Saturday, 20 June 2020

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!


Wednesday, 10 June 2020

QR50 - Handlebars

Regular readers will know that the kit of parts did not include an original set of handlebars, which throws up a couple of problems relating to the rear brake lever and the size of the bars themselves. We'll talk about the rear brake lever another time, but if you take a look at these pictures you will see that the bars are much higher and wider than the original equipment:


We can see from the picture below that the original equipment bars rise maybe half the distance from the top yoke to the bottom yoke. On my bike, you can see this rise is almost as much as the full yoke to yoke distance. Reducing this height would mean losing the brace.


The additional width is simply outrageous:


The original bars are actually welded to a sheet metal cradle that bolts to the top yoke - they don't use the clamps my bike has. In these two pictures, you can also see that the ends of the bars are more or less the same length as the seat width - mine are much longer.



The bends above the top yoke are inboard of the stanchions on the original bike, so the centre section between the clamps would have to be reduced. This would mean losing the clamps.


Tuesday, 9 June 2020

QR50 - assembling the forks

We are approaching assembly time on the QR50 build now, and it will be nice to get it off the bench and to get back onto the Huntmaster. It's been fun and it will be a smart little bike from which I have learned a lot, but I have too many projects at the moment and I want to see the Grandchildren riding this one.

So, while I wait for the gasket set, and for some time to start on the tinware let's assemble the front end. I've used the hone I made to clean the paint out of the yokes, and I use an M8 bolt and a bit of sheet metal to open the clamps a bit, so I can slide the new stanchions in. This is simple, though the balance on the bench is now a bit front-heavy. I hang a big weight on the back.


Looking at my handiwork I notice that the top yoke hits the oil filler - so that was why it was dented on both sides. If you look at this picture, you will see the reason - the steering stop is bent out of the way:


That's easily fixed with an adjustable spanner.


Next, I can assemble the front brake and put the wheel on. It looks great.


Sunday, 7 June 2020

W/NG - Smoke and tappets

Having recently retired around the time that the sun came out and the Coronavirus lockdown regulations were loosened here in the UK, the bikes have been seeing a bit of use. This week, I went out with my son on a ride around Coltishall, Norfolk:


That's his Interceptor, which is a fine machine with power low down, a nice seat height and good balance. We tootle around for a bit, testing out the W/NG's new baffles which seem to be cutting the noise down but also seem to have affected the idle - it now dies more readily than it used to.

However, I adjusted quite a lot of play out of the tappets before I left and that reduced the clatter quite a lot, and the bike seems to be going well. I had it up to 60 on the way home, though by the time I stopped there was smoke pouring off the cylinder head and there was quite a lot of oil about - disappointing, as I had resealed the rocker shaft unions which had been weeping for a while. I resealed them discarding the traditional fibre washers for soft aluminium washers, so we will see how that pans out.

So, back in the workshop the spanners are out to have another go at those unions. There's oil everywhere - under the tank, on the mudguard and down tube, all over the timing cover. It has never been this bad.

Then the penny drops - Numpty Spannerman has been at it again, taking stuff to bits and not putting it back correctly. The front rocker cap has gone.


I've often found that I've subconsciously registered some change in engine note or handling performance during a trip, only to realise the cause much later - the senses are very good at picking up small changes. This time, on the way down I had noticed a deepening of the engine note and on arrival there was more oil about in new locations - differently shaped dribbles even.

So that spelled the end for the old brass rocker caps, one lying in a gutter somewhere in Norfolk and the other consigned to the spares box, to be replaced by these fine reproduction examples from the AOMCC Singles Spares scheme. Also shown here are the clips that hold them in place - this is a W/NG only part, and provides some deterrent for the caps to loosen off completely.


Whilst I had the tank off, I took the opportunity to check the tappets again, look at the decompressor seals and check the timing. The tappets and timing were spot on but while I was removing the rocker box bolts to fit the new clips I returned the clutch cable to it's proper route - it's not supposed to go through the tank mount like this:


Here's the decompressor, removed and dismantled:


I've fitted a Dowty washer between the body and the rocker box to seal that joint. Third from the left is the rubber washer, which is rock hard - I fitted a small O ring behind this. O rings are not for use in dynamic sealing applications, but the decompressor rarely moves so I think it will be OK. I've had a quick look for an oil seal that will fit in here but that seal is maybe 2 mm thick - way too thin for an oil seal. Perhaps I will turn a simple carrier to fit a couple of O rings or change the decompressor body to allow an oil seal to fit.


I'd not noticed this weld repair before.

So that was a useful couple of hours work - I had a look at the clutch adjustment as well. These old bikes are so easy to work on.