Member postings for old mart

To make sure that any error is in the spindle and not the MT arbor fitted would be to mark the spindle and tool and then refit the tool at 180 degrees to its original position. If the error is the same, it is the spindle and if it changes, the tool is suspect.

I have a couple of test bars,one about 7" long and the other 12" with MT2 ends and centres, bought for the lathe. They are both more accurate than my measuring equipment. Very useful also for testing Morse tapers, but care must be taken freeing them from the taper for fear of damaging the centre at the end.

Edited By old mart on 13/09/2022 14:28:32

I have the laydown inserts in 11,16 and 22 sizes. There are limits of the thread pitches with each size and the minimum hole size they will fit in. It is possible to make custom holders for a specific job if the standard tooling ends up being slightly too big if you also have a mill to make them. Here is one that I made with a coarse ACME form to manage a tight fit.

Jason, you must have delved deep into the Sherline part numbers to find out they were selling the DPMT type which is as rare as hens teeth. I hope the DCMT will fit in the toolholder as the bottom of the DPMT insert will be slightly smaller than a DCMT one.

Our slips will never wring together, but rust is a danger as it stands proud of the surface and must be scraped gently off. The tiny pits left would be bad if they covered most of the surface, but ours are about 10%, fortunately. While I have instruments that can measure down to 1 micron, in real life, I would be content with 10 microns at best for actual work and 50 generally.

My mistake, Baz, the common DCMT 07 02 (02 or 04) would have the second pair of numbers being the thickness, followed by the tip radius, commonly 02 or 04 in mm.

So the commonest inserts of this size would be DCMT 07 02 02 (2mm tip rad) or DCMT 07 02 04 (4mm tip rad).

The aluminium grades are usually designated H01 and can be called DCGT---- or DCMT----, depending on the source.

Edited By old mart on 12/09/2022 20:07:38

Looking at your insert, and assuming the tool shank is 10mm, then the insert is DCMT 07. any numbers after the first two, such as 02 or 04 will be the radius of the tip in mm.

Plate is flat like a wall, and bar is cylindrical like a tree trunk.

With a smaller lathe, the inserts designed for aluminium used with small depth of cut would be my choice, I use them for finishing cuts on steel and have also used them on titanium aircraft parts, we have plenty of spare bits waiting to be made into something else at the museum.

If your inserts are identifiable, you can get certain types in pairs rather than boxes of ten from APT, which is a good way to experiment.

Edited By old mart on 12/09/2022 14:22:43

An ambitious project, especially if you intend to include the quill feature which is very useful to have. Occasionally, heads of various sizes come onto the market and it would be easier to overhaul and adapt an existing one for your mill.

Clickbait, maybe, but why did you bother to reply, Robert?

I cannot believe this Northern Post feature, can you?

**LINK**

Electric iron cable is normally white braided cotton and about the right size. It could possibly have the sleeve removed to fit over the exact diameter core. Also, it could be dyed the correct colour.

In the American forum, The Home Shop Machinist, there have been several threads showing a variety of cranes made for lifting heavy parts of mills and lathe chucks from the machine to their storage shelf or bracket. The biggest chuck that we have for the museums 9 x 20 Smart and brown lathe is 6 3/4", and that is as much as I can manage without lifting gear. A 5" mill vise is as big as I would want to lift, a 6" weighs almost double that.  We also have a tilting/rotary fixture that can hold a vise or 4 jaw chuck which weighs about 80 pounds, which used to be used occasionally on the round column mill, but much too big for the Tom Senior. It has only been used once this year, as I bought a much smaller tilting plate for most uses.

Edited By old mart on 11/09/2022 16:08:40

If it is flat plate, I would produce the bore first and make an arbor to hold it, as already mentioned. When it is on the arbor, just touch a tool tip against the side to make a mark slightly bigger than the finished diameter and remove it from the arbor and hacksaw just outside the mark for a rough diameter. Then refit to the arbor and turn the OD. The dimensions mentioned leave no allowance for finished size or thickness.

I am confused by the metal description. 75 x 80 x12 mm BAR?

It could be better to get hss ground thread taps, and if possible have the sizes for brass kept separate from the ones used for steel. That would be more expensive, so only buy sizes as they are needed. I can recommend Tracy Tools.

I would not like to part off a bit of 304 stainless, even having industrial parting tools. The parting depth would have to be an inch. Tapping that alloy could go badly wrong also. The tapping would be subject to the length of the tap, the outer half of the hole might have to be clearance for the tap shank. Drilling the hole could be problematic, because of the alloy, I would drill the larger diameter halfway through first and then finish with the tapping size hole, not the other way around.

The slip gauges at the museum would all fail testing even to workshop grade. A stack of 4 would probably be 0.0001" undersize, which is plenty good enough for our requirements. When I got the box, I had to remove a thin film of rust from most of them, with a scraper and oil, not abrasives. A new Stanley knife blade works well and won't scratch the surface if used carefully.

There is a difference between die qualities, and small ones are much more difficult to use, practice with different types of steel will find the most suitable type. There is no substitute for having plenty of spare metal to practice on before committing to the actual workpiece. If possible, perform the most difficult proceedure early on so that less time and effort is wasted if it fails. Sometimes it can be better to tap a hole to Loctite in a length of good male thread rather than make a workpiece out of a single piece. Of course, with screws, that would only work if the head was large relative to the thread.

The accuracy of lever type indicators is less important than their ability to detect runout. For accuracy in actual measurement, the plunger type is designed to be fixed to a dedicated stand sitting on a surface table, and easy to check using slip gauges. With the lever type, each model is designed to work wilh a compatible length arm at right angles to the workpiece. As the angle changes, small errors accumulate. That has no importance if, for instance you are adjusting round work in an independent 4 jaw chuck, the final zero needle movement is all you are aiming for.

An instance of a dial indicator not being accurate in measurement, but functioning perfectly well is the co-axial type indicator used in milling for centering a bore with the spindle. The numbers on the dial are meaningless as there are a number of different types and lengths of lever probes and angles set used with one instrument, which mean the movement bears very little relationship to the pointer movement. Since the object is normally to attain zero pointer movement, that doesn't matter.