1. May 25, 2007

### NoTime

I need a 3/8-16 full thread (Tap) 1/2" long hex bolt with a left hand thread.

Anyone know where I can get one without paying a minimum order fee.

2. May 25, 2007

### Staff: Mentor

What does it fit into? If it's a vehicle or other product, maybe the parts house for those vehicle would have one? Why is it a left-hand thread?

3. May 26, 2007

### Danger

Pretty much the only reasons for a southpaw twist are for safety. One is restricted to gas or fluid applications (pipe thread), so that the wrong canister can't be hooked up by accident. The other is when a rotating part that might 'unscrew' the bolt or nut is involved and a locknut or cotter pin isn't indicated. My old lawnmower, for instance, had LH threads on the left wheels to prevent the bolts from loosening during constant forward movement. I think that a lot of early cars were likewise.
If you can't find the proper one otherwise, it might be worth your while to buy an LH tap-and-die set and make your own. I don't know about the price of that, but my RH set cost about $30 CDN. That's probably around$25 USD. That's still probably cheaper than a batch lot of special order bolts.

4. May 26, 2007

### NoTime

Thanks for the replies.
It's a clutch retainer bolt for an old chainsaw.
So the counter rotating shaft bit applies.
No longer available from manufacture.

I did find a place that will sell me the correct bolt, but minimum order is $25. I suppose I could try checking more repair shops for old stock. No luck so far with that idea. I have a car with left handed wheel nuts. 5. May 26, 2007 ### Danger I wish that I could remember where I saw it; there was a TV item about a fellow who collects chainsaws. He has something like 1,000 of them. He can't be the only one. Maybe you could float an ad trying to find one and see if he/she would be willing to part with a bolt. There's another approach that might be the easiest and most practical, which I didn't think to mention earlier. In a situation like this, I'd be inclined to drill the hole a bit oversize and re-tap it for a rightie. That could be just a matter of using a larger bolt, or you could Heli-Coil the hole and use one of the same size. With something like Lock-Tite, the rotation shouldn't loosen it. There is a possibility of that throwing the rotating assembly out of balance, though. 6. May 26, 2007 ### Q_Goest McMaster Carr has 3/8"-16 x 3/4" long,$17.55 each. P/N: 90306A29
http://www.mcmaster.com/
Do a search on "bolt" and just follow the icons.

7. May 26, 2007

### NoTime

I found this 90211A292 at $7.03 instead. Grade 8 steel. I don't think the zinc plating will make any difference. Also cutting the extra half inch off the steel bolt is going to be a lot easier than cutting a 1/4 inch off stainless. Oddly the 1" stainless steel bolt is only$10 instead of \$17 for the 3/4".

What is their shipping like?
Looks like the site won't tell me untill *after* I put my credit card in.:uhh:

8. May 26, 2007

### NoTime

I have considered getting a turnbuckel

9. May 26, 2007

### Danger

Oh great...
Then you'd have Hulk Hogan jumping around in your saw.

10. May 26, 2007

### FredGarvin

Shipping from McMaster is not a gouge. I order from them at least 5 times a week.

I would make sure that you're not going to get the stainless bolt if the retainer it's going into is stainless. You'll end up with a galling problem.

11. May 26, 2007

### NoTime

Thanks.
I'm always leary of shipping charges.
Seems like too many places make up for the low price in shipping.

Stainless screws with stainless nuts is an issue?
I never heard of that, but I learn a lot poking around here.
How bad a problem is it?

12. May 26, 2007

### NoTime

If he'd jump around with the saw, while I sit back with a beer...:!!)

13. May 27, 2007

### FredGarvin

It may not be too much of an issue if it is just a nut and bolt. It gets a lot worse with things like pipe fittings and hydraulic fittings that have large thread surfaces. It will most likely just seem like they are tough to get apart.

14. May 28, 2007

### NoTime

Galling is usually fairly serious.
I see some of that working on cars.
If you're lucky a thread chaser will clean up the important (expensive) part.

I get the impression this is more on the microscopic level where it wouldn't be readily visible.
Is this correct?

15. May 30, 2007

### Q_Goest

Hi NoTime,
Sorry for not responding earlier, I was on vacation over the weekend. Looks like Fred was able to respond to your questions though.

<Thanks for the help, Fred!>

Regarding galling, it's not just a 'microscopic' problem. Stainless steel (especially 300 series) has a nasty tendancy to gall which is similar to a welding process in which the two materials bond to each other. It can be such a strong bond that unthreading may be impossible. I've seen lots of stainless parts that simply had to be discarded because they couldn't be taken apart.

Just a side note, one trick I found to get them apart is to soak the joint with a good thread tapping oil (not WD40 or penetrating oil, but real thread tapping oil) and to just work the part in and out a million times till they finally come loose.

16. May 30, 2007

### Danger

What about heating or cooling the joint?

17. May 30, 2007

### Q_Goest

Hi Danger,
Like you, I've used a torch to loosen up steel bolts that have rusted together, but galling is different. I'm not sure what exactly the process is at the microscopic level (maybe someone else can chime in), but the parts may as well be welded. The more you try to loosen the bolt, the worse things get.

At any rate, I've not heard of anyone using a torch to loosen a thread that's galled, and austenitic stainless steels are notorious for this problem.

The best solution I've seen to prevent stainless bolts from galling in the first place is to use Dow Corning Molykote 321. It's a spray on lubricant that dries in about 5 minutes. Once dry, parts can be assembled. I've not had any problems with bolts that have been treated with this spray and it's not expensive. Just a few bucks for a can that'll last for a few hundred bolts.

18. May 30, 2007

### Danger

Hmmm... I wonder if it might involve Van der Waals forces? I wouldn't expect any kind of chemical reaction.
I'm quite unfamiliar with stainless steel, other than knowing that I don't ever want to try working with it again. I had some 16# stainless plates made up one time to cover the holes where locks had been removed. It took me 3 hours and half a dozen bits to drill 4 stupid little 3/32" holes for the mounting screws (for one plate).

19. May 30, 2007

### NoTime

Thanks for the help everyone!

I'll have to remember that Molykote stuff if I get into dealing with stainless.

20. May 30, 2007

### NoTime

Yea! On drilling the stuff. :grumpy:
I've had reasonable success cutting it with a sawsall blade rated for the purpose.
Does anyone know good drill bit for this purpose?
Would a tungsten carbide bit work better?

Danger, your mention of Van der Waals forces made me think of something.
I have no real idea if this is meaningful, but
There is a phenomenon called vacuum welding.
Take away all the air and clean metals can weld together.
Now steel obviously has exposed charges (otherwise it wouldn't rust) that are likely to bind to the non symmetrical charge shell of an O2 or N2 molecule.
Now stainless steel doesn't rust so exposed charge groups seem unlikely.
It occurs to me that fastening the screw and nut could drive all the air molecules out of the contact area allowing vacuum welding to occur.

I wonder if someone here actually knows what occurs.