Reaming theory for valve guides

[cardiffrob]

I made some valve guides in Meehanite for a vintage car. Now there is a shortage of the 7mm valves so I may need to go up a size to 9/32 (7.14mm). Is it the case that the .14mm can be sorted out by the use of a 9/32 reamer down the 7mm hole or is it likely to get knackered?
Is there a % max that a reamer can cope with? Would it work if I got the shank of the reamer ground down to 7mm to lead-in the 9/32?

Thanks.

Rob.

 

[slim_boy_fat]

Adjustable reamer, using several passes if necessary??

A random Google search https://www.google.co.uk/search?q=a...rome..69i57.5810j0j7&sourceid=chrome&ie=UTF-8

 

[fizzy]

Taper reamer followed by a finishing one.

 

[penfold]

It's a bit more than reamers are supposed to shift but I'd be tempted to give it a go; what's meehanite like to cut?

 

[brightspark]

its a quality cast iron close grained

 

[scott0031]

Taper reamer followed by a finishing one.

Huh?

It will be fine. Depending want you want from the reamed hole the pre-size makes a difference, but as a standard ream on something like that I would naturally go for a .1 under size you are .14 under under size. I would suggest you use a nice new reamer though as a worn one could make the valve tight and that can sometimes be troublesome trying to remove a tenth or so.. Mic the valve and the reamers and do a test before trying on the real thing is wise if its possible.

 

[fizzy]

Huh?

It will be fine. Depending want you want from the reamed hole the pre-size makes a difference, but as a standard ream on something like that I would naturally go for a .1 under size you are .14 under under size. I would suggest you use a nice new reamer though as a worn one could make the valve tight and that can sometimes be troublesome trying to remove a tenth or so.. Mic the valve and the reamers and do a test before trying on the real thing is wise if its possible.

It is a long time since I used one but

http://www.tracytools.com/taper-pin-reamer-imperial?product_id=1447

Or have I been using them wrong?

 

[doubleboost]

I have some new adjustable reamers if you need to borrow one

 

[scott0031]

It is a long time since I used one but

http://www.tracytools.com/taper-pin-reamer-imperial?product_id=1447

Or have I been using them wrong?

Well those are for taper pins which is exactly what it says they are. Taper pins are normally used for a collar held to to a round bar to lock it in place place like a handle to a shaft fairly common on machine tools.

You probably are using them wrong by the sounds of it. Just to try to help you understand the mechanics of it. If a taper reamer was used on a bush it defeats the object of having a bush in the first place, you are taking away the material you need to act as the bush. Reamers are used to produce accurate, true, sized holes with repeatable tolerances.

 

[penfold]

its a quality cast iron close grained

Should be fine then.

 

[ronan]

I've seen a hardened steel ball being pushed through bushes to burnish and size them, might not be a good idea with cast iron guides though. What engine is it from ?

 

[penfold]

Is that not more usually a means of locking a bush in its orifice?

 

[frank horton]

go get the part head or block, u didn't if it was OHV or SV.......to an engine shop cos u'll need the seats cutting to line up with the valves stems.........
if poss go to a shop with "SERDI" equipment, it's the best there is.......formula 1 and all that.........it costs no more .............
if they do the guides, seats and grind the valves (in the machine) u won't need to lap them in.......promice.......
frank

 

[8ob]

go get the part head or block, u didn't if it was OHV or SV.......to an engine shop cos u'll need the seats cutting to line up with the valves stems.........
if poss go to a shop with "SERDI" equipment, it's the best there is.......formula 1 and all that.........it costs no more .............
if they do the guides, seats and grind the valves (in the machine) u won't need to lap them in.......promice.......
frank

As above, getting the valve to hit the seat square after reaming without some kind of guide is virtually impossible. http://www.mig-welding.co.uk/forum/threads/making-cast-iron-valve-guides.72361/page-2#post-994234

 

[ronan]

go get the part head or block, u didn't if it was OHV or SV.......to an engine shop cos u'll need the seats cutting to line up with the valves stems.........
if poss go to a shop with "SERDI" equipment, it's the best there is.......formula 1 and all that.........it costs no more .............
if they do the guides, seats and grind the valves (in the machine) u won't need to lap them in.......promice.......
frank

http://cylinderheadshop.com

 

[Shox Dr]

http://cylinderheadshop.com

I was going to use him a while back for a bigbore to a 1450cc Harley motor. He was based in lincs, but then moved to south west ireland. So it never happened.

Last time I looked at his site, it made no sense to me; I couldnt findout where he was, or if in fact if he was still machining

 

[ronan]

I know that a lot of people stopped replacing valve guides when they were worn and instead relined them, supposed to be a better job and of course stops the wear on the head drifting the guides in and out.

 

[ronan]

I was going to use him a while back for a bigbore to a 1450cc Harley motor. He was based in lincs, but then moved to south west ireland. So it never happened.

Last time I looked at his site, it made no sense to me; I couldnt findout where he was, or if in fact if he was still machining

He was in Ireland for a while, but that must have been 15 or 20 years ago now. He went back to the uk and was in Wimbledon afaik.

 

[Cobbler]

I know that a lot of people stopped replacing valve guides when they were worn and instead relined them, supposed to be a better job and of course stops the wear on the head drifting the guides in and out.

I seem to recall, for some vehicles you could get valves with oversize stems, so you could ream out the guides to save changing them

 

[cardiffrob]

Thanks, everyone. It is one of those OHV conversions to a SV engine. The guides are new on 2 valves and the rest are quite good. I was hoping to pilot the new reamer down via the old 7mm holes to help reduce the seat grinding needed. Grinding in the new valves will be easy. I've got fixed 7mm and 9/32 reamers plus some adjustable ones to cover the sizes. It would have been great to thin down half the 9/32 along the length to 7mm so it does the job in one go.
I'll have a play next week to see what I can do.
Ta.