Special cutter to create valve guides

[Philip MajorParticipant @philipmajor52482]

Hi, I am building a Forrest edwards 5 cylinder radial engine, and the drawing calls for valve guide to be cut into the head, please see photo, anyone know where I could get a cutter to do it? I have tried to make my own, so far not good results, I wilnexr try to make a "C" type cutter to make a spigot? Any ides appreciated id is .250 od .500

 

Edited By Philip Major on 30/09/2021 08:48:15

Edited By Philip Major on 30/09/2021 09:04:05

[Philip MajorParticipant @philipmajor52482]

5 cylinder radial cylinder head valveguides

[Michael GilliganParticipant @michaelgilligan61133]

Start here, Philip : **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=103028&p=1

MichaelG.

[JasonBModerator @jasonb]

Personally I've never been a fan a valve seat cutting tools and always prefer to set up the head so that I can drill & ream the guide, bore the counterbore and TURN the seat all at one setting on the lathe. All* my IC engines have then just had a very quick lap with 1000g Silicon carbide powder/oil mix to seat the valve and I have not had a single one with low compression due to valve leakage. It may need a simple jig but worth it with 5 heads to do.

*One exception where it was not possible to do it as above due to position of valve and I had problems with that one sealing.

[Ian PParticipant @ianp]

Just a thought, I wonder if the OP referring to a method of cutting the external annular recess/counterbore that the spring sits in?

Ian P

[JasonBModerator @jasonb]

If it is that then best to look at the external reamer thread and follow the links to hollow endmills.

[noel shelleyParticipant @noelshelley55608]

Hollow end mills or rota broaches ? Noel.

[John ReeseParticipant @johnreese12848]

Hollow mills are outrageously expensive. The annular cutters (Rotabroach) is quite a bit cheaper. Another option is a trepanning tool in a boring head. It looks like a very wide cut so a rigid machine is needed.

I may have a 1/2" hollow mill. I could loan it to you if shipping from the US, customs, etc. would not be prohibitive. I will look today to see if I have that size.

[John ReeseParticipant @johnreese12848]

You might consider valve guides as separate pieces pressed into the head.

[Ian PParticipant @ianp]

I only speculated that the OP was enquiring about the external machining rather than the valve seat side of things and whilst a Rotabroach or some sort of hollow endmill might do the job it could be more cheaply done with a standard slot or endmill with the head set up (on a simple alignment spigot) on a rotary table.

Probably lots of other ways of machining the recess, but best wait until we know more from the OP (I dont know the engine and there is not enough of the drawing to show the full profile), maybe the head is a casting with the spring recess already present.

Ian P

[JasonBModerator @jasonb]

Ian, It was me misreading what wa sneeded the 0.250" ID and 0.5" OD would be right for the protruding guide and recess around it, the head is cut from 7075

[John ReeseParticipant @johnreese12848]

I checked, the closest hollow mill I have is 9/16 ID and 1 1/4 OD.

[John ReeseParticipant @johnreese12848]

The rotary table idea is a good one. It would require a 20* wedge on top of the RT.

[John ReeseParticipant @johnreese12848]

It always helps to know what equipment the OP has available so we could suggest solutions that best fit the tools available.

If OP had a lathe with a faceplate and a 20* wedge this could be a lathe job.

[Ian PParticipant @ianp]

Machining the head from solid looks to be quite a challenge!

If the fins are cut with slitting saw then the valve stem housings would get slotted too (based on the image Jason showed). Some of the other slot details look tricky too (like the ones parallel to the bottom face).

Endmill on rotary table for the spring recesses would have to be very long as there is only a 1/8" annular gap, similar cutting tool problem if done on the lathe faceplate.

Ian P

[John ReeseParticipant @johnreese12848]

If OP had shown the dimensions defining the recess He would have received better advise. The rendering of the part shows features impossible to machine unless the valve guides were separate pieces pressed into the head after the fins were cut. Whoever designed the head had no understanding of how to machine it.

[Author]

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