• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

For those thread nerds.

Share this page

Those prices seem high to me; I have what appears to be identical to the first set and it was only $50 @ Sears.

Kind of depends on what cars you are working on and what threads they use. 78 MGB might well have lots of metric threads; but TR2-6 have practically none at all. (And the very few they do have are generally not found in sets).
 
I was worried about the sizes being to odd to be included in a set. The mg seems to jump a bit between metric and standard
 
Even the "inch" sizes on a TR3 aren't always common ones. Just this weekend I was checking the wiper spindles, which appear to have 5/8-24 threads where they clamp to the body. And there are just enough British Standard threads around (mostly British Association, but some BSF as well) to get you in trouble. A 2BA thread looks an awful lot like 10-32, but you'll be sorry if you start to run a 10-32 tap through them (or die over them). BTDT

My point is to buy a general purpose set, and then add to it as you find the 'specials'. I use dial calipers, a thread gauge and a 5x jewelers loupe for identifying threads, plus a chart like the one at
https://mdmetric.com/tech/tict.htm
 
Bolts, nuts, and screws on a MGB are SAE fine thread almost anywhere. No metric (as long as the pieces are original) or Whitworth, at least as far as I know or found on my '70 MGB (Sprites and Midgets are the same). Carbs may have a few odd bits depending on the model.
 
Be thankful in a way that you don't own a T series, as far as tools go. 99% Whitworth nut and bolt head sizes. I had to buy two sets of Whitworth tools just to work on the TF. All the threads are BSF (British Standard Fine), so a set of taps and dies were in order to repair threads messed up by a DPO jambing in metric and standard size thread bolts! Now, to work on the engine, it has some French bolts and threads! :disgust: PJ
 
An MGB has SAE fasteners. The only exceptions I can think of are the filler hole plugs for the shock dampers. There may be metric sizes in the carb, but I don't think so.

A set of SAE thread chasers would be the most appropriate. Buying them as you need 'em "onesies" would be my advice unless you plan on doing work on a LOT of machinery besides the MG.
 
Doc's right. Your MG "Should" be almost 100% SAE threads. I have that first set you posted. It does seem to cover a lot of the fasteners on LBCs. It would not be wasted money, but the money might be better spent on a tap and die set. then you can repair threads as well as make new ones with the same tool. The chasers won't cut new threads. The only advantages to the thread repair tools is that they will reach almost to the bottom of a blind hole. You would need a bottom tap to do that, and a regular tap set does not include those. and the chasers are designed to be used with regular wrenches and sockets instead of tap handles. For some reason no one can put a decent set of tap handles in a tap kit.
If all you're looking to do is clean out threads before you reassemble things, one of those thread chaser kits is really nice to have.
 
I have an odd "need" to run any thread I take off something with a tap and die. Just to clean it up and let it go back together nice and snug with out getting caught up on some piece of dirt or rust. Then on another post I learned that was a bad Idea and that they make a special tool that wont cut just clean. It would be for little else then make me feel better about details. Im really just starting to build my personal collection of tools again. Sold most of to finance getting married and moving from NY to ID. Banjo, my dad was born and raised in Horseheads. When I was little I remember driving through the town and seeing a mural of horses on the side of some brick building on the left as I turned right at "some" intersection. later in life we took our LBC and got lost on the roads that seemed to be made for these cars in the outskirts between there and syracuse. I wouldn't say Im getting home sick... just missing the green, the REAL green.
 
WillR said:
Then on another post I learned that was a bad Idea
Click to expand...
A persistent myth, IMO, except for highly stressed fasteners. Yes, it weakens the threads by a tiny amount (assuming they were rolled threads to begin with); but any normal design will have assumed that the threads were that weak to begin with. I've been routinely chasing most threads with standard taps or dies for many decades without a failure. Exceptions would be things like cylinder head and connecting rod bolts/studs/nuts; which should be replaced if there is any doubt about their condition. Ditto wheels, driveshafts and so on.

However, the chasers do make things a lot easier when there are obstacles nearby; because you can turn them with the same wrench or socket that you would normally use. Lots of times there isn't room for a tap or die holder.
 
Not so sure I'd call it "myth" but a bit of common sense goes along with which fasteners you could use taps/dies on instead of chasers. Randall, you're spot-on with being reluctant to use taps/dies on high-stress components like head bolts/studs, wheel studs, etc. Any fastener seeing constant loading, whether tension, torque or shear would be best replaced if questionable rather than taking a tap or die to it. Alternately, chasers to clean it.

I'd rather pay for replacement con-rod and bearing cap bolts than take the chance the engine would grenade itself 'cause I didn't, to save a couple quid. And for those kinds of fasteners I will usually go with Grade-8 stuff, just to be safe.
 
I have nothing to add to Randall's and the Dr's posts concerning common sense and when to chase threads. However, the only thread chaser tap I own is for spark plugs and I bought it to clean up threads for an oxygen sensor on my daily driver. For as long as I have owned cars I have cleaned up threads using standard taps and dies. There are junk taps and dies out there but in general if they appear to have a good ground finish they are a good investment for chasing threads. Avoid the $10 carbon steel taps and dies that sometimes show up in the bulk bins at places like Northern and HF.
 
Amen on the cheap taps, Doug. All they're good for is getting practice at removing broken taps from important/expensive parts. :wink:
 
DrEntropy said:
I'd rather pay for replacement con-rod and bearing cap bolts than take the chance the engine would grenade itself 'cause I didn't, to save a couple quid.
Click to expand...
Of course, then you are taking a chance that the new bolts aren't up to snuff. :smile:
And for those kinds of fasteners I will usually go with Grade-8 stuff, just to be safe.
Click to expand...
There is a whole lot more to fastener design than just tensile strength, and the differences may not be obvious. I wouldn't dream of using common hardware store fasteners in a highly stressed situation. Besides, Grade 8 isn't all that strong (even if it does meet spec). An ordinary SHCS is about 20% stronger than Grade 8.

Fortunately, with Triumphs, there is an easy way to tell if there is something special about a fastener. All of the "common hardware" fasteners have a part number that starts with two letters. If the factory used a 6 digit part number, then there is something special about the fastener.

I agree 100% on the cheap taps. The last ones I bought didn't even cut the right depth!

I've been reusing Triumph fasteners for going-on 40 years now, and never had a failure. In fact, the TR3A engine I "rebuilt" in 1974 still runs today (although it hasn't done a lot of miles due to other problems with the car).
 
I'm sorry to say that you're mistaken. The MG has BSF threads. The number of threads/per inch is the same as SAE fine, but the pitch is different. Usually the SAE bolts will work, but there is a difference.

Also there are three tools for repair threads. Thee is the standard tap and die, which most people use, but when used for repairing damaged threads, they may take off too much metal. There is the thread file. But the correct tool for repairing damaged threads is a rethreader or thread restorer (https://www.summitracing.com/parts/shc-952105?seid=srese1&gclid=CLT6orXajb8CFQIT7AodsFwArQ). They take less metal off.
 
WillR said:
Banjo, my dad was born and raised in Horseheads. When I was little I remember driving through the town and seeing a mural of horses on the side of some brick building on the left as I turned right at "some" intersection.
Click to expand...
Yup. the mural is still there on the corner of Franklin St. and Grand Central Ave. I'll try to get a pic for ya. It's on the edge of the infamous "Hanover Square" the 5-way intersection with no traffic signal. You just need to remember that the traffic coming from Main St. does not have to stop. Everyone else does. Plenty of fender benders there.
 
maynard said:
I'm sorry to say that you're mistaken. The MG has BSF threads. The number of threads/per inch is the same as SAE fine, but the pitch is different. Usually the SAE bolts will work, but there is a difference.
Click to expand...
Threads per inch IS the pitch! And BSF does not use the same pitch as SAE fine. For example 1/4 BSF is 26 tpi, while 1/4 NF is 28 tpi.

You may be thinking of BSW and SAE coarse, which are the same pitch for most sizes (notable exception being 1/2" where BSW is 12 tpi while SAE is 13 tpi). But I'd be really surprised to find many of those on a 78 MGB.

One easy way to determine if you've picked up a BSW or SAE fastener is whether your SAE wrenches will fit it snugly. BSW bolts & nuts use a larger head than the equivalent SAE bolts & nuts and the head is (usually) not a common inch size. For example, 1/4 SAE uses a 7/16" head; while a 1/4 BSW is .445" across the flats (roughly 57/128").
 
Sorry about the mix up. I meant thread angle instead of pitch. BSF is 55 degrees, UNF is 60 degrees.
 
Well aware of the BSF/BSW differences AND the metallurgical properties of SAE fasteners and materials. Too many hours with ASTM/ASME spec's. Buying from reputable suppliers lessens the chance the things will fail, too.

A '78 MGB has only four British sized/threaded bits I can think of, those are the aforementioned plugs on the dampers.

maynard said:
Also there are three tools for repair threads. Thee is the standard tap and die, which most people use, but when used for repairing damaged threads, they may take off too much metal. There is the thread file. But the correct tool for repairing damaged threads is a rethreader or thread restorer <LINK>. They take less metal off.
Click to expand...


I think that's what I was advocating from the beginning.
 
Back
Top