3/8" x 26 Cycle Thread Recoil Tap Size?

[Paddy_SP]

I'm in the process of putting an 850 motor together, and was not best pleased to discover that two of the threads for the head bolts aren't there any more. Some halfwit has attempted to sort them, but clearly gave up after drilling out the old threads. I've ordered up a pack of Recoil thread inserts, but they don't come with an installation tap, and I can't find one anywhere except in an expensive kit. I would therefore be most grateful if someone here would be kind enough to tell me what the correct tap size for the insert should be!

 

[kommando]

Depends upon the spec of the insert which is determined by the maker so to be 100% right it has to be a Recoil one, I would hazard a guess that 7/16th X 26 would be the closest you could get other than recoil tap but for a head bolt I would not risk anything but a Recoil tap.

 

[Paddy_SP]

Depends upon the spec of the insert which is determined by the maker so to be 100% right it has to be a Recoil one, I would hazard a guess that 7/16th X 26 would be the closest you could get other than recoil tap but for a head bolt I would not risk anything but a Recoil tap.

Thank you - being a Sunday I haven't tried to contact the suppliers to see what they can tell me, so hoped someone on here would know!

 

[kommando]

The data you need might be in here

http://www.alcoa.com/fastening_systems_ ... atalog.pdf

at 68 pages it will be a long read.

 

[Paddy_SP]

The data you need might be in here

http://www.alcoa.com/fastening_systems_ ... atalog.pdf

at 68 pages it will be a long read.

Many thanks for taking the trouble to dig that out - I spent some time going through the same document this morning, and unfortunately discovered that while it gives part numbers, it doesn't give any relevant dimensions.

 

[texasSlick]

From Alcoa website"

Recoil® STI Steel Taps

Recoil taps differ from standard taps dimensionally and only Recoil Screw Thread Insert (STI) Taps are suitable for use with Recoil Wire Thread Inserts.

Recoil taps are manufactured to precise standards from either High Speed Steel (HSS) or (HSS-E) with ground threads and are available with taper, intermediate and bottoming leads.

They have a larger diameter, but the same pitch as a standard tap in order to accommodate the wire insert. Spiral point and spiral flute machine taps are also available for volume production purposes.

For all sparkplug applications, pilot nose taps are recommended and are available for common metric thread silzes. The Recoil thread insert when installed into a correctly tapped hole will provide the applicable internal thread tolerance for the installed bolt.

Note: Tapped hole size can be significantly affected by variations in drill size, parent material, or lubricant so in close tolerance applications some testing for an optimum combination is recommended.

Per the highlighted text, it appears you will have to spring for the proper tap.
Slick

 

[Paddy_SP]

Thanks for the helpful info - I'm prepared to pay for the tool if I can find one without having to buy an entire kit as I've got everything else I need!

 

[comnoz]

Save yourself some money and some grief. The recoil taps are special thread and don't match any standard size taps.

If you use the fine thread recoil insert in aluminum it will not last very long as the thread pitch vs diameter is a poor match in aluminum.

Buy some tymeserts which are like a helicoil except they are solid and thicker. They use a standard thread pitch on the OD so you don't need to buy a tap. And they last much longer in this application. Jim

http://www.timesert.com/

 

[texasSlick]

Save yourself some money and some grief. The recoil taps are special thread and don't match any standard size taps.

If you use the fine thread recoil insert in aluminum it will not last very long as the thread pitch vs diameter is a poor match in aluminum.

Buy some tymeserts which are like a helicoil except they are solid and thicker. They use a standard thread pitch on the OD so you don't need to buy a tap. And they last much longer in this application. Jim

http://www.timesert.com/

Thanks Jim. This is good info. I hope I can remember this should I ever have the misfortune to need it.

I wish this Forum had a special category to catalog information such as this.

Slick

 

[Paddy_SP]

Save yourself some money and some grief. The recoil taps are special thread and don't match any standard size taps.

If you use the fine thread recoil insert in aluminum it will not last very long as the thread pitch vs diameter is a poor match in aluminum.

Buy some tymeserts which are like a helicoil except they are solid and thicker. They use a standard thread pitch on the OD so you don't need to buy a tap. And they last much longer in this application. Jim

http://www.timesert.com/

Many thanks, Jim - your experience is very much valued! Sadly, TimeSert (whose products I know well) don't appear to do a 3/8" x 26 insert. As this is going into cast iron, I don't think there should be a problem.

 

[comnoz]

Save yourself some money and some grief. The recoil taps are special thread and don't match any standard size taps.

If you use the fine thread recoil insert in aluminum it will not last very long as the thread pitch vs diameter is a poor match in aluminum.

Buy some tymeserts which are like a helicoil except they are solid and thicker. They use a standard thread pitch on the OD so you don't need to buy a tap. And they last much longer in this application. Jim

http://www.timesert.com/

Many thanks, Jim - your experience is very much valued! Sadly, TimeSert (whose products I know well) don't appear to do a 3/8" x 26 insert. As this is going into cast iron, I don't think there should be a problem.

Yes, going into cast iron with a recoil is fine. I figured you were referring to the threads in the bottom of the head. Unfortunately your still stuck with buying the special tap unless you can borrow one. If postage wasn't so high I would send you mine. Jim

 

[Paddy_SP]

Yes, going into cast iron with a recoil is fine. I figured you were referring to the threads in the bottom of the head. Unfortunately your still stuck with buying the special tap unless you can borrow one. If postage wasn't so high I would send you mine. Jim

I very much appreciate the sentiment, Jim - many thanks!