Installing thread inserts

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TomB
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Installing thread inserts

Post by TomB » Sun Jan 19, 2020 3:14 pm

Next plea for help on my hapless attempt to restore my “they were flooded” machining tools. Currently I am close to finishing my Grizzly G4030 horizontal bandsaw (the old version with the dark paint). It’s currently first priority because I need it to cut replacement steel for the horizontal mill which I need to make parts for the 3-in-1 lathe/mill. (Basically, this is a story of everything I try going wrong when I get to some detailed step that was not foreseen in my planning.) Currently I’m hung up on having to put thread inserts into the bracket that holds the blade guide bearings on the feed side of the pivoting top. The bracket when it left the factory had 2 3/8-24 internally threaded holes. They hold short shafts with dual blade guide bearings. Between when the saw left the factory and now the internal threads have completely disappeared. My plan is to replace them with thread inserts so I bought some from Fastenal and when they did not seem like they would work I bought a kit of inserts from McMaster Carr. So, I now have an insert that will do the task 3/8-24 UNF in the inside and 1/2-13 ??? on the outside. The ??? is because the outside thread on the insert is not at all like any standard I have seen. It sort of looks like a ½-13 UNC but it has a .050 flat root between the threads. However, the directions that came in the kit say a standard ½-13 tap with a 29/64s tap drill should be used.

I’m at the point where I’m ready to enlarge the holes for the inserts but I can’t afford to mess up the process since I have no way to make a replacement bracket. To see how this was going to work I took a ½-13 nut and enlarged the hole. First to 29/64 as the directions state then to 30/64 but the insert will not thread into the nut with either enlargement. What should I expect and how should I go about putting in these inserts?

Tom B

whateg0
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Re: Installing thread inserts

Post by whateg0 » Sun Jan 19, 2020 4:58 pm

I guess these aren't helicoil inserts, so I'm not sure about them. In general you want the insert to fit tighter in the hole than the screw will fit in the insert. Otherwise when you back the screw out the insert would come out too. A picture might help us visualize what you are seeing, but I think what are finding is normal. Others might have dealt with those particular inserts and know better though.

whateg0
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Re: Installing thread inserts

Post by whateg0 » Sun Jan 19, 2020 5:00 pm

Do you have the installation tool or are you just trying to thread them in by hand?

Dave

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carlquib
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Re: Installing thread inserts

Post by carlquib » Sun Jan 19, 2020 9:08 pm

Thread serts generally come with a specific tap for the thread sert in question or they will specify what the thread for the insert should be if you don't buy them in a kit. If you aren't sure of yourself start with a helicoil insert first, then you will still have multiple chances to install a thread insert that has the thread you are interested in. If your attempt at the helicoil fails you can move to a thin wall solid insert and if that fails you could move to a thick wall insert assuming you have the room for the larger hole required for the heavy wall insert.

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John Evans
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Re: Installing thread inserts

Post by John Evans » Sun Jan 19, 2020 11:19 pm

Sounds like you have a "Keen-Sert " repair insert as that is how they work. Forget messing with a nut ,drill and tap you hole in a piece scrap steel or alum. then try the insert .A picture of the insert would confirm what you are working with. Does the instructions say to use some form of installation tool? That style inserts claim to fame is only standard taps are needed for install. What was the McM -C kit number? i personally use Heli-coil style inserts but they require special taps and install tools. Most of the repairs I did the wall thickness around the hole only allowed the use of the Heli-Coil style,think MC cases etc. Heli-Coil kits are not cheap !!
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Lew Hartswick
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Re: Installing thread inserts

Post by Lew Hartswick » Mon Jan 20, 2020 9:27 am

I sounds like he was trying to put the insert in without taping the hole first.
...lew...

whateg0
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Re: Installing thread inserts

Post by whateg0 » Mon Jan 20, 2020 10:59 am

In his last paragraph in the op, he says it requires a tap, so I don't think that's the case. And the nut would have threads already formed, of course. I think he just didn't expect the insert to be snug like it is.

TomB
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Re: Installing thread inserts

Post by TomB » Tue Jan 21, 2020 3:55 pm

I’m back. My schedule has me driving to Albany NY every Monday to visit with my wife. She is in a dementia care nursing home. That keeps me away from forum all day.

My only experience with inserts was calling them out on some tooling I was designing/documenting in 1966. On that encounter I had the advantage of my Sr Engineer and the Tool/Model Maker guiding me. My recollections may be inaccurate but they are all I have to base my comments upon.

To Whateg0: The ones I’m trying to use are not helicoil type. I bought helicoii type from Fastenal along with the required tap and insertion tool. When I got home and studied them they had the insert metal bent crosswise at the first thread heix. That allowed the insertion tool to work but it meant the insert could not be used for a through thread. Seems like there must be another insert type but the Fastenal employee did not know enough to help me. He had actually sold me the wrong tap, one for the internal thread rather than the external thread. I did buy the insertion tool but unless I can deal with tang I now have no use for it.

To John Evans, Lew Hartswick, and Whateg0 again: The inserts I bought from McM are Keen-Sert type. They have the 4 knives that pound into the thread to lock them. The kit I bought McM 90284A300 comes with sizes 10-32 thru ½-20 UNF inserts and 6 installation tools. The installation tools do not guide insert installation and instead just provide a guide for tapping in the knives. I am thinking the only way to guide these inserts while installing them is via a UNF threaded bolt that has the unthreaded section diameter reduced to fit inside the knives.

To Carlquib: The two holes I’m dealing with have almost 3/8” wall thickness so I can try lots of things. It to took me a bit of measuring but I finally understand what you meant. Since the major diameter of the helicoil is .4375 and the minor diameter of the KeenSert is 29/64=.4531 the helicoil will fit inside the KeenSert with .0156 to spare. That makes me want to follow your advice and go with the Fastenal inserts.

Which leaves me with one question ‘Does the portion of the helicoil thread that sticks out for the insertion tool to grab, break off and if so with what tool?’

Tom

whateg0
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Re: Installing thread inserts

Post by whateg0 » Tue Jan 21, 2020 4:12 pm

The helicoil has that tang to drive it in, as you noted. But after the helicoil is in place, you tap the tang with a short rod and it breaks off so you are left with just the threaded section.

I don't recall now, did you buy a helicoil kit? Or just the individual pieces? I am guessing the kit, since you got the insertion tool. The tap that comes with it isn't a standard tap, as I recall. It matches the desired thread, but one wire thickness bigger.

Dave
Last edited by whateg0 on Tue Jan 21, 2020 4:16 pm, edited 1 time in total.

whateg0
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Re: Installing thread inserts

Post by whateg0 » Tue Jan 21, 2020 4:15 pm

helicoil.jpg
The part in yellow is what you would use to drive the tang off of the helicoil. Really, anything that fits through it will do the job, though.

Dave

John Evans
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Re: Installing thread inserts

Post by John Evans » Tue Jan 21, 2020 4:46 pm

As I said Keen-Sert's claim to fame is no special tools needed to install. Drill and tap the hole to the correct thread for that insert install and drive in the locking ears with what ever flat item is at hand. All of them I ever installed threaded in with my fingers on the ears. Heli-coil drive tang can be broken off with a piece of rod or long nose pliers. Like I said earlier drill/tap a piece of scrap and try threading in a insert. My normal use is M/C cases etc where the wall thickness around the hole precludes use of anything other than a Heli-coil. All styles have there place ,a 3 style is called Time -sert ? I think. Do use the correct 2A class tap as higher class [tighter fit] may cause issues.
Last edited by John Evans on Tue Jan 21, 2020 5:31 pm, edited 1 time in total.
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TomB
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Re: Installing thread inserts

Post by TomB » Tue Jan 21, 2020 5:10 pm

whateg0 wrote:
Tue Jan 21, 2020 4:12 pm
The helicoil has that tang to drive it in, as you noted. But after the helicoil is in place, you tap the tang with a short rod and it breaks off so you are left with just the threaded section.

I don't recall now, did you buy a helicoil kit? Or just the individual pieces? I am guessing the kit, since you got the insertion tool. The tap that comes with it isn't a standard tap, as I recall. It matches the desired thread, but one wire thickness bigger.

Dave
I did not buy a kit. I walked in and asked the counterman to find me a thread insert and he came up with several insert bags each with 3 inserts (they varied in length). Then he went to another shelf and came up with taps. I took the 3 that he had out as going with the insert. One is 3/8-24 class 2A while the other two are 8 and 10M. A week latter I stopped at another Fastenal (in Albany) but got less help. While there I saw insertion tools and picked up one that fit the size inserts I had. I don't have the short bar for the tang but I have sets of punches. I looked on the internet and found I should be using a 25/64 drill and I have them. Tomorrow morning I'll get into shop and see if this will all work.

Thanks to all for the advice.

Tom

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