Phil and Co. Guide reaming?

[RobThomas]

Hello Phil, and other engine tinkerers.

I wonder if anyone knows if you can get A-series specific valve guide reamers and how accurate are they? I have a job where a 7mm guide needs to be reamed out to 9/32 inch (7.14-ish mm) in a cast iron guide. Can it be done or will it need opening out closer to the finished size?

Also, how hard is it to cot down a valve rim on a standard Minor exhaust valve? How would you know if you had hardened/stellite tips and rims???

[Declan_Burns]

Rob,
There are adjustable reamers in the range 6.75 ... 7.25 mm available or imperial ones.
http://www.ebay.co.uk/itm/RDGTOOLS-EXPA ... 950e66d5af

I would think that a valve rim would need to be ground down rather than cut.
Regards
Declan

[les]

You could open it out to the finished size with the reamer mentioned.

[RobThomas]

Thanks, guys. I guess I should have said "Cut...on a lathe". I'll try to take one down in the lathe tomorrow and see how it goes.

I didn't know if the reamer could be inserted and then widened out in-situ or if it had a tapered start on it.

[philthehill]

Rob
The valve guides should only be cut/opened out on a lathe to ensure concentricity.
You could use a 9/32" taper pin reamer mounted in the tailstock chuck to achieve the required result.
Several 9/32" taper pin reamers on 'e' bay at the moment.
I would prefer a lightly used reamer over a new reamer as less likely to cut excess metal - a bit like using a used tap to clean up a female thread.


To reduce the size of valve head it really should be done in a valve reconditioning machine again to ensure concentricity.
The machine will accurately grind the head size to suit what ever metal the valve is made from.
Do you have a grinding attachment for your lathe?
I have seen a Dremmel type grinder attached to the lathe cross slide which did the job nicely and accurately.
Phil

[Declan_Burns]

Rob,
They have a taper and should be removed and adjusted. I would do this on the lathe and if you have a chuck collet to take the valve guide even better. I would turn the chuck manually with the reamer mounted in the tailstock. These reamers are not designed to remove large chunks of metal so take it very slowly. No more than 1/4 turn on the adjuster on each pass and do not reverse the chuck when retracting the reamer.
Do a few practice runs on scrap tubing to get the feel for it.

Regards
Declan

[BLOWNMM]

Rob
When reaming oversize it is not good for the reamer to take much more than one thou per cut preferably 1/2 thou to really look after your reamer blades. The adjustable reamers that Declan refered to have a taper on the end. As to reducing the head size I have used valves with a head dia. of 35 mm. and machined them down to 32 mm. which I am using in my MM, using the cross slide. However I had them professionally finished ground to ensure concentricity. If they are hardened or 'Stelite' faced and you are not using Carbide or Ceramic Tooling you will soon know about it.
Bob

[RobThomas]

Thanks, everyone.

The guides are already installed in an alloy head and have been slightly worn over the years. The guides are fancy shaped so are going to be a PITA to get remade so I thought I'd see if the next diameter up (9/32 Minor size) valve could be adapted. The original valves are also worn so going up one size would solve several issues at once. I've found 9/32 diameter valves with suitable sort of collet/keeper dimensions and would only need to decrease the valve diameters and knock a couple of mm off of the top of the valves. I've already machined a keeper and collet set and have finally got the right clearances and sizes to miss the valve train.

The valves are angled so I'd need to jig up the head to get the reamer to go in squarely.

[philthehill]

Rob
Are you not able to remove the valve guides so as to able to do the job in the lathe?
Phil

[RobThomas]

I guess so, but I'd rather avoid knocking them out. After 50 years in there they might get damaged with the force required, regardless of how carefully it gets done.

Angle plate and Mill? I have a Hobbymat MD65 Lathe/Mill like this one...
http://2.bp.blogspot.com/-XOpMSKqIqIw/T ... Y_5491.JPG

[oliver90owner]

Guides still in situ? Seems like you need a mill, not a lathe. Remember, too, you will need to recut the valve seats for concentricity. With machine reamers lubrication can change the final dimension slightly - cutting oil will result in a marginally larger hole than plain oil lubrication. Adjustable hand reamers are not the favourite among model engineers.

Head fixed to table should give 'perpedicularity' if every thing is trammed in accurately.... oops, not vertical valves, I see.

RAB

[BLOWNMM]

Cutting fluids or coolant should not be used when machining or cutting cast iron whether by lathe tools, milling cutters, reamers or any other method.
Bob

[philthehill]

Rob
Do you access to a press?
Whilst those guides have not been out in 50 plus years - warming the head in the oven and then attempting to press out the guides may be worth a try. Trying to press out the guides is better than hitting the guides/removal tool with a hammer.

A second option is if you have a pillar drill of which the table has the ability to rotate and angle - bolting the head to the table and then angling/rotating as required and using the chuck with the reamer fitted and rotated by hand may be a way forward.

As regards lubricant:
If the valve guides are cast iron they should be as above reamed dry with the reamer continuing to be rotated in the same direction even when removing the reamer.
If not pure cast iron - soda water may be used - make sure that you drink the whisky first

For general information:
Reamers should not be rotated backwards as there is the possibility of picking up metal and damaging the item being reamed.


Phil

[IslipMinor]

warming the head in the oven

Aluminium head and cast iron guides? Warming the head to ~100°C should help to press the guides out.

At the moment am working on a friend's 1927 Austin Seven, and it seems every other paragraph in the manual in the sections for dismantling the engine and gearbox starts with 'heat the crankcase/gearbox case etc. in an oven to 100°C'. It certainly makes getting the various ball and roller bearings out fairly straightforward. The 2 main bearing crank uses a ball + roller bearing for the front main bearing and a roller bearing for the rear main. Lubrication is 'splash' feed, no pressure feed to the crankshaft bearings.

Same applies to reassembly, before starting 'heat the crankcase/gearbox case etc. in an oven to 100°C'!

If you do need to remove the guides, make sure that there is no radius on the drift where it contacts the end of the guide. Yes, did not check and removing one of the Austin Seven guides that was already damaged was fine, but drifting the new one in swelled the end and cracked it - brand new guide!

Small undercut on the drift, another new guide and all is fine. Pressing is definitely better than using a hammer - I might have got away with the radius if had used the press.

[oliver90owner]

Cutting fluids or coolant should not be used when machining or cutting cast iron whether by lathe tools, milling cutters, reamers or any other method.

I know there is plenty of graphite in CI as a lubricant to cut dry, but I always cut threads in CI with oil as extra. It collects the particles for cleaning off later. I am told that using oil with a reamer results in a tight hole cut, so that is the other cutting situation where I would likely use extra lubricant. So it is a case of 'not needed' rather than 'should not' I would think. I would imagine it would be difficult to clear flood coolant of the fine grinding paste (it's bad enough cleaning up the lathe or mill after cutting dry) and may well wear the ways prematurely.

RAB

[BLOWNMM]

It can be messy and difficult to thoroughly clean the swarf and dust from machinery. The fine particles can easily be inhaled with detrimental results. This is why I always use a vacuum cleaner when machining cast iron to get rid of the mess at the source rather than all over the machinery and anywhere in the workshop the fine powder settles. It also stops inhalation of the dust.
Bob

[RobThomas]

Just to finish this thread off for the benefit of anyone searching for info in the future...

I heated the head in the oven to 180 c (Roast Chicken temperature) for 1/2 hour, lay it down on a pile of old overalls, sprayed down the old guide with some stuff designed to freeze waterpipes during plumbing repairs and popped the old guides out. I made a removal tool by lathing down a piece of brass bar to an OD just smaller than the hole in the head (0.5 inch approx), countersunk the end slightly, bored a tight 7mm hole in it and sunk a 7mm old valve stem in to give concentricity. One whack, out they popped.

Measuring the old guide OD it came out at .501 inch, so 1 thou oversize. I made a new one in the same dimensions. I used the tooling dry apart from adding some cutting oil to the bit where it would be exposed to the public and the finish was much brighter, presumably from an oil/cast-iron polishing.

Material is Meehanite, £13 for 12 inches of it. Took about 2 hours each since I don't really know what I'm doing!

altaguide.jpg (107.5 KiB) Viewed 2990 times

[philthehill]

Rob
Considering you say that you do not know what you are doing It looks all very good to me.
Phil

[RobThomas]

Thanks. The lathe is metric and the guide is mostly imperial so I've had a few brain f4rts. It took a while to realise that the cross slide needs to move 1cm to knock 2cm off of the diameter but this slide needs you to wind the dial round '2cm' to get that 1cm off of the radius. I'm sure there is some sort of iron-curtain logic behind it.

The best way to get the OD concentric with the ID is to bore the main hole and then insert the cut off valve stem in there and hold the end in the chuck. That way you have the ID hole centred between the chuck and the headstock. I still need to find a 7mm reamer to go in the morse taper or follow some advice to drill the hole 7mm and then run a split plastic rod with some abrasive paper and some oil to hone the clearance. Bob??

Where can I find really good 7mm drill bits that won't wander??

[firedrake1942]

Having worked vice in my former career, this topic heading took a few seconds to get straight!