# Smallpart drilling advice.



## Hoodoo Valley (Nov 14, 2006)

So, I have 6 pipe cutter wheels that have an axle bore of .350 and I need to get them adapted to .250 since about the only way to get something on the order of 11/32nds is drill rod, but then I need to thread each end, so I need to get these cutter wheels to pivot on 1/4 X 20 bolts which after much consideration, is the only combination that will suite my needs. went to a machinist forum but everyone there save for one or two people were chumps, so here I am asking where I should have asked in the first place.

Here's what I need to do....... I need to drill a 1/2 hole through a .350 hole that has a slight bevel on each side in extremely hard steel. There are a number of bits that are up to the task such as ARTU brand bits or abrasive bits so this is not the problem. My problem is one- holding the cutter wheels stationary for the boring and two- insuring that the hole is centered. One would naturally think that with a hole already there, and especially with a slight bevel at the beginning edge of the hole, that the bit would center, especially if I used a slightly larger bit, then another slightly larger bit and so on, however, even when I used a vertical mill, dropped in a correctly fitting sized bit in the chuck, down in the hole and secured things then put in a slightly larger bit, the hole still was not directly centered. The mill did have a slight bit of run out, but even still, it was visibly off center. Now, all I have right now is a drill press which will not be as accurate as a mill, but likely more accurate than the mill I had access to. 

So how do I do it? I'm open to suggestions, but before you fire away, I do have a drill press vice and a vintage Japanese metric run out meter that is very precise! I've exhausted every venue looking for cutter wheels that fit my application but that have a workable sized hole that a bolt will fit through. Tried adapting the intended axle pivot that goes to these cutter wheels I have that suit my specs but the cannot be easily threaded since they would be 11/32nds and too short to thread anyways. My only solution is to drill out to 1/2 inch, these cutter wheels, then get 1/2 inch nylon bushings set up for a 1/4 inch hole. 

Any ideas about this?


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## RC Wells (Dec 26, 2008)

My suggestion is to build a hardwood vice adapter as a holding fixture and then use a centering drill bit such as this: https://www.fastenal.com/products/d...yl3:"604413 Spotting 9and Centering Drills"|~


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## Hoodoo Valley (Nov 14, 2006)

So you think one pass with that style bit? I suppose you could burn in a bit and then check with a mic to see if you are centered. Be nice to have some sort of vice that rotated in axis with the chuck sort of like a lathe then you could use the run out meter on the piece as well as the bit.


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## RC Wells (Dec 26, 2008)

It depends on hardness of the material being drilled if one pass will do the job. I suppose go slow and use a lot of oil and see if it does the trick. 

I generally use a lathe and rotate the stock when possible, but have used these bits in the rotating head too. They also work in a commercial style drill press with a morse taper to chuck adapter and a dual axis vice so I can center the part being drilled. 

I have used the services of Cenco Grinding to build hard steel collets with true center holes a few times. A bit on the pricey side, but when needed they came through. http://drillblanks.com/


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## sixbales (May 18, 2011)

Alternatively, you could get some 3/8" x 1/4" steel bushings and turn them down to 0.35" OD.


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## marc_hanna (Apr 10, 2017)

Based on the tools you seem to have and if it's a hardened steel, I would use a carbide drill bit on the exact size hole you want and drill it in one shot. I would do this in the drill press . Whatever fixture you use should locate on the side of the cutter blade in order to keep it square to the drill bit. Make sure you're not running the bit too fast or you will burn the corners off it. Plunge through it at about 0.010" per revolution in order to cut a fairly thick chip. 

If you need a better finish then the drill will provide, I will drill and ream, but then your cutter costs have gone up quite a bit.


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## RC Wells (Dec 26, 2008)

I went searching for the vice like I have on my big drill press, could not find mine - antique I guess, just like me. But I did find something similar: https://www.amazon.com/Palmgren-Rot...=2025&creative=165953&creativeASIN=B0006577Y6

They use jaws like a lathe and can be centered. I would expect an older machine shop would have one around. They were made obsolete by affordable milling machines, so could likely be acquired pretty reasonably.

Found some on Granger.com for around $200.


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## Hoodoo Valley (Nov 14, 2006)

Well, I worked at a weld / fab shop and was laid off on excellent terms and the owner destroyed my table saw, so he owes me a favor....... Kinda thinking about having his machinist through my project on his lathe or vertical mill......


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## RM-MN (Sep 11, 2015)

It might be a good idea to turn your problem around. You have a very hard material with a precision hole in it. Maybe it would be easier to adapt the holder for that size of shaft? I doubt that nylon bushings would hold up to the forces on the cutting wheel so I'd throw that idea out.


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## Hoodoo Valley (Nov 14, 2006)

RM-MN said:


> It might be a good idea to turn your problem around. You have a very hard material with a precision hole in it. Maybe it would be easier to adapt the holder for that size of shaft? I doubt that nylon bushings would hold up to the forces on the cutting wheel so I'd throw that idea out.


No, the cutting wheels aren't going to be used for cutting wheels in this application. All together different category.... I'm building a specialized cutter and the cutting wheels are part of a tensioner. More details on that upon getting a working prototype and I get the device in production and on the market even if it will be small scale........... 

I attempted to chuck up a 1/2 inch nylon bushing on a bolt with nut on the other end to keep it from turning, and used a piece of angle aluminum with abrasive, and it was working but gawd awful slow, and worried about stressing beyond design, the lower bearings on my 1930s era drill press.


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## Gundog (Apr 17, 2013)

You might be better off to have a part made to suit the actual design of a tensioner rather than trying to make something work that was never designed for what you are doing.

I own a small manufacturing business making my own parts for my designs. Owning a few small machines would aid you in your designs and proto types. When you own your own machine tools it will change how you look at things in designing you start with a part you have in mind then how you will make it as apposed to what can I find that is designed for something else I can make work. A small mill and lathe from Harbor freight would allow you to make a few simple parts.

Many times it takes several prototype parts to get it right even if you machine plastic and make a working model then you can send things out to a professional machine shop to get your working model to go to market and get your patents going.

I have 2 US patents so I have been down this road a few times. You might even consider a 3D printer. Cad and Cam software has came a long ways and is fairly easy to learn these days and cost has come way down you might be surprised at the current cost of these things. It is invaluable to be able to make your own prototypes to get things working.

I started with a few small manual machines with my first product I patented and still sell today and I am still a very small shop but I have several CNC machines now and make my living doing this.

Mike


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## agm48 (Jan 25, 2017)

If you haven't drilled the wheels yet, I would consider having some bushings made. McMaster-Carr can make whatever you want. Not sure at what cost, but I've always been satisfied with their service.


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## thepumpguysc (Jan 25, 2015)

Heres a thought.. how about using "softer material" like the "big guys" do, doing the job required AND THEN getting it hardened.. problem solved..


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## z445guy (Mar 10, 2017)

Hope yoi didnt drill them yet but if you go to a plumbing sypply house, the cutting wheel you have lools like the same one my pipe cutter for steel pipe made by ridgid tools 

Sent from my SAMSUNG-SM-G891A using Tractor Forum mobile app


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## Cal1320 (Dec 29, 2018)

I agree with using .375 x .250 bushings. You can hold the bushings in a collet and use a lathe to turn them down to .370. You may be able to do this with a drill, file and a collet. A collet will hold the small bushings much better than a chuck because of their design (look up ER32 collet).


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