Tailstock power feed

for the Myford ML7 (and similar lathes)

This idea came from the web site www.torchmate.com
This design is my own to suite my lathe and the materials I had on hand.
This page finalized 21 Jan 2003

Feeding drills using the tailstock can be tedious. Also, a slow and even feed will give a better finish, and possibly better accuracy too. (Initial test bears this out, as I used it to feed the drill for making the brass washers for it's own fastening bolts)

So, I am making (at 10 Jan 2003) a device to enable me to power feed the tailstock. It consists of 2 parts, a collar that fits the tailstock ram, and a plate with a notch and means of fitting it to the topslide. In my case, I will bore it to size to fit the toolpost and clamp it in the same way that my tool holders are clamped.

In use, the tailstock is allowed to run free, the collar is placed on the front of the ram, the plate is attached to the topslide so that the notch can engage the collar. In this way the ram can be released by backing the cross-slide out.

Here is the drawing I am working to:


Overhead general view.
I used this setup to drill the brass bar for the washers that go under the bolts in the device. Since I have no center drill I make a small depression in the center of the face with a normal turning tool, then drill 3mm. This normally comes out nicely on center. This operation worked very well, with the 1.8 thou per rev power feed entering on center and smoothly drilling for about 5mm before I released it and backed out to clear chips before it packed up.
After this operation I drilled 6mm for a close fit on the M6 bolts, then 'parted off' with a junior hacksaw, 2 washers about 1mm thick. Though one side was faced on each, the other size I just cleaned up with 120 grit sandpaper on a block as total flatness on both sides is not required.

You will see on the toolpost pages how I put a similar brass washer under the heads of the clamp bolts on the tool holders. I find this reduces the friction significantly when clamping up and makes for a nice smooth action (and I can get higher clamping force with less effort :-) As mentioned elsewhere, the bolt threads are also polished with a wire wheel or abrasive mesh wheel to smooth out the cadmium plating. This also helps to create a nice feel to the clamping action.

Last edited February 20 2013 09:55:24.

A nearly horizontal view of the setup, with the drive block set on the toolpost, and the ring on the tailstock ram. The tailstock lever was left loose for this operation, though one could instead clamp the tailstock down and remove the handwheel to allow the ram to move, as is done with tailstock levers. I will try this method sometime and report on it (see sidebar). The drill bit is 3mm in this image.

23 Jan 2003 : I tried the alternate usage of clamping the tailstock down and allowing the ram to run free by removing the handwheel. I was drilling a piece of BMS rod to 10mm for a pulley sleeve. I started by making a conical depression, then drilled 3mm to some 42mm depth. Followed this with 6mm, and then 10mm. These are HSS drills, unresharpened, but used, though not blunt. Lubrication provided by dabbing on chicken fat with a brush at each chip clearing. The ID of the sleeve had to be 11.2 to I bored to that from 10mm. When I parted the sleeve off it was in the remaining 10mm drilled part. In the stub remaining in the chuck I could not see, nor feel with a wobbler held in the bore, any eccentricity in the drilled hole (remember this is some 40mm into the stock). I could detect eccentricity with a caliper between the turned outside diameter and the drilled ID, but I had to do it carefully as it is very little.

Would I have got the same result with the tailstock floating free? I don't know, but I will do the next similar operation with it free and the ram clamped and find out.

Last edited February 20 2013 09:55:23.

Here is an intermediate stage, showing the ring before final drilling, tapping and splitting. I started with a nearly square, rough sawn, block of 1/2" plate, 51mm on a side. That was mounted in the 4jaw to run flat and very nearly centered (wasn't critical so i didn't waste time). It was then bored to 1 inch (25.5mm) inside diameter, to fit my tailstock ram.

A stub arbor was then made from an offcut of 32mm round bar (steel) with an M6 tapped hole in the end for a retaining bolt. The fit must be a close slip fit. Be careful here if you use aluminum for the ring, as if you fit it unlubricated it may cold weld onto the arbor.

Fit the ring to the arbor, and turn about 5 thou off the face across the corners until you just have a full circle visible. Remove from the arbor and mark a line half way between the inner hole and the faced circle. This is the drilling line and it is much easier to drill the square block than a finished circle! Drill from one edge to 5.2mm right through (5.2mm is my tap drill size for M6 in aluminum, standard tap drill of 5mm I have found to bind excessively). At this point you could tap to the tangent point where you will later split, and counter bore 6.2mm from the other side to the tangent point, then counter bore for the cap screw. I elected to finish turning the ring before that and make a counterbore with a guide spigot to guide it into the curved edge. Don't forget to chamfer all edges as you go, tools with sharp edges are unpleasant to use.

Last edited February 20 2013 09:55:25.

Counterboring the ring
I had to make the counterbore by milling 3 teeth into a piece of silver steel that I had turned to have a 5.2mm guide spigot, and a 10.5mm body size. I didn't harden it, as the initial test in aluminum showed success though I could have done the clearance next to the guide better, it rubbed there a bit but I just pressed on as the ali swages out of the way.

To do the drilling, I first mounted a 5.2mm drill in the chuck and used that to align the ring in the vice. I then inserted the counterbore, applied some paraffin (kerosene) to it and drilled at 1250 rpm. About halfway down to depth it started to bind, and I applied some oil (42 weight hydraulic which I use on the lathe) to the guide spigot which freed it up properly. After this I mounted a 62mm drill and bored down to the split level, followed by tapping (using the 6.2mm portion as a tap guide, though 6mm would have been better). Finally, I split it with a hacksaw and cleaned up the edges with a triangle file to give nice chamfers.

Last edited February 20 2013 09:55:25.

A closeup of the counterbore that clears the screw head. The counterbore itself was homemade in rather a hurry. I piece of silver steel was sawn off (a little short - tool steel is pricey to me). The end was reduced to 5.2mm to fit the 5.2mm drilled hole in the ring (I use 5.2 as M6 tap drill in aluminum as I find it prevents the tap grabbing the ali). The next section was reduced to 10.5mm, just enough to clear the nominal 10mm head of the M6 cap screw. The piece was then clamped on the topslide and 3 teeth milled into the 10.5mm part. These teeth were then filed for clearance and it was tested. It cut, so I had at the ring without further ado in the drillpress. This was later regretted as I had not cleaned up the cutting edges nicely and the cut was a little 'groovy'. I had made the whole tool a bit short and you can see where the end of the 10.5mm portion was reached and scored the bore, and also where the chuck contacted the OD of the ring on the right.

Last edited February 20 2013 09:55:26.

Closeup of the ring and it's clamping components. The bolt is a Allen cap head screw, hardened and chrome plated, which I had to beg off a friend who owns a lawnmower repair business as no hardware store in town stocks them, but he does.

Last edited February 20 2013 09:55:27.

Showing the brass washer under the bolt head. The threads were also 'polished' on a fine abrasive wheel (or wire brush, in the drillpress). I find this makes them feel much smoother in operation as the factory cadmium plating is quite rough. The same abrasive wheel made my 3M was used to give the brushed finish on the drive block. Note that the clamp bolt is an M6x50, and the block is 50mm wide. This gives aproxiamately 25mm of thread engagement, which I feel will minimize wear due to the clamping action, over time.

Last edited February 20 2013 09:55:27.

This is the abrasive wheel I use for the 'brushed look'. It is made by 3M and is about an inch more in diameter when new, and is expensive.

Last edited February 20 2013 09:55:28.

This is the counterbore I made. A bit rough, but it worked.

Last edited February 20 2013 09:55:28.

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Last modified: February 20 2013 07:52:52.