This is a short article on how to impart a seam free, mirror-like finish, to larg(ish) areas of metal. You will also discover how to cover yourself, your workshop and your mug of coffee in pretty snowlike flakes of glittering metal. I am referring to flycutting.
As confessed elsewhere I am not a great enthusiast of grinding my own cutting tools but the opposite is true of grinding up cutters for flycutting. In my case I bought myself a set of three flycutters from RDG Tools for around £15.00. From the teachings of John ‘Bogs’ Moore I learnt how to grind up the HSS blanks supplied with my flycutting set.
At this stage I can do no better than reproduce an article prepared by ‘Bogs’.
Here is a quick C-o-C to show you the tool in graphical format (getting technical words now as well).
The first one is showing the 1/4 round, second is the back rake and the third would be classed as bottom rake.
You actually grind 1 & 3 at the same time, then put 2 on last.
Number 4 is how you finally put a razor edge on the tool. I use an Arkansas stone with oil, but you could use a diamond lap with water to stop it clogging, or just a fine emery stone with a touch of oil. This is also how you touch it up during use.
If you ever have a go at some real tough stuff, you will most probably end up with a flat on your main radius. In that situation you have to do the 1 – 3 regrind to get the curve back.
The angles are non critical, but I put a fairly large one on so that it can easily cope with a range of materials. In fact, if you were cutting brass all the time, you could do away with #2 (back rake) completely.
What I have done this morning is go into the shop and ground one up to show you a close up of the finished article.
It was a little dangerous trying to grind with my left hand, keeping one eye on the tool, and take a piccy using my other hand and eyeball. I know I am adaptable, but not that much. So what I have done is ground it up, and flatted out non essential bits with a black marker.
These pics are as they came off the wheel without final sharpening.
Actually the bit marked top is really the forwards facing part of the cutter, I just marked it up that way to help with the grinding sequence. I just hope I haven’t confused you all.
This is the way I grind for getting a good material removal plus nice surface finish. Just remember, start wacking this thru a bit of tough stuff,
Remember, you can click on each picture for a larger image
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- This is the set of fly cutters complete with HSS blanks available for around £15.00 from suppliers such as RDG Tools.
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- Creating an air-tight seal between cylinder and valve plate is made easier with the use of a flycutter to produce a smooth flat surface.
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- A top view of the radiused tip.
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- Illustrating the bottom rake
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- Bottom rake untouched
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- Showing the back rake
Dear John,
Just the article I needed, thank you for taking the time. I have been reading tru-out every article in this site and it has been enormous help. I have 9/20 lathe and MFL20 Mill, and almost everything else I would eventually need use to start for a model engine in my home workshop, but courage… I have made few “turners cube”, and my own QCTP, and Tailstock Cam Lock, fine.. But, I dont know my skills have up to it? but I see modelling is something else. you make it sound so easy.. but I have one qustion before; I have a fly cutter, and every few times of use, I strip my mill’s slow gear.. do you think fly cutter has something to do with it or it is just quinsidence? can it be related? This has happened three times…
Thank you in advance,
Kind regards,
Unal
Hello Unal
From the work you have already produced you should have no difficulty in making a model engine. Just make one part at a time, if at first you are not satisfied with the result toss it in the scap bin and try again. I am sure you will make good progress as your confidence grows.
It is quite possible that you are taking too deep a cut with your flycutter and this is stripping the nylon gear drive wheels. Very light cuts with plenty of lubrication are the order of the day particularly when machining steel. One thing you may consider is converting your mill to belt drive to reduce this problem.
John
I just wanted to thank you for the great article. This is a good explanation, and showing the radius and tool angles really helped. I have used my flycutter several times and although the cut wasn’t terrible it didn’t provide the finish I had hoped for. I read your article and reground my tool and it now produces a fantastic finish. Thanks for taking the time to produce these tutorials.
I just finished my first wobbler. I have your paddleduck plans and can’t wait to start on them.
Glad we were able to help. Good luck with Paddleduck. Maybe you will let me have some pictures for publication. It would be a welcome addition to our page on Visitors Projects.
John
THANKS I’M SURE I WILL HAVE MAY QUESTIONS IN THE FUTURE.
REGARDS JOHN
what is a fly cutter? i am a complete novice
Hello John
A flycutter is used in a milling machine to impart a good quality finish over a large surface. (They also impart a covering of fine chippings over all surfaces in the workshop, both human and inanimate oh, and in your mug of coffee too.)
Take a look at RDG Tools and you will see several types. I bought the set of three and have found them invaluable. Early on I bought ‘Model Engineering’ by Peter Wright and found this very helpful in explaining the different procedures and tools required in model engineering. A good investment especially for newcomers.
John