Spiral adjustable reamers

Hi,

Chatting with a friend about IC engine valves and valve guides, there are two approaches in play.

One is to have the valve guide reamed dead size and to achieve the clearances with reduced diameter valve stems. The valves are specified and purchased with the appropriate stem diameters to give the required clearance - 2 thou on the inlet and 4 thou on the exhaust.

The other approach is to have the valves dead size and achieve the clearance on the guide. The problem comes when mixing things up and then the need to open out an 11/32" valve guide by 2 or 4 thou to suit a dead size valve arises.

The normal parallel blade adjustable reamers seem to be very hit and miss and can be hard to get turning smoothly in the bore. This may be a quality problem with the reamers I suppose but I spotted adjustable spiral shank reamers on Ebay. Unfortunately the Australian supplier is reluctant to ship as he has struggled with stuff getting lost in the past. I would like to give one of these things a try, but I can not find a source in the UK.

Does anyone know where such devices can be sourced in the UK?

Unlike the usual type of adjustable reamer they only have a range of 0.010" so OK for valve guides, but probably not too useful generally. Any other ideas also gratefully accepted, the valve guides may be iron, or one of the bronzes and have a working length of over 2 inches.

Ian

Can you not just get +0.002" and + 0.004" reamers if that is the clearance you want? Someone like Drill services will have them

Terry’s used to supply over-sized valve stems for those wishing to ream out worn guides, thereby avoiding replacement. Ford bored the guides directly in the head, I believe, so no alternative for those.

All valves are just made to dead size these days - less inventory, I suppose. Fitting new guides is likely a precision change these days, too, so no reaming if done carefully.

I have never come across oversized valve stems. Certainly not a common method of dealing with valve guide wear. Guides are cheaper to replace than valves, so why would you? And the guides wear much quicker than the valves.

I have used ordinary straight flute adjustable reamers on valve guides all my life. Never really a problem. Usually these days you are only taking out a thou or two where the guide has shrunk a tiny bit under press fit, or the end has deformed slightly from using a hammer and drift to fit guides cold into a cast iron head.

It's a matter of fine adjustment of the reamer to take small cuts to get to size. You can measure the setting of the blades with a mike as you go and take it in small increments. The first third of the blade is tapered so you set the reamer so the tapered part sits inside the valve guide and cuts just on the last bit of the taper as it blends to the straight section.

And if a new reamer grabs on bronze guides, you can make it less grabby by running a small abrasive rubbing stone down the cutting edge to dull it off a bit.

Those spiral adjustable reamers were a bit of a motor mechanics tool and seem to be a thing of the past. You might find them for sale out of the USA though. They seemed to like them a lot in the day. Plus you can get straight or spiral flute fixed reamers that are the couple thou oversize required. Usually a special tool that costs a lot more though.

And an adjustable spiral reamer is going to be no less "hit and miss" than an adjustable straight reamer. It all comes down to how you adjust it.

Edited By Hopper on 19/05/2021 23:24:53

Edited By Hopper on 19/05/2021 23:27:41

Hello,

Sorry if I am teaching you to suck eggs, I've never used an adjustable ream (yet!) so I wont comment on that topic,

However the firm I work for produce things called direxpander reams:

https://www.dk-holdings.co.uk/engin/direxpa.html

That link explains what they are, diamond expanding reams. I am not sure if these would work for your application as I don't really know what diameters you are working with, the range that we commonly make is 6-60mm however I am pretty sure we have done some tiny ones, they just work on a slightly different principle.

There are Chinese copy's to be found on eBay, so one could experiment. The ones we make usually have a lead in, a parallel sizing section and a lead out. This means they are quite labour intensive to produce (all finished on manual Jones and Shipman cylindrical grinders) and so are in no way cheap, the Chinese ones at the cost they seem to be might not made to the highest standards so take that as you will.

I hope that is of some use

William

I have never come across oversized valve stems. Certainly not a common method of dealing with valve guide wear. Guides are cheaper to replace than valves, so why would you? And the guides wear much quicker than the valves.

Perhaps you are too young, have a poor memory or was not involved in that sort of thing? I am talking here of the 1960s. Specifically, a 1500 Cortina head hotted up by a well known and respected engineer. Guides were bored directly in the head as I recall.

Car went like the proverbial off a shovel but the head was soon moved on when a 1650 block was fitted (the compression ratio was just a lot too high, at the time for even the top grades of fuel🙂 ).

Maybe your experience of parts available, in that era, is a little limited?

The formula Ford engine builders now tend to use "K Line" ( memory for the name ?) Valve guides, these are pressed into the head and sizes achieved by pushing a hard ball bearing through the guide.

I have not used these myself because the engines I work on are pre war and tend to be agricultural in nature.

Taylor Jones as a reamer supplier comes to mind for the odd sizes required but at a cost.

Correct. My experience of 1960s UK Ford Cortinas is zero. Thankfully. Dealing with the madcap engineering of British motorcycles of the 1960s is plenty enough for me these days. But even they had replaceable valve guides.

Edited By Hopper on 20/05/2021 08:23:53

Not just them. K-Liners are pretty much industry standard for engine reconditioning shops these days. Quicker and easier than changing the whole guide. Ream the old one out, in line with the existing seat, and press in a liner than swage it with a steel ball to lock it in and size it all in one go. Works well on motorbikes too. Although, I stick with cast iron guides on the real vintage stuff that runs hot and lubrication system is not the best. And I ream them with adjustable straight reamers.

Just to clarify, these are old JAP engines and we are not dealing with wear, just two different approaches. One supply organisation uses dead size valves and gets the clearance in the guide, the other uses dead size guides and gets the clearance on the valve stem. What we are doing is mixing the two systems, we want to use the dead size valves from one outfit in the dead size guides from the other, hence the need to open up the valve guides.

There is a good reason behind wanting to do this by the way....we want the valve head sizes of one engine in the other. The valve guides are not interchangeable between the engines.

We are machining new head castings so could more or less easily make custom valve guides, but it would be a quick fix if we could easily and reliable open out the dead size valve guides to suit the non standard valves.

I should also add that like many home workshop enterprises we are cheap always looking for low cost solutions, so had discounted the lovely but expensive adjustable diamond hone. Buying two new reamers is probably affordable.

Ian

Now that sounds like an interesting project. Cast iron guides should be a doddle to ream with a straight adjustable reamer if its in good condition. Bronze can be a bit trickier. New reamers tend to catch on the material unless the cutting edges are dulled off. You could always set the guides up in the lathe and size them before installation.

Or for removing that few thou on just a couple of jobs you could make a toolmaker's reamer by turning a piece of silver steel to size then cutting the end at a long oblique angle and then harden and temper it.

I have both T&J and 'Summit' brand adjustable reamers which will cut in increments of between less than a thou to around 3 thou as they have leads on their front edges of their blades. My experience of import adjustable reamers is that these do not have a lead on their blades, at least not on the ones I have seen.

For a definitive valve guide size with excellent wearing properties I have a selection of valve guide broaches. These were 'salvaged' from the Triumph Meriden factory when it closed. These broaches remove around a tenth thou per tooth and finish with a double sphere, giving a 'ballised' finish. For a job like Ian's I would seriously consider making such a broach - ream to -0.001" then finish with the broach.

Valve guides are a critical item in an engine - there are numerous examples of poor understanding of the required sizing and finish required in a guide. One of the latest examples was the McLaren MP4/12c which suffered repeated valve catastrophes (dropped valves!) during development which delayed the release of the car for 15 months whilst the problem was discovered and resolved.

I can post some photo's of the Triumph broaches if you need more information.

Martin

Hi Oily Rag,

A picture of the Triumph broaches would be interesting thanks.

Ian

I can't imagine how they would work at all without the usual taper on the first third of the blade. Perhaps that is why IanH has found them unsuitable. All my adjustable reamers are ancient, made by (now) dead white males and thus totally lacking in post-modernism.

And yes, a pic of said broaches would be of great interest. Their provenance being of equal interest too. Piece of history that.

Edited By Hopper on 21/05/2021 06:23:19

I used to lap finnish valve guides with an adjustable Acrolap. They expand to suit the fit required you just need to make sure the guide is cleaned after lapping. They come in a range of sizes from 3mm to about 25mm.

David

Here are the Triumph broaches - made by BSA!

The etching on the broach says "BSA Broaches Co, MCO No. 2359?, ST 3828W, TRIUMPH" (the ? indicates 'unreadable' )

Finally a close up of the 'Ballising' area:-

The Ballising final size is 0.3142" for the final 2, 0.3141" for the 2 preceding 'balls' - the final cutting flute is 0.3140", and the first of the 5 final flutes is 0.3136" - note that these final 5 flutes are not 'rived'. the final 'rived' flute is 0.3135".

Hope this helps.

Regards,

Martin