Member postings for old mart

I think you will have to try and get a manual for the lathe, or wait a little longer for an expert user to post. If the tailstock is not adjustable, then the only way to get it in line would be by moving the headstock, and that definitely requires the exact procedure.

Edited By old mart on 10/11/2019 20:08:49

The square is a Mitutoyo combination square which might sound less than perfect, but it is very good indeed. It was the only set in the calibration system at work, and Brian who did most of the shop floor calibration was an incredibly fussy B, when he tested my Mit digital calipers, he noticed the wear at the tips, 0.0001"! I haven't tried it on its own, as it would have to be clamped down lightly, and the edge is only about 3 to 4 mm wide. I did mention getting good results with the Elliot shaper table, it is a good British make.

Edited By old mart on 10/11/2019 20:03:34

If the spindle is threaded (you didn't say so) then just screw it on a few times to settle it down and then true up the front face ready for the chuck. I have a number of screwed on backplates with registers from 0.0005" clearance to well over 0.010" slop, and they all run true and repeat.

You are dead right about my not knowing what is exactly happening, see my thread on 2-4-6 blocks.

You first need a test bar to suit the bed length of your lathe. I have two Indian made ones, both with MT2 at one end, one has about 5" and the other 9" of parallel length. Both have centres in their ends. I chucked up a piece of steel about 10mm diameter in the chuck and turned a 60 degree point on it. It must not be removed from the chuck (or collet) until after the alignment is complete, and if it is re used at a later date, it must have the tip recut before testing. Put the bar in between the temporary centre and a dead centre in the tailstock and run a dti fixed to the saddle along the plain part of the bar and adjust the tailstock sideways until it is exactly in line with the axis of the lathe. The height can also be checked with the dti on top of the bar. This is not so easy to adjust, and won't be a problem if it proves to be one about 0.07mm or 0.003" high at the right end.

These test bars come in MT1 upwards to suit all sizes of lathe. I bought mine on ebay, and they are better than I can measure.

You can also put the MT end in the tailstock to check that the quill is lined up.

 I wonder if the headstock would have to be moved if the tailstock is fixed? You still need to know whether the tailstock quill is in line with the bed axis first in this case.

Edited By old mart on 10/11/2019 18:22:07

I would guess that Senior used something like this, if they used a mill:

Its the narrower gap that would need machining, the other one incorporates a tapered jib. The minimum diameter of cutter which would cut the entire dovetail is 35mm, and that size would cut about 2/3 of the wall thickness of the bosses off. Yesterday, we removed the cross slide and I relieved the centre portion of the dovetail with a file. The area which was filed allowed for a minimum of 1 1/2" bearing surface remaining at each end at maximum travel of the X axis. The travel is asymmetric, being slightly further to the right than to the left, actually leaving about 4 1/2" at the left end, and 3 1/2" at the right, so something like 6" was relieved.

The mill was re assembled, but we did not have time to find out if there was any improvement. Next Wednesday we will know.

I wonder how Senior cut the dovetail in the first place?

Edited By old mart on 10/11/2019 17:23:13

I have also asked Brian for the details of his inverter, with no success.

Mark, do you run more than one machine at once, and if so, how many?

The X axis of the Tom Senior light vertical at the museum has a bit of play. It has 18 5/8" travel and if the bed is pulled forward or pushed back, it can move up to 0.004", especially if it is to one extreme or the other. I have checked the knee and cross slide Y axis and when they are locked and they do not move, so the X is the culprit. The Ways on the cross slide are about 14" long, so I assume that the bed is pivoting very slightly as the ends are more worn than the middle. Now I have had a look at the design of the cross slide, it cannot have a 55 degree dovetail cutter run along it to true it up as there is nowhere enough room to get one in. A 20mm diameter one would just fit, but the length of the cutting edge would only reach half of the dovetail surface. The picture shows how close to the dovetail, the cast in bosses for the X axis leadscrew nuts come (top side).

Edited By old mart on 10/11/2019 16:50:49

Just measuring my 2-4-6 blocks fooled me into thinking they were a perfect pair, as the dimensions matched, although if I had measured several points the discrepancies would have surfaced.

It seems patently obvious to me that disconnecting the motor from the VFD when the motor is not running will not harm the VFD. There is no current flowing between them at the time.

As for the pastry mixer, it seems the switching between the VFD and the motor is only used when the motor has already been stopped by the VFD and is nothing to do with emergency stopping, but only an extra means of isolating the mixer.

 My use of latching emergency switches works quite well as when the stop circuit is broken, the start switch is inoperative. If I was changing the tooling and someone pressed the start switch, nothing would happen.

Edited By old mart on 09/11/2019 22:10:09

I recon that the minimum spec for a mill should include an R8 spindle and leave the Morse tapers where they belong in drilling machines and lathe tailstocks.

Hi John, welcome, posting photos is very easy, even I have managed it.

Hi Richard, I'm sure there will be a lot of tractor lads asking for and giving advice on this forum.

When I was a kid in the country (West Sussex), the estate had a Fordson Major which ran on petrol and TVO, hand crank only, no electrics except the magneto.

As for my 2-4-6 millimetre blocks, I think they went up the hoover.

All equipment used for testing must be far more accurate than your actual product. I have micrometers in microns and tenths of a thou, but am pleased to achieve +-0.02mm or +- 0.001"

There might be a chance for them to be trued up, as Chris, another volunteer at the museum is going to have a word with a friend of his who uses a large surface grinder at work.

Amongst the stuff I have is an Elliot shaper table which is probably pretty square, and when I used that, it would seem that the T S is not in such a bad shape as I feared.

I bought two on ebay, a common size 5" and a baby 2", they are beautifully made, either toolmaker or apprentice made. To make one, you would need a lathe, a mill, a surface grinder and a cylindrical grinder, plus heat treatment equipment for the intermediate stages.

Many years ago at work, I found a strange tool in a job lot of stuff they had bought, and one of our apprentices recognised the general shape as being that of a sine bar, but it was not straight. The body was about 5 or 6 inches long and the curve of the body was about a two foot radius. I did not know what a sine bar was at the time, but I remember it very well, and the lad was not winding me up. I posted on the H S M forum about it a year or so back, but nobody had ever heard of a curved one. I don't remember if there were any means of attaching it to something being machined.

Most three jaw rear mounting scroll chucks can have the holes drilled through to the front. If the original holes are 8mm, then drill them 6.2 through to the front and counterbore them for 6mm SHCS. You will find that is is possible to drill another three holes on the same pcd, usually so all the holes are spaced at 60 degrees, ( check first though for space). SIX holes are plenty for your threaded flange. Four jaw independent chucks are commonly front fixing and would be easier.

When the mill is stopped with the normal stop switch (normally on) the VFD display goes to "rdy" (ready) and pressing the start switch (normally off) restarts the motor. When one of the emergency buttons is pressed, it works exactly the same as the normal stop switch, but latches off. The VFD display goes to "nst" (no start) and pressing the start switch will not start the motor until after the emergency stop switch is reset.

All of the VFD manufacturers specifically prohibit switches between the VFD and the motor, they would never say that if it was contrary to legislation.

My old firm had dozens of sets on the shop floor as well as inspection grades and a couple of reference sets which were kept under lock and key most of the time. All of the sets had calibration dates on them and if any slip failed inspection, a replacement was found, and it didn't matter if it was a different make, it was the size that mattered. As we had an account with Mitutoyo, most of the replacements came from them.

Ceramics and carbide slips are nice, but very expensive.

My box is a mixed lot, not one of which would be allowed by an inspection department.