View Full Version : Threading old bronze propshafts--for keelbolts...
06-27-2001, 03:36 PM
Bronze bolts are real hard to come by in these parts. I need some to bolt a lead keel to the boat (new construction). I do have some old 1" bronze propellor shafts that I was thinking I could cut to length and tap. Before I run off and buy the tap and stuff, I just wanted to check with you regarding this pipedream of mine.
And while your on the phone...I hear about "crevice corrision" regarding s/s .
What about using 1" s/s threaded rod instead? The boat is a 24'9" Canoe Yawl, strip planked. ( I plan to embed the bolts...and probably everything else! in our favorite modern googe.
Your thoughts and this forum are always appreciated.
06-27-2001, 04:11 PM
Prop shafts are, allegedly, great stuff for keel bolts.
RE SS keel bolts. Based upon what I've seen I wouldn't use it. Also full-length threaded rod would create a nifty path for water to travel.
06-27-2001, 04:51 PM
I second Ed and would go with the bronze prop shaft.The threaded s/s rod is probably 1in. before threading so the root diameter would be less=less strength.Also even embedded in epoxy,googe or whatever you are creating a perfect enviroment for crevice corrosion.Just add moisture.
06-27-2001, 05:33 PM
As long as the shaft is sound you should be O.K., look for electralosis on the outboard end and cut clear of stuffing box and cutless wear where it may have work hardened.
06-28-2001, 10:58 AM
It would be a lot easier to cut the threads on a lathe, and they'd come out nicer. Not something everyone has in their garage, though.
06-29-2001, 04:32 AM
I second the points made about Stainless.
Re using bronze, just make sure that it hasn't dezincified if the base material is Manganese Bronze - aka high tensile brass. I'm sorry but I don't know the US terminology.
If the shaft when cleaned has pink blotches or patches, then I wouldn't use it as a keelbolt.
Re threading, unless all that stuff about spinach is true, you won't be able to thread 1" accurately by hand. Suggest your nearest machine shop.
Wilson, if you decide to go with 1" shafting for your keel bolt stock you're either going to have far meatier keel bolts than needed or you'll end up paying a machine shop to turn them down to a diameter that is more suitable for your design. You can order silicon bronze round stock from the Canadian division of Alaskan Copper and Brass (located just outside Vancouver B.C> ), phone number 1-800-667-5456. A 12 foot length of 1/2" silicon bronze round stock is about $45.00 U.S., 3/4" is about $92.00 U.S. here in Seattle. You might find that screwing around with that scrap shaft might not be worth it. Kind of like kicking a dollar out of the way to pick up a dime. Consider buying new stock from ACB out of Vancouver, you'll probably be using more bronze bolts, etc in your boat anyway. I don't know any of the details regarding shipping from Vancouver to your front door. Good Luck.
06-29-2001, 09:53 AM
What? 1" keel bolts for a 24' conoe? Dude....use 1/4"....buy round stock if you want and thread the ends. You've never tried to hand cut 1" threads, have you? lol its easier to buy the right bolts...go mail order. Cheasapeake Fasteners of Annapolis should have it in stock. Atlas metals of Denver sells the round stock. Whats the boat fastened with? copper rivots? go bronze.
06-29-2001, 04:26 PM
If you have the proper die-stock setup, cutting the threads isn't so bad. Getting a vice big enough and strongly mounted enough to hold the shaft, may pose a more significant problem. I have an antique Oster adjustable stock with several sets of teeth that allows cut to be made in several stages. It has two 24" 3/4 pipe handels, and it helps to have a body on each.
06-30-2001, 01:22 AM
Wilson, I would be much more inclined to use something like 1/2 inch bronze than 1 inch. Anyway, if you really want to use that bronze shaft then before you go to machining it, you'll have to anneal it first. After machining it you will have to harden it back up.
As to cres bolts.... bad idea. You could bed them, seal them, bless them and pray over them until the cows come home and it won't change the critical fact that no stainless steel alloy does well in an anaerobic environment. What makes Grade 316L Cres (i.e. marine grade stainless) corrosion resistant is the fact that -given it is being used below the waterline- it is IN THE WATER FLOW. Close cres up away from air or flow and you'll have trouble eventually.
By the way, crevice corrosion isn't exclusive to stainless steel, but that's another story......
07-01-2001, 05:56 PM
You can get all the bronze stock you want from Jamestown Distributors in Rhode Island. Their web page is: http://www.jamestowndistributors.com/cgi-local/SoftCart.exe/index.htm?E+scstore
They do mail order. In their catalog they have 1/2-13" silicon bronze threaded rod for $9.50 per foot, 5/8"-11 for $12.88/ft and 3/4"-10 for $16.50 per foot. The nuts and washers are: NUTS - 1/2" $.45 ea, 5/8" $.85 ea, 3/4" $3.30 ea; Washers - 1/2" $.45 ea, 5/8" $.62 ea, 3/4" $1.25 ea
1" washers are - $4.00 ea and 1"-8 nuts are $11.25 ea.
07-06-2001, 09:00 PM
Hi fellows, I`ve checked out the mail order possibility but 9.50$ a foot is 20 bucks canadian with duties etc. plus shipping here to north eastern Canadan is "prohibitive". BC would be canadian prices but as the crow flies probably farther away than Jamestown.
Yes I understand that 1" is a little overkill. The ballast keel is only 1300 lb. and the plans call for only four 5/8" bolts up front with another 8- 1/2" bolts ( 4 on each side of the centerboard trunk)
Dale, I have also seen a couple sets of those 2' handles and dies at work. Years ago
most steel piping arrived here by ship in bulk and 12' lengths. The shop keeper cut off and threaded whatever the customer wanted.
I think I can get my hands on one of those set of dies and hopefully one of the mens experience.(Probably would never let me touch them without him being around anyways..)
The reason I bring up the stainless issue is because I remember reading in WB an article on the Bruce King designed sloop ANTONISA, built by Hodgdon Yachts to an unbelievable high standard, but to my knowledge used stainless steel keel bolts, 1 1/4- 1 1/2" if memory serves, go figure... Anyhow probably will go with buying some, keep those lovely shafts for the rudder or something...
Thanks for the advice,
Wilson, the pipe die that you are talking about is for "pipe threads" which are tapered from start to finish so the screwed on fittings will tighten up and seal. It definitely WILL NOT work for cutting threads on bolts, which are straight from start to finish. I'm afraid that you are back to square one my Canadian friend. And don't use stainless steel. Buy the silicon bronze round stock. Get the money for it by having a garage sale, hock something, sell your blood at the local blood bank, hell, deliver pizza for a couple weeks. Good luck
07-11-2001, 07:58 PM
So how come there are two Wilsons in this racket, both apparently in eastern Canada?
I cut a lot of thread on 5/8 bronze rod to make bolts for my boat using a handle with about a three foot span. Quite a workout after you have done a few. When it came to the 1" keel bolts, I took them to the neighbourhood machine shop. Some things (like sanding floors in a house) are worth paying someone else to do.
07-12-2001, 09:12 AM
How about taking your bronze stock down to the local high school shop or tech school and seeing if the class wants to do a lab on how to cut threads on the lathe? http://media5.hypernet.com/~dick/ubb/smile.gif You might not get 100% yield, but if it's scrap to start with, you might get enough "free" keel bolts out of it to do the job. Just a wild thought...
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