# Finding distance between two holes

 Forum topic by Nubsnstubs posted 06-10-2017 12:13 AM 1163 views 0 times favorited 11 replies
 Nubsnstubs1403 posts in 1872 days 06-10-2017 12:13 AM Just a verification needed. I need to drill 2 holes to match up on my PM lathe. I can’t get up under the ways to find my centers, but can get the distance from outside to outside of each Allen bolt head. The distance is 4”, the bolt head is .550”. If I subtract the size of one bolt head from the 4”, leaving 3.45” on center, would that match up to the PM holes?........ Jerry (in Tucson) -- Jerry (in Tucson) www.woodturnerstools.com

## 11 replies so far

 Gene Howe10894 posts in 3570 days #1 posted 06-10-2017 12:49 AM Seems right. -- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton jbay2662 posts in 1041 days #2 posted 06-10-2017 12:58 AM That would be center to center measurement. REO929 posts in 2216 days #3 posted 06-10-2017 01:18 AM Yup you got it jerry! Nubsnstubs1403 posts in 1872 days #4 posted 06-10-2017 02:51 AM Thanks, guys, I thought that was it, but old age, ya know…... Now I’ll proceed and get some stuff set up for my lathe. .......... Jerry (in Tucson) -- Jerry (in Tucson) www.woodturnerstools.com hotbyte991 posts in 3117 days #5 posted 06-10-2017 11:58 AM You could also measure from outside of one to inside of the second which is equivalent to subtracting the diameter. The advantage being you don’t need to know bold diameter. Nubsnstubs1403 posts in 1872 days #6 posted 06-10-2017 01:59 PM You could also measure from outside of one to inside of the second which is equivalent to subtracting the diameter. The advantage being you don t need to know bold diameter. - hotbyte If my poor old legs, tired old body, and real old eyes would have let me me do it that way, that would have been my preferred method.There wasn’t really enough room for the calipers with out interference from the lathe body, so I took the easiest measurement and figured I could do the math. Then senior moment stepped in, and cause me to have second thoughts about what I just did…. When looking for hole centers, 99% of the time it’s done the way you mentioned Better yet, if Powermatic would have heeded my suggestion of putting all leg mounting holes on the outside instead of up and under the ways, I wouldn’t have had a need to ask this question. :O).......... Jerry (in Tucson) -- Jerry (in Tucson) www.woodturnerstools.com MrRon5085 posts in 3385 days #7 posted 08-02-2017 05:13 PM You will get close, but not exactly. There is a clearance around each bolt, so the center of the bolt is not necessarily the center of the hole. Woodknack12369 posts in 2522 days #8 posted 08-02-2017 06:48 PM Like hotbyte I measure from left side to left side, or outside to inside, however you want to say it. But whatever works, works. -- Rick M, http://thewoodknack.blogspot.com/ Jack Lewis326 posts in 1220 days #9 posted 08-06-2017 09:13 PM Jerry; Just buy another lathe and measure before you put it together. Rick M. has the idea on the nose! -- "PLUMBER'S BUTT! Get over it, everybody has one" Nubsnstubs1403 posts in 1872 days #10 posted 08-07-2017 03:46 PM Jerry; Just buy another lathe and measure before you put it together. Rick M. has the idea on the nose! - Jack Lewis Jack, I can’t even afford to pay attention. How do you expect me to buy another lathe? I already did what I had to. I have been using Ricks and hotbytes method for at least the last 20 years, or maybe longer. Just about 3 months ago when I wanted to drill the holes, I had a mental fart, and couldn’t remember how. That’s why I posted this question, just to verify. At almost 71 years old, things are starting to take a little longer to remember. Just like an old computer, I’m getting slow. You will get close, but not exactly. There is a clearance around each bolt, so the center of the bolt is not necessarily the center of the hole. - MrRon I’m gonna disagree Ron. If both holes are the same size, center is center. The only time the bolts won’t be in the center is if the holes are oversized, and you just screw the bolts in or the holes were drilled different than the mating holes. ........... Jerry (in Tucson) -- Jerry (in Tucson) www.woodturnerstools.com Dark_Lightning3254 posts in 3251 days #11 posted 08-08-2017 03:08 AM Jerry; Just buy another lathe and measure before you put it together. Rick M. has the idea on the nose! - Jack Lewis Jack, I can t even afford to pay attention. How do you expect me to buy another lathe? I already did what I had to. I have been using Ricks and hotbytes method for at least the last 20 years, or maybe longer. Just about 3 months ago when I wanted to drill the holes, I had a mental fart, and couldn t remember how. That s why I posted this question, just to verify. At almost 71 years old, things are starting to take a little longer to remember. Just like an old computer, I m getting slow. You will get close, but not exactly. There is a clearance around each bolt, so the center of the bolt is not necessarily the center of the hole. - MrRon I m gonna disagree Ron. If both holes are the same size, center is center. The only time the bolts won t be in the center is if the holes are oversized, and you just screw the bolts in or the holes were drilled different than the mating holes. ........... Jerry (in Tucson) - Nubsnstubs Whenever a hole is drilled for a fastener, it is drilled at some size larger than the fastener in order to accommodate the variation in the articles held together, and in the diameter of the fasteners. This is a standard mechanical engineering practice. -- Random Orbital Nailer

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