Valve seat cutters

Valve seat cutters

Author
Discussion

Humph7ey

Original Poster:

17 posts

74 months

Sunday 25th November 2018
quotequote all
I need to know what cutters are used. The seats I have cut are 45 degrees but I want to order a cutter that opens up the throat as it is now too small. I have been offered a 30 or a 70 degree but dont know which to order. These are advertised on ebay from India with a diameter. Is this the larger or smaller?

GreenV8S

30,152 posts

283 months

Sunday 25th November 2018
quotequote all
This is a very specialised job and is usually done by experienced machinists in a dedicated mill where everything can be aligned carefully. Even there it takes skill to cut the seat accurately. If you don't even know what the valve seat angle is, this suggests you aren't experienced in this area. In that case I'd advise you to get the seats cut by a specialist. This is not a DIY job.

paintman

7,669 posts

189 months

Sunday 25th November 2018
quotequote all
Consequence of getting it wrong could be a new head.
I too would advise getting it professionally done.
If you put your location you might get some recommendations.
In the Leicester area I would suggest Neyta Motor Engineers. Been there for years & I've used them several times for various engine work - incl head skims, valvework & the odd sheared bolt (the last being an inlet manifold bolt on a RRC V8 head) - & not had a problem.

Edited by paintman on Sunday 25th November 12:28

Humph7ey

Original Poster:

17 posts

74 months

Sunday 25th November 2018
quotequote all
It is for a 1929 Austin and it is not the first time I have done valve seats as I even made new inserts from cast iron bar. Previously I made a spotfacing cutter to bore for the seats. I have a 45 degree cutter but need to open the throat of the new inserts to match the valve better. Is the cutter usually a 70 degree one for opening the throat?

227bhp

10,203 posts

127 months

Sunday 25th November 2018
quotequote all
90' opens the throat. 70 is the bottom angle cut which leads you from 45 to 90, 30 is top cut in the chamber.

227bhp

10,203 posts

127 months

Sunday 25th November 2018
quotequote all
Would it have been really that difficult to Google 'valve seat angles' and look at some diagrams? If you can't manage that how are you going to cut a valve seat?

Humph7ey

Original Poster:

17 posts

74 months

Sunday 25th November 2018
quotequote all
Thanks that is a great help.

Humph7ey

Original Poster:

17 posts

74 months

Sunday 25th November 2018
quotequote all
I spent most of my working life as a machinist and toolmaker but while I can still cut a thread on a lathe it is sometimes difficult to understand angles. Something to do with age.

Weekendrebuild

1,004 posts

62 months

Saturday 21st December 2019
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Humph7ey said:
I spent most of my working life as a machinist and toolmaker but while I can still cut a thread on a lathe it is sometimes difficult to understand angles. Something to do with age.
Just reading this thread I would like to apologise for all the patronising bds on here . Most these people couldn’t change a CV boot . Good on you for having a go. my dads old mate used to work on a mill he could make pretty much anything from metal . He’s rebuilt loads of engines quiet a few old BSA ‘s of late .

DeadCatWalking

85 posts

51 months

Saturday 21st December 2019
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30 degree is the top cut from seat to chamber. 70 degree is the bottom cut from seat to throat. All angles are referenced from the valve head i.e. the perpendicular to the valve stem.

Humph7ey

Original Poster:

17 posts

74 months

Saturday 21st December 2019
quotequote all
Thank you for all your helpful messages. I have since repaired a few old side valve engines using ordinary cast iron which was in use long before leaded fuel. I think you guys say L head.