Mini Lathe - Machinist's Hammer

For a while now I have been looking at YouTube videos relating to model engineering, thinking about an LBSC 'Tich' 2 1/2" gauge steam locomotive I started to build while still at school. I've looked at lots of videos of folk building & repairing Stuart Turner steam engines and have been toying with the idea myself.

The thing is, what is the point? I don't want something that gathers dust on a shelf. My son suggested that we build a steam bicycle and I have started to look at some calculations and have even considered a suitable engine... but these things are expensive if you build from a kit. Not that that is necessarily a barrier, but one wouldn't want to make a mistake with expensive castings. That idea may grow, or it may not. We will see in the fullness of time.

However, I still have a bit of a hankering to build something from a kit, but something I can use. I'd like to see what kit suppliers provide, and I'd like to experience having someone provide the materials and the drawings for me to follow, rather than supplying and maintaining the momentum myself.

I've read of folk recommending tools made from Hemingway kits and have looked at a few myself. I decided to take the plunge and bought what is probably the smallest kit in their lists, the Machinist's Hammer. It's described (and you can buy it) here:

http://www.hemingwaykits.com/acatalog/Machinist_s_Hammer.html

I don't have a hammer around the lathe - I always reach for the 1/2 lb engineer's hammer on the metalwork bench, but hey, let's have a go. The kit was ordered during lockdown and Kirk at Hemingway responded very quickly. The kit arrived in a couple of days.

Two packages of materials came in a large jiffy bag, nicely wrapped with a two page set of instructions and a drawing printed on good quality A3 paper.

There are various bits:

• a piece of aluminium round bar for the aluminium pein
• a piece of bronze for the hammer head and the bronze pein
• a a piece of 1/2" round steel bar for the handle
• a short piece of 1/2" round steel bar for the nut which holds the head to the handle

The instructions give you a work plan which I shall largely follow, with the exception that they suggest using a mill to drill the central hole through the head, followed by an end mill to machine the registers for the handle and the nut. Since I don't have a mill, I will hold the head in the four-jaw chuck and machine the registers with a small boring bar.

There's always more than one way to achieve something, and one of the most interesting things about making stuff is figuring out how to do it with the tools at your disposal.

Starting with the aluminium pein, we face and centre drill:

Then we can bore to 1/2", making sure to break the edge with a small chamfer:

Next, we chuck the bronze head & pein and mark off for the 5/8" pin:

Before we go any further, it's good to check the run out. I usually get to about 0.01 mm:

The bronze is easy to turn with carbide at high speed, but the chips are sharp and go everywhere:

The aluminium pein is held in place with high-strength Loctite and pressed home with the tailstock during curing:

Next, we make a decorative groove with the parting tool and turn down the aluminium pein to the finished diameter:

That's it for now - but I should have drilled the cross-hole at this point...

This is a new technique for me - turning between centres. I made this lathe dog to use with my new faceplate to turn the long taper on the hammer handle.

Here's the dog and it's drive pin:

Before we turn the taper though, we will need to machine some other features of the hammer handle. The head is held in place with a special nut which we will make later, but first the handle needs a 5/8" length of M6 thread. Here, I'm turning the shoulder for the head to sit on and the parallel pin for the thread:

With the thread cut using my tailstock die-holder, I take the handle & hold it in a nut in the vice. I want to paint it with Dykem to mark out the features I have to machine:

First, I have to cut these three rings using a 1.5 mm parting tool. These are partly decorative and partly for grip:

While I have the three-jaw chuck on the lathe, I will make the nut. This is just a bit of 1/2" round bar, with an M6 thread to match the handle and a screwdriver slot; it's got a reduced diameter to fit in the head producing a shoulder to retain the head.

Cutting the thread with a spiral flute tap - I'm turning the lathe by hand:

Parting off. The lathe is much more rigid with the new cross slide gib strip:

Cutting the slot with a hacksaw and a needle file:

Having completed the nut, I removed the three-jaw chuck from the lathe. The aluminium pein of the hammer head has a fine turned finish and I wanted to use the ER40 collet to avoid damaging it. First job is to turn the second groove in the correct position and to the same depth as the first one:

Next, we turn it to 1" OD and finish at high speed.

That's the turning finished, but the peins are slightly over length:

The ends are 'crowned' with a file to give this raised dome:

Now on to the hole for the handle. I'm drilling it in the four jaw chuck, which just about accepts it; it's easy to get the centre point longitudinally between the two grooves, but radially is a bit more difficult. I'm using this knife blade which is both flat and hard - it will tip if the centre is not exactly aligned:

Here I've just finished the 7/16" hole through the middle, nicely on-centre. I wish I had drilled this before I did the finish turning - the chuck jaw marks are quite visible.

The counterbores were made in the lathe, with a small boring bar:

The handle fits nicely:

The dimensions on the drawing don't give any tolerances - the nut is very tight in the head. I'll have to relieve it a little:

Before I get into turning the handles between centres, I want to modify the chuck guard so that it can still be used with the faceplate and drive dog in place. I've added a bracket to lift it upward and toward the tailstock:

Here, the tailstock is offset as far as it will go - not as far as the 0.167" specified in the drawings. I will have to pull the tailstock apart later. 

This is the first time I have turned between centres - access is easy and it goes OK, but to use any speed the drive pin on the faceplate needs a counterweight. I make this with an M10 bolt and three nuts.

The counterweight works fine up to about 800 rpm, which is handy because the long taper takes ages to turn. I use the power feed to save effort and improve the finish:

I polish the handle in the lathe, with some 120 grit emery tape:

It's almost finished now. I need to trim the aluminium pein to length and polish out the marks I made with the chuck jaws.

That done, I can trim the handle to length and make the hemispherical end with a combination of taper turning on the compound slide, filing and polishing:

And that's it!

Starting on the engine!

Well, summer's here and the bike is coming together. I've finished my welding work, the wheels are still away, and most importantly I have some time away from work to get to grips with things at home.

So, in a break from repainting the kitchen we will start work on the bottom end.

 

I'm dithering around polishing the crankcases which is a noisy & messy job & which stops me rebuilding the engine. Someone also suggested that polish would hinder cooling - but equally it is obvious that the engine was once polished - it is deeply tarnished now, but you can see it is still very smooth - you can also where it wasn't polished!
 

But, I have all the parts and can get moving with the rods & cranks.

 

You'll recall from previous posts that the rods have been cleaned and polished and have spent the winter protected by some pipe insulation in their own box. I have small end bushes and big end shells from Drags along with new big end nuts, also from Drags.

 

These are shown in the adjacent picture and will have to be pressed into place and reamed to the finished size.

 

The sizes are shown in the table below and are around 11/16" - but will have to be sized to fit the factory specification using a suitable adjustable reamer. In this case we will use a 21/32" - 23/32" reamer, which are readily available but are of highly variable quality. Beg, steal or borrow a decent one if you can! If you must buy an internet cheapie, take a look at a few things before you use it and if it is no good, send it back!

Take the reamer to pieces. Measure the length of each blade, and make sure they are equal.

1. Look at the retaining nuts, make sure they are not too loose and clean the threads
2. Clean out the grooves in the reamer body and make sure the blades can sit snuggly down in the grooves. You don't want any swarf in there.
3. Put the reamer back together, and measure the diameter across two opposite cutting edges (this only works on six blade reamers) at each end of the blade. The dimensions should be the same! They are not supposed to be tapered. Repeat the operation for the two other pairs of blades.

So, to fit the bushes. You can use a press for this, if you have access to one, but a bench vice comes a close second. You could also use the draw-bolt method, but I suggest the loads are probably too high for that approach. These bushes are quite tight.

1. Find a socket or a piece of tube which is small enough to support the small end eye, but large enough, both in length and internal diameter, to receive the old bush.
2. Open the vice enough to receive the rod, the socket and the new bush plus a couple of millimeters.
3. Find a piece of soft sheet (brass for example) to protect the end of the new bush.
4. Align the socket, the rod eye and the bush. You might benefit by putting a short rod of about 1/2" OD inside the assembly, just until you have the new bush a couple of millimeters into the rod, just to keep things lined up.
5. Nip the whole lot up in the vice with your protective sheet on the jaw pressing on the new bush.
6. Operate the vice to push in the new bush, pushing the old one out into the socket. You will probably find the initial force required is much higher - and you might get a bit of a bang as the bush starts to move. This is normal. Don't be afraid to apply a bit of heat to the small end eye to get it moving - but go easy, this is aluminium. No Oxy-acetylene here!
7. Carry on pushing until the new bush is more or less flush with the face of the rod. My bushes are about 0.5 mm over length at the moment.

The next job is to drill the oil hole. Do this before reaming and you don't need to worry about deburring later. The Square Four has 3/16" holes in the small end eye.

Next - reaming to size. Get ready with your gudgeon pin, your internal micrometer or bore gauge & a 1" micrometer.
 

Now, adjustable reamers are really scraping devices. They are designed to scrape out small quantities of metal from holes and as you have seen (from when you inspected your new reamer) they are not as rigid as solid reamers and can only be used to take small cuts.

When you set the reamer up for the first cut, back off the adjustment collars (i.e. screw them away from the square end of the reamer) to reduce the diameter of the reamer until you can put the reamer into the bush. Now adjust it larger until it just begins to touch the inside of the bush. Turn it using a tap wrench a couple of times with some oil.

Be careful to twist the reamer such that it is concentric with the bush; make sure the blades pass right through the bush. That way you will minimise the potential to cut a tapered hole.

You want to increase the size of the hole in very small steps, testing with the gudgeon pin at each stage -  DON'T SKIMP ON THE CHECKING!! Small end bushes are relatively cheap, but replacing them repetitively is tiresome. Increase the size of the cut by turning the collars by 1/8 of a turn each time, and turning the reamer in the hole 3 or 4 times. Always make sure that the top collar is tightened down.

 

A few more thoughts:

• NEVER turn the reamer BACKWARDS – can You could break or chip a blade.
• Never put more than ¼ turn on the collars
• If the reamer jams, loosen the blades and pull the reamer out and start again. Remember a jam will leave a number of ridges and these have to be cut away or it will happen again.
• Make certain that the collars are tight.
• Clean the reamer after each pass.
• Do not push down on the reamer too hard or it will jam. Take it slow and easy - this is supposed to be a hobby remember? You don't need to hurry, you are enjoying yourself right?
• On each turn try to stop in a different place.
• Use oodles of cutting oil.

So, now we have our reconditioned connecting rod:

So, repeat the operation for the other rods and you will end up with a little heap of scrap like this:

So here is a table showing the dimensions I have ended up with:

	Small End Bush	Big End
Factory Specification	0.6868” 0.6863” 0.003" wear allowable	1.375” min (journal)
Cylinder 1	0.686”	1.3765”
Cylinder 2	0.6869”	1.3745”
Cylinder 3	0.6863”	1.377”
Cylinder 4	0.686”	1.3775”

I had to order a couple more bushes from Drag's since I wasn't happy with No. 2 & No. 3. The table above shows the new dimensions.

And now, over the last couple of days I have polished the cases. I made sure that I polished only the areas that were polished in the factory all those years ago:

Next stop, bottom end assembly!