Making new tappet adjusters.

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Making new tappet adjusters.

This topic has 26 replies, 14 voices, and was last updated 23 February 2023 at 12:08 by Howard Lewis.

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19 February 2023 at 13:44 #16427
Andrew Tinsley
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@andrewtinsley63637
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19 February 2023 at 13:44 #634182
Andrew Tinsley
Participant
@andrewtinsley63637
The tappet adjusters (basically a threaded rod and adjusting nut) need replacing.

I have sourced some long, high tensile, 1/4" UNF grub screws and grade 5 nuts. The grub screws have a hex slot rather than a screwdriver slot which is easier when it comes to adjustment.

It is the other end of the grub screw that presents a small problem. I need to make them hemispherical to fit into the top of the push rod.. I don't have a ball turning device and apart from the use of warding files, I don't have a good idea of how to do the job!

I am sure I am missing a trick here or overthinking the solution, so any suggestions? Otherwise it will be files and Mk 1 eyeball.

Andrew.
19 February 2023 at 13:57 #634184
peak4
Participant
@peak4
Maybe an HSS form tool and a basic lantern chuck in the lathe
If you can find one the correct diameter, you could even use a woodworker's carbide tipped router cutter in the toolpost, as the form would then be ready ground.

Bill
19 February 2023 at 16:36 #634211
noel shelley
Participant
@noelshelley55608
Bill has it ! A form tool at that size, ground from HSS. Rough out screw end to 45* to get rid of the bulk then finish with the form tool. Noel
19 February 2023 at 17:04 #634217
Andrew Tinsley
Participant
@andrewtinsley63637
Now why didn't I think of that. Thanks Bill and Noel. I have this vision of form tools as being for much larger jobs.

Thanks again,

Andrew.
19 February 2023 at 17:09 #634219
Roger Woollett
Participant
@rogerwoollett53105
How about a ball ended endmill in the drill chuck?
19 February 2023 at 18:21 #634227
Andrew Tinsley
Participant
@andrewtinsley63637
Probably showing my ignorance, but isn't a ball ended end mill, one that has a ball or hemisphere on the end? I want a ball or hemisphere on the tappet adjuster, not on the cutting tool, or have I totally misunderstood your suggestion?

Regards,

Andrew.
19 February 2023 at 18:43 #634230
Roger Woollett
Participant
@rogerwoollett53105
You are quite right. I was thinking of the end of the push rod.
19 February 2023 at 19:56 #634246
Mike Poole
Participant
@mikepoole82104
I was wondering if a grub screw will be hard enough for a tappet adjuster? They are usually very hard whereas socket headed fasteners are made from material selected and heat treated for toughness. Depending on your application the grub screws may have a shorter than hoped for life. Of course they may last for ever if they are relatively lightly stressed.

Mike
19 February 2023 at 20:19 #634247
KEITH BEAUMONT
Participant
@keithbeaumont45476
I have made similar form tools by using silver steel,driling a hole at an angle,to give the wanted radius Grind away to leave half of the drilled hole , harden.Usualy works quite well.

Keith
19 February 2023 at 20:22 #634248
Chris Evans 6
Participant
@chrisevans6
I tend to make my tappet adjusters from silver steel and simply harden with a blow torch. Works for me but the old Sloper only does around 300 miles a year.
19 February 2023 at 22:19 #634259
Andrew Tinsley
Participant
@andrewtinsley63637
I thought of using grub screws (with a hex hole) as most of the work has been done. The ones I have ordered are quoted as being high tensile and meeting AINSI B18.3 standard. Anyone know if that spec is suitable for my intended use?

Like Chris, the tappet adjusters will get a very easy life in my Petter driven alternator. Used for power cuts only, apart from annoying the neighbours when test running and annoying them even more when there is a power cut.

Andrew.

Edited By Andrew Tinsley on 19/02/2023 22:34:17
19 February 2023 at 23:18 #634263
Hopper
Participant
@hopper
They might last an hour or two unhardened or maybe a bit more. But they might mess up the ends of your pushrods and fiinish up costing you more money in the long run too. I would buy the correct parts. They take quite a hammering due to the tappet clearance and there is a reason every manufacturer hardens them..
20 February 2023 at 02:45 #634274
John Olsen
Participant
@johnolsen79199
There is a technique for turning small ball shapes which might work for this. You take a piece of silver steel rod a little larger than the ball size, and drill a hole in the end a little smaller than the ball size.Face the end and then harden. Fit the other end into a file handle, and arrange a rest in the tool post close to the job. Having roughly formed the ball end with a 45 degree chamfer, use the hand turning tool to form the ball, moving it around the end of the job so that it can cut. The circular cutting edge on the inside of the hole will form the ball. The outside edge is not a cutting edge and should never contact the job.

I've used this technique to form ball ends on tiny handles as small as about 1/8 inch or so. A refinement is if you can manage to face the end back at an angle to give some relief to the cutting edge. This sort of tool will work for a range of sizes, the smallest being the size of the hole.

Otherwise, you can make a form tool from gauge plate by drilling a hole the size you want and then cutting away the bits you don't want to leave a half or quarter circle cutting edge.

Case hardening should be enough for the tappets for a vintage style of engine.

regards

John
20 February 2023 at 09:35 #634296
Andrew Tinsley
Participant
@andrewtinsley63637
Hopper

Unfortunately the tappet adjusters are no longer available to buy, hence making them is the only solution, So you give the home made ones a couple of hours before they ruin the push rods? Goodness knows if the grub screws can be hardened, I wouldn't know where to start looking for AINSI standards.

Looks as though it might be better to go Chris Evans route and make them out of silver steel and harden them? I have never had much luck threading small diameter silver steel, I always finish up with a very ragged thread. Doesn't matter if I use a die or screw cut, the silver steel is good quality stuff (Coventry Grinders).

Andrew.
20 February 2023 at 10:25 #634302
Hopper
Participant
@hopper
I don't know how long they would last for sure. The only way to really tell would be to run them for an hour and inspect carefully. May well be all right for occasional emergency gen set use. But I would not expect them to last too long if not hardened.

I don't have trouble threading silver steel but use good quality dies. I don't know if high tensile bolts would have enough carbon in them to harden like silver steel. I think they are more of an alloy steel than high carbon content, but have never looked it up. I am sure it is out there somewhere.

1/4 UNF tappet adjusters from something else might fit? Lister?
20 February 2023 at 13:41 #634325
Clive Hartland
Participant
@clivehartland94829
The ball ends will have to be polished to match the pushrod cups, case hardening may be the best way .
20 February 2023 at 14:14 #634332
duncan webster 1
Participant
@duncanwebster1
Allen screws are probably some alloy steel, we need a metallurgist to comment on whether case hardening is a good idea. Above my pay grade.
20 February 2023 at 15:38 #634338
Robert Butler
Participant
@robertbutler92161
Posted by Andrew Tinsley on 19/02/2023 13:44:33:

The tappet adjusters (basically a threaded rod and adjusting nut) need replacing.

I have sourced some long, high tensile, 1/4" UNF grub screws and grade 5 nuts. The grub screws have a hex slot rather than a screwdriver slot which is easier when it comes to adjustment.

It is the other end of the grub screw that presents a small problem. I need to make them hemispherical to fit into the top of the push rod.. I don't have a ball turning device and apart from the use of warding files, I don't have a good idea of how to do the job!

I am sure I am missing a trick here or overthinking the solution, so any suggestions? Otherwise it will be files and Mk 1 eyeball.

Andrew.

Try A series tappet adjusting screws

Robert Butler
20 February 2023 at 17:37 #634354
Andrew Tinsley
Participant
@andrewtinsley63637
Hello Robert,

Good thinking, but A series tappet adjusters are 7/16" UNF. As I found out long ago!

Thanks,

Andrew.
20 February 2023 at 20:44 #634386
bernard towers
Participant
@bernardtowers37738
Sorry but 803 A series are 1/4 UNF
20 February 2023 at 20:48 #634387
bernard towers
Participant
@bernardtowers37738
Andrew I think you have your wires crossed, the spanner size is 7/16 which makes the thread 1/4
20 February 2023 at 20:52 #634388
Andrew Tinsley
Participant
@andrewtinsley63637
Well you live and learn! I have had just about every A series engine except for the 803! These all had 7/16" UNF tappet adjusters!

Thanks for that Bernard, I should have more success looking for those..

Andrew.
20 February 2023 at 21:27 #634397
Andrew Tinsley
Participant
@andrewtinsley63637
Hello Bernard,

The tappet adjusters on the Petter are 1/4" UNF, checked with measuring the diameter of the adjuster and a thread gauge.

For the A series tappet, I inadvertently typed 7/16". It should be 5/16" UNF !!!!!! Thanks for correction. The adjusting nut is 7/16" across flats and the very later A series had 1/2" across the flats, adjusting nut.

Thanks,

Andrew.

Edited By Andrew Tinsley on 20/02/2023 21:30:33
21 February 2023 at 15:15 #634492
Howard Lewis
Participant
@howardlewis46836
The tappet adjuster screws, and threads in the rockers, on the 803 cc A Series were 1/8 BSP from memory

1/8 BSP ,is 28 tpi, same pitch as /4 UNF, but different tread form.

Indeed that is where I inherited the drill and tap from my father., or was he wrong?

Howard

Edited By Howard Lewis on 21/02/2023 15:17:49

Edited By Howard Lewis on 21/02/2023 15:18:25
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