LD19 Plug Bolt Thread Question

[romanroman]

Hello,

does anyone know the thread pitch on the LD19 plug bolts circled in the attached image? Or where to get some? Is it sealed by thread and teflon tape or does it have a conical interface like an AN fitting?

ideally I would like to use a button gp head to seal it to improve clearing with the wheel and wheel weights.

thanks

[tlracer]

IMG_20231126_213515.jpg
3/8 UNF, conical seat

[romanroman]

Do you know who sells these? I seem to have misplaced a few.

[QUOTEdo=tlracer;659108]
3/8 UNF, conical seat[/QUOTE]

[Charlie Schmidt]

https://www.pegasusautoracing.com/pr...p?Product=3233

[tlracer]

The end taper of the std screw is 90 deg. If you want to improve clearance, you could substitute a 3/8 unf cone point set/grub screw.

[Garey Guzman]

Automotive seats are "typically" 45° while AN seats at 37° so they are not good to mix.

You could use a short plug and seal with a copper crush washer. That should minimize the height and maximize your clearance.

[romanroman]

Automotive seats are "typically" 45° while AN seats at 37° so they are not good to mix.

You could use a short plug and seal with a copper crush washer. That should minimize the height and maximize your clearance.

the aluminum 37 flair is also only good to 200psi. I wonder if I buy a set screw and machine a 45 degree tip onto it. Maybe that will work along with some teflon tape or sealant compound.

[romanroman]

Automotive seats are "typically" 45° while AN seats at 37° so they are not good to mix.

You could use a short plug and seal with a copper crush washer. That should minimize the height and maximize your clearance.

the aluminum 37 flair is also only good to 200psi. I wonder if I buy a set screw and machine a 45 degree tip onto it. Maybe that will work along with some teflon tape or sealant compound.

[Garey Guzman]

I believe that the pressure rating you quote of for the system, not the flare seat sealing capability. The system pressure weakest points would be the hose crimp/connection or capability.
Teflon disintegrates in brake fluid. The pressure of the braking system should have a mechanical seal like mating flares or a crush washer designed for the application.

My suggestion would be that either needs to seal on the cone, if there's a cone at the bottom of that hole, or with a crush washer. I don't mess around with brakes, they need to be 100% at all times so if you REALLY have a clearance need, the plug will need to have a mechanical, metal-metal seal.

[fletch]

Could you just machine half the height of the hex head away?

[Lotus7]

Could you just machine half the height of the hex head away?

To some extent, maybe.
The 'crush' on the washer may be compromised by the now-thinner bolt head, if it flexes with increasing torque on the thread as its tightened.

[fletch]

I would agree if it was a standard bolt that has a clamp load involved. But if you look at the top bolt in the first picture, the head is not making any contact. It looks to be bottomed out on the taper?
If that is the case, you could also shorten the bolt at the taper end, as long as the taper still bottoms out first.

[BeerBudgetRacing]

Why not use a short 3/8-24 with a button head or some other low profile head with a crush washer?

https://www.mcmaster.com/products/sc...rive-screws-8/

And not have it bottom out.

[tlracer]

I would agree if it was a standard bolt that has a clamp load involved. But if you look at the top bolt in the first picture, the head is not making any contact. It looks to be bottomed out on the taper?
If that is the case, you could also shorten the bolt at the taper end, as long as the taper still bottoms out first.

Yes, the seal is entirely at the taper (same as a bleed screw), ie. the hex head is there only to allow it to be tightened.

Because of this, it should be possible to to achieve the same seal using a cone point set-screw (or grub screw as we limeys know it!) which has the same taper angle. That would seal in the same way but without the protruding head.

[J Leonard]

Why not use a short 3/8-24 with a button head or some other low profile head with a crush washer?

https://www.mcmaster.com/products/sc...rive-screws-8/

And not have it bottom out.

What's in the bottom hole opposite the bleeder? Looks to be what you want, rounded head, low profile.

[Lotus7]

I would agree if it was a standard bolt that has a clamp load involved. But if you look at the top bolt in the first picture, the head is not making any contact. It looks to be bottomed out on the taper?
If that is the case, you could also shorten the bolt at the taper end, as long as the taper still bottoms out first.

yes, if the taper is the seal; in that case, as a prior replyer said, just use a headless plug

[DaveW]

the aluminum 37 flair is also only good to 200psi. I wonder if I buy a set screw and machine a 45 degree tip onto it. Maybe that will work along with some Teflon tape or sealant compound.

My aluminum calipers have steel bleed screws that tighten directly into the aluminum body. As long as those are sufficiently torqued and not stripped, they don't fail or loosen.

Teflon tape doesn't dissolve in brake fluid, so that is not the reason it could leak. However, it is not recommended for anything over ~200 psi since it will "flow" and leak with excess pressure.

The 37-deg flare fittings that are ~200 psi pressure-limited are those where either the male and/or female are aluminum, and yielding of either can compromise the connection. That usually applies to fittings over -6 AN. Smaller fittings don't have enough stress from internal fluid pressure to be an issue.

[problemchild]

At the risk of simplifying this problem, I have bought bleeder assemblies at my local oval racer supply store. The body has external 1/8NPT threads and the bleeder screw uses a 1/4" wrench. I buy a 4-pack for under $20 and use them in tee fittings adjacent to my brake pressure sensors. I have also used one to repair a crashed caliper that literally had the bleeder portion broken off. You can drill and tap anywhere you want, in the original hole or not.

I will have to look for a link.

[problemchild]

4/$19.85
https://us.bicknellracingproducts.co...em/BRC220-0064
There is even a Canadian store so Roman won't need to ship across the border.
The top pic is my usual application. The tees cost more than the bleeders.

[romanroman]

That is not mine in the photo. I did not have time to take a photo. But the top plugs sit under the rim lip and tear off the wheel weights. I thought there might be a simple off the shelf solution but I will most probably use a a button head screw and a crush washer or a set screw with a machined tip.

Thanks for the reply’s

[Mike B]

But the top plugs sit under the rim lip and tear off the wheel weights.

I always tell Hoosier to put the wheel weights on the outside of the wheel.

[Charlie Schmidt]

hardware store socket head set screw and crush washer?

can you still buy those tapered crush washers meant to repair an AN fitting?

[David Clubine]

That is not mine in the photo. I did not have time to take a photo. But the top plugs sit under the rim lip and tear off the wheel weights. I thought there might be a simple off the shelf solution but I will most probably use a a button head screw and a crush washer or a set screw with a machined tip.

Thanks for the reply’s

We have the proper plugs in stock.

David Clubine

Britain West

[romanroman]

We have the proper plugs in stock.

David Clubine

Britain West

thanks Dave!