Member postings for Neil A

Re-grinding a crankshaft is a real art. The absolute skill lies with the man on the grinder.

Having watched the re-grinding of an over 6 foot long fully nitrided 8 throw crankshaft, the sight of the pins being ground and the whole shaft swinging off-centre is really impressive. The care that has to be taken to ensure that the metal is not overheated and cracked at the transition from the soft newly ground surface into the hard nitrided fillet radius is not for the faint hearted.

Depending how much the undersize was, sometimes the fillet radii would need to be re-formed as well.

Having successfully avoided creating heat cracking, the shaft could then be re-nitrided and be fit for further use. In the 1980's and 1990's re-grinding a crankshaft was undertaken on a regular basis. It has to be said though, that not every shaft was successful, but at a cost in excess of £15000 pounds for a new shaft at the time, it was worth the effort.

All I had to do was put the numbers on the drawing, that was the easy part.

Neil

You don't need to worry about the draw bar, it extracts completely within the height of the motor beside it, although you don't need to take it completely very often, mine usually stays in place even if there is no cutter attached.

Neil

Just a couple of observations on where you intend to place the mill, just check the height from your worktop to the overhead lockers, maximum height of the SX2P with the head raised is approximately 750mm.

The other thing to consider is that the hand wheel for the X axis is on the right hand side of the table, if you position the mill over the draw and cupboard join you may find yourself with a long reach for the hand wheel over the angled worktop. You have probably thought about that already.

Your workshop looks too nice to be covered in nasty swarf!

Neil

I have been using a Sieg SX2P for three years now, as far as accuracy is concerned I have had no problems, the motor also has enough power for all the cutters I have used, so I have no complaints there. The main difference to many other machines is that the SX2P does not have a quill feed, this means that the whole head of the machine has to be raised or lowered for any plunge type operation.

The torsion spring used to balance the head is a little too weak at the top of the column and quite stiff at the bottom. This is the main cause of what has been referred to as "head droop". Under certain conditions the head is not controlled by the torsion spring very well, particularly at the top of the column, and can perform an uncontrolled drop for quite a distance. If the fine feed knob is engaged this is less of a problem, as the drop is limited to the backlash in the rack and pinion, the stick and slip that uses experience. I have taken to setting the height limit block so that the tool will not hit the work if this occurs.

Many users have fitted a gas strut instead of the torsion spring to overcome this problem, but it is still not always perfect. I don't have a gas strut fitted, but I use my left hand to push against the torsion spring lever to give some resistance to any tendency for the head to drop, usually when the lever has reach the horizontal position it will be OK. Not very elegant, but it works for me.

My choice of the SX2P was dictated by the space that I had available for the machine, particularly the height of the column and the length of travel required for the X axis of the table. I also wanted an R8 spindle. The SX2P has been large enough for the models that I make, I don't make locomotives.

If I were to be buying again and had the room I would go for the Sieg SX2.7 Hi-Torque version. It has far more features than the SX2P and as already pointed out, you will always find the extra space on the table useful.

I hope this helps with your choice, the SX2P is not a bad machine, I quite like it, it has it's quirks, but it could be better.

Neil

https://uk.cagp.com/auctions/catalog/id/201?page=1

There are some interesting items for sale in this auction. Perhaps too large for most of us.

Neil

That had me puzzled for a while, why would you change to low carbon steel to make a car? Then I realised it was only the process for making the steel that was going to be low carbon, not the steel its self.

Just shows how news reports can be written to make things sound totally different to the reality of the news. I don't suppose the writer knew that "low-carbon steel" was a particular group of steel specifications.

As Mark Twain once commented: "Facts are tricky things, best left to the experts".

Neil

Edited By Neil A on 16/06/2021 12:20:43

The last time I think this device was described was in MEW No251.

The article, by Jacques Maurel, had detailed drawings of his version of the sharpener.

Neil

Duplicate post, sorry.

Neil

Edited By Neil A on 30/05/2021 11:51:16

I think you need to be very careful when using a worm and worm wheel with a heavy out of balance load.

I have seen theoretically non-reversible worm and worm wheel arrangements run away on an large engine turnover frame when the load had not been balanced out sufficiently with counter weights. Quite scary moments for the people using it.

Neil

SOD has it.

Its for measuring crankshaft deflection when the engine is solidly coupled to what ever it is driving. The gauge is usually fitted between the webs of the crank throw nearest to the load, "the drive end". Then shims are fitted under the engine or the load until the deflection is within the specified limits. Still a very relevant piece of measuring equipment.

Used on larger engines as you need to be able to get inside the crankcase through the crankcase doors.

Neil

Edited By Neil A on 29/05/2021 17:40:15

Edited By Neil A on 29/05/2021 17:47:50

Have you looked at Harold Hall's web site for his article on machining the 10V. It is well worth reading even if you decide not to follow his examples.

He does not drill the holes in the sole plate for mounting the bearings until he has made the crankshaft so that he can get the end float right.

For the standard mounting he decided to make a fixture that he used as a jig for positioning the holes in both the standard and the sole plate.

Neil

Just had a thought, although I can't help very much on a Bantam lathe as I don't know how its change wheels are arranged, You might get some ideas if you look at the "Little Machine Shop.Com" web site.

They have a calculator for change wheel setups, albeit for mini lathes, under their learning centre, "how to articles".

This might give you a starting point for your setup. No guarantees.

Neil

I'm afraid 5/8 x 27 TPI UNS is the standard American microphone mounting thread. Everyone else uses 3/8 x 16 TPI Whitworth.

What idiot indeed!

Sorry I can't help with your change wheel setup.

Neil

In MEW 251 Phil Dawes showed his approach to using a counterweight to balance the head of a Sieg SX2P. Might be worth you having a look at that article to see how he did it.

Neil

I have had an SX2P mill for some time now, still with its original torsion spring and lever arrangement. I also have had the stick/slip problem, I feel that it is connected with the bedding in of the gibs as I have been able to adjust it out on my machine, maybe I'm lucky. I have also experienced the head run down the column by itself because the torsion spring does not provide enough upward force when the head is at the top of the column, very disconcerting when it happens. I now always fit the limit block so the tool will not hit the work until I am ready to cut metal, just in case.

As regards the backlash in the rack and pinion system I now push on the torsion lever with my left hand to provide a bit of resistance to the downward force, not really the way it should be, but it has worked for me so far.

I did wonder if it would be possible to fit some sort of short stroke hydraulic damper between the head and the limit block to push against and so limit the speed of any downward travel. I have not really thought that one through at the moment, just an idea that might work.

Fitting a ball-screw would be nice if it were not for the amount of machining necessary to do it. There is a thread on converting an SX2P to CNC if you want to see what is involved.

I'm just waiting to see if anyone comes up with a relatively simple solution, at the moment I just live with it. I find the machine is fine in every other aspect.

Neil

Personally I cheat for screwcutting.

I go to the LittleMachineShop website, "Learning Centre", "How to Articles", then "Change Gears for Threading" as my starting point. It is for a Mini-Lathe with only a 2 train gear set, not the 3 train that you need for your lathe. But in conjunction with your threading table, it gives a good idea what you need. I'm afraid it does not do it all for you, you still have to fiddle with the gear sets to get a good arrangement.

Some Imperial TPI could probably do with having additional gears to those that you have, something for another day perhaps.

I hope it all works out.

Neil

I have just run through my original suggestion for the gear setup and I don't think it will work because of tooth tip interference. I think that I have tried all the combinations of that setup.

I have another setup where the tips just run clear, but again it depends on whether it will fit in the banjo length.

(40/42) x (40/60) x (50/80)

There will be clearance between the 42 tooth and the 50 tooth gear. Assuming the gears are 1 Module the gap will be 2mm.

I should have checked the first one more thoroughly.

Neil

Jason - I think you have put the second 40/80 round the wrong way in your calculation, is the "Duffer Rule" catching?

I have had a little go at this, it all depends if you can fit the train on the banjo.

(40/40) x (20/60) x (50/42) with a 2mm leadscrew this gives 32.004TPI.

As I have said, it all depends if it will fit on the banjo. I hope it does.

Neil

Should have said, you may have to change the order of the drivers and driven gears to fit.

Edited By Neil A on 14/02/2021 21:09:13

When I bought my Flexispeed lathe in the mid 1970's from the Norfolk lathe & Tool Company, I asked about screwcutting gears and was sent a leaflet showing how they had arranged the set up.

There was a 16 tooth gear fitted into the spindle in place of the worm gear.

This always meshed with the 32 tooth side of a double gear, the double gear had 32 and 16 teeth.

There was then an idler, either a 56 tooth gear meshing with the 32 tooth side of the double gear, or a 64 tooth gear meshing with the 16 tooth side of the double gear.

The idler then meshed with the lead screw gear, the tooth count of this gear was 24, 26, 30, 32, 36, 40 and 44.

There was a fixed plate fastened to the left hand side of the headstock and a conventional banjo or quadrant as they called it.

I hope you can follow all that?

The cost of the gears at the time was £12-50 + VAT carriage 60p. As I had only paid around £30 for the lathe kit, if I remember correctly, it seemed too much so I never bought them. The number of threads available did not seem to cover all the threads I thought I might need.

Some years later I made my own screwcutting attachment, I cut a set of gears from aluminium with a home made 24DP single point cutter in exactly the range that Bazyle has given, I cut the extra 20 tooth and also a 70 tooth gear. I should really have cut a 57 tooth gear for 19TPI, ( 1/4 and 3/8 BSP), maybe I will do that as an exercise sometime.

Neil

Funny you should mention the number of holes in the covers.

My 10V of mid 70's vintage has 4 holes in the bottom face of the cylinder to the standard and 6 holes in the top face for the cover. I've just checked the drawing to make sure.

The design seems to have changed a bit over the years.

Neil