Bolt finish, 1914

[Guest Al Brass]

Hi everyone,

I have a 1914 Hupmobile 32 and I have the engine out at the moment. The crankcase is aluminum, quite large and unpainted, like original. It seems that the various bolts and hardware around the engine have never been painted or protected and I am wondering what I should do about this. Should the bolts remain unpainted (with a tendency to rust) or should I be trying to paint the bolt heads and nuts, say black. What approach have others taken with similar cars with aluminum crankcases.

Regards

Al

Christchurch

New Zealand

Edited July 19, 2011 by Al Brass (see edit history)

[Seldenguy]

Al -I have treated them in two different ways. The real early cars('00 to'10) I leave them natural(beadblast) steel, rattle can a internal tooth lockwasher in clear coat for under the bolt head or nut, assemble and hand paint the head or nut with clear coat. 1910 and up I use black with the same procedure. I have never been told it was wrong.--Bob

[Rusty_OToole]

There is a very old way to put a black finish on hardware. Heat the bolt with a propane torch and drop it in a can of linseed oil. It will come out with a hard black coating.

I think when the bolts were made, they did this.

[Guest Al Brass]

Thanks for your replies guys. I'll try the linseed oil idea and see how that goes or I can paint them as suggested. I don't think any manufacturer would have individually painted bolts and nuts so some type of treatment seems most likely, .... or they didn't do anything and were left bright, to eventually go rusty. There is no evidence left so I assume that if they were treated, it has come off and so the linseed oil idea seems plausible.

Thanks again

Al

[Rusty_OToole]

I believe the bolts were dumped into vats of oil as they came off the assembly line, still hot. This gave them a black finish that was moderately rust proof and of course a slight coating of oil would preserve them in the box until they were sold.

Today they use some kind of zinc or cadmium plating.

[MochetVelo]

I've used the Eastwood metal blackening solution followed by a semi-gloss clear coat. It looks nice, but you have to be careful not to chip it with the wrench.

Phil

[Guest Al Brass]

Plating of hardware on early cars looks terrible to me and the older the car, the worse it looks. Oiled bright steel is going to look the nicest but oiling every nut and bolt is just not going to happen.

Al

[ply33]

When did they start/end Parkerizing bolts? I notice a lot of the fasteners in the 1928-33 Plymouth Master Parts Book are listed as Parkerized steel. Searching the net, it seems that has been used, along with bluing, by gunsmiths since pretty much forever. Maybe some of those bolts on your 1914 were preserved by Parkerizing...

[Guest Al Brass]

There are several bolts in unaccessible places that have been preserved by oil and they shown no sign of any finish, other than plain bright steel.

Al

[Curti]

I believe the bolts were dumped into vats of oil as they came off the assembly line, still hot. This gave them a black finish that was moderately rust proof and of course a slight coating of oil would preserve them in the box until they were sold.

Today they use some kind of zinc or cadmium plating.

Isn't this the way they hardened the steel? Is it possible to remove the hardness or add hardness to the point of making the bolt brittle like a file?

I think the temperature is somewhat critical.

[Bhigdog]

There's a few ways to approach this. First, any bolt you use should not have stength marks on the head. They will need to be removed. Also the head profile is probably different than a modern head bolt. You may be able to modify a modern head. If you are going to try blackening a bolt by heating, it must be heated to redness then quenched. This will form scale, depending on the carbon content of the steel will alter it's strength, and if it's zinc plated will burn off toxic vapors. A grade five zinc plated bolt can can be made to mimic unfinished older bolts by bead blasting or acid removal of the plating and a light abrasive brushing, then a coat of clear. Another solution would be to use stainless bolts, remove the marks, modify the head as needed, brush finish and install. If you use stainless a coat of thread anti seize is sometimes reccommended...........Bob

[jdome]

There is no way to make modern bolts look like brass era bolts. The cross section of pre-20's hex is 1/16 or 1/8 wider and about twice as tall as a modern head. A mix of old and modern fasteners stand out like a sore thumb. You can buy original style, thick head bolts from Restoration Supply but be prepaired to pay $2 - $6 per bolt, depending on size. I turn my own from hex stock. You should check the on-line catalog of McMaster-Carr, industrial supply. They do not sell the thick head bolts but they sell what they list as "Heavy Nuts" which are the correct oversized nuts. You can buy a box of 100 - 3/8 for about $8. They sell other hardware, tools, and od size taps & dies that you might need.

The original bolts had some type of blackened finish. I haven't tried the linseed oil trick but I have tried the Eastwood Kit but was not satisified with the results. A coat of flat black paint is a better substitution. I'm working on a brass car now and I'm sandblasting the bolts and painting them with flat black, high temp. manifold paint. It sprays on thin and doesn't require primer. Per instructions on the can, after the paint air dries, I bake them in an old toaster oven to cure/harden the paint. The baked on paint holds up to wrenching without chiping.

It is against my religion to use stainless steel hardware on my brass cars, so I'm always looking for old style steel fasteners. The old style round head, slotted, machine screws with real round heads are getting hard to find these days too. You'll find a lot of these in #10, #12, 1/4" and sometimes 3/8" on most brass cars.

[Guest Al Brass]

Thanks for your thoughts on this. CAT brand bolts have a taller head than standard and that is an option I sometimes use. They're not too bad price- wise either.

I am fortunate with this job because I have the bolts and they are mostly in very nice condition. One or two nuts were a little rough but, like you, I went through my old ones and found some spares of a very similar style. The size I'm dealing with here is 1/2" AF (5/16 UNF) so they are standard thread and head width. One or two of the bolts are situated in a fairly covered spot and the look like they were only ever bright. My problem is the exposed ones tend to rust and that looks bad, even if original

As mentioned previously, the linseed oil process looks pretty good to me and so I will do the crankcase-to-sump bolts (all 36 of them) and see how it lasts. If it doesn't hold up, I can always remove them and try another process.

Modern style fasteners do look bad, I agree. Just like stainless steel hex head hose clamps, plastic coated wiring and crimped connectors :eek:

Thanks for sharing your thoughts and experience.

Al

[Curti]

I have purchased high hex bolts from MaMaster Carr they are grade 9 standard thread only. I grind off the markings off the top of the head, remove the plating and parkerize them. I tumble my fasteners in a rock tumbler with Turkish emery to remove rust etc. I found out quite by accident that stainless steel when tumbled comes out looking like regular steel. It doesn't have the stainless steel 'look' . I use stainless nuts washers and lock washers, but never bolts. I like the idea of the heat cured flat black paint. I would be inclined to spray it over black parkerizing so if it does chip it would be black under the paint.