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Central, IN | So I am a little stumped and more then happy for some good information in this area. I have bought winters drill bits for a long time and have gotten along great with them. If I grabbed a 1/2 bit it would drill the hole and I could put in a 1/2 bolt. Same with 1/4,3/8 etc etc. Best I can find winters isn't really selling bits any more so I found another company at the farm show that I thought was going to give me the same quality after talking to them. So I put together an order for what I needed to refill my stock which was a pretty good order becasue it has been awhile. I go to drill a half inch hole and can't get a bolt to go in. On top of that the hole doesn't look to be round but more ob longed. I grab another new bit and same thing. So I call the compay and here is what I get told. Am told a 1/2 bit won't drill a hole for a 1/2 bolt. Instead I need to use a reamer after I drill the hole in order to make it work for a bolt????????? Are ya kidding me or is this for real. This is the first time in my life of having this happen or hearing this. Please tell me if this guy is right or not. And the ob long hole is my drill no matter what it has to be my drill. If I am wrong please tell me but I feel like I just waisted a chunk of change. |
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| Never heard or that I would send them back. |
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Lawton MI | Unfortunately it sounds like you got some junk Chinese bits. I would send them back. What they're saying is a bunch of manure. |
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South Central Illinois | Do you have a good way to measure the diameter of the bit?
Calipers?
Maybe take it to a machine shop for measurement. |
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| It takes .004 of an inch clearance per inch of diameter to get a bolt through a hole. |
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| Machine shops generally use a .530 inch bit for a 1/2 inch bolt.
That being said, I can get a 1/2 bolt in a hole I drill with a 1/2 bit.
INDY |
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Westport, IN | I agree. I've always used 1/32 oversized bit when using bolts. I wouldn't even try to get a 1/4 bolt in a 1/4 drill hole.
Also a two flute bit, especially on thin metal will make a oblong hole. It can be minimized with good clamping.
Was your old bits some kind of custom bits? Maybe take some pictures.
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Cornwall ontario | A perfect 1/2 inch hole shouldn’t have enough clearance for a 1/2 inch bolt to fit properly The bit making an oblong hole would indicate it is not sharpened properly having one side of the cutting lips longer than the other |
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Wisconsin | I've seen it myself where certain drillbit's cut oblong holes but seem to actually cut pretty decent other than not a true hole. In my ruff drilling just ream it to fit no big deal to me. If I was a more professional and required a good bit I'd purchase some and pay the price. Actually calling the company and getting that response would get my back up and maybe get their product returned in front of a farmshow crowd in a not so polite fashion. |
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United States | Ive been using Winters Drill Bits for years. When drilling 3/8 drill bit then install a 3/8 bolt . I wish they were still in business.
Byron EcIn .
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| I suspect the previous bits were ever so slightly oversized to accomplish what you say. Using the same size bit for a bolt is usually an interference fit for me.
Now if they just don’t cut well, probably just not good bits. |
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Southern Alberta Canada | LOL, I'm so happy to successfully drill holes it never occurs to me they might be slightly undersized, I usually just blame it on burres or a worn bit, ream the hole with the bit and carry on. I almost always go a 64th or 32nd over these days as well unless it's a critical fit project. If you think about it almost all holes in factory made stuff are very loose, anything that requires precision is aligned with dowels.
One thing that really bugs me though is flatwashers, many are oversized almost to the next size up, what's with that?
Edited by Offroadnt 3/2/2018 07:40
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Swaledale, IA | I would have asked them how can my 1/2" drill bit fit in the hole and the same diameter bolt cannot? Magic |
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w/c Illinois | A regular twist drill will always make a hole that is shaped like a clover leaf. If you want a perfectly round 1/2” hole you will have to use a reamer.
Edited by Rock Road 3/2/2018 08:07
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Central ND | Nope....... a true half inch hole wont fit a true half inch pin or bolt.They are both the exact same size and there is interference, so a hole has to be tecnically a few thousanths larger for a non interference fit.. Measure you old bits and also your new ones with a micrometer, its the only way you will ever know what is really going on...If your old bits fit half inch bolts and pins the center point may have been off center and wobbled out a larger hole or they are larger diameter than they say they are.
The reemers are more for perscision sizeing a drilled hole and can be found in fractional sizes to meet the needs of percision. Personaly, I dont own a reamer(but should)
Edited by School Of Hard Knock 3/2/2018 09:29
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East Central Ia, S. Waterloo | My fathers old Craftsman drill bit set holder has three sizes listed below the bit. One for the bit size below that the size to insert the corresponding bolt and a third for the tap size. Their not all the same, pretty handy. |
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central mich | Off road
The difference in washers is US vs SAE class.
If you buy US class many times these washers will fit the next size up. Most farm stores and chain stores only sell US clase.
SAE class are smaller in OD than US but fit the bolt size.
Also in SAE you can buy different thickness washers.
We do not use US washers for anything unless
building wood crates or skids.
Edited by jimgen 3/2/2018 15:30
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Pilot Grove, Missouri | Agree on the washers. I usually use washers that are sold as one size smaller than the bolt I am installing. Patrick |
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North Central Illinois | Actually they are telling you the truth. Go to a machine shop and tell them your dilemma. I think you will find they use a bit slightly larger than 1/2" for a 1/2" bolt. |
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NW Washington | You should drill a hole a 1/32 or 1/64 larger than the bolt size if you don't want an interference fit. So for a 1/2 bolt drill a 33/64" hole or a 17/32" hole.
A set of Letter sized bits will let you finesse things a little better in some cases. |
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Big Sky Country | whack it thru with a hammer and you got instant lock nut.
A complete set of hammers is very first tool to own.... |
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Montezuma, Ohio | This chart might help. https://pages.mtu.edu/~suits/misc/tapsizes.html |
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N.E. MO | I always oversize bolt holes unless they are to be tapped or some other special circumstance. In the structural world, code calls for bolt holes to be oversized by 1/16" for steel to steel connections. You don't want any sort of binding between the bolt and the hole, or it can interfere with the clamping action of the tightened bolt, which is what you are trying to achieve. |
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North Central Kansas | I've found that twist drill bits generally cut a couple thousandths larger than the actual bit diameter measurement.
The problem with bolt or pin interference is sometimes caused by the bit cutting undersize when breaking thru the opposite side.
This will leave a smaller land that is only a few thousandths smaller than the rest of the hole. The land can usually be removed with a chamfer bit or perhaps a rat tail file.
I generally drill using the same nominal size bit as the bolt. One way to get the bit to drill a little oversize is to grind one flute slightly more than the other creating an off center point. This will cause to bit to orbit slightly while drilling and create the oversize hole.
If trying to get a hole that is the same exact size as the bit first drill it with the next size smaller. Then use the on size" bit to follow the hole and act like a reamer.
I agree that 1/32" oversize is about right for most bolt holes but sometimes a closer fit is needed.
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E. CO, exactly half way between NE and OK | If I want to drill a 1/2" hole, I use a 1/2" bit and put a 1/2" bolt in it. If I want a 1/4" hole, I use a 1/4" bit and put a 1/4" bolt in it. |
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| that's how I usually do it , wack it through with a big wrench , then wonder why the nut won' t start
usually can't find a hammer , but that's ok any wrench or tool can be a hammer |
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Central Missouri | I'm a machinist so I probably don't know what I am talking about. But a 1/2" bit shouldn't drill a hole to fit a 1/2" bolt. I typically drill .015"-.030" over depending on the job.
If a drill bit is drilling oval holes it's not perfectly perpendicular to the part to isn't set up rigid and is going in at an angle or wobbling.
Also any bit that has been resharpened will drill holes larger than the bit diameter because as it gets ground down the webs get thicker.
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| +1 for Clarkburn
Edited by 7150 3/2/2018 21:05
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Southern Alberta Canada | jimgen - 3/2/2018 08:48
Off road
The difference in washers is US vs SAE class.
If you buy US class many times these washers will fit the next size up. Most farm stores and chain stores only sell US clase.
SAE class are smaller in OD than US but fit the bolt size.
Also in SAE you can buy different thickness washers.
We do not use US washers for anything unless
building wood crates or skids.
I can only wish for washer selection like you have down there, even our SAE washers seem to be way oversized, I really don't get it. I suppose I could try to order washers but it's one of those items you don't think about much until you go to use them.
A flat washer isn't rocket science, they stamp out a billion of them a day, why not build the actual right size die? |
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Southern Alberta Canada | PopC - 3/2/2018 17:01
that's how I usually do it , wack it through with a big wrench , then wonder why the nut won' t start
usually can't find a hammer , but that's ok any wrench or tool can be a hammer
Just thinking, the threads on a bolt are usually smaller than the shank (at least mine are) you never damage the threads with a size on size drill bit hole? |
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east central ND | I am starting to play around with machine tools and micrometers in my shop. It is a whole different world of measuring. Calling something “1/2 inch”. And having it measure 0.500” is two different things. My eyes have been opened, and a lot of head scratching and math has been the result.
Edited by D6Joe 3/3/2018 15:40
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Central Missouri | I confuse people a lot because I never write numbers as a fraction, always as decimals. My dad is one of them. I had an old machinist I used to work for tell me one time fractions are for carpenters and welders, machinists use decimals. |
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North Central Kansas | One advantage of drilling size on size (1/2" bit for 1/2" bolt for example) is that the bolt sort of acts like a dowel pin.
It not only ensures more precise alignment of the mating parts but can also prevent the start of any movement that over time will wear out the holes.
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Westport, IN | But now you get to watch the radius of the shoulder head connection. Without a washer, the radius will seat and become loose. |
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Drill bit to hole size question....
