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The ubiquitous spring

Discussion in 'Gunsmithing and Repairs' started by P95Carry, May 31, 2003.

  1. P95Carry

    P95Carry Moderator Emeritus

    Incredible ain't it .... our guns would not function without them!! IMO perhaps one of the most ''taken for granted'' components .... even down to a humble trigger return.

    I have a useful book on spring making by Tubel Caine and a print out from Brownells (or small book thingie) ...... and also have spring stock on hand, also from Brownells.

    Over time I have had partial success at spring work but always tend to get my failures at tempering stage. Does anyone have any other text book, web source .... whatever, that is useful for ''how to'' type info. I can manage but nowhere well good enough ... i want to learn more. This despite being a degree qualified engineer (long ago) ....... never really got far enough into practical from the theory metallurgy. Actually ''doing'' and succeeding is a different ball game!

    Always seems to have that ''black art'' mystery to it.
  2. tex_n_cal

    tex_n_cal Well-Known Member

    It depends a lot on what type of spring you're making.

    I do it professionally, mostly for automotive stuff. I did make some extra-power mainsprings for my Ruger #1, once:)

    Are talking about leaf springs, or coil type springs?

    Small leaf spring that you use in guns are usually made from either 1095 or 1075 steel. Yes, theoretically you can just heat them with a torch, and quench in oil, but you really want to run them in a controlled atmosphere process, to reduce decarburization.

    Once you have them properly quenched, you can give them about 700-750 degrees to get them back to spring temper.

    I've been making springs for about 17 years, and the damn things still surprise me from time to time.:D
  3. P95Carry

    P95Carry Moderator Emeritus

    Thx for responding tex ......... it's leaf that always give me the headache! I have had a few successes but way more failures. I always take immense pains working up the profile .... care with final finish such that the piece was virtually polished ..... then tho the critical stage .. the heat treatment.

    Sometimes I have not drawn enough temper and damn thing snaps ... much more usual tho is over tempering ... and finishing up with a soft ''putty'' spring .... undeserving even of the name ''spring''!:D

    I usually used heat and quench (used motor oil) ...... and then tried to use a small home made sand box for my tempering .... I do not however have a thermocouple suitable for temp measurement .... plus never really knowing what ideal time factor to apply.

    I guess I still yearn for more literature . to give more pointers .... plus in fact .... actually spending out on a decent thermocouple.
  4. tex_n_cal

    tex_n_cal Well-Known Member

    Well, here's a quick and dirty way...

    After quenching, it should be too hard to cut with a file. On thin metals, you really don't need more than ten minutes of soak time at red heat to get it austenitized and ready to quench.

    A hardness tester is preferred. an inexpensive way to check tempering is temp-stik crayons. They are calibrated to melt at various temperatures. You just mark the part, and keep adding heat until the crayon melts.

    30 minutes is plenty of tempering time, and at 700 degrees decarb is not really an issue, so you may just temper them in air.

    If you cast bullets, a lead pot isn't too far off the right temperature.

    On leaf springs, don't forget to radius the edge where the material flexes. A square edge sets up a stress raiser and a natural starting point for cracks.
  5. P95Carry

    P95Carry Moderator Emeritus

    Once again tex .. thx. Re the edges of leaf springs ... yeah, I do include radiusing edges as part of preping ... another reason I polish is to hopefully remove any stress areas (like scratches).

    I have taken note of your points .... appreciated.:)
  6. Jim K

    Jim K Well-Known Member

    One problem is that different kinds of spring stock require tempering at different temperatures. While the old "torch it till it looks right and dunk it" may be OK with a lot of experience and with known material, it is pretty hard to beat a good furnace.

    If you are going to make springs, it is a necessary investment. Also buy spring stock from a supplier who will provide the specs it needs. Big springs, like mainsprings for old shotguns or flintlocks, are a particular pain.

    As to the awful feeling when you sweat hours over making a spring, only to have it "SNAP!!", you are not alone. A lot of us have been there. Those who have done it professionally also have had the pleasure of sweating those hours, getting the spring just right, and then hearing the customer complain about paying $40 when he can "buy a spring at the hardware store for ten cents".

  7. P95Carry

    P95Carry Moderator Emeritus

    Jim, I'd have to admit you are of course right re investment in a furnace ..... trouble is I qam and always have been a 'casual'' spring maker .. so never felt I could justify the expense.

    IIRC the spring stock I currently have from Brownells does carry some info which helps ..... in theory!!:D
  8. eddieleon

    eddieleon Active Member

    If you need a furnace I would suggest to watch the papers for a small kiln. Those used for pottery get sufficiently hot and the ones for porcelain get into the 2000 - 2500 degree range. Some are only like 6x6x6 inside and attain their working temperature quickly.

    My wife makes porcelain dolls and used kilns are pretty inexpensive. I've seen some large ones go for $100. If there is a problem with them they are sometimes give aways and repair is very simple electrical work. It is only expensive if you cannot do it yourself.

    If you find one and need help on the net, call me or e mail me.
  9. Traveler

    Traveler Well-Known Member

    AGI (the American Gunsmithing Institute) has a pair of tapes showing Bob Dunlap (the head of the gunsmithing program at Lassen College) teaching how to make springs. They are well worth the money.
  10. P95Carry

    P95Carry Moderator Emeritus

    eddieleon ..... thx .... I think I will keep a lookout for a small kiln ...... main deal will be having some sorta reasonable temp control. I am conversant with things electrical so if I find one needing repair .. shouldn't be any great biggie.

    Traveler - thx also ... sounds good .. I must explore that avenue I think.
  11. eddieleon

    eddieleon Active Member

    Normally there are several ways to determine the temperature in a kiln.

    First there is an istrument called a kiln setter. This is a cylindrical tube through the wall of the kiln with a trigger that is held open by a temperature sensative ceramic bar. When the kiln reaches the trip temperature of the bar, it trips, and throws a switch killing the electricity to the heating element.

    Second, a theromocouple through the wall of the kiln will tell the temperature where you can cut it off manually. Or a milivolt switch in circuit with the thermocouple will trip the contactor and kill the current to the element.

    Third, most kilns will have an inspection hole is in the side of the kiln. Thru this you can visually check the color of the spring if you are familiar with the temperatures of the metal. Also the temperature tatletale crayon, paint, or chalk that melts when a temperature is reached can visually be seen through the inspection hole.

    Remember, the kiln will hold a temperature for as much as several hours (depending on the structure of the kiln). If the spring material is to be kept at a certain temperature for a certain length of time, kill the power and time the trip then open the kiln.

    Actually the thermocouple would be the most accurate for that single use that you would be putting the kiln to. If you do use a thermocouple, check it for accuracy as all that I have used in production process can vary from the standard at which they are tagged.

    One source of kilns is sometimes a school auction or just the classified in the paper. Many times the new wears off a hobby and someone needs to clean out a garage or at a death of a member of a family.

    Also remember that the electrical heating of a kiln can be expensive. Therefore, the smaller the better as long as it fulfills your needs.

    If I can be of service call me.
  12. P95Carry

    P95Carry Moderator Emeritus

    Further felicitations eddieleon ...... your input there is much appreciated. I don't know when I will get round to finding a kiln (so many guns still on the ''list''! :) ) but I have bookmarked this thread and be assured, if i get point of finding the kiln (small one) I will surely be in touch for info if needed.

    Thx again Sir.:)
  13. eddieleon

    eddieleon Active Member

    It is pleasant to think someone can use some of this superfilous knowledge that I have accumulated.

    much obliged eddie

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