Plugging crankshaft oil ways

I made the crankshaft below and cross drilled the oil ways which now need plugging. What is the preferred method of plugging these holes, they are 2mm and 3mm diameter.

Grub screws with loctite?

Mike

I would cut down a tap and tap them, then fit grub screws.

Another two possible methods -

1. Make short tapered pins with 1.5 to 2 degree taper and a 1 to 1.5 thou interference and press them in.

2. Find a steel or stainless steel hard ball with 1 to 1.5 thou interference and press them in.

Plus dot punch around top of hole to make sure they stay there. Presumably there's an oil pump which one o' them'd do a mischief.

There are commercial plugs available for this.

The drawback is that they need a shoulder to butt up against for the setting operation.

An example are Lee Expansion Plugs

or possibly a cheaper version Expansion Sealing Plugs

Edited By Nick Hughes on 26/09/2019 09:49:43

Thanks for the replies, I do not think tapping and grub screws would be practical , I was hoping

there may be a soft plug I could use and press in.

Those Expansion plugs look good , I will read up on them.

I'd be concerned about a soft plug creeping and loosening over time.

A hard ball or tapered plug pressed in with a few tons force is much less likely to loosen.

I have used the Lee type expansion plugs in industry, and generally they work OK, but we would get the odd leaker. The price was rather high also. If the fit is right, press fit balls or plugs into steel parts don't leak, up to 500 psi pressure, and don't loosen, The price is right too, and they just need a plain hole, no shoulder.

We used Lee plugs in aluminium brake manifolds and shimmy damper units for aircraft which tested at 3500 psi. The finish in the holes was significantly better than a drilled hole, but tiny leaks in something like the op's crankshaft would not matter at all. Also Lee plugs require a stepped hole, or pressing in the expansion plug would just push the hollow part down the hole, so they will not be suitable.

How about turning brass plugs to at least size and size with the hole, (or maybe half a though larger? )

Put in the freezer overnight , warm the crankshaft thoroughly, with a hair drier, and press the brass plugs into place. The plugs should be a tight fit, and as the engine runs,and warms, the brass will expand more than the steel, and so become a tighter fit.

Just a thought!

Howard

Hi Howard , yes that's the sort of plug I was thinking, I don't think the oil pressure on

the little engine will be too high to pop a plug out.

You could easily get away with a light press fit for the plugs and Loctite when they are assembled. Use steel plugs with a visible turned finish, and they will bond in the drilled holes beautifully. Use 638 for fast curing, or 620 for a slow cure, they are both very strong and will not worry about oil or the temperatures in an engine.

 After 24 hours, flush through with brake cleaner, or carburettor cleaner, to wash out any surplice uncured Loctite.

Edited By old mart on 26/09/2019 21:29:23

Edited By old mart on 26/09/2019 21:31:03