mreisner
Well-known member
Does anyone have a source for them? I need a 9 mm one, full length. Thanks.
Metric left hand drill bits.
- Thread starter mreisner
- Start date
cherrybomb
Well-known member
McMaster Carr at $28.90,ouch,what are you working on?
Left-Hand High-Speed Steel Drill Bit Black Oxide, 9.0 mm Bit Size https://www.mcmaster.com/product/29855A69
What are you doing where it needs to be exactly 9mm?
RoninB4
Well-known member
....
A customer tried removing a bolt on a clutch shaft on a side-by-side not knowing about left-handed drill bits. He drilled it to the point where the root of the threads of the bolt is basically all that's there, it's an M10 by 1.25 bolt so I'm hoping I can get it out with a left-handed 9 mm. Threaded part of the bolt that's left is fairly deep in the shaft so I can't get an rbrt extractor down in there as it is too short, and he doesn't want to drill it oversized and put a helicoil back in there which I think is what we're going to have to do anyways.
Isn't a 9mm too big in that case?
Do you have any left handed that are close? Personally I've never had the left hand but work, Soni usually drill it close and pick the threads out, or fubar the hole and helicoil it anyways
jar944
Well-known member
8.647 mm root diameter.. so really close for hand drilling.
It's going to be right on the borderline, but the decimal equivalent that I had was the size below it and it won't quite catch. To make matters worse this is a service call, if I had it back in the shop I could put it up on my list see what I'm doing it close to high level and probably pick the threads out or get in there with a tiny burr and cut the shell that's left and fold it back in on itself.
whateg01
Well-known member
If you're already that far gone, just drill it with a right hand thread, then decide if it needs some sort of insert
Honestly I still don’t understand why it needs to be 9mm or metric at all. Just cause the bolt was metric don’t mean the LH drill bit to extract it needs to be metric. The bolt don’t know the difference.
idk if anyone needs anything other than SAE LH drill bits in 1/16 inch increments tbh. Maybe you do I just don’t see the need. Your either drilling a hole and can use RH or your extracting from something and just use the closest size you got.
Grandson snapped his clutch bolt on an atv. Since it was in a recessed hole I turned a bushing that was a slip fit in the clutch and drilled the bushing with the nearest LH bit I had. Got lucky and the bit grabbed the screw and backed it out easily. I have to say that he snapped the bolt by over torquing it so it was not rusted in there. I have had great luck with LH bits and even better when I can use a bushing to hold it centered , either down the hole or threaded or slipped onto a stub if I can,
lg
no neat sig line
lg
no neat sig line
The next bigger standard drill bit will take all the threads out of the shaft. I'm hoping to snag what little bit of the bolt remains with the left-handed bit and get it spun out that way. From what I understand the shaft is hardened and the bolt appears to be not as hard so I'm hoping it will snag and spin.
So there’s less than 1/32” bolt material left on the sides? Since SAE come in 1/16 sizes so if one size is too big because it would strip the threads on the shaft, and the next size smaller won’t catch at all, then that means 1/16 different is too big an increment in drill size which means divide that by two and you got under 1/32 material left of the bolt? If my math is right sorry Im honestly not great at math
not trying to give you a hard time just trying to learn in case I come across something like this because in head idk why you can’t use 1/16 size smaller SAE bit than whatever one is too big
You sure about that?
They come in 64ths but honestly idk why most people would need more than 1/16 on the upper end like 10mm or 3/8 inch but they exist. 23/64 is damn close to 9mm tbh if you really want that @mreisner or maybe 11/32 if you want a little smaller
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Cruzan80
Well-known member
Yea sorry 23/64 and one step smaller is 22/64 or 11/32 I edited and fixed the first post so nobody gets confused by my mistake
jayemm
Well-known member
Whatever size you buy, get more than one.
cherrybomb
Well-known member
I know Grainger carries a large selection of drill bits,fraction,metric,letter and number.Many different lengths and left and right rotation
RoninB4
Well-known member
McMaster is almost always more expensive on everything. Try searching for industrial supply houses like Travers Tool or anyplace that caters to machine shops. Price for an 11/32 (8.71mm) left hand drill was under $15 last time I checked.
Yeah 9mm will over size the minor diameter.e.g cut into the female threads. If you want to try and save the hole I'd try and drill 7.5 or 8mm then try and pick it out.
For anyone not familiar with metric threads, a rule of thumb is that your tap drill size is the diameter minus the pitch (for example 10mm-1.25mm=8.75)
Wish I could do that, but the threaded portion is about an inch and a half down in the hole. Hoping to just catch the end of it with the 9 mm when it comes later today. Customer is starting to come around to the idea that we're probably going to have to tap oversize or do some type of oversize and then put an insert in it.