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Thoughts on cutting broach vs. needle file for shaping worn holes when hand bushing

Twoflower

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Hello, all...

I'm about to start my first bushing job on a Hermle grandfather clock movement with a couple of problem areas that need rebushing. I've spent lots of time over the past few months reading everything I can on this forum about hand bushing, watching videos, etc. I've read Bangster's excellent post on hand bushing.

The general opinion seems to be divided between making a worn pivot hole symmetrical with a cutting broach, and making it symmetrical with a needle file. I have a spare Urgos grandfather clock movement I purchased cheaply from Ebay that I intend to practice hand bushing on, and I'm happy to try out both the needle file and cutting broach method (broach approach?).

The winding arbor pivot holes on this movement are particularly bad, one with about 0.7 - 0.8 mm of wear from a 3 mm pivot. I'm thinking that whichever method I end up trying, I need to find either a needle file or cutting broach with a 3 mm diameter somewhere on it for making the pivot symmetrical before broaching/reaming to size. My current plan is to find the 3mm point on the broach/file with my calipers, and mark it so I don't end up going larger than 3 mm when removing material on the unworn side of the hole.

What do you all think about needle file vs. broach, especially for wear from such a large pivot?
 

bruce linde

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The general opinion seems to be divided between making a worn pivot hole symmetrical with a cutting broach, and making it symmetrical with a needle file.

says who? i don't think i've even heard anyone recommend using a cutting broach for this. the goal is to maintain the position of the center of the hole.

being able to file deliberately is essential. i can't see how a cutting broach would allow for this kind of accuracy, as you would have to spin it around... as opposed to just using the current rotation of a circular needle file.

now, i will alternate between using the file method and carefully achieving the same result using my bushing machine and properly-sized cutter... the filing method requires magnification, whereas the bushing machine method requires absolute/secure positioning and clamping so the plate doesn't move.
 

wow

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If you are hand bushing using reamers and a hand bushing tool, the reamers are made in a half moon shape for the purpose of cutting only one side of the hole until the hole is round. Once it is round, you can continue with the reamer, cutting all sides equally, until the reamer pops through. The reamer cuts the exact size hole you need to pop in the bushing and it is very tight. The only time a broach may be needed is to cut out the ID of the new bushing so the pivot fits properly. Do you have reamers and a hand tool?
 

Twoflower

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says who?
I've seen a few people on YouTube doing it with a cutting broach, and perhaps a member or two in the forums allude to using a broach. I do see more people explicitly recommend a file. However, I've also seen a few members say they never use files at all. Using a broach for this seems awkward and a file seems more appropriate to me.

Do you have reamers and a hand tool?
I haven't purchased anything yet. I have a few assortments of KWM bushings that I purchased cheaply on Ebay, and they have the right size bushings for the job. I intend to buy the proper KWM reamers soon. I'm trying to get a good feel for what other tools I might need, such as files or broaches, before I put in an order.

Will, I'm afraid I don't understand how you're able to ream a hole properly if it isn't already round. I can see how it would work well if both reamer edges are in contact with opposites sides of the hole. What happens when the reamer edge opposite the cutting edge reaches the worn part of the hole and is no longer in contact with the hole edge? It seems like you'd only have one side of the reamer touching the hole edge and it wouldn't ream evenly any longer.
 

wow

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You mark the side of the oblong hole that you need to cut to get it back in the center and no longer oblong. Since the reamer only cuts on one side as you turn it, you can cut the unworn side until the hole is round and back in the center of the original hole. Using a broach or file creates a lot of guess work and they are tapered making it difficult to cut a straight hole. The KWM reamers and bushings are made so the hole cut by the reamer is the perfect size for the bushing to fit tightly. I still use my hand bushing tool when the bushing needed is in a spot where the bushing machine will not reach. Look at a photo of the reamers and you will be able to better understand.

CFD8A509-3575-40BE-B519-3E06BE37B443.png 82CA508C-D9F9-498D-BD21-11BD9C0F4457.png
 

Twoflower

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I see how positioning the reamer like this (red, cutting edge at upper left) would ream the hole out properly.
pivot hole 1.JPG
So you're saying that once the reamer turns clockwise to the following position (cutting edge at upper right), the hole will still be reamed evenly? The lower left worn portion isn't going to throw the reaming off somehow? Once you hit the wider area it seems like more of the reamer will slip into the gap and the point that your reamer is turning around isn't centered in the original pivot location any longer, it has shifted toward the worn area. If you let the reamer move down through the plate when you hit this wider area, then you're moving the axis of rotation to the lower left, no?

pivot hole 2.JPG
 

Kevin W.

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I was taught, file first, then use cutting broach.
 

bruce linde

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i started bushing by hand... really enjoy the hand work of filing.

i only recently got a real bushing tool and have started letting the KWM cutter even out the hole. you can also start with the next size down, and/or ease your way deeper carefully to round out the hole without losing center.

i know enough to be dangerous.... listen to the real guys like wow, RC, etc.
 

wow

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I usually turn cw first and then ccw and then look at the hole and the needed center to determine if it needs to be cut in that direction more. If the hole is really oblong bad, it may take several cuts in the unworn direction before the hole is round and centered. Usually, on most, there are only two or three holes that require more than two cuts in the unworn direction to get the hole round. Once it is round, if the center mark is centered on the hole, just ream away 360 degrees until it pops through. Then pop in the bushing, check the pivot in the new bushing, broach it if necessary, and you are done. Practice on old worthless plates first. Once you get the hang of it you can bush both plates in half an hour or less depending on how many bushings are needed.
By the way, Bruce, thanks for putting me in the group with RC, but I’m a long way from that group. I’m learning every day.
 

RJSoftware

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I think your terminology is in error. Nobody would use a needle file ever as they are generally way too big for the job. A file is used to file away excess length, above or below plate surface, but never in the bushing hole, unless it where a monstrous size bushing.

I think the terms are reamers and broaches you are looking for.

Broaches are long thin tapered needles. They can be smooth and serve the purpose of burnishing, which smoothes and work hardens the inner surface of a bushing hole.

Broaches can also be designated for cutting. Typical broaches that cut have flat sides that extend from tip to near handle. The better broaches have 6 sides, cheaper ones have 4. You can even convert a smoothing broach to cutting by grinding a flat side along it's length.

The reamer is at tool designed to create a precise diameter. In lathe work, when we drill a hole with twist drill, the hole produced from a twist bit is not really precise. Due to fluting space and expansion caused by debree.

A reamer takes one side out and has sufficient debree relief to avoid stretching the hole. It is more precise.

A broach hole is tapered, even if broached from both sides of plate. It is not as precise but for clockwork generally accepted.

The KWM reamer #3 and its associated handle are probably the most popular tool for bushing repair. The KWM bushing packages save hours of work for merely pennies. The KWM bushings are perfectly friction fit into the holes the KWM reamers create. There is no need for any elaborate setup, just reamer bit, handle and bushings.

Also, you can choose KWM bushings with small bushing holes and pivot gauges open them up with broaches. So you use both worlds. The advantage is being able to tightly friction fit material in the plate instead of time taken to turn a bushing to fit plus make starter hole.

An additional note is some use cylindrical shaped rods from things like pivot gauges or aka plugs go-no go, to open holes, creating taperless holes. A point or cutting edge is formed and performs more like a smoothing broach but perfectly cylindrical, like hybrid. The key here is precise diameter.
 
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Twoflower

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I think your terminology is in error. Nobody would use a needle file ever as they are generally way too big for the job.
There are a decent number of threads on the forums regarding needle files for the exact purpose I'm asking about, which is making a worn pivot hole symmetrical. Bangster's hand bushing guide supports this as well. I'm still green to hand bushing, but I'm rather confused to read what you've just said based on months of scouring the forums.

I do sincerely thank you for the rest of the information in your reply, but I'm aware of the function of those tools and the info unfortunately doesn't address the topic of my post. Again, thanks for taking the time to reply.
 

RJSoftware

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Needle files , even the smallest, are larger than most all bushings. Even winding arbors arnt that large. Most needle files are at least 3 to 4 inches long and at least 1/16 to 1/8 wide at thick end.

A needle file is a crude way of restoring bushing center. I suppose on larger holes for main wheel arbors, but that cant apply in general as 99% of the rest of bushings are much smaller.

The issue with broaches is walking hole back to center. I always prefer to use KWM reamer as was explained to make center. To walk a broach simply press perpendicular with fingers on both sides of plate, encouraging the cutting action in desired direction. A small amount pulled out to reduce diameter. Simply put pressing to force broach to only cut one side of hole while turning.

The larger KWM size reamer is not #3.

Also, there is usually significantly more plate material, usually, at winding arbor. Sometimes I can get away with peening hole closed slightly, then open to snug fit with larger broach. This works because of extra thickness of some plates at winding arbor.

Another issue is usng, obtaining bushing wire. I don't think there is a standardization of sizes as compared to K WM.

You could simply plug holes after rounding with file but then you got to drill starter holes that you can then broach.

Or it may be that I have neer been privy to any genuinely small needle files. I know bushing wire is hollow in cente arand comes with variety of od an id.
 
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Twoflower

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As I said in my first post, one of the problem bushings on the movement I'm working on is for a 3 mm pivot on a winding arbor. Literally the last two words in the post are "large pivot". I'm quite confident that I can find a needle file of the appropriate size for this hole.

I wanted to focus on community opinions regarding filing vs. broaching in my given scenario. If there are any more thoughts about that specifically, I'd love to read them.
 

RJSoftware

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filing, broaching and reaming. 3 different things.
My vote = reaming for OD of bushing, broaching ID.

But if KWM had exact bushing I needed withcorrect ID I'd skip broaching ID

Reaming and filing is to get kwm bushing or bushing wire into plate.

Broaching or hybrid mentioned previous, is remake bushing hole.

Smoothing broach is different. It is a form of burnishing, pivots are als burnished. Burnshing smoothes and hardens surface. Point of this is to show how terms are mixed up in this trade.
 
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bruce linde

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wait a second... them's some pretty absolute statements, and i think they're incorrect. i think the following terminology is more accurate.

needle files are by definition very small files. there are needle files of all sizes, but i use the round ones from generic timesavers needle file sets to even up the wear in pivot holes before bushing... UNLESS they require something smaller... in which case i use higher quality smaller needle files, also called 'escapement' files. this set, for example, is wonderful, and cost a lot less than swiss vallorbe files... and i have not yet encountered a pivot hole too small for the needle point on the round file in this/my set!


now maybe we're being to broad in referring to all kinds of small files as needle files, but it seems to be across the (message) board. :cool:

also, in the clock world you have cutting broaches and smoothing broaches... as well as regular ones. regular broaches are for running straight through a hole to round it or make it square. you can read more about broaching here: What Is a Broaching Tool? | Types of Broaches | Miller Broach ... note that regular broaches are classed as 'push' broaches and 'pull' broaches. here's some great info on broaches:


the reason you wouldn't use ANY broach for the problem/issue being discussed is because you need to... wait for it... 'file' :) away a small bit of the pivot hole to mirror wear on the opposite side of the hole. a small needle file is EXACTLY what you want to use... not a cutting or reaming broach. you want magnification, and a delicate/small little needle file... unless you're using KWM or other set size reamers.

if you go that route, you can use a hand-held reamer holder, or an intermediate device of some kind that help keep the ream perpendicular to the plate, or a full-on bushing machine already equipped to do so by design.

the OP (original poster) asked about using a cutting broach or a needle file. in my (admittedly limited) experience, cutting broaches tend to be five-sided. you would have to carefully twist a multi-sided cutting broach back and forth while pressing it against the sides of a pivot hole to try and accomplish the task in question, and i just don't see how you could do so easily. a precision needle file is designed for the task, where a multi-sided cutting broach is designed to self-center in a hole and cut evenly... .which means the pivot hole needs the wear mirrored 180 degrees opposite using a needle file... at which point you could then (cutting) broach by hand.

again, step one is: insure whatever you do will preserve original center and then use broaches or reamers to make the hole the right diameter.
 

murphyfields

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First off, is Twoflower a reference to Pratchett's Discworld?

I have to admit that I was really confused by terminology when I started reading this. To me, this

1606751989082.png

was a reamer, this

1606752287519.png

was a broach (which I just learned is actually spelled brooch...who knew)

and a file was a piece of metal with an abrasive surface, sometimes flat, sometimes cylindrical, sometimes tapered, sometimes curved.

Now I have learned that reamers, which I thought were always tapered, are used to make nice circular holed with straight sides, women rarely wear broaches.

Then I learned about these diamond reamers which are actually closer to my idea of a file

10-Piece Diamond Reamer Set

Once I wrapped my head around the fact that there are some generally used terms, but there are also other common uses for the terms, things started to make sense for me.

As I now understand it, that hand tool approach is to file the oval hole untile it is centered on the original hole, broach it until it is round, and then either continue to broach until it is the right size, or ream it to the proper size.
 

Elliott Wolin

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Although the OP asked about bushing by hand, for completeness I'll mention that with a good drill press (little to no runout, less than say a few thousandths) you can use a centering point to center the quill on the original pivot hole, clamp the plate, then use a very rigid center drill to create a circular hole, then ream to size (using the drill press if it can go down to a few hundred RPM, or by disengaging the drive mechanism and rotating the quill by hand with the reamer in the chuck).

I understand some experts skip the centering point, or center drill, or even clamping, but I'm scared to do that.

Note: the runout is small enough if the bushing fits tightly in the reamed hole. You can check your drill press by reaming a hole in a clamped plate and testing the fit of the bushing. Runout will cause the hole to be oversized and the bushing will be loose. Of course, you could always use Loctite, but it's better to have a nice, tight fit. I would test a couple of reamer sizes before regularly using a drill press.
 

RJSoftware

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Ah, ok for larger stuff, but I'll pass for the smalls.

I got reasonably small pivot file set, one I even ground away part of tip so to file flats on clock hand bushings that I turn. After I drill tiny hole equaling distance between parallel sides of square arbor, I have to reach inside collet and file 4 flats. It works but it's crude.

If I didn't have my KWM reamer set I would rather grind one or two flat s on a smoothing broach so as it cut, it can be walked.

What I have been trying to convey is the approach gets more difficult, the smaller we get. I just cant see how files would work well on for example French clock.

Don't get me wrong I know they are good for cutting teeth or making parts.

I'll just stick with KWM reamer and bushings. As to drill press, just another unnecessary step and usually results in slop fit. My understanding is it requires what is called "sensitive drills".
 
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RJSoftware

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I am curious if any of you have small enough needle files to round up a french clock bushing that had worn oval and if you used bushing wire to repair it?

I am curious if all this time I have missed out on better type of needle file.
 

bruce linde

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i don't do a lot of french movements, but here's a photo of my escapement file in a .8mm hole. the tip of the file is .40mm

needle.jpg
 

D.th.munroe

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I've used broaches to center holes.
To walk a broach simply press perpendicular with fingers on both sides of plate, encouraging the cutting action in desired direction. A small amount pulled out to reduce diameter. Simply put pressing to force broach to only cut one side of hole while turning.
Basically just like that.
Dan
 

bruce linde

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just curious... why would you use broach for this as opposed to a needle file... maybe something about cutting sideways?

and... do you pick different size broaches, i.e., one that would cut out what you want cut out as efficiently as possible?
 
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D.th.munroe

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For me it was just trying different methods from books or articles, and had not heard of the needle file method for a year or so before I came on this board in 00-01, Then later maybe in John Plewes book?
And yes I used different sizes to fit the holes.

Chapter 3 in Penman's Clock Repairers Handbook shows the use of broaches with a guide clamped on the worn side. (I don't agree with scribing marks on the plate though,except where it will be removed)
I think it was Dave LaBounty who somewhere described something like the method RJSoftware posted above.
Oddly DeCarle doesn't mention it at all.
Dan
 

bangster

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Have you looked at the pictures in the Bushing By Hand article to see the difference between cutting broaches and bushing reamers?

Trying to make a lopsided hole round with either a broach or a reamer is a Fool's Errand in my opinion.
You will never preserve the original center by nibbling one side except by pure luck. Because there will
be nothing to guide you on how much to nibble. Filing an equal lobe on the other side of the hole gives
you a guide.
 

D.th.munroe

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Most of the methods I read and learned back then, was to find the original hole then set up a preacher and scribe a circle with a compass type tool (I'm sure I saw someone made one on here) a bit larger than the wear (this is where Penman says to scribe an x across where the original center was) and that was the guide for the broach, check with the preacher and then use then reamer and check again.
Dan
 

shutterbug

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If your plate is clamped securely in the hole centered position, and you nibble the hole slowly with a reamer mounted in a good drill press or a bushing tool, it will eventually cut a round hole on center accurately. In my humble opinion, filing depends on your eye and is not going to be as accurate, especially on smaller holes.
 

Old Rivers

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Hello, all...

I'm about to start my first bushing job on a Hermle grandfather clock movement with a couple of problem areas that need rebushing. I've spent lots of time over the past few months reading everything I can on this forum about hand bushing, watching videos, etc. I've read Bangster's excellent post on hand bushing.

The general opinion seems to be divided between making a worn pivot hole symmetrical with a cutting broach, and making it symmetrical with a needle file. I have a spare Urgos grandfather clock movement I purchased cheaply from Ebay that I intend to practice hand bushing on, and I'm happy to try out both the needle file and cutting broach method (broach approach?).

The winding arbor pivot holes on this movement are particularly bad, one with about 0.7 - 0.8 mm of wear from a 3 mm pivot. I'm thinking that whichever method I end up trying, I need to find either a needle file or cutting broach with a 3 mm diameter somewhere on it for making the pivot symmetrical before broaching/reaming to size. My current plan is to find the 3mm point on the broach/file with my calipers, and mark it so I don't end up going larger than 3 mm when removing material on the unworn side of the hole.

What do you all think about needle file vs. broach, especially for wear from such a large pivot?
Suggested reading:


See Post #5 by Jerry Kieffer.
This is one of the best recommendations for "Bushing on a budget" I have ever seen.

Bill
 

RJSoftware

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If your plate is clamped securely in the hole centered position, and you nibble the hole slowly with a reamer mounted in a good drill press or a bushing tool, it will eventually cut a round hole on center accurately. In my humble opinion, filing depends on your eye and is not going to be as accurate, especially on smaller holes.
Most definitely..!
The importance of being precise shows up in the gear's mesh.

The mesh is so critical. It's not just teeth engage other gears. There is a percentage of engagement and a percentage of relief space. I think the rule (dont quote me) is 90% engagement and 10% space. Gears just cant be butted up in full engagement as the space is needed to facilitate sliding action. Likewise, they should be engaged enough. Too little promotes early teeth wear.

So considering this, finding the sweet spot when depthing gears using depthing tool. For those unfamiliar, the deapthing tool holds two gears apart and by adjusting a finely threaded screw the gears are gradually brought together. The gear mesh is tested for smoothness of action and examined by loupe for relief space between gear tip and bottoms.

The satisfactory result of the depthing tool is transferred to the clock plate by the tools pin points. Coordinates can be obtained by depthing for and aft gear mesh. A tiny circular scratch from each creates an X marks the spot.

To nail this point home, these measures are soo small they are measured by perception. There is no mechanical way of producing the exact ratio for repair people. So mesh that get lost requiring depthing tool restoration are restored by best guess perception, feel and limitted visual. Also understand, clock depthing tool is exceedingly rare but you can make one. It's on my to do list. Most depthing tools online are for watches. The tool is rarely used. Most of us count on hit or miss.

That is why it is critical to produce the finest X that one can make using the remnant un-ovaled portion of the original bushing hole. To maintain the manufactured exact bushing center. I prefer to use sharp razor to make the slightest scratch. I am careful to avoid even blade thickness offset. It is that critical.

I never believe someone cant do something. There are many ways to skin a cat. I must admit I was wrong about needle files. Somehoe most mine are larger. But still, when I can lean of mechanical efficiency vs pure skill, I give myself a break and lean on the tool side.

The selling point of the KWM is it's cheap. I might be inclined to use a KWM reamer in drill press. Never done it. I understand just to turn bit in drill press by hand. To first touch tip to the remnant and rely on drill press guidence. I think going back and forth full circle should avoid runout. This would probably be better than eating out unworn side by hand while guessing effort to maintain center of visual X.

But reality there is mine is probably wrong size. It's an awkward bulky thing and I can feel the runout click when I manhandle the headchuck..

So, oh well. Meantime, I walk the #3 KWM reamer best I can to the center of my finest scratched X that I can.
 
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bangster

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If (1)your plate is clamped securely (2) in the hole centered position, and (3) you nibble the hole slowly with a reamer (4) mounted in a good drill press or a bushing tool, it will eventually cut a round hole on center accurately.

That's a mighty big "if", Shutt. Better to say it MAY cut a round hole accurately (Lord willin). :emoji_slight_smile::emoji_scream:
Making sure all 4 conditions are satisfied is no small potatoes.
 

shutterbug

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It sounds harder than it is, bangster :) A centering point finds the center position. Hold it there while you clamp the plate securely in position. Make sure the tool has very little runout, or the results will be disappointing. Turning the reamer by hand rather than under power gives a better feel for how it's doing. Too much pressure will force the plate to move, not the good part of the hole (which is what you are cutting for the first few turns).
 

Elliott Wolin

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Turning the reamer by hand rather than under power gives a better feel for how it's doing. Too much pressure will force the plate to move, not the good part of the hole (which is what you are cutting for the first few turns).
This is a reason to use a center drill before the reamer. You just need the center drill to round out the hole and remove any eccentricity. With this done reaming is simple, there's no reason for it to wander (assuming negligible runout). Note that a regular twist drill bit won't work, they are not stiff enough and will wander around.

Machinist's center drills, note how rigid and robust they are, they are designed not to wander:

center drill.jpg
 

shutterbug

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I've never used one for that purpose, so can't comment on their effectiveness. They are great for starting pivot holes though ;)
 

Kevin W.

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Thats funny. Been using a needle file for quite a while, Thats how i learned, and sometimes i still have to go back to the needle file too RJ.
 

D.th.munroe

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Elliott that is what Penman uses in his book for this.
And I was mistaken I just watched Dave LaBounty just used a hand reamer not a broach.
 

RJSoftware

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I dont see any reason to go back to file if you have right sized reamer. We are still talking bushings? The KWM reamers are tapered to a point, so its just too easy.
 

Kevin W.

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Cutting broaches and files, thats how i started.
 

kinsler33

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The Timesavers diamond reamers shown in post 16 make splendid, fast-cutting needle files. You can hold them in your fingers, in a pin vise, or you can keep one chucked in one of these:Rotary Tool Kit, 80 Pc.. It looks disturbingly cheap, so I bought several and still can't kill my first one three years later. Be careful, for the diamonds cut brass very quickly, but the points will fit through every hole I've encountered.

For anything that feels critical, use these files (or any others) by hand. Once a hole is symmetrical you can ream it out with a drill press set at a slowish speed. The reamers can be chucked directly into the drill press, whose major function is to hold the reamer perpendicular to the plate.

M Kinsler
 

hickorydickorydoc

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Bangster and others in the needle file camp are correct, in my opinion. A drill bit, a cutting broach, and yes even a reamer, KWM or Bergeon, will tend to move toward the middle of the hole you're pushing them into, even if you think there's no run-out. With an egg-shaped hole, it's going to walk away from the original pivot center. The smaller reamers can actually catch in an eccentric hole and twist and/or break - don't ask me how I found out.
I check the train for wear by moving the wheels back and forth by hand, marking with a Sharpie the worn side of the bad holes. Then use a needle file to take brass off the good side until you have a round-ish hole that should maintain the original pivot center. Then use reamer for your bushing. Broaches are only for opening up bushings to the correct diameter
 

shutterbug

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The point you guys seem to be missing here is that the plates are clamped into position. They won't move during the 'nibbling' as the reamer removes material from the unworn side of the pivot hole. Only when the exact same amount of material has been removed, will the reamer start touching the worn side of the hole. There's no guess work, no "it looks pretty close", ... none of that. If it's centered to start and reasonable effort is made to make small cuts so the plates will not be forced out of position, it will cut a perfectly sized hole right where the original center was when the clock was new.
 

Elliott Wolin

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To borrow a meme from backpacking, where HYOH or "Hike Your Own Hike" means don't judge other people's way of doing things on the trail if they know what they are doing and it works for them, I submit we embrace BYOB or "Bush Your Own Bush". If it works for them and they know what they are doing, so be it!
 

D.th.munroe

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I have to agree with Elliott. There is many different ways to do things.
Some people frown upon using a broach for final finishing of the pivot hole as well so is this wrong? I still do it.
Using broaches this way doesn't dull them, it's not anymore working pressure than using it normally, unless your giving it way to much sideways pressure, or have cheap broaches, your just guiding it in the correct direction to center the hole. I'm not saying I do this anymore, or suggesting it's the correct way, a file works as well, but from experience it can be done successfully.
I am finding it disheartening that more and more of what I learned early on from respected professionals (BHI accredited) and from people who went to good horological schools are opined as incorrect, or impossible to do with success.
Dan