Hand turning slots in piston for '0' rings.

[Tony Bird]

Hi,

In another thread I mentioned hand cutting a slot for an '0' in a piston and someone asked how this was done in metal? As others might be interested and I have just fitted two '0' rings to another piston using the same technique I took some photographs which might explain the way I do it.

I first used a lathe when I was in school in a metalwork class I think it was a Myford ML7. When I left school I became an apprentice in the watch, clock and jewellery repair trade and for the next 5 years I only used lathes fitted only with a 'T' rest


1. The 'T' rest on my Boley Leinen watchmakers lathe it is hinged so it can be moved out of the way for measuring.



2. The most commonly used hand turning tool for metal, a graver with a lozenge shaped end.



3. A 'T' rest I made for my Myford Super 7B along with a commercially made 'T' rest I bought second hand which is used for both wood and metal.



4. A homemade rest that fits in the tool post.




5. The piston from an old model steam locomotive which is to have two '0' rings fitted. The '0' rings are Viton with an OD of 1.25" and an ID of 1".





6. The graver to be used is for parting off, it is made from a piece of flattened silver steel which has been hardened and tempered.



7. The 'T' rest to be used is home made from a piece of angle, the usual tool post has been removed from the cross slide. The slots in the piston were made using a parting tool.



8. The graver is being used to widen the slot.



9. The slot is now wide enough so the '0' ring fits so it doesn't touch the sides of the slot.



10. The slot is now just deep enough so the '0' ring can be revolved under the graver resting on the piston.



11. The two slots finished and ready for '0' rings to be fitted.



12. Finished. If the '0' rings are fitted correctly they should just revolve in their slot in the piston.



If you have hand turned wood turning metal is just the same, place the 'T' close to the work piece and present the tool just below the centre line just as a fixed tool would be set. You use both hands and have to press quite hard especially when turning slots. Brass and bronze are reasonably easy to turn steel needs a lot of pressure. I don't know about aluminium I haven't hand turned it. I do a lot of hand turning as it is quick and needs little set up and puts less load on the work piece than using a fixed tool. Most of the jobs are cosmetic fancy shapes and the like, I will try and find some photographs and post them. I have friends who come to my workshop and play once a week and several of them hand turn very well after only an hour or so playing. Like using fixed tools it works better if the tools are sharp!

If there is something that isn't clear please ask.



Regards Tony.

 

[Tony Bird]

Hi,

A lot of the hand turning I do is for cosmetic reasons. I was asked to make a copy of a vintage model Bowman safety valve.












Regards Tony.

 

[Tony Bird]

Hi,

Looking for something else and found this short video of shouldering a 6BA nut to fit into a hole in some sheet metal.



Regards Tony.

 

[Oilydog]

Thanks for this Tony. I am a jeweller and have just bought a small lathe with a T bar facility. The post is very helpful and I will be practicing with my gravers.
Presumably you use hand turning techniques in conjunction with traditional engineering methods where greater accuracy is required?

ATB

 

[goldstar31]

Thanks Tony for mentioning what is an almost forgotten lost art in turning.
Like you, I have a hand rest which has moved from a succession of lathes from its original Pools Major( which few have heard about) to the present Myford Super7B. Again, the graver is actually an early tangential tool.

Whilst the late George Thomas and Tom D Walshaw( Tubal Cain) described their construction and use in their excellent books- and both are remembered by appropriate castings ( Hemmingwaykits), it all seems to be ignored- except for horology.
For those who want to try a rest( ouch), putting a bit of suitable round bar or tube in the tool post is one way. I recall that we had something similar on Boxfords when we were making Northumbrian small pipes- and doing the fancy work on chanters and drones.

However, for cutting piston grooves, might I suggest that the rear parting tool and appropriately shaped 'parting tool' might give equally accurate results.

My thanks for such detailed information which I hope will be taken up.

Norman

 

[Tony Bird]

Hi,

Presumably you use hand turning techniques in conjunction with traditional engineering methods where greater accuracy is required?

I don't think that hand turning is any more accurate than using fixed tools, but for me it is often the faster option. For the most part when fitting '0' rings a slot created by a parting tool is opened out to suit the '0' ring. In the horological trade a lot of parts are fitted rather than measured mostly because a new bit is being added to an old one and with small sizes it is often easier just to make a part to fit. Turning and fitting balance staffs is a classic example, where the new staff has to be the correct length, fit the old balance wheel, hair spring and roller and the largest measurement is often 3 mm or less. It isn't practical to try and measure the holes that the staff has to fit. Where practical I have carried these techniques over to things that could be measured but I find it quicker and easier to make the parts fit.

Regards Tony.