Member postings for old mart

Go for the PB larger one, the only slight drawback is a small loss of bed length as the body will be longer. Also the larger bore comes in handy at times when the job is a bit bigger. The chuck bodies which screw directly on to the spindle without a backplate will save a little length.

As you are near to Arc eurotrade, I would pop over and see their products. They are a top quality and well respected firm. As for dro's, they will save you much time and bother, switchable instantly from imperial to metric, and also eliminate the never ending bother of compensating for backlash. I have one on the Z axis and would dearly love them on the X and Y also. Go for them if they are within your budget.

The small MT2 spindle is a limitation unless you are expecting to work on small projects.

Seems like my old boss must have monkeyed with his clock to get it running backwards after all.

Years ago, it was common to have electric clocks powered by the mains, they depended on the frequency being stable. My old boss back in the 70's had one of those clocks on the wall of his office with the live and neutral reversed, so the hands rotated anticlockwise. The numbers on the dial were reversed to match.

The trouble with getting larger diameters of saws is the speed of rotation needs to drop. I would be worried about running an 80mm saw above 30rpm. As for solid carbide saws, they are expensive and very easy to break. Remember that to hold a saw with a 22mm bore requires an arbor of a greater diameter, so you loose cutting depth. There are lots of saws on ebay, some have greater tooth counts, which would be an advantage.

Thanks to ChrisB for the diagram, it makes understanding the problems much easier.

We have a Proxxen drill sharpener at the museum, which is quite good when you have had some practice. It can manage up to 14mm, but drills under 3/16" may be too short to hold. I bought an er8 straight shank collet holder and can hold drills down to 2mm.

The only way to get a square end to the slot, is to use a saw which has a radius large enough to reach the full length of the slot, not forgetting the radius of the mandrel. Drilling a cross hole where the end of the slot goes is a good idea and must be done first. If the slot is to be 2" long and the mandrel is 1 1/2" diameter, the saw diameter will have to be a minimum of 5 1/2" diameter.

I know the feeling, I always double check the readings on my cheapies, funny how my two Mitutoyos always give perfect measurements, and they are nearly 30 years old.

They are expensive, but for small work, very useful. The one I looked at had a 5mm bore, it would be easy to make an arbor.

Dead right, ndiy, I was thinking lengthways.

One other thing, it is safer to leave out any keys that come with the arbor.

Perhaps they forgot to counterbore the backplate.

You don't say what depth of cut is required, unless it is 7mm. Remember the cut will not be straight, it will be the diameter of the saw, so the ends of the cut will tail off to zero. The spindle speed will have to be very low, 100 rpm or less if possible, and the saw will have to be kept lubricated, tapping oil would do.

Arceurotrade have a good selection of arbors and saw blades.

Miles Hellon's thread on the Tom Senior contains serial numbers against dates which I used to guess our machines vintage. As I mentioned earlier, there is no build stamp on the head to match it with the rest of the machine. As the head is a major sub assembly at least as complicated as the rest of the machine, it may well have been a completely separate build.

If you look closely at a slot drill, you will see that it will not produce a flat bottomed hole. Nearly flat may be within your tolerances, however.

I took the camera into the museum today for the pics of the quill bearing outrigger and the nearly finished spindle. The spindle halves are awaiting the arrival of the Loctite 620. I had a rare flash of inspiration today regarding the undersize drawbar hole in the spindle. I looked in our box of reamers and found a sharp 7/16" hand reamer. I reamed from both ends of the top half of the spindle and was left with about 3" in the middle to do. I turned down 1/2" of the reamer to 8mm and found some 1/2" AF hexagon steel bar. I turned about 5" of the 6" length I cut to 11mm diameter, and drilled an 8mm hole in it. The reamer was silver soldered to the extension and the whole bore is now 7/16".

I will be sticking to my self extracting design with a bronze nut about 1" long with a 1/4" thick flange at the lower end loctited about 3/4" from the bottom of the drawbar. The flange will bear against the end of the top half of the spindle, (see the picture.

Today, I finished the outrigger lower bearing holder and the spindle. The two halves of the spindle fit with about 0.0006" clearance and screw together. I forgot which thread pitch I had used in the bore of the lower section, and to make matters worse, I have lost my unified thread gauge. I searched the cupboard of unknown measuring equipment and found a little thread gauge with 26 and 28 tpi. It turned out to be 28 tpi. Now I have the two halves screwing together with the minimum of clearance, I now have to wait for the Loctite 620 to arrive.

Mike made a special spanner to hold the spindle when the drawbar is tightened and released as there is no large pulley to hold in the TS head. He also made a spindle bearing preload adjuster spanner. The design isn't as well thought out as the drill mill as to adjust the bearings, you have to drop the quill out of the head, or take the motor, pulleys and their support off of the head to reach the nut.

Next week, we will be painting the last parts and I will buy a 1hp six pole three phase motor. The six pole motors run at about 1000 rpm, which with the four speeds by belt and a VFD, will give the range I require, somewhere between 150 and 3000 rpm.

Now I know that a self extracting drawbar is easy to make when I get round to it. There will be a bronze threaded sleeve with a flange at the lower end, trapped within the spindle and loctited in place.

Photos next week.

Looking at the washer/disc held on with the rollpins, it might be only a chisel or sharp screwdriver that is needed to remove it. Bearings can take a certain amount of hammering, I belt the drawbar of the mill every time to break the R8 taper.

Clackson autolocks are definitely not the answer.

Maybe large diameter heat shrink tubing. If you get some 70mm diameter, and can get it to shrink on without slipping, then put successive layers on, the constriction is considerable. I would expect that the horn requires heating before it can change shape, and the use of a heat gun to shrink the tube would be sufficient.

Possibly, if the horn is straight, it might be possible to push it through a die made from metal with a tapered hole in it. I still think heat is required.

I don't have the serial number at present, but it seemed to be of 1969 vintage. All the major cast iron parts have the build number 7, except the head casting has no number I can find. The bed is the long style. I was going to make the top half of the spindle, with a mill and rotary table, it is easy to cut that style of spline. Now I am going to cut the bottom off the existing spindle and attach it to the R8 end. The drawbar will be made of 7/16" 431 stainless steel, the only stuff I could get in 400mm lengths. The bottom 3/4" will have the 7/16" UNF thread, the remainder will be turned down to 10mm and the top will have a 10x1mm thread for a 19mm af long nut with locknuts either side and a bronze thrust washer. If there is room inside the spindle above the R8 tooling, I might be able to make it self extracting. I was worried about fitting the two halves of the spindle together. There will be 1 1/2" of close fitting overlap, plus 1/2" of 26tpi thread pulling the halves up to a shoulder. I looked in the Loctite site for a sleeve and bearing fit retainer that did not go off too fast. I have 638, but fitting the parts together and screwing them up tight might have ended badly. 620 is a much slower curing grade and should be fine.

ps, the s/n is 2961

Edited By old mart on 09/08/2019 16:51:59