Member postings for old mart

Its unobtanium, are you sure of the density?

I just lookedat a 1.5hp two pole motor and for the TEC brand, the rpm/frequency/power figures are listed.**LINK**

No, I couldn't get an insert in that small a starting bore. The smallest insert with 8 ACME would be IR16 size, and I have my doubts whether the insert could be cut down smaller leaving only one of the three edges to do the job and still be attached to a custom made holder. There is just a possibility that a cut down one could be silver soldered to a holder, but I am not sure at all. APT sell these inserts singly, but you would also have VAT and postage. Be careful to measure the pitch of your new leadscrew, 3mm trapezoidal is very similar to 8 ACME.

I just tried it, and it works. Whatever next!

Boris would be off the Little Orme, North Wales.

Edited By old mart on 19/11/2020 16:58:43

I have seen several variations of the little tables and would think that they would be entirely suitable for the basis of a mini mill holding cutters up to 5mm.

Those dentists picks are very useful.

The dumbell test and a test bar compliment one another, both are needed, as neither can do all the tests on its own. If you do have a dead centre for the tailstock that is not perfect, then testing it at different positions can frequently find the sweet spot, and the centre should be marked accordingly. This is where a test bar between centres comes in handy. I have two of 7" and 11" long. They also are useful when centring the rotary table on the mill, and checking chuck runout.

Manofkent, go on the "inverter drive supermarket" and look at the three phase motors, they usually have the speed and power output at various frequencies. I found that the 1hp six pole motor I chose worked well from 25 to 75 Hz. The power output drops off quickly with lower frequencies. I also bought a 0.75 Kw Scneider Altivar from them which was so easy to set up using their quick start guide. The whole setup cost me about £350, for 1hp.

Welcome, Salty, theres more wealth of knowledge for Myfords than anywhere else on this forum, not to mention every other subject under the sun.

Welcome, Jay, I wouldn't worry too much about it, just make sure the tape is doing its job and get machining.

It is difficult to measure the runout of a drill chuck with a Morse Taper. I would chuck up a piece of barstock and turn it to a size to fit the drill chuck. Tighten the drill chuck onto the bar and measure the runout of the MT. We have a lot of chucks at the museum, including several new British made Jacobs. The best tested is a 13mm R8 integral keyless Cutwel branded chuck, with 1/4" it is 0.0005" tir at the jaws and 0.001" tir at 2" out, and with 1/2", it is 0.001" at the jaws and 0.002" at 2" out. The others average at 0.003" to 0.005". You have to test with known true stock.

The tailstock took a long time getting it the correct height, the quill in line with the lathe axis, and the offset true. I turned a piece of 3/8" steel in a collet to a 60 degree end and did not disturb it during the testing. I found that a live centre in the tailstock was not good enough, even though it was a new Rohm. The testing was carried out with a 11" test bar with MT2 at one end, made in India. The test bar is better than my measuring capabilities. Fitting the MT end into the tailstock quill made checking the alignment in both the horizontal and vertical planes easier. The tailstock quill was checked at both ends of its travel. This tailstock quill is a new one that I happened to find on ebay, the taper in the original was not very good.

I have tapped CI many times with holes from 2BA, 6mm, 8mm, 1/4 bsf 5/16 bsf and unc and 3/8 unc, plus 3/8 bsf helicoil. I have not noticed any particular looseness with any of them. I do use top quality drills, not hand sharpened, as there is a tendency to drill oversize unless you are very good indeed grinding them. I do use a taper tap if possible followed by a plug tap if the hole is blind.  If possible, do some tests with very slightly undersize drills, to find out how close you come to breaking the tap. Tap CI dry, no lubricant and a drill guide to hold the tap square at first does help.

Edited By old mart on 18/11/2020 20:50:06

I knew it was something like that with the windscreen. I would have expected that all new fasteners with the correct part number would have been issued for the job. I'm also surprised that 8-32 screws did not strip out of the 10-32 holes when they were torqued up.

I have a Pratt 6 3/4" three jaw chuck with serrated jaws, It has 1/4, 5/16 and 3/8 inch coarse threads, and as whitworth and UNC are similar in these sizes, I had difficulty identifying them.

Airbus use both Unified and metric in their aircraft. There should be no danger of mixing them up, as you don't get the fasteners out of a sack when working on aircraft. It was a cardinal sin committed when somebody put screws that were too short in that airliner windscreen.

The Atlas 12 x 24 lathe that the museum inherited sits on a welded steel table with a drip tray. We put a large block of aluminium under the headstock, about 35mm thick and that allowed room under the tail end for adjustable bolts rather than shims. The Atlas manual says to use a sensitive spirit level across both ends of the bed to get them matching with no twist, I'm not sure if my Moore & Wright level is sensitive enough, but the "leveling" should be easier when the lathe is up and running. Some shim stock would be easy to get hold of, even cutting up an aluminium beer can would provide a usable source of material.

Thats the ticket, always get the job done the simplist way, just be sure the donor will not be missed at a later date.

Having a lever type indicator with a magnetic base is very useful for checking alignments. When you took the finishing cuts at both ends of the bar, did you cut in the same direction each time? It would be normal for the end furthest from the chuck to be slightly bigger, but more than 0.1mm is cause for concern. I would check the spindle bearings first, that definately requires an indicator.

Edited By old mart on 17/11/2020 15:29:01

Since only some jobs require maximum speed, and the gearing was changed to limit the max rpm to 1500, then as long as proper attention was taken to oil the bearings regularly especially when maximum speed was used, then I would not have any worries if I had one of these lathes. White metal has been used in faster applications and modern oils are so much better than those available when the Myfords were made. I use semi synthetic 5W40 motor oil in the Smart & Brown because it is superior at room temperature than any mineral based oil.

I have done similar things on the Smart & Brown model A at the museum. The Norton QCGB only goes to 8tpi as standard, so to do 4 and 5 tpi, I had to double the gear ratios and select 8 and 10tpi. There is a safety link in the gearing, and as I was concerned about that breaking part way through, I disabled it. Great concentration was needed to avoid a disaster. I used the back gear, but the option of hand winding is safer, as you have time to think. You can easily make a handle, or there are many ready made ones for the Myford lathes.

Edited By old mart on 16/11/2020 19:14:47

The inserts are for aluminium, TPHW 2204 right handed. They use a 4.5mm screw. Not interchangable with the standard TPKN or TPUN. They have a corner slightly chamfered. They measure 20mm and 4.8mm thick.

Edited By old mart on 16/11/2020 18:42:04