SS bolt on coil??

I was hunting today with a friend. He mentioned he had a crack on the ears of his Xcal coil. I explained to him he likely had kept tighting the bolt as the coil would loosen pulling them in..... that and would lean on it in the water. Then i noticed...... what the heck a SS bolt connecting his coil to the straight shaft. He said he couldnt find a nylon bolt that size and his had broken. I figured man that things going to go nuts..... amazingly it didnt seem to notice it. I realize it notices targets going across the coil.... apparently it doesnt notice when moving together. Soooo why does one worry about the aluminum shaft being to close to the coil. First for me.

Dew

The coil needs "motion" to detect, ie. the coil moving over the metal target. When the bolt is fastened to the coil, it moves "with" the coil as if they are one. I am not sure how a metal bolt would effect the magnetic field... it has to effect it to some degree and psooibly lose depth. That's why they supply a plastic bolt with the unit (plus its cheaper I guess). Stainless isn't magnetic and that might be why it seems to work okay. I carry a few spare plastic bolts and wing nuts with me all the time for that reason... they are cheap insurance!

Yes stainless steel is very hard to detect...

Nautilus machines come with stainless bolt and wing nut for their coil's...

Keith

I have seen alot of older Whites detectors with SS bolts on the coils. I had some on some of mine and changed them just to be sure.

Yes...the SS bolt moves with the coil and is basically undetectable as it becomes "one" with it. However...in answering your other question regarding the plastic spacing from the rod tip to the actual connector at the coil...the rod too becomes "one" with the coil. BUT that is in the motion discrimination mode. In the static all metal mode a different picture is seen. Metal introduced next to the coil field will sound off louder as it gets closer to it. However...if the metal is small like a bolt it can be detuned to a point as to not interfere noticeably. Some of you "more technical" folks correct me if I am wrong.

Schultzie - I think you may be on to something. Any metal object within the field does distort the magnetic field. The affect may be slight with certain metals but there should be some affect. It would be interesting to run that test Mike Hillis came up with where he progressively burries a coin 1" deeper and in between he marks off on paper where the coil picks up the coin as far as how far forward and back from the coil center. A bit hard to describe but he ends up with a 2D drawing (almost 3D as you can stack the papers in a sense) to show how far up and back the coil picks up the coin at each depth. The interesting thing is that the field goes a bit in and out and is not at all even like many drawings show.

Keith, surprised you find stainless steel hard to detect. Stainless washers hit like a good coin for me, same with stainless fasteners. I run in to plenty of 'em!

If you rest a quarter or a (large enough) bolt on top of the coil...... on most detectors...... the unit will bell-tone overload........... and stay in overload until the metal object is picked up off of the coil. Food for thought.

A metal bolt used to fasten the coil to the shaft may not be (audibly) detected......as it is moving at the same speed of the coil; yet, there is a electromagnetic footprint distortion of the EM field-pattern. Using metal bolts can induce blind-spots; hence, Mfr's switching to nylon nut/bolt assy's. They can be readily found in various sizes in Lowes/ACE/Home Depot and good hardware stores.

Stainless is LESS magnetic......... especially the higher grades (more nickel content).

Simply put non mettalic bolts are readily available if not from a hardware store the manufacturer itself. With all the different coils hard to say if an SS bolt would have any effect.

We all know plastic bolts can break so along with an extra pair of headphones, digger, batteries and skeeter repellent always carry a spare in my trunk.

Many older units had mettalic bolts and imagine the company in question tested them for effects besides plastic has become more durable, coils have become more powerful
which evolved into all present day units for the most part being fitted with a plastic coil bolt...

I would think that a SS bolt on any Minelab FBS machine would effectively disable the PINPOINT function/mode.



Edited 1 time(s). Last edit at 11/01/2012 03:16PM by Yeasty.

We saw no affect by the bolt being there even in PP mode on the Xcal.... no over load. But then it is a motion PP. As far as SS..... ive got a ton of SS rings to say they come in pretty darn clear.... and pretty deep. As far as those plastic bolts.... believe it or not they are NOT that easy to find. Ive been to about every one of the know HW stores and now carry them in the Xcal size. Closet bolts seem to be the closest thing. I can see what Tom is saying about blind spots, we never tested that. Maybe there is less affect with it being on top of the coil as opposed to the bottom as well. My biggest concern to him was cranking that thing down so hard with a SS bold. I see major problems coming with that. I just was surprised ..... and hadnt really thought about metal being that close to the coil.

Dew

On the E-trac, a lot of stainless steel parts can read similarly to small gold jewelry items, and have dug very many at beaches. Some read as non-ferrous, from 12-09 down to 12-01, and are very weakly to weakly attracted to a magnet.
Others, like SS forks and spoons, read as ferrous (ferrous value of 35), and can be weakly to strongly attracted to a magnet.
The most difficult to detect are right in between the non-ferrous and ferrous types. The conductivity value is near zero, and is barely detectable. Probably is made to be extremely non conductive and non magnetic.
Most of the stainless steel hardware (washers, nuts, bolts) encountered has read as non-ferrous on the E-trac.

Detecting since Feb, 2010
E-trac with 18"x15" SEF, 13" Ultimate coil, Pro coil, Minelab 8" coil, 4.5"x7" SEF, Sunray target probe
CTX3030 with 17"x13" DD coil, 11" DD coil

There's different grades of Stainless..

Some will read higher than other's..

One thing I have noticed on some of the older Tesoro's that came with a stainless bolt and brass inserted inside plastic nut was if you changed out the metallic for plastic when hunting through iron debris you could get an ever so slightly better clipped reading on non ferrous item's..not night and day but just an ever so slightly diferent signal to make you stop and investigate...

what worries me more than that is the style lower rods that manufacturer's used to use even the first t-2's had them , and that was the aluminum lower rod then an 8 inch isolator made of non mettalic....

Keith

The best marine grades of stainless are non magnetic such as 316 and 316L. 304 and 305 are the most common fasteners in the marine industry these days. Usually barely magnetic although some of the Chinese stuff is so off spec it's definitely magnetic. Oh the arguments I've had with marine parts suppliers over their stainless grades. I won't even get started on lumber and plywood specs.....

I think Kieth has it pretty well nailed on SS grades and brews. I don't see any one mentioning that when you initiate pinpoint many units make a snap setting of the magnetic range so you need to start off target and come back to it even though you are active non-motion detecting mode. That is why you cannot fire up your propointer in the hole. You render your target invisible if it is in range.
Just a thought
Oh and virtually every place carries nylon toilet seat bolts- they work fine!

Past(or)Tom
Using a Legend, a Deus 2, an Equinox 800, a Tarsacci MDT 8000, & a few others...
with my beloved, fading Corgi, Sadie