pen mark was made so that the chuck could be mounted without trying to get the right combination by trial and error a second time. The chuck was mounted so that the Buck logo was at the spindle mark for repeat mounting on the ideal pins on the lathe spindle.
The final machining job was to bore out the centre hole to 1.625. This is larger than the spindle bore and chuck centre hole at 1-1/2, but smaller than the hole in the original backplate. Although the lathe is Metric, I work in Imperial measurements, hence the use of inches in this article.
Dave
The Emerald Isle
I try to obtain bits and pieces for the lathe when I can find them at advantageous prices. Consequently early on in my ownership, I picked up an 8" D1-4 backplate for next to nothing because it might come in handy one day. That day came along about 6 months ago. On our favourite online auction site I got a 6 Buck 6 jaw Tru-Grip chuck that had been badly advertised (for a Hardinge lathe) so I was the only bidder. It had hardly any use in its previous ownership, but it did need a backplate.
All fitting information was available from the Buck website and it soon became clear that the chuck would not fit directly to my spare backplate. Hmm. Good money wasted? Not a bit of it. In the metal stock pile I found a slice of 8 Ali that was just waiting to be used as an adapter for the backplate. Normally I would have preferred to use steel or cast iron, but needs must...
The first job was to whittle away the diameter to get it down to about 6-1/4 diameter. The backplate was thinned down until the locating screws were just still buried (about 1/8 removed), this in order to reduce the total overhang of the chuck when finally fitted. A register was put on the front in order to locate the adapter.
Next, the slice of Ali had a recess machined to make it to a push fit onto the backplate and a 1 hole was put in the centre.
The Ali disc was reversed and rough machined down to leave the boss against which the Tru-Grip pads would bear. The thickness of the main body ended up at about 1/4.
Then it was off with the 4 Jaw and on with the backplate again and the embryo adapter pushed on to it. To ensure it stayed in place I put a threaded rod through the spindle with a thick washer on the adapter and a suitable plug at the other end of the spindle. This allowed me to finish machine the boss for the Tru-Grip adjusters. I briefly considered gluing the Ali to the backplate, but didnt want to take any chance that it could be distorted when the heat was applied to separate them.
I was now able to match the outer diameters of the backplate and adapter. This pair would be reduced to the correct diameter once the chuck was mounted.
There was now a wait while I looked for suitable length cap screws to go through chuck and backplate. I then realised after receiving them that I didnt have the correct tap for the (1/4 BSW) screws that arrived. Tap ordered. Then, the VFD decided to throw in the towel so there was another months wait seeing if it was economic to repair the VFD or get a new one. Got a new one from Newton Tesla but my old remote controller didnt match up with their device. Presently, I am running the lathe directly through the VFD until I can work out the new wiring scheme.
In the meantime, I temporarily fitted the chuck, holding it to the backplate combo by the Tru-Grip adjusters. This allowed me to mark out the bolt hole positions using a specially made centre punch that just slid down the holes in the chuck. The bolt holes drilled and tapped. Before removing the assembly from the spindle, I secured the two parts together with 3 toolmakers clamps. Because I could not fit the backplate to my rotary table, the assembly was clamped to the mill table on parallels and the punch marks were located using a sticky pin and DTI. Sorry, forgot to take any pics here.
Got to get this job finished. Lathe now operational, new backplate mounted on the spindle and started to reduce the diameter to perfectly match the chuck. When the diameter was getting close to what was required, I removed the chuck but didnt realise I had machined away the register!
Oops! Fortunately, the adapter was tapped as well as the backplate, so it was a question of matching up the screw threads to finally reduce the diameter to what was required. (Because both parts were threaded, there was only one possible orientation). With all 6 screws in place and tight, there was no runout between the two parts. A felt pen mark was made so that the chuck could be mounted without trying to get the right combination by trial and error a second time. The chuck was mounted so that the Buck logo was at the spindle mark for repeat mounting on the ideal pins on the lathe spindle.
The final machining job was to bore out the centre hole to 1.625. This is larger than the spindle bore and chuck centre hole at 1-1/2, but smaller than the hole in the original backplate. Although the lathe is Metric, I work in Imperial measurements, hence the use of inches in this article.
Dave
The Emerald Isle
