Helicoil sized cap screws?

broke · Jan 4, 2018

I've got a job that requires helicoils to be installed after plating, so I can't install them. I need to be able to use those holes for a 2nd Op fixturing and before I make my own cap screws I figured I'd just see if anyone has a lead on some?

Does anyone make helicoil sized cap screws. I can't be the only one who would use them, right?

Larry Dickman · Jan 4, 2018

I've been looking for them for years with no luck. I need to stop and make my own, total PITA

Bobw · Jan 4, 2018

Even if you did find them, I'd bet it would be such a low volume item that the price
would be out of this world.

I've always made my own... Or drill and tap for the real thread size in the first op, then
drill and tap the STI when its done. Obviously that won't work if the hole position is real tight.

I wonder if you could put a non-locking helicoil onto a bolt with loc-tite, and squeeze it down
til the loc-tite cures??

Bigbore050 · Jan 4, 2018

You could install a tangless helicoil and then easily remove it. Tangless come out just as easy as they go in. But the install and removal tools are more expensive and can get really expensive if you have multiple sizes to deal with.

DMF_TomB · Jan 4, 2018

yoke said:
I've got a job that requires helicoils to be installed after plating, so I can't install them. I need to be able to use those holes for a 2nd Op fixturing and before I make my own cap screws I figured I'd just see if anyone has a lead on some?

Does anyone make helicoil sized cap screws. I can't be the only one who would use them, right?

.
most people use EZ-lok instead. they come like 3/8-16 to 1/2-13 so you can use 1/2-13 til you install it then use 3/8-16
.
Solid Threaded Inserts | Carbon Steel Inserts | E-Z LOK

gustafson · Jan 4, 2018

helicoil drills are a decent clearance drill, so just thru bolt

or turn a bushing

maybe there are some weird special thread bolts that would do it, but I doubt they would fall in perfect enough to take any torque

DMF_TomB · Jan 4, 2018

there are places that make special screws. but minimum order more likely at least 10,000 or 100 lbs and cost could be over $1 per screw depends on size. carbide insert screws sold at $10. each most likely are special made probably $2 each and sold for $10 each to make profit or get the money back to have them made
.
i have had teflon skived to certain thickness and minimum was 50 lbs and like $5000. and had enough to last over 10 years. if you need something special have it made

AARONT · Jan 4, 2018

Bigbore050 said:
You could install a tangless helicoil and then easily remove it. Tangless come out just as easy as they go in. But the install and removal tools are more expensive and can get really expensive if you have multiple sizes to deal with.

I started making my own helicoil removal tools from high speed steel blanks. They work much better then off the shelf and last longer too. Grind the tip to 25-30° angle and then put a 10° relief on both sides. A couple smacks with a hammer and it digs in real nice to allow you to pull it out. I have removed 90 3/8-16 helicoils with this method before having to regrind.

broke · Jan 4, 2018

I had thought about just installing an insert then taking it out but there a ton of holes ranging from 2-56 to 6-32 and I need to use too many per part to make installing and removing them feasible. They are all blind so no chance of running a thru bolt and they are tight tolerance so no chance in drilling them out larger.

If they were commercial available, how often would you buy them and what price could you swallow?

Larry Dickman · Jan 4, 2018

yoke said:
I had thought about just installing an insert then taking it out but there a ton of holes ranging from 2-56 to 6-32 and I need to use too many per part to make installing and removing them feasible. They are all blind so no chance of running a thru bolt and they are tight tolerance so no chance in drilling them out larger.

If they were commercial available, how often would you buy them and what price could you swallow?

I'd gladly pay $10 a piece for 8-32/ 10-32. When building a tool, which is always a rush, not having to make any more parts than I have to would be worth it.

BTW, not trying to be critical of people just trying to help, but fucking eh. Are we the only ones that work to a spec, and can't just redesign the part and do what we want?

Bobw · Jan 4, 2018

Out of curiosity I had to look..

If you could find them, A #9-32 would be perfect in a 6-32STI hole.

A 6-40 would be a few thou small on the PD for a 4-40 STI. Maybe get 'em plated.
or some teflon tape, or it might just work.

2-56... ?????

rcoope · Jan 5, 2018

Larry Dickman said:
I'd gladly pay $10 a piece for 8-32/ 10-32. When building a tool, which is always a rush, not having to make any more parts than I have to would be worth it.

BTW, not trying to be critical of people just trying to help, but fucking eh. Are we the only ones that work to a spec, and can't just redesign the part and do what we want?

It's because half the time on PM some brings a hard problem because it's a dumb design. Of course the other half the time it's just a hard problem. I encountered exactly this helicoil situation very recently when to meet a deadline I needed to do some project testing before a part had gone to anodizing, so before he helicoil went in. We ended up adapting an older part instead for the test but it would have been better for the project to have had helicoil screws. Of course if they were commercially available we'd have dumb designs where the final product was to be assembled with helicoil sized screws!

broke · Jan 5, 2018

Larry Dickman said:
I'd gladly pay $10 a piece for 8-32/ 10-32. When building a tool, which is always a rush, not having to make any more parts than I have to would be worth it.

BTW, not trying to be critical of people just trying to help, but fucking eh. Are we the only ones that work to a spec, and can't just redesign the part and do what we want?

Not sure I understand this statement.

Much of the work that we do is precision components that have extensive plating/anodizing/brazing/welding before coming back to us for final machining. Some of those processes such as brazing will turn a small tapped hole into mush which makes all the helicoils necessary. If we installed them before some of the plating they would be ruined.

It's less a poor design than it is a necessary reason for an expensive part and complicated schedule. Could it ever be any other way?

Leg17 · Jan 5, 2018

DMF_TomB said:
.
most people use EZ-lok instead. they come like 3/8-16 to 1/2-13 so you can use 1/2-13 til you install it then use 3/8-16
.
Solid Threaded Inserts | Carbon Steel Inserts | E-Z LOK

^^^^^^^ what he said ^^^^^^^

The term 'Helicoil' is sometimes used generically, like 'crescent wrench'.
See if the customer will accept a different insert and explain why.

Larry Dickman · Jan 5, 2018

yoke said:
Not sure I understand this statement.

Much of the work that we do is precision components that have extensive plating/anodizing/brazing/welding before coming back to us for final machining. Some of those processes such as brazing will turn a small tapped hole into mush which makes all the helicoils necessary. If we installed them before some of the plating they would be ruined.

It's less a poor design than it is a necessary reason for an expensive part and complicated schedule. Could it ever be any other way?

I think you mis understood. What I meant was this. For every post asking a legitimate question, there are at least half a dozen replies suggesting redesigning the customers part for them. This thread is a perfect example.

I get where you're coming from, I deal with it every day. Most aerospace parts are covered with STI threads and we need to use them for tooling.

DDoug · Jan 5, 2018

Silver solder some helicoils to some capscrews ?

adama · Jan 5, 2018

If you have die heads and chasers they easily open up enough to cut the over size on the next size up Skt bolts, just turn the shanks down to suit buying over long bolts as your blanks to get the heads - shank part for zero effort!

Larry Dickman · Aug 30, 2019

Ok, I hope I don't ruin anyone's day by dragging up an old thread, but I found a cool solution to this problem.

It occurred to me that TimeSerts are a solid insert with a nominal ID and an STI OD. I picked some up as I'm building a tool for a part where I need to hold it down with holes tapped for helicoils. Timeserts have a shoulder on them that's supposed to seat in a spot face, so I ground the shoulder off and inserted a screw with red locktight. I needed to put a washer on first as the clearance hole in the washer is smaller than the timesert. Works awesome and it cost $0.88 including the washer.

trevj · Aug 31, 2019

Larry Dickman said:
I think you mis understood. What I meant was this. For every post asking a legitimate question, there are at least half a dozen replies suggesting redesigning the customers part for them. This thread is a perfect example.

I get where you're coming from, I deal with it every day. Most aerospace parts are covered with STI threads and we need to use them for tooling.

Aye, airplane parts.... Takes three major Gods and a couple lesser deities to get changes made, even if it's all in house design and build.

Otherwise, it's MIL-TF-D41 all the way. Make It Like the F-ing Drawing For Once!

Wondering. Would Nylon screws work to seal the holes? Cheap material. Added to the die head idea, seems a reasonably easy in-house build.

Bill D · Aug 31, 2019

I think you have to make bolts with the needed shank size. the other choice is to make custom bolts of the correct diameter and make custom taps and dies to fit. Starrett does this on some stuff.
Easier and cheaper to adjust the shank size.

Helicoil sized cap screws?

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