Member postings for old mart

You might have a go at selling them on ebay, a German enthusiast might want them. There are 7mm threads used today on bicycles I seem to recall, but I doubt if the pitch is 1.1mm.

The loose register trick is exactly what I did with the er25 adaptor on a lathe backplate. Only a small ammount is required, about 0.004", 0.1mm and the normal screw clearance will allow exact lining up if it is necessary. I have bought a small quantity of higher quality collets in the most used sizes, Cutwel and Vertex. Remember, if the collet is not perfect, the fine adjustment may have to be carried out each time the workpiece is changed, as there is no way of indexing the collets in this system.

The wobble that you got is very large, did you face off the backplate at the same time as producing the register? Is the depth of the register less than the depth of the recess in the collet plate? Have you checked the running of the taper inside the collet plate, you will need a lever indicator to do so, the plunger dti's will have difficulty reaching inside. Poor quality collets may have up to 0.003" runout which is bad.

Edited By old mart on 03/06/2020 17:33:47

I didn't even bother to produce a keyway in a spacer I made when I made some extra gears for the S & B model A. The gears needed to be displaced axially in some configurations, so a spacer was needed to go one side or the other. Originally, the spacer would have had a key like the gear, but I just filed down the half of the key which was under the spacer, and turned the key round in its slot depending whether the gear was inboard or outboard.

Before buying mechanical micrometers, you need to make up your mind whether to choose imperial or metric. I have both types and have no bother which I use, the lathe and the Tom Senior are imperial, but the drill mill is metric. That is only a suggestion, as converting one to the other is easy, you can use your digital calipers as a converter any time. The last time I bought a micrometer, I got a bargain, a NOS 25-50mm with a length bar in a nice box with instructions, quite old as it is made in the DDR.

I have several digital calipers, three cheap Chinese 150mm/6" size and my old 150mm/6" Mitutoyo and the heavyweight 300mm/12" Mitutoyos. I can trust the Mits to measure exactly, inside or out, but not the cheapies, especially not inside.

A set of tee shaped rocker gauges is worth getting, and getting to know well. For bores, if you don't have the means to measure inside accurately, the safe way is to make a plug gauge. Say, if your bore was to be 50mm, then a double ended plug gauge with one end 50mm and the other 49.95mm would work quite well. When the small end fits, you are close and the full size should not quite go in. Size for size will not fit without force.

It is worth gradually building up a few good make second hand micrometers, they are usually easy to judge from their cosmetic condition whether they have been abused.

I used to give the apprentices metal to tap in different sizes for them to screw in bolts until they broke, or the thread stripped. It was a very educational task, and quite popular with the lads.

Its a shame that there doesn't seem to be a way of telling exactly where in the world members come from. It would influence the recommendations for suppliers.

Is there any way to increase the swing of the motor? Would changing the length of one or both belts help.

The drill mill at the museum manages all the changes ok, but the belts I bought to replace the originals did not work, I had to get some very similar lengths.

That middle pulley has a limited swing, are you sure it is not being brought up against its stops by the belts being the wrong length?

If you have the time you might get a length of link belting and then you can experiment. I would think the manufacturers would have done the sums regarding belt swapping when designing the mill.

Is there any way to increase the swing of the motor? Would changing the length of one or both belts help.

The drill mill at the museum manages all the changes ok, but the belts I bought to replace the originals did not work, I had to get some very similar lengths.

That middle pulley has a limited swing, are you sure it is not being brought up against its stops by the belts being the wrong length?

If you have the time you might get a length of link belting and then you can experiment. I would think the manufacturers would have done the sums regarding belt swapping when designing the mill.

I have recently bought a couple of internal grooving tools with 16mm shanks, MGIVR 2016-2 and MGIVL 2016-2 (l & r handed) which take the common double ended MGMN 200 inserts. They are 2mm wide, 1.5mm and 3mm are also available, but you have to buy the matching holders for each width.

I would use the narrower 2mm to produce the 3mm groove by alternate multiple overlapping cuts. Tool height needs to be about 0.002", 0.050mm above centre, and minimum possible tool overhang. Keep blowing the swarf away as you cut.

Edited By old mart on 01/06/2020 22:04:31

Don't worry, the plate will be perfectly ok. You now know that lining up the degrees to zero on the compound doesn't mean much. It is possible to get the compound parallel to the spindle axis, but its a lot of bother.

I know that your plate will be perfectly usable as we have a large quantity of faceplates and chucks at the museum. The supposedly best backplate I made has a register with 0.0005" clearance on the spindle. It is a pain to screw on and off. The loosest one has at least 0.020" clearance, it is easy to fit. They both repeat perfectly each time they are fitted. Remember what I said about screwing the plate on and off a few times before final machining of the front face.

The next time you make a backplate, you will make one with greater accuracy, but in the real world, it won't work any better than your Mk 1.

This is one of the rare times that you can get away with these errors, most other threading jobs will not be so forgiving.

Grooves for o rings rarely have a radius, they are normally square. You should post the full dimensions of your bore. O ring manufacturers have suitable groove sizes on their websites.

It's a shame about the lockdown, there is a little faceplate about 5" diameter lying in some junk at the museum, and the thread is small, but I can't get in there to look at it.

It depends how deep the threads are in the cast iron. If you can manage 4 diameters, there is very little chance of it stripping before the screw breaks.

I would cheat and use the mill and rotary table with a 1/16" end cutting tool. But I have the patience to go round and round for a very long time. I wonder how tight the tolerances are, or even if the piece could be made from two parts Loctited together?

I was looking at my 25mm Sandvik boring bar which takes TCMT 110204 and uses 2.5 mm screws with a torx 7 wrench. I was going to suggest 2mm with a T6 wrench but I was too slow.

I would think it uses round belts, judging from the angle of the vees in the pulleys. Leather with a simple link of bent iron wire for the join. Its hard to tell from just the pics, but a 100mm chuck looks possible. Give us the measurement from the centre of the spindle straight down to the frame. You have six speeds over a quite good range with a very strong looking back gear.

Edited By old mart on 31/05/2020 20:11:08

Edited By old mart on 31/05/2020 20:15:37

Something like this?

UcAAOSwKk5cW8ga">https://www.ebay.co.uk/itm/Brand-New-High-Quality-Optical-Punch-Set/333160596743?hash=item4d91eb4507:gUcAAOSwKk5cW8ga

Now you have it screwed on to the spindle, it needs bedding in a bit. Make sure every bit of swarf is removed from the internal thread using a small wire brush. Also deburr the ends of the thread, a Dremel comes in useful here if you have one. Clean and oil the threads and with lowest back gear engaged, screw the plate on and off several times, fairly tight. Use a strap wrench to start it unscrewing. The plate must come into contact with the face of the spindle, if it gets tight before contact is made, you will have to cut back the threads a little adjacent to the 1.75 register in the plate.

A light facing cut or two will ensure the plate is true to the spindle axis.

Edited By old mart on 30/05/2020 15:09:19

Make a note of the spindle diameters of your motor and see if it is the same as the candidate motor. Are you in a position to do any modifications? The projection of the spindle should also be checked. As these drill mill motors are usually in an accessible position at the back of the machine, changing it should be fairly straightforward.

I would opt for a 0.75 Kw motor. I chose a 0.75Kw for the Tom Senior R8 conversion and find the power is just right, it is easy to back off a tiny bit if anything starts to sound strained.

That 6.5A may be the starting current for your motor.

The motor I chose is a six pole TEC which runs at 935rpm @50Hz. I run it between 25 and 75 Hz (467 to 1402rpm). The motor will run slower, but looses a lot of torque, and cooling is compromised. The pictures of this particular motor show the end mount which I required, but it came with detachable feet. The original belt speed change is still used in addition to the VFD. Check out the VFD range from the same supplier, I bought a Schnieder Altivar 0.75 Kw from them and their "quick start guide" made wiring and programming so easy.

**LINK**

Edited By old mart on 30/05/2020 14:44:07