Author Topic: Tap size for 8 x 1.25 Helicoil (Read 40870 times)

Skonnie Boy · « **on:** October 19, 2011, 12:21:45 PM »

Hey, I have 8 x 1.25 helicoils and a whole mess of taps. What I don't have is the kit, where the right sized tap is provided. Would a 10 x 1.25 tap work for providing a home for said helicoil? They seem to be the same diameter. Any advice?

dave500 · « **Reply #1 on:** October 19, 2011, 12:42:44 PM »

i always thought helicoils had there own odd ball taps?maybe ring a bolt supply shop and find out?

Skonnie Boy · « **Reply #2 on:** October 19, 2011, 12:50:57 PM »

Yeah, the size of the provided tap (needed to bore out the hole for the helicoil) seems to be a proprietary secret.

And I thought I was so clever by buying a metric tap and die kit. Oh, well... $41 later...

dave500 · « **Reply #3 on:** October 19, 2011, 12:57:46 PM »

itll be handy further down the track.

Skonnie Boy · « **Reply #4 on:** October 19, 2011, 01:35:21 PM »

Yes. If we weren't put on this earth to accumulate tools and parts we'll never need, then I don't know what for.

crazypj · « **Reply #5 on:** October 19, 2011, 01:39:28 PM »

Pretty sure it is just a 10x1.25.
I know 6mm uses 7x1.00.
Some of the other sizes are specials though
Re-coil are exactly the same but much cheaper (and available in Autozone, Pep-Boys, etc)

mrbreeze · « **Reply #6 on:** October 19, 2011, 02:19:37 PM »

There is no such thing as "too many tools" !!!

City Boy · « **Reply #7 on:** October 19, 2011, 02:36:08 PM »

Hi Skonnie.I just measured my helicoil M8x1.25 tap.It appears to be 10x1.25 but may be 3/8ths and the pitch gauge does not fit perfectly.Maybe drill a test hole in a scrap piece and test with a 10x1.25 tap and coil.The coils themselves are inexpensive right? Rock On

bryanj · « **Reply #8 on:** October 20, 2011, 01:20:24 AM »

Are you sure it's not 9x1.25? iTs best to buy the proper helicoil tap as the threads need to be correct to hold the coils.

Of all the rethreading inserts i think only Keenserts use a "Standard" outer thread

MRieck · « **Reply #9 on:** October 20, 2011, 05:10:30 AM »

Taps for helicoils are labeled "STI". I have bought bottoming taps for the inserts as blind holes present problems with the standard taper taps.

crazypj · « **Reply #10 on:** October 20, 2011, 08:19:48 AM »

6mm insert is 7mm OD when fitted.
Anyway, I've never measured 8mm insert (not sure why, I measure just about everything

)
measure thickness of insert across 'diamond' and double it (the steel wire cross section <>)
It will be around 1mm so 8mm+1+1 = 10mm.
Obviously, if it's less than 1mm section you will need a smaller tap (and larger if it's bigger)
$40.00 is overpriced.
Try Victor machinery Exchange in NY, they have kits and single taps (but they do have a minimum order)
I usually have trouble spending too much, minimum is never a problem

Skonnie Boy · « **Reply #11 on:** October 20, 2011, 08:38:41 AM »

Yeah, I noticed how close the 8 and 10 x 1.25mm were. The coils themselves are inexpensive.

Its all a moot point, though. The tap I had didn't have any taper to it, making it near-impossible to carve out a new path. I spent $40 and got the kit. Had to do this now, otherwise I got no way to work. Aside from having to negotiate the frame, it was pretty easy. Done a few helicoils before.

Oh, and for bonus points, I'd fixed it earlier with JB Weld. If anyone tells you you can't fix a stripped header bolt mount with JB Weld, they're wrong. You can't really tighten the hell outta it, but it works. Also, if you add a blob on the bolt behind the header mount, it acts as a stopper, preventing the bolt from falling out even if it becomes unscrewed. It worked for a couple thousand miles this summer. Love that stuff.

754 · « **Reply #12 on:** October 20, 2011, 09:18:21 AM »

So mic the od of the tap and let us know..
Cant measure the coils as they close up on installation..

fmctm1sw · « **Reply #13 on:** October 20, 2011, 12:06:24 PM »

I have a kit at home that came with the tap, I can measure it later today. I'm pretty sure I bought it to thread a mirror mount...

crazypj · « **Reply #14 on:** October 21, 2011, 12:35:32 PM »

I guess I could have just measured mine, couldn't be bothered though

fmctm1sw · « **Reply #15 on:** October 21, 2011, 12:43:07 PM »

ahh, I measured and forgot it. I wrote it on my shelf, I'll post it when I get home...

fmctm1sw · « **Reply #16 on:** October 21, 2011, 01:28:03 PM »

Quote from: fmctm1sw on October 21, 2011, 12:43:07 PM

ahh, I measured and forgot it. I wrote it on my shelf, I'll post it when I get home...

.3785 is what I got...

crazypj · « **Reply #17 on:** October 22, 2011, 07:28:42 AM »

That's 9.6mm

754 · « **Reply #18 on:** October 22, 2011, 08:40:55 AM »

That would be very very close to a 3/8 x 20 tpi tap... just off the top of my head..

so now we know, dont even THINK of using a 10 x 1.25 tap..

Skonnie Boy · « **Reply #19 on:** October 23, 2011, 12:22:07 AM »

Amen to that. The 10 x 1.25 was about 24mm, while the supplied tap was about 23 or less. I don't have batteries for my caliper, so I just eyeballed it.

Needless to say, to future generations of SOHC searchers, don't use a 10 x 1.25 tap to provide a home for your 8 x 1.25 bolts. The taper's all wrong anyway. And stay in school, don't do drugs. And so forth.

dave500 · « **Reply #20 on:** October 23, 2011, 12:33:16 AM »

#$%*,,go to page 17 onwards here.
http://www.helicoil.in/pdf/HeliCoil%20Catalogue.pdf

crazypj · « **Reply #21 on:** October 23, 2011, 11:59:24 PM »

After looking through those charts, 10x1.25 is the ONLY non Helicoil tap you can use.
Spec is 9.8mm to 10.35mm

754 · « **Reply #22 on:** October 24, 2011, 07:15:36 AM »

I woud use a 3/8 a 20 but not a 10 x 1.25.

btw KBC has an amazing assortment of non standard pitches, if you ever have a need for them, fairly cheap too..

Skonnie Boy · « **Reply #23 on:** October 24, 2011, 01:50:18 PM »

KBC? That some sort of canuck operation? Man, what I wouldn't give for a Harbor Freight located in the city.

Lord help me if I ever need something with non-metric thread pitch. Because then I'd likely be working on a British bike, and I'd be proper screwed.

Oh wait, bad pun sorry.

754 · « **Reply #24 on:** October 24, 2011, 07:35:34 PM »

KBC Tools is a USA company.. they have a pretty good selection of stuff..

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Author Topic: Tap size for 8 x 1.25 Helicoil (Read 40870 times)