Member postings for old mart

Don't forget that backlash can also be due to end float in the leadscrew.

Assuming the belt is a toothed type and some of the teeth broke off, they may have been responsible for the stalling. These belts have a number on the outside, and are very easy to get. They don't have to be very tight as the teeth do the driving, but as already mentioned, check whether the pulleys are in line and parallel.

Sorry, I'm not familiar with steam engines, you will have to decide where the grease goes, any parts which are bearings need a little as long as you avoid contaminating the joints to be bonded. I use 638 normally, but had to use 620 recently, as I was not sure of completing the assembly fast enough before the 638 cured. The 620 is just as strong, but takes much longer to cure. A little Loctite on the shaft is unlikely to displace any grease as the joint is assembled.

Edited By old mart on 01/09/2019 20:02:22

Yes, if you use a very thick type which won't get where the Loctite goes. When the Loctite has had time to cure, you can wash the grease out with solvents if you want. We used to use this exact procedure to fit and pretension the studs which held propeller hubs onto the gearbox output shafts of C130J Hercules and other turboprops. We used to use a thick silicone grease thinned down with a solvent like trichloroethane, and brushed on carefully with a small artists brush and allowed to thicken up before assembling.

Edited By old mart on 01/09/2019 18:09:09

When you have pressed the remains of the bearing inner off the shaft, you may find that the burnishing of the shaft has made the rear bearing to be an easier fit when it is replaced. When fitting the new bearings, there must be a way of applying pressure to both inner and outer races simultaneously to avoid damaging them.

The acetal nuts will be more forgiving of leadscrew wear, so they would be a good way to start the renovation.

I have recently done some work on a Tom Senior X axis leadscrew which is 3/4 X 5 ACME. Firstly, I extended the thread by about 4 inches at one end to allow the fitting of two nuts for backlash reduction. Then I had to rework the entire length of thread to match the wear in the centre part. There was no visible wear, but having adjustable backlash without attending to the wear variation was not an option. I was single pointing and using the travelling steady on the lathe to get the insert to just rub the flanks of the most worn parts, to cut the less worn areas to match. It is very easy to line up the tool when the thread pitch is so coarse, so the work was done in several sections, and on both sides of the thread. It has been quite successful, the leadscrew runs right through the nuts smoothly without any discernible backlash, although I have not tested it properly yet. The old nut had about 0.030" backlash and looked like a vee thread, there was no flat top of the thread left.

The delivery is free!

There is an excellent web site dedicated to the small Chinese lathes, showing how to improve them and much more: **LINK**

Oilite type bushes are easily available on ebay. They can be bored on a lathe without compromising the porosity, but reaming should be avoided.

I tried some Bovril some time ago after not eating any for many years, and was surprised to find that it is made by the same process as Marmite is. It is now suitable for vegetarians, but tastes exactly the same as the old beef formula.

Loctite 290 is a useful one to have for threadlocking. It is suitable for use on many threads after they are assembled as its very low viscosity allows it to penetrate by capillary action. It isn't likely to work on nylock nuts, or good fitting countersunk screw heads, as they may be too well sealed. It is a lower strength type, safer on small thread sizes.

I recently used 620 sleeve and bearing fit on joints which were likely to lock prematurely if 601 or 638 were used. It is just as strong, but much slower setting.

It is always best to make sure that threads are degreased first if Loctite is to be used, but once cured, most grades are unaffected by oil. Temperature resistance varies, most grades are ok below 300C.

Edited By old mart on 31/08/2019 22:00:41

I would try testing what would happen if the front hole in the steady was repositioned. Looking from the chuck side, the steady minus the front screw could be pivoted until the vertical finger is directly above the spindle axis. At this point, the horizontal finger should be checked to see if it is in line with the spindle in the horizontal axis. If those two positions can be achieved, then the front screw position in the steady can be remachined. The new hole at the front of the steady will be further from the edge where there is plenty of meat.

Taking your design to extremes, assuming all your tools are the same size, would be to put the round groove directly in the top of each tool. It could be done with solid carbide bullnose cutters, although the ends wouldn't stay sharp very long.

I had the work shift slightly in the chuck when parting off, and it destroyed one end of my Kennametal 26mm blade which holds the 1.6mm inserts. I am very careful with it now, only one end left and 7 new inserts which only fit that exact blade. I try to avoid parting off in a three jaw chuck, four jaw independents are much more secure.

I always lock the saddle when parting or grooving.

Edited By old mart on 28/08/2019 20:44:52

Today, I thought I ought to check whether my conversion to R8 has been up to scratch. With the er25 collet holder nice and tight in the spindle, using Vertex and Cutwel collets and trying 6,10,and 16mm shank endmills, the runout was 0.0003" tir on each size. Then I tried out my Osborn Titanic II, with 16mm, and 1/4" shank endmills and got 0.0005" tir on both. All the careful setting up of the spindle parts and the lower bearing outrigger has paid off. I had been worrying about how the two halves of the spindle would run, especially as the SKF lower taper roller and the Timken upper taper roller ran on different halves of the spindle. One drill chuck runs from 0.002" to 0.004" and the other larger 16mm one runs 0.004" @ 16mm, dropping nicely down to 0.001" at 6mm. The self extraction with the drawbar works very well, just 1/4 turn between pulling and pushing.

Not everything is quite as fortunate as that, however, I found out that my boring out of the motor pulley isn't deep enough, so it has to go back up on its mandrel for another 14mm of bore.

Sorry, I don't understand when you say the cutting part is to the right, (picture 5). As for chuck clearance, what about the SHCS sticking out? I also cannot understand why the steel should go blunt so quickly in brass. Have you tried a file on it after tempering, if the steel is low carbon mild steel, it will still be soft after any heat treatment.

Edited By old mart on 27/08/2019 17:36:18

At the museum, having had many donations of tools over the years, we have many taps which were made for specific jobs in industry. Many only have factory code numbers and can never be identified, and others which are usable at first glance, have + or - tolerances added, which could be disastrous. My favourites are a set of three 0.7" buttress thread taps, they look wonderful, but I cannot think of a use for them.

If the ground flat stock is gauge plate, it is the equivalent of silver steel. I would try hardening it, polishing it and then heating it very slowly from the other end until the tip area is light straw, before quenching. After tempering, finish hone with a fine diamond lap. If the dimensions allow, grind the end so that the plan view is biased to the right, yours is to the left, which is not so well supported by the groove in the holder. So far, I haven't needed anything narrower than 1.6mm, the width of my smallest carbide inserts for 26mm blades. I'm not sure of the best profile for brass, it is a matter of trial and error.

I'm sure you know that the measuring equipment must touch exactly on the centreline, and this also applies to the tool height, internal and external.

Got it, the first time I looked, the "QC" was black and I ignored it. Now it is blue, must be magic!