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7x10, 7x12, 7x14 Mini-Lathe Information

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Here are some drilling tools that will help you get your holes drilled properly.

start with a transfer punch to locate the holes

then use a center punch to indent the workpiece

then use a center drill (yes, they break!) to drill out a pilot hole

then use a machine screw drill (the one on the top) for less flex. otherwise, go with a jobber bit. notice the difference in length.

here's a great size comparison between a jobber drill, machine screw drill, and spotting drill bit.

these are all 1/2" dia.

it's a good idea when working with the smaller mini mill and mini lathes to buy a set of machine screw drills as it helps with your limited z-axis travel. they're also stiffer and less prone to "walking".

when tapping, use a tap block. this one was made in 15 minutes or so.

this makes sure your holes are perpendicular to the workpiece!

you can download and print a free drawing of this tap block. it takes only 15 minutes to make.

wait! there's more. here's another device used to help locate the center of a pre-drilled hole. it's more like a variable-holed transfer punch. the black holder has the large cone and the center pin is used to mark the center. works ok.
want to drill LARGE holes in your mini-mill? while this is not advisable as you may burn out your controller in doing so, it's been used successfully on our mill. just proceed with caution. largest size here is 1.25" dia.
chuck a bit into the tailstock using one of these bits. this is a 3/4" bit. can't use this with a 7x. you might be able to, but even the 8x will complain a bit when using this bit.
this is actually mounted in the hf8x12 lathe. it's a JT33 taper so you could replace it with your existing drill chuck shank (but you'd probably want to get a better one anyway). note that this adds additional length to the already limited Z-axis travel.
here's a JT33 Rohm-brand drill chuck.

there was considerable run-out of the stock chuck so a better quality R8-JT33 arbor and drill chuck should solve that problem.

there is one drawback to the rohm chuck. the inside depth is roughly 1/2" less than the stock chuck therefore decreasing the amount a bit can be chucked. there is also no through hole in the chuck, so removing the arbor will require using wedges to wedge the two apart.

here's a great forum thread on how to remove the chuck from the arbor. to recap, you can use wedges that come from both sides of the arbor. squeeze them together and voila!

not sure this is a good idea, but i may drill a through hole in the chuck to increase bit depth...

this is one reason why you don't want to use an end mill in a drill chuck.

this was a piece of plywood being rabbetted with a 1/2" 4 flute endmill with a 1/2"+ depth of cut.

the drill chuck pulled itself out of the jt33/58 arbor.

if you need to make nicely rounded holes, use a reamer. they are long unfortunately, so in order to use the larger sized ones in the mini-mill, you have to cut the shank a bit. this set is an over/under set good for making press-fit holes.
plan on using jobber drill bits or straight shank reamers (shown above)? make sure your lathe can handle it!

this is a 5.5" L x 1.5" dia drill rod being reamed with a 1/2" reamer, the workpiece is not chucked - note the total bed length! still quite a challenge. the bit could be shortened...


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