Author Topic: Valve seat cutting  (Read 3319 times)

Offline Amblejo1

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Valve seat cutting
« on: February 17, 2021, 10:43:38 AM »
I have reached the nerve wracking phase of my Alyn Foundry Gardner 0 build i.e. the inlet valve chest.

This needs two 45 degree valve seats and in the construction notes, Graham the designer suggests making a small valve seat cutter for these which are 3/8" diameter.

Having just found a brand new, unused 10mm, 90 degree spot drill in my odds and ends box. I'm wondering if this could produce the valve seats I need?

What does the panel think?

Thanks....John

Offline pgp001

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Re: Valve seat cutting
« Reply #1 on: February 17, 2021, 11:44:19 AM »
That sounds like it might do the job.

But have a go on some scrap of the same material to see how good it cuts before you risk your actual parts

Phil

Offline Amblejo1

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Re: Valve seat cutting
« Reply #2 on: February 17, 2021, 12:03:31 PM »
Great idea - why didn't I think of that??

Its cast iron which drills very nicely, so the surface finish should be OK.

The seats are in a recess, so visibility is not good, but mocking it up will give me useful guidance for how much material to remove.

Thanks Phil.

Offline Charles Lamont

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Re: Valve seat cutting
« Reply #3 on: February 17, 2021, 12:30:46 PM »
Dead slow speed, to a depth stop. But even so I would be very concerned about chatter marks, which would be very difficult to correct without making the seat too wide.
If this a new set-up just to chamfer the seats, I would be even more worried about concentricity.
I have successfully used the home-made, hand-held, piloted cutter method myself - more work, but less chance of a cock-up.

Offline pgp001

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Re: Valve seat cutting
« Reply #4 on: February 17, 2021, 01:16:14 PM »
Just to add.........

My comments above are based on the assumption you will be doing this with a milling machine and have everything held very rigidly etc.

If you were thinking of using a drilling machine, then you are heading for trouble.

Phil

Offline Jasonb

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Re: Valve seat cutting
« Reply #5 on: February 17, 2021, 01:17:01 PM »
Personally I never use a CSk or other type seating tool unless the design prevents my usual method of boring the bole behind the seat, reaming for the valve and turning the seat with the topslide set over all in one setting on the lathe. That way I only spend maybe 60secs lapping in the valve and all my engines have run with no more work to the valve seal.

Offline GordonL

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Re: Valve seat cutting
« Reply #6 on: February 17, 2021, 02:10:57 PM »
A counter sink will only work if you use it while maintaining the original setting you used to drill it in the first place. If  your setup is changed even a little bit the CS will not be centred on the original hole and will cut one side more than the other. There are several drawings available showing a seat cutter made from drill rod and rotated by hand.

Online Vixen

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Re: Valve seat cutting
« Reply #7 on: February 17, 2021, 03:37:10 PM »
A piloted cutter will ensure concentrically. If you can stagger the cutting edges so they are at irregular angles (unlike a counter sink) the chances of chatter marks will be greatly reduced.

Mke
« Last Edit: February 17, 2021, 04:42:56 PM by Vixen »
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Offline Dave Otto

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Re: Valve seat cutting
« Reply #8 on: February 17, 2021, 04:28:48 PM »
There are photos on post 157 of my Pacific build that shows the piloted cutter that I made to cut the exhaust valve seat for that engine.
https://www.modelenginemaker.com/index.php/topic,1326.150.html

Dave

Offline Amblejo1

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Re: Valve seat cutting
« Reply #9 on: February 17, 2021, 04:38:56 PM »
The piloted, hand turned cutter seems to be the way to go as I have already lost concentricty by moving the table of the milling machine.

Many thanks for your thoughts which have returned me to reality  :)

Offline Amblejo1

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Re: Valve seat cutting
« Reply #10 on: February 17, 2021, 06:30:21 PM »
Thanks Dave Otto for the link to your piloted seat cutter. I am in awe of your work.

Seeing the two part exhaust valve took me straight back to my restoration, a couple of decades ago, of a full size Ruston Hornsby AP engine. That had a badly pitted exhaust valve which was made the same way, so I reproduced it the same way with good result.

Also in full size, I made a piloted valve seat cutter for a Wolseley WD2 engine - somewhat bigger valves than the Gardner model, but I should be able to scale down to make something usable.

I have some doubts about my ability to turn a 1/8" valve stem truly parallel for the Gardener model, so I may well follow your lead and make two part valves.

Thanks to you and the other respondents for stimulating useful thoughts and pointing me in the right direction

Offline Dave Otto

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Re: Valve seat cutting
« Reply #11 on: February 17, 2021, 09:24:00 PM »
Thank you for the kind words, I got the valve seat cutter idea from George Britnell an amazingly talented model engineer.
Yes the two piece valves were widely used on early engines cast iron heads and steel stems, Like you I have also made a number of them for full sized engine restoration projects.

Dave

Offline gbritnell

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Re: Valve seat cutting
« Reply #12 on: February 17, 2021, 10:25:41 PM »
Hi John,
To add a little to what has already been said. Valves and their respective seats seem to be one of the major stumbling blocks when building an I.C. engine. Having worked on full sized engines, both car and motorcycle, I decided to make a cutter which would work similar to the full sized counterparts. The old school way of grinding the seats was to insert a rod into the valve guide hole then slide the appropriate grinding stone onto the rod. This was driven by an electric motor tool. For motorcycles the had a similar process except instead of a grinding stone a cutter with carbide inserts was slid down the rod and turned by hand. If a person wanted a 3 angle valve job he would use 3 different cutters, a 45 deg. for the seat area, a 30 and a 60 to reduce the seat area to the proper width.
With the motorcycle type cutter in mind I made one from drill rod as Dave had shown. The one other thing I did was to offset one of the cutting teeth (angular position) The reason being if you have ever used a countersink sometimes it would create a chatter and being as the teeth are at equal angles the chatter would just get repeated as each tooth would fall into the same depression. My thought was to offset one tooth and therefore there would always be a supported tooth. For smaller valve stems I added the enlarged area between the cutter and the guide to stiffen the whole tool.
I'm attaching the drawing that I made of the tool.
gbritnell
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Offline Dave Otto

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Re: Valve seat cutting
« Reply #13 on: February 18, 2021, 01:07:21 AM »
Not easy to see in the photos, my cutter has 5 flutes for the reasons George has indicated above.

Dave

Offline Brian Rupnow

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Re: Valve seat cutting
« Reply #14 on: February 18, 2021, 01:16:42 AM »
I'm here to tell you---George Britnell saved my bacon when it comes to valve seating. Way back eleven or twelve years ago on my very first i.c. engines, I simply could not get the engine to run because of leaking valves. I was so frustrated that I was ready to take up tap dancing instead of machining model engines. And then along came George and his wonderful valve seating tool. I built the tool to George's design, my engine ran like a charm, and I've used that tool on every i.c. engine I've built since. George is my hero!!!---Brian

Offline Amblejo1

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Re: Valve seat cutting
« Reply #15 on: February 18, 2021, 10:55:16 AM »
Many thanks for posting the drawing of the seat cutting tool George.

That will help me a great deal.

It will probably take me much longer to make the tool than it will to cut the valve seats, but there is great satisfaction to gained from doing a job well isn't there?

J

Offline Art K

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Re: Valve seat cutting
« Reply #16 on: February 18, 2021, 11:54:21 PM »
I just have to reply to this. I haven't made George's valve seating tool but I do plan to, using Dave's 5 tooth design. Brian I have to say this forum would be much different today had you taken up tap dancing. :lolb: I do have a friend who can heat treat stuff for me but it has to be S7 to not send up red flags.
Art
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Offline tangler

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Re: Valve seat cutting
« Reply #17 on: February 19, 2021, 02:23:05 PM »
Here's mine, a simple guided D bit (with an odd number of cutters - 1  :) )





Stay well,

Rod


Offline pgp001

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Re: Valve seat cutting
« Reply #18 on: February 19, 2021, 03:03:54 PM »
Here is a tool I made for re-cutting the valve seats on my Austin Seven engine, it based on an R8 collet blank.
The actual cutter is made from a broken 1/4" screwed shank end mill.



I also opened out the throats with a boring head to get better gas flow.



Phil
« Last Edit: February 19, 2021, 03:09:19 PM by pgp001 »

 

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