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Author Topic: Threaded inserts  (Read 1385 times)

Offline Ara Dedekian

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Threaded inserts
« on: January 05, 2018, 10:57:46 PM »

       How reliable are threaded inserts? I used them to attach a radial mount to a firewall.

       Ara


Offline Doug Moisuk

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Re: Threaded inserts
« Reply #1 on: January 05, 2018, 11:08:05 PM »
I have switched to them instead of blind nuts in maple motor mounts. I will never go back. I install them with JB Weld.

Offline Ara Dedekian

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Re: Threaded inserts
« Reply #2 on: January 06, 2018, 06:37:18 AM »
I have switched to them instead of blind nuts in maple motor mounts. I will never go back.

    Doug

       That's what I decided having installed just the radial mount. They eliminate the hassle of having to access the blind side of a firewall or bearer on a rebuild. And seems they would eliminate compressing the maple mounts if placed flush with the top. Just curious as to how well they hold up.

    Ara

Eric Viglione

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Re: Threaded inserts
« Reply #3 on: January 06, 2018, 06:59:16 AM »
They work great for some applications! Just don't get too cute like I did and try to use them for landing gear mounts with aluminum 4-40 screws, or you may find that the aluminum galls to the brass. Silly stunt guy was trying to negate the added weight of the brass. Oops! Work fine in that application with regular hardened 4-40 though, and I still use for those, because yeah, cutting into a plane to chase a slipped blind nut is no fun. That said, a properly installed Dubro blind nut is still probably the best and lightest option. The cheap knockoff blind nuts are the only ones I've ever had trouble with, because they are stamped, soft and thin. You can actually see the cheap ones pucker in the center if you really crank them tight, the little teeth sheer off easily and then will spin. I still have not found any superior to the Dubro.

Online Brett Buck

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Re: Threaded inserts
« Reply #4 on: January 06, 2018, 07:17:26 AM »
I have switched to them instead of blind nuts in maple motor mounts. I will never go back. I install them with JB Weld.

       I tried to use the inserts and had nothing but problems, it was so bad I never got past the point of installing them in the engine crutch. How in the heck to you have enough extra wood on the engine side of the mounts to enclose the giant hole? Even when I ran the mount right into the side of the crankcase, the threads still stuck through the wood, and I had to clamp a block on it just to drill the hole without the bit wandering out the side of the mount. It just doesn't seem like there is enough space.

     Brett

Online Massimo Rimoldi

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Re: Threaded inserts
« Reply #5 on: January 06, 2018, 08:25:33 AM »
Hi.
Our Russian friends use a very simple system that combines the advantages of the insert and put the security of the nut on the other side of the crutch.
Obviously you need a small lathe or someone who produces a little bit of hardware.
The attached drawings (which I borrowed from here: http://f2rus-ru.1gb.ru/forum/36--bis----/464-----.html ) explain the system and with the help of Google Translate you can take away some other curiosity.
Obviously the cylindrical surface of the insert must be roughened to favor a good anchorage.
For anchoring I prefer UHU PLUS Endfest 300 ( http://www.uhu.it/images/uploads/prodotti/schede_tecniche_e_di_sicurezza/st-D5346.pdf ) more fluid than JB Weld (then "wets "better) and above all more readily available in Europe.

Massimo

Online Lauri Malila

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Re: Threaded inserts
« Reply #6 on: January 06, 2018, 09:47:23 AM »
Ciao Massimo,

I make similar inserts as V. Salomatin (Our Russian friend), with exception that I don’t think that glassfiber pads between engine and wood is a good idea. Dural is much better.
I use 2024-t3 for my inserts and so far there is zero problems.
The lenght of inserts is same as thickness of wood, so there is not really compression stress in wood.
I make the inserts longer than necessary, then mill the recess for them dural pads.
If I remember right, outside diameter for my M3 threaded inserts is 4,2mm. The inserts are then lightly knurled by rolling them between 2 files.
I too use Endfest, it is important to heat the bearers before & after applying the glue.

Lauri

Offline Bootlegger

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Re: Threaded inserts
« Reply #7 on: January 06, 2018, 11:35:41 AM »

  Does any one make them out of steel? All I have seen are brass.   Thanks
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Online Massimo Rimoldi

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Re: Threaded inserts
« Reply #8 on: January 06, 2018, 11:56:22 AM »
The first time I used the inserts (1994) I obtained them from iron and drowned in a crutch of carbon fiber.
Everything is mounted in a model with installed a Saito .50 4T.
The model is hanging in my garage and still flew a few years ago.
The only problem in using iron can be the weight, about 8 gr. altogether for 4 pieces .........

Hi Lauri,
As usual, however, your accomplishments are much more "professional" than many others.

Massimo

Offline Cody bishop

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Re: Threaded inserts
« Reply #9 on: January 06, 2018, 07:03:33 PM »
They work great for some applications! Just don't get too cute like I did and try to use them for landing gear mounts with aluminum 4-40 screws, or you may find that the aluminum galls to the brass. Silly stunt guy was trying to negate the added weight of the brass. Oops! Work fine in that application with regular hardened 4-40 though, and I still use for those, because yeah, cutting into a plane to chase a slipped blind nut is no fun. That said, a properly installed Dubro blind nut is still probably the best and lightest option. The cheap knockoff blind nuts are the only ones I've ever had trouble with, because they are stamped, soft and thin. You can actually see the cheap ones pucker in the center if you really crank them tight, the little teeth sheer off easily and then will spin. I still have not found any superior to the Dubro.



Eric I have found that blind nut’s made my micro fasteners are better then Dubro you should give them a try

Offline Phil Spillman

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Re: Threaded inserts
« Reply #10 on: January 06, 2018, 08:33:09 PM »
I use inserts by Micro-Fasteners. Drill the appropriate hole;dip appropriate hex head screw(3/8" to 1/4") in Vaseline, coat insert with you choice of epoxy, run home with hex nut driver, let cure over night!Remove short screws in the morning insert will stay put! If ever removal should be necessary create your own tool by using two appropriate sized plain hex nuts, not ESN nuts. Use a flat open wrench to back out insert buy turning the lower lock nut while or immediately after heating with a strong Weller Soldering gun to soften the epoxy! Clean up removed insert and reuse at your leisure! Been doing this for over 20 years with no problems what so ever in spite of many Experts telling me to never use inserts!

Phil Spillman   
Phil Spillman

Offline RknRusty

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Re: Threaded inserts
« Reply #11 on: January 06, 2018, 09:14:49 PM »
I've had very good results with Dubro inserts, but do not like Great Planes inserts at all. The GP product has a notch for a screwdriver which is just a waste of good brass. Keenserts (http://www.aircraftfast.com/keensert-inserts.htm) are a good option too.

I prefer to screw epoxy or JB coated Dubros in with a Vaseline coated hex bolt as Phil mentioned, later cleaning the threads with a bristle brush and solvent. If the bolt heads are stuck in the hole the next day, a quick touch with a soldering iron will release them easily. Just don't heat-soak them.

If I'm installing them in maple beams that are underneath plywood doublers, I countersink the plywood and make the insert flush with the face of the maple. That will keep them from making a splintered mess of the doubler. Then an aluminum pad between the engine and doubler. On my last profile plane, I cut the doubler away just enough so the aluminum pads sat right on top of the maple.

Only once have I thought the hole was too close to the edge of a beam mount, so I opted for blind nuts on that one.

I'd like to have some 2-56 size inserts for adjustable profile fuel tank mounts, but haven't found any that small. If mounting into balsa, I've put the inserts into a dowel plug and glued that into the fuselage.
Rusty
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Online bob whitney

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Re: Threaded inserts
« Reply #12 on: January 06, 2018, 09:34:33 PM »
I have been using the brass inserts for quite a while .I have them in my S/T 60 powered big Job which is over 5 years old .I do wish that they came in longer lengths  they don't crush the motor mounts like blind nuts

if u have a lathe u can make your own smaller ones for 3/48 or 2/56 bolts use brass ,aluminum or stainless course threaded bolts about 12 /20 or 24's and tap them out and make them as long as u like we do this for our F2C team racers for the motors and tank mounts
rad racer

Offline Steve Helmick

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Re: Threaded inserts
« Reply #13 on: January 07, 2018, 01:33:44 AM »
If cost is no object, I'd vote for Keen-Serts. I once bought some in 4-40, but they were about $6 each, and that was almost 30 years ago. They were also very short, and not sure you could buy long enough ones to make them viable in Maple...but maybe. Check McMaster-Carr if you wish. IIRC, they're all stainless steel. Install with JB Weld.

I've wondered about mounting an engine on wood with threaded inserts flush to the engine lugs. Would there be less vibration absorption that way?  I recall Tom Knoppi telling me about using pieces of "All Thread" or "Redi-Rod" epoxied into CF plate crutches on F2C's, but they're smaller engines than what I'm interested in using for stunt. Drilled and tapped after installation in the crutch, OBTW.  I'm not sure I'd do it that way. I'm also not sure if the threaded rod he used was garden variety mild steel or something more zoot, but even crumby steel would be as good or better than brass, right?  D>K Steve
« Last Edit: January 07, 2018, 01:52:37 PM by Steve Helmick »
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Online Lauri Malila

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Re: Threaded inserts
« Reply #14 on: January 07, 2018, 08:53:25 AM »
i think there is no need for steel inserts, except for maybe when inserts are mounted in carbon. Good quality aluminium ones are strong enough. Remember that you can have much longer thread, that is often problem with blind nuts. Blind nuts are usually not made from best steel for strong threads as they are stamped/formed from sheet material.
Long ago there was good quality machined (square) blind nuts, sold by Kavan if I remember right. First ones were of good steel. At some point material was changed into some sort of brass and they were not good anymore. L

Offline Geoff Goodworth

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Re: Threaded inserts
« Reply #15 on: January 07, 2018, 06:18:56 PM »
I use the inserts from Micro Fasteners—and I have 4-40 and 2-56.

I used them successfully in the somewhat soft bearers in my ARF Oriental by leaving them a fraction proud then sanded flush so the engine is screwed down onto the inserts and the timber.

Sometimes—as Brett noted—there is not enough timber to support even the fairly small OD Micro Fasteners inserts so t-nuts must be used. On the ARC/ARF Vectors that I have, even the t-nuts needed to be located carefully to ensure adequate support for all three pins.

Rusty, I read somewhere that the 'screwdriver slot' isn't. Rather, it is intended to assist with cutting the thread into the timber. If you are trying to drive the inserts in with a screwdriver in the slot, I think you are using the inserts upside down.

I use a socket head cap screw and two hex nuts to drive the inserts and normal epoxy as the glue. After the inserts are driven home, I remove the cap screw and nuts and drop them straight into iso-propyl alcohol to clean the epoxy off before using them again.

Offline john e. holliday

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Re: Threaded inserts
« Reply #16 on: January 08, 2018, 10:01:57 AM »
I have been using blind nuts from RTL Fasteners.   So far on about a dozen planes no problems. D>K
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Offline phil c

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Re: Threaded inserts
« Reply #17 on: January 08, 2018, 11:49:31 AM »
I've used brass inserts(common in injection moulding).  The Dubro ones are probably the same or similar.  They need to have a very coarse outside thread, about that is interrupted so the wood has someplace to go.  Drill the hole slight smaller that the minor diameter on the insert(number drills).  Driving the insert into the hole can generate enough torque to seize the screw into the insert.  I back thread a nut onto the installation bolt that can be used to unlock the screw from the insert. A washer makes sure the insert ends up flush with the wood.

To get enough wood around the insert the motor mounts, usually 3/8in wide, should be drilled with the inserts centered on the wood. The use the motor as a guide to relieve the mounts so it will drop in.  The motor lugs should rest on the inserts, otherwise you'll be squishing the wood and torqueing the engine case.
phil Cartier

Offline Fredvon4

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Re: Threaded inserts
« Reply #18 on: January 08, 2018, 12:07:19 PM »
I have several sizes of threaded inserts never used for any model engine attachment

Mostly because each time I build the crutch and fitted for the engine the distance to the inside edge of the maple was not very much

I learned long ago how to use typical blind nutz and set them very well and in some cases a additional metal plate on inside of a profile nose...never had one I could not insert or remove the 4-40 bolt from...despite my world famous figure nine into rocks, mud, dirt, grass, and asphalt/concrete

I note my buddy Rusty above mentioned Flat Blade screw driver slots in some inserts.... sorry but usually the stupids that market things actual have WRONG install instructions

If you think the two slots on the insert are for a Flat blade screw drive to install them.... you are wrong... that is the start side of the insert and is designed to allow the cut wood bits to escape as the insert is inserted.... almost all inserts that are not  Heli-Coil, should be set with a correct size bolt and LOCK nut...not a flat blade screw driver

I do a lot of cabinet grade wood working and use a LOT of brass and steel inserts...some 3/4 inch deep and I drive many in with a heavy screw gun in a bunch of different hard woods..... just like preparing a hole for metal thread tapping--- the correct drill must be used.... and most of my 1/2" to 3/4" long  inserts never get glue...then again they are not subject to fuel or any vibration...just a cabinet drawer, door, or shelf

simply my observation.... if they work for you great!

BTW I can get  brass or steel threaded inserts in 6-32 x 1/2" deep for $3.85 per 20........jest sayin

Bet  most here do not get the point



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Offline Motorman

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Re: Threaded inserts
« Reply #19 on: January 08, 2018, 01:01:41 PM »
If inserts are working then ok but, I like to have something with a shoulder on the other side of the wood.
There will be a sunny day and we will fly our airplanes.

Offline RknRusty

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Re: Threaded inserts
« Reply #20 on: January 08, 2018, 08:17:02 PM »

Rusty, I read somewhere that the 'screwdriver slot' isn't. Rather, it is intended to assist with cutting the thread into the timber. If you are trying to drive the inserts in with a screwdriver in the slot, I think you are using the inserts upside down.
Geoff, I thought the same as you say, for cleaner thread cutting. Then, more recently, I saw a Great Planes advertisement boasting of their handy screwdriver slot. I think you might be right, and I should have stuck with my original belief too. Someone in advertising at GP probably just assumed it was for a screwdriver and didn't care if he was wrong.
DON'T PANIC!
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while you're doing it!

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Offline Geoff Goodworth

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Re: Threaded inserts
« Reply #21 on: January 09, 2018, 01:06:09 AM »
Hi Rusty

Yes, ignoranuses in positions of apparent authority are a worry.

I was shocked by comments that I saw on our Australian Broadcasting Corporation coverage of the Sydney–Hobart yacht race.

This airhead female was gibbering about the yachts travelling a different speeds of knots per hour.

Seriously, where do these airheads come from.

Offline john e. holliday

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Re: Threaded inserts
« Reply #22 on: January 09, 2018, 10:27:10 AM »
College.   Look at the so called professors that are trying to teach them. VD~
John E. "DOC" Holliday
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