Toolpost mounted drill chucks are nothing new, but I had never been enthusiastic about the idea, although I had never tried one, except on a turret lathe. I saw some advantages but they never seem to justify the extra hassle of setting up when you needed it. However, QC (quick change) toolposts have partially removed that objection. Out of curiousity I had intended to try one anyway, one of these days.
"One of those days" arrived when I had some long holes to drill and it seemed like it might be much quicker to clear the flutes using a toolpost mounted drill bit, as it was something that was on my list to make one day I thought that I would make one before doing the holes. I found a suitable block of 4140 in the scrap box just waiting to be useful. I machined dovetails in the back so it fits directly on to the QC post, rather than some that I have seen which bolt into a tool holder.
These two photos show the dovetailed channel to fit the QC toolpost.
My original thoughts when I decided to do this was to use a quick change block with a simple parallel hole in it with means for clamping, just like those off the shelf ones for holding large diam. boring bars. In fact I was planning on sharing my big boring bar holder. I was going to get or make an MT2 sleeve with parallel outside, but it seemed to make more sense to bore the block with the Morse Taper directly.
However, I then decided to go for an R8 collet holder instead of the MT2. I have chucks mounted on R8 and MT but I went for R8 simply because it is much easier to make. A parallel bore coupled to a short relatively steep taper is easier to get right than a long shallow MT. My compound rest doesn't have enough stroke to do a full length MT2 in a single setting anyway.
These photos show the toolpost mounted drill chuck, or more generally the R8 mounting block.
After using it for the first time I can say that it definitely fits into the category of "I wish that I had done this ages ago". It is just so much nicer to use than the tail stock for drilling. It is more rigid in all directions, there is no oscillation on the locating key which you sometimes get with a tail stock and of course you can feed and withdraw quickly. With a DRO, drilling to depth is more accurate. If you use an end mill, in a tailstock mounted drill chuck, chatter can be a problem sometimes. That is unlikely to happen with the toolpost holder. I have tested this with several size endmills and it works great. This is another advantage of using a collet holder rather than a Morse Taper, you don't even need to use a chuck, an R8 collet holds a tool much tighter and truer. I can also fit an ER collet chuck in the R8 if necessary
Before trying the toolpost drilling method one of my objections was the time spent aligning the the chuck to the lathe spindle axis. In practice this has turned out to be a non-issue. I have a fixed vertical alignment maintained by a fixed spacer/stop so that only leaves horizontal alignment to worry about each time.
Note the non-adjustable height stop on the top of the block. This ensures reasonable repeatability of the centre height.
For those times when precise alignment is necessary I clock a piece of parallel bar in the chuck from the lathe spindle, as I outlined in a previous post about tailstock alignment. http://www.homemadetools.net/forum/t...ight=tailstock
Clocking the chuck for precise alignment, quick, simple and accurate.
For less precise needs I made a very simple and fast to use alignment tool. In a piece of plate I cut a V to fit the bed V that the saddle uses and on the other side a flat to rest on the bed. Then I put a drill bit in the lathe spindle chuck, offered the plate up to the drill and drilled though, then reamed the hole. Then when I want to use the toolpost chuck, I just chuck up a short piece of ground bar the same size as the hole, put the plate on the bed and adjust the cross slide until the bar fits in the hole.
So although originally a skeptic, my use of toolpost drilling has made me a convert. Well worth the minimal time needed to made it, so simple that there was no need for drawings, CAD or pencil. I am also so glad that I didn't do the obvious and use an MT2, the R8 makes it more useful. The original reason was that it was easier to make. MT2 sleeves are available to fit up inside a R8 sleeve, so I still have the option to use my large drill bits with MT shanks. An MT3 to R8 is overhung but nothing like as much as an extended tailstock. So making a single block only for R8 still gives a pretty good solution for MT2/3 as well.
PS. One of my original concerns about toolpost drilling was that if the centre line of the drill is offset from the toolpost centre bolt then the inline drilling force will create a moment tending to rotate the toolpost out of alignment. This offset is clearly seen in the photos above. I was pleased to discover that my fears were unfounded. Of course we need to remember that normal turning tool bits also apply a moment and so the toolpost friction needs to resist that.
Thanks for watching.
nice! I made a couple of these - just 3/8-24 threaded 3/8in arbors - and I use them alot, for much the same reason. Plus my lathe has only 1 1/2in tailstock travel, which is a pain.
Something else that I've gotten a surprising amount of use from is a toolpost mounted live chuck (spun my a cordless drill). Really handy for cross drilling shafts or locating holes in a plate if you don't have a dividing head.
Nice one Tony, I like the way you have made it so versatile with the collet options.
I sometimes use my live spindle in this mode or run it when using very small drills, my lathe is flat belt drive with plain bearings so I tend to keep speeds on the low side.
I used to operate a Colchester 2000 and that came with a crosslide attachment for power feed drilling which I used a lot, drills used were anything up to 3 inch dia, the other turners said they had never seen it used but never took it up.
Still a good demonstration, it's a technique I use especially with MT2 drills or precision borer, with a drill holder which has a stopper at the bottom, used directly in the tool holder with a concentricity corrector(Centricator) it's easier to go perfectly centered on deep holes when chips give problems for example.
I never have so good results in precision on 100mm. deep or more when used conventionally, with the TH it's more rigid then I'm totally in accordance with you about this technique.
ps. i hope you can understand me, difficult to explain something in english this morning…
Thanks Tony. some time back I made a straight shank to fit one of several 1/2" drill chucks I have and by luck the diameter of this shank is a good fit into one of those boring bar blocks I have with my quick change blocks (minus the sleeve). But I am not sure I understand your "simple and fast alignment tool"- would you let us see some pictures of this please?
My first thought was to do as you did and use a straight shank to fit a boring bar block.
Here is a pic. of the alignment tool. It is made from 6mm steel plate. It will vary in detail depending on your lathe bed style, mine has the common one V plus one flat. The V does the lateral location. If you have a lathe with both flat ways then you will need to get the lateral location from one side.
Thanks for all the ideas, I want to make one using a small sewing machine motor to drive it with several different pulleys for speed.I do not really understand the alignment tool you made up. Would it not be easier to put a short piece of drill rod in the drill chuck and slide it into a collet on the lathe and tighten up the drill spindle and loosen collet, now on center line. Thanks for the ideas.
Using a collet as you describe would work, but mostly it would be a pain, it would involve removing the work piece at each tool change. If the work was set up in a 4 jaw chuck or on a face plate, you would have to unset the work, fit a collet, do the alignment, remove the collet, reset the work piece and do this every time that you change from a turning, facing or boring operation, or anything that requires the cross slide to be moved.
My alignment tool works in very similar fashion but it is very quick and without the hassle.
My alignment tool is quite accurate. After machining the V and the surface to sit on the flat way, I used a drill bit and reamer in the lathe spindle to drill and ream the hole so it is true to a reasonable degree to the lathe spindle axis.
BTW. Since I made that R8 chuck mounting I have made another but only for a drill chuck, rather than mounting it to the side of the tool post this one mounts on the front which avoids the possibility (mentioned in the original post) of twisting the tool post. This latest mounting was really a second thought. I wanted to be able to mount a drill chuck in the vice on a milling machine, I saw that if I cut the dovetail groove in the block I could use in both the mill and lathe. It is quite useful because it saves some drill bit changes. For example I could have a small bit in one chuck and a larger bit in the other.
Here are some pix of its construction and fitted to both a lathe and mill. The holes serve no purpose being in the block for use in an earlier life.
Click thumbnails for full size.
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