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Member postings for old mart

Here is a list of all the postings old mart has made in our forums. Click on a thread name to jump to the thread.

Thread: Thread Bare
01/07/2019 18:03:48

Studding in metric fine may be hard to obtain, if there is sufficient wall thickness, then helicoils are much easier.

Check out ebay listing 173833058997.

 Michael Gilligan's post shows a source, but it is very expensive for only 25mm lengths.

Edited By old mart on 01/07/2019 18:08:59

Thread: How to use a round column mill
01/07/2019 15:19:40

Could we have more pictures of the mill? Possibly a name and there may be more info on the "lathes UK " site.

Thread: Modding a fixed steady
01/07/2019 15:12:01

That is very similar to the fixed steady I bought to use on the Smart & Brown model A. A base was made to fit the bed of the lathe. The reason I bought it was that original ones cost an arm and a leg. The shortcomings were exactly the same and I shortened the original fingers to allow 100mm stock if required. I also made a set of fingers with sealed ball races to span 14-80mm. It is certainly sturdy enough to be useful. With the use of a mill, making the fingers is easy.

If the original fingers are shortened, they will not reach smaller diameter stock, unless an extension is made for them.

Thread: How to use a round column mill
01/07/2019 12:45:56

Round column mills don't usually have an alignment strip. They clamp the head securely and rely solely on the quill for Z axis. Whether yours can be used moving the Z axis depends upon the fit of the rectangular strip stopping any tendency for rotation. This could be verified using a dti when the head is free to move up and down to see if the head can be rotated on the column. More than 0.002" movement would be too much.

Thread: Snail Problems
30/06/2019 20:19:39

When I was small, spending summer holidays with my aunt and uncle, I was given a bucket with salty water in it and searched the front garden for snails. I found hundreds. When I was even smaller, my mother found me chewing away on snails which I had picked out of a stone wall.

Thread: Tungsten Putty?
30/06/2019 20:10:30

Densimet is also excellent for storing isotopes, it can be moulded and sintered and is machinable. Mostly tungsten with iron, there are several types. The 1/2" ground bars I use are quite strong. Parting down to 1/8" diameter and snapping off proves it is similar to breaking a drill blank of the same diameter.

After the Iraq war there was a lot of criticism regarding the contamination caused by depleted uranium.

Thread: Start of Tom Senior refurbishment.
30/06/2019 19:57:27

I got the er22 threading insert holder the other day, the smallest available is 25 x 25, so the mill produced a dustpan full of chips which flew off red hot, some landing on me. The 3/4 x 5 ACME thread has a large helix angle, so the threading tool is tilted at 4 degrees. Four inches of extra thread plus an inch of runout relief mean 5" projecting from the chuck. I will be using the fixed steady at the right hand end of the lathe and also the travelling steady. The travelling steady has two pieces of 1" brass angle 1" long screwed to the original end which I thought was not wide enough to span the 5tpi thread.

I'm thinking of pre-setting the travelling steady by skimming the faces with a 3/4" end mill in the lathe chuck.

Thread: Annealing stainless steel
30/06/2019 19:35:04

Keep the speed of the drill dead slow and only use sharp ones. Maybe you could get some carbide drills.

I believe austenitic ss is non magnetic.

Thread: Info needed on Crown chuck
30/06/2019 19:21:37

I would recon from the finish and fit that it is a good Johnny foreigner. It looks like it may date from the 60's. 

It is a design that I have not encountered before, probably common to small chucks. The operating screws are RH thread and screw down into the body. The jaws have a lug which engages with a groove halfway along each screw.

Edited By old mart on 30/06/2019 19:22:41

Edited By old mart on 30/06/2019 19:28:16

Thread: The website needs an update
30/06/2019 19:18:48

I'm so glad when someone else makes a mistake, it means I'm not alone.

Thread: A Chinese puzzle!
30/06/2019 14:24:31

Even liquid nitrogen will not shrink a small diameter by much, a domestic freezer has little chance of working if the interference is more than 0.0001". You could try heating the bearings to 140C, the lowest most modern fan ovens will go to, which will not damage them. Measuring the bearing bores can be difficult, a set of rocker gauges would be the most economical and quite accurate with care.

Thread: Tungsten Putty?
30/06/2019 13:58:03

Depleted uranium is radioactive, seems a funny sort of container for isotopes.

 Tungsten has a relative density slightly greater than uranium and slightly less than gold.

Edited By old mart on 30/06/2019 14:03:24

Thread: HSS Tool Bit Size
30/06/2019 12:07:38

Surely, it depends on the difference in height between the bottom of the toolpost and the centre height. The same goes with a qctp with the holders at their lowest position. The largest shank size that will fit adds to the stiffness.

The 9 X 20 which I use has all of its tools milled down to 17.53mm so as not to need shims, but using this size is rather rare.

Edited By old mart on 30/06/2019 12:08:46

Thread: Tungsten Putty?
30/06/2019 10:35:03

Google "densimet", it is a tungsten alloy of around 18 relative density.

At the museum, we got an American tipjet powered helicopter powered by hydrogen peroxide. It never went into production and is mainly a pile of bits.

Among the parts was a quantity of densimet bar stock, 1/2" one end and 12mm at the other. They are about a foot long. I have made boring and threading bars out of them which work very well. It mills, turns and parts off with carbide inserts and can also be tapped with hss. Some taps work and some don't, it may require a tap intended for aluminium, as it might tend to workharden.

I have made several solid carbide boring bars by silver soldering the tips of steel bars on to the shanks, but densimet can be one piece because of its machinability.

Thread: Info needed on Crown chuck
29/06/2019 22:33:32

Amongst the tools left to the museum there is a 4" four jaw independent lightweight Crown chuck. Apart from slight surface corrosion the chuck shows no signs of ever having been used. We also found a backplate with a tiny thread which I haven't yet measured, about 1"x 8 or so. The chuck is marked "foreign", does anyone know where it was made?

Thread: A puzzling design in Nurnberg museum
29/06/2019 22:17:36

That first link in Brian G's post might have a simple explanation, opposed piston cylinder on one side of the engine and coupling rods on the other.

Thread: Is this chuck too big/heavy?
29/06/2019 21:52:07

I have a choice of two 4 jaw independent chucks on the S&B model A. A 160mm Chinese and a 6" Toolmex lightweight originally intended to screw directly onto a Myford. The Toolmex weighs half the weight of the Chinese one, and the jaws are half the size, so the size the workpiece dictates which chuck is used.

I bought a serrated jaw Burnerd of 6 3/4" which is as heavy as both the four jaws put together. It only gets used occasionally, no worries about speed as it is Ductile iron and the lathe max speed is only 1400 rpm and the plain bearings are easily able to cope with the load. I always check clearances and set stops if necessary whether or not the chuck is in danger of fouling parts of the lathe.

 One slight drawback of larger chucks is that you loose length which can be a problem with shorter machines, the model A is only about 21" between centres.

Edited By old mart on 29/06/2019 22:00:15

Thread: Using a lathe
28/06/2019 20:43:03

Back in the early sixties I used a Colchester at school, possibly starting from the age of 11. The law has changed so much since, health and safety is the watchword.

About three years ago a pair of nice young ladies from the councils health and safety visited the museum. They had no idea whatsoever about uranium, radium, thorium and tritium being present in old aircraft,and when they saw the lathe, drill and mill, they didn't have a clue. They said they would be back, but no sign of h&s since.

I put the useless chuck guard on the drill and one on the lathe with a microswitch interlock. The lathe chuck guard has been a boon as I can stop the spindle without bending my back.

Thread: Removing Broken Tap
28/06/2019 20:26:05

I broke a 1/4 bsf tap about three diameters deep in mild steel. The drill had been undersize so I only had myself to blame. The workpiece was in the mill vice, so I left it where it was and used a solid carbide drill of about the core diameter using the fine feed very slowly. The carbide cut through the hss beautifully and I could just tip the remaining bits out. I re drilled with the correct size and found a replacement tap.

I would not want that to happen very often.

Thread: Harden Boxford Main Spindle Key?
27/06/2019 22:47:03

Key steel is tougher than mild steel, Boxford must have had a reason to use an unhardened one. If you make a close fitting replacement, which can slide with the minimum of play, it should be fine. Make a couple of spares, and maybe use a little moly grease when re assembling.

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