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Seagull Parts and the Mini Lathe

Posted: Sun Jul 05, 2020 10:49 am
by Raya
When reassembling a couple of early 102 Seagulls, I found that I was missing one of the 5/16 brass bolts (#1378) that secures the end cap. John didn’t have one and Sheridan only supplies the later cheese head design. It seemed to me that a replica bolt wouldn’t be too hard to fabricate on a lathe from a suitable piece of brass hex bar. I had only two problems with this approach in that firstly, I didn’t have a lathe and secondly, I had never used one before. This was a perfect excuse to procure said item and also venture into the rabbit hole of you tube videos in search of enlightenment and knowledge in the world of metal turning.

While unable to justify the outlay of several thousands of dollars for a piece of machinery to produce just one bolt, I somehow convinced myself (if not my wife) that a one thousand dollars spent on a less expensive mini lathe might somehow prove to be a worthwhile recreational purchase in the time of Coronavirus lockdown. So, it came to be, that a wooden crate containing a bright red Seig C3 mini-lathe was delivered to my house on the day before Good Friday. (While Seig is a German sounding name, the lathe was of Chinese origin.)

The definition of a lathe is said to be a precision machine used for producing scrap metal from perfectly good material. That’s probably a fair description but somehow, I did manage to replicate, to my satisfaction, the missing bolt and associated washer (#1378W) without injury to myself or machinery. Next on my list was slightly trickier starting pulley dome nut (#1268) followed by a couple of bent type bracket thumb screws (#1330).

As I slowly gained confidence, experience, (and a growing pile of scrap metal), I decided to see how many different Seagull parts the mini lathe could duplicate regardless of my immediate needs. Forum members with a Colchester lurking in their basement would probably regard a mini lathe as not much more than a toy, but I was able to manufacture a surprising number of parts. I found that using the lathe was different from most of my other power tools in that that it required little dexterity but rather requires the operator to have a good knowledge of the machine, correct tools, operational speeds and measurement instruments. A dial gauge and calculator are a must. The skill is in setting up the machine for the operation more than operation itself. Here are some of the lathe operations that I managed to achieve.


I found that the mini lathe could easily turn brass, aluminium, mild and stainless steel. The main limitation of a small lathe was the depth of cut, especially for the steels. You need to take numerous small cuts to reduce the diameter. One part that turned out well (pun intended) was #1266, the alloy flywheel cover. Prior to about 1952 there was no script on the cover making plain aluminium suitable for these Seagulls. I first cut out a rough shape with a jigsaw then machined them to size. I had to make up a fixture to hold the plate in the lathe.


My lathe is metric and Seagull threads are imperial. The bag of reduction cogs that came with the machine couldn’t produce the threads I needed. In lieu of trying to source an imperial lead screw and half nut, I purchased a 63 tooth cog, which, through an improbably twist in mathematics, allows some inch ratios to be achieved. I have made up an Excel spreadsheet to calculate various ratios in order to be able to duplicate some of the weird thread pitches that the Seagull demands.
I did use the lathe to make a sliding tailstock die holder which is by far quicker than changing cogs when cutting standard size threads. The mini lathe struggles a little to cut the threads using the die holder as the spindle speed is electronically controlled and lacks torque at low revs. It is necessary to continually back off to clear the swarth in order to stop the motor stalling.

Spring making

I had some success making springs for the throttle and fuel cap vent. The trick was to make a mandrel of a suitable diameter so that after the spring was wound it would spring back to the required finished diameter. I made up a nozzle for the tool holder to feed the wire on to the mandrel while I turned the lathe by hand. I tried both music wire and SS spring wire and both worked well although the music wire looks closer to the original spring. As an experiment, I made up a mandrel to suit the propeller spring and wound on some 304 SS rod (in a vice, not using the lathe). The spring looks identical to a bought one but haven’t tried it out to see how it stands up in real life. I tried to make the small spring in the HT lead without much success.


You can purchase a milling attachment for the Sieg lathe but I opted instead to adapt a tool holder for holding my parts. The milling attachment is not cheap so I will hold off on this purchase for now. I was able to successfully mill screw head slots of various sizes using the just the tool holder.


I bought a cheap knurling tool from China and used it successfully when making the fuel cap vent screw. The only other part on the Seagull that I can think of with a knurl would be the fuel tap plunger. I haven’t made that part yet.

I certainly wouldn’t recommend purchasing a mini lathe to save the cost of purchasing parts however there is a certain degree of satisfaction when the duplicated part ends up looking pretty much like the original. I have used the lathe for other projects and don’t know how I managed before I had it. Future projects include machining cork fuel washers as well as possibly propeller shafts and bearings. Making your own parts is an enjoyable and satisfying pastime. The photo below shows some of the Seagull parts that my mini lathe has produced.
Seagull Parts.jpg

Re: Seagull Parts and the Mini Lathe

Posted: Sun Jul 05, 2020 6:43 pm
by Rig pig
Nice job, no workshop is complete without a lathe, now you need to talk your wife into the absolute need for a Bridgeport....... it's a slippery slope you have started on :lol:

Re: Seagull Parts and the Mini Lathe

Posted: Sun Jul 05, 2020 7:27 pm
Great work, you obviously got the feel for it, a lathe... great piece of kit to have.

Re: Seagull Parts and the Mini Lathe

Posted: Sun Jul 05, 2020 9:03 pm
by Charles uk
How did you harden the springs?

Re: Seagull Parts and the Mini Lathe

Posted: Sun Jul 05, 2020 10:50 pm
by Raya
The smaller springs are made from both music wire and stainless spring steel. The music wire was readily available from local hobby shops but I had to order the stainless from China. (Cheap, but delivery took 6 weeks) Because the spring wire is formed cold, there should be no further treatment needed for them to retain their "springyness".
The prop spring was just an experiment to see if I could make one. I used 304 SS round bar and not a specific spring steel. I'm not sure if the carbon content of 304 is high enough to harden using heat so will have to read up on the subject. I don't really need any propeller springs so heat treating might be an experiment for another day.

Re: Seagull Parts and the Mini Lathe

Posted: Mon Jul 06, 2020 4:02 pm
by Sandro Picchio
Very good!

That is the way by wich little by little I acquired all my tooling. You have to do a job that can’t be done without a special tool. You buy the tool and it remains for future jobs. Of course a lathe is not a light step, but you see how much satisfaction it is giving you.

My lathe instead (a Grazioli 150 from 1960) was in the way in the middle of a workshop, unused after a company relocation. They asked for € 250 and I jumped on the occasion.
The transport cost almost as much. It is all cast iron and weighs 1000 kg.

My compliments for the pieces you made after so short a learning, especially for the threaded ones.

A picture of your machine would be welcome.

Rig pig, among the mills just the Bridgeport is my dream but I am afraid it is and will be only a dream. One needs a lot of room, apart from the money. And a mill involves a quantity of expensive tooling.


Re: Seagull Parts and the Mini Lathe

Posted: Tue Jul 07, 2020 2:56 am
by Raya
Thank you Sandro. Here is a picture of the Sieg lathe and accessories that I purchased. I have since bought some additional carbide tools as well a quick change tool post. I will keep adding to my collection of accessories and tools as time goes by. The ones from China are good value if you aren't in a hurry.

We used to have an old Colchester lathe at work that the workshop forman cherished. I didn't pay much attention to it at the time but realise now how good a machine it was. I bet Seagull had a few of these in their factory.
Sieg C3 Lathe.jpg

Re: Seagull Parts and the Mini Lathe

Posted: Wed Jul 08, 2020 11:40 am
by Oyster 49
I have the same lathe, in the UK several sellers market them, mine is a Chinese made Chester lathe. Works well for small items.

Re: Seagull Parts and the Mini Lathe

Posted: Wed Jul 08, 2020 12:18 pm
by Rig pig
The seagull is the newest thing in my workshop, I have a Smart and Brown lathe from the 50's and an equally old Pallas V1 vertical mill, I haven't got the head height for a turret mill.