Increasing the capacity of the Unimat SL (DB-200)
Unimat DB200 mini lathe capacity is quite small and it cannot accept
big diameter parts. To accomplish this, usually there are blocks that
raise the headstock and the tool holder, so that larger parts can be
fed to the lathe. The original raising blocks are quite expensive though, unless
you build them yourself. However, I managed to make the lathe to accept
larger diameter parts without any raising blocks, which apart from the
cost, ensures a more rigid setup, than if raising blocks were
I realized that the jaws of both the 3-jaw and the 4-jaw chuck can be reversed and when doing so, much larger diameter parts can be held without extending the jaws too much out of the chuck, which would otherwise cause them to hit onto the linear movement bars. This is shown into the picture above. Just make sure that the jaws align properly as you re-insert them in reverse into the chuck. Parts almost as large as the chuck diameter can be held that way. Rigid and at no extra cost!
However be careful when using large diameter parts if you intend to use the parting tool. The parting tool cannot remove material all the way to the center of a large diameter part. Either get a bigger parting tool or use the trick I did. When parting needs to be done, remove material up to the maximum point you can with the parting tool. Then do another parting operation, right next to the first one. Then do a third parting next to the second one. Repeat the parting operations as many times as needed so that there is enough clearance for the body of the cutting bit to be inserted inside the now partially parted part without hitting it with its sides. Now you can continue the parting operation deeper into the part, since the there is enough clearance and the cutting tool can go deeper into it.
You can do just a partial parting and then use a hand saw to complete
the rest of the parting by just cutting the part (with the lathe
switched off of course). Then remove the part from the lathe, flip it
and insert it from the other side into the chuck, to make it flat and
polish the rough surface due to the hand saw cut.
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