Reel Repair by Alan Tani

Thanks for the great post,and references.  Ive always had fits trying to tap tiny holes in sst, and even mild steel.  Your pointers are sure to help.  Thanks for making this a great forum as we all learn by doing, and seeing

 Something that I have found very useful for hand tapping threads is a little hand tapping block about 1" thick & however long & wide you want to make it. These are super easy to make from a scrap of aluminum, pick the flattest side of the material you can find, put it in your vise or whatever you have but make damn sure that the top surface is square to your machine or drill press spindle. You want to drill that hole a square as possible to this surface.Next you want to measure the major or biggest diameter of whatever tap you are going to use, drill your hole all the way thru, this allows your chip to fall out the bottom, drill about.003 to .005 bigger than your largest diameter on your tap, you want your tap to slide thru this block nice & easy without having a lot of slop. Deburr the hole top & bottom. Now to use this block simply put the flat side down ( the side you drilled the hole from), over the hole you intend to tap & gently start your tap. This pretty much insures you a good straight square threaded hole. I can't tell how many hundreds of holes I've tapped this way, I can't tell how many times these simple little blocks have saved my #### on jobs. How do I know about little things like this, well I've been doing Manual Mill & Lathe work building & machining small to medium sized Prototype & R & D parts for over 20 years in job shops & companies that had small machine shops in them, some of them we where doing things & parts that the CNC machine could not do or in a lot of cases we ( the guys in the Proto dept would not tell them how to do), I know it 's rotten to do this but it's was job security for us, like very precise angle holes drilled thru some very expensive parts. It was fun for the most part but sometimes these little complex close tolerance parts could & would get on your nerves. I'm retired from the industry now but I still have my tools. Ed

There's a whole lot of experience that went into the writing of this thread.  Had to learn it all the hard (expensive) way.

Albert, I wish Adam (Threese7ens) and yourself would share would share more of your experiences with us.
-steve

What would you like to know?

Quote from: oc1 on May 21, 2021, 07:32:57 PM
Albert, I wish Adam (Threese7ens) and yourself would share would share more of your experiences with us.
-steve

Quote from: Three se7ens on April 27, 2016, 03:25:54 AMI tend to take this stuff for granted, because its part of what I do every day.  But its far from common knowledge, and a few keys make the difference between broken taps and curse words and a job going smoothly.

Unless you have a machine shop with a particular need to have a tap of every size on hand, or you just like spending absurd amounts of money on tools you won't use, don't buy tap sets or full drill sets.  Quality is of the utmost importance when tapping holes, especially in difficult materials like stainless steel.  Quality taps are expensive, and worth every penny.  Just buy the sizes you need, and the corresponding drills. 

Looking up the recommended tap drill size is usually the first mistake.  Unless it specifies otherwise, the chart is for 75% thread engagement.  This is good for aluminum.  If you try it on stainless, you will break taps all day long.  Steel and stainless steel (and most hard materials) only require about 60% thread engagement for the tapped hole to be stronger than the fastener.  At my work, 60-65% engagement is a standard for stainless.  Anything more is practically guaranteed to break taps in a CNC machine.  I use this a lot for picking the correct drill size:

http://theoreticalmachinist.com/TapDrillSizeCalculators 

Once you know the size drill to use, you have choices in drill bits.  Id recommend at least HSS, but I prefer cobalt for stainless.  Carbon steel should be avoided, as its very easy to overheat and kill the temper.  If that happens, it will never hold an edge again.  HSS and stainless can tolerate far more heat without losing their temper.

I also prefer to use screw machine length drills, unless I need the extra depth of a standard length drill bit.  The shorter screw machine length bits wander less and are stronger.  Eg. http://www.mcmaster.com/#standard-drill-bits/=125okp2

Using a center punch or center drill is a good idea to keep the drill from wandering as it starts in the hole.  Its more important with standard length drill bits, the screw machine length bits tend to tolerate starting a hole a little better. 

Now onto taps.  First off, stick to the big names.  Dont be tempted by that $20 tap set at harbor freight.  Id even recommend avoiding Irwin unless you are in a pinch.  Greenfield, YG1, and widia are very good, and OSG and Emuge are better.  Just like the drill bits, you will want to avoid carbon steel taps.  HSS and variations of it are the way to go. 

There are 3 different kinds of lead.  Taper taps have a lead in of 5-7 threads and are good for through holes in thinner stuff, and for starting tapped holes.  Plug taps have 3-5 threads of lead, and are your general purpose tap.  Bottoming taps are designed to cut full threads as close to the bottom of the hole as possible.  They are difficult to start, so when they are needed, its recommended to start with a taper of plug tap before finishing with the bottoming tap. 

In addition, you have 2 more options.  Straight flute taps are generally considered hand taps.  For best results, these need to be backed off regularly through the tapping process to break the chip, and keep it from jamming up in the flutes. 

Next you have spiral point, or gun taps.  These have straight flutes, but have an angle ground into the start.  This angle causes the chips to curl up ahead of the tap.  These are best for through holes, as the chips will pile up in the bottom of blind holes.  But they perform better than straight flute taps, and do not need to be backed off like straight flute taps. 

http://www.mcmaster.com/#standard-taps/=125osvz  The taps for through hole are spiral point, while the closed end hole taps are spiral flute.

Spiral flute taps should be considered special purpose taps.  They are weaker than straight flute and spiral point taps, but they do pull the chips out the top of the hole.  Best for finishing blind holes, but must be used with care when tapping by hand.  Pretty much an industry standard for CNC machines though.

One last thing:  use cutting oil when tapping holes!  It makes a big difference.  Lots of good choices out there, I like Tap-Magic, Anchorlube, and especially Union Butterfield tapping oil. 

Mcmaster Carr has a mind boggling selection of taps and drills, but they do have pretty good descriptions of their uses.  And everything they sell is good quality.  Most is name brand, but they dont typically show the brand on their website. 

I hope this helps, and if anyone has any questions, feel free to ask. 

I know this is an old post, but wow it is a good one. These days, a lot of guys are making their own frame posts or bars, and other parts that need threaded holes to upgrade or repair their reels. I am something of a hobby machinist, and one thing I would add is that it is utterly essential to have a good tight drill press and chuck, for drilling, and to hold the tap, by whatever means, absolutely coaxially to the hole. In other words, if the hole is straight in 90°, then the tap needs to be held at exactly that angle, in both the x and y axis. Usually, unless you have crazy skill born of great experience or just a superb aptitude for handling tools, that means some sort of jig to keep your alignment perfect and consistent, or else your mill or drill press holding the tap. It is really easy to lean the tap a degree or two, which can cause difficult tapping.

I should add that when you use your mill or drill press to keep a tap aligned, you don't use the motor to turn the machine's spindle, except maybe in soft metal like aluminum or copper. Instead, you lower the chuck with the quill feed, the uppy-downy handle thingamabob, while you turn the chuck by hand. A slight down pressure ensures a good start, and once you are several threads in, the tap will pull itself. Back it out a quarter turn as needed, to break chips. There are specialized taps that are made for machine tapping and break their own chips, but you won't find them at Tractor Supply, no. If you use your drill press for tapping a hole and happen to back the tap all the way out before you have finished threading the hole, then to continue, don't use the drill press to resume threading. Secure the tap in a tap wrench and start it by hand. By now the tap should hold itself straight, and if you try to re-start with the drill press, you could get off to a bad start, cutting new thread not exactly aligned with the old.

I use Tap Magic, usually, though I have resorted to Marvel Mystery Oil and other oils due to running out of the good stuff. Any oil is better than no oil, but a proper thread cutting oil is gonna be best, hands down.

Centerpunching is essential, especially with home shop quality drill presses, or worse, hand drilling. You don't want your drill doing a waltz all around your intended hole location. I centerpunch, and then use a center drill of appropriate size, before the money shot. My use of center drills on the lathe sold me on them and now I use them for starting most any hole, especially bigger ones.

Another trick is to always clamp the part on the work table of your drill press or vertical mill. Clamp it, and check the angle of the surface being drilled so the hole goes in true and the part does not wander while drilling, which can easily happen with very thin and flexible drills or very long ones. Yeah, short drills are better when you don't need a deep hole, but sometimes you have to use ordinary Home Depot or Harbor Fright standard length drills or else wait on the amazon or McMaster shipment to arrive. Choking up as much as possible will help to make a truer hole. It won't hurt a thing for part of the fluted length to be up inside the chuck. Also, it is usually best to "peck drill" rather than drill the hole in one go. Drill a bit, then pull it out and knock the chips off the bit. Drill a little more, pull it back out. Especially for a through hole, you get a cleaner finish when you peck drill and if you ignore advice to always clamp your part when drilling, it is less likely to fling it round and round and break all the knuckles of the hand that shouldn't be holding the part in the first place.

Most drill presses are multi speed. It might not be obvvious that it is. Sometimes it is a matter of opening the machine up (unplugged!) and moving the belt from one pair of pulley sheaves to another. Lower speed, higher torque. Within reason, lower speed rather than higher speed will make better hole. There are optimum feeds and speeds for all metals but with home hobby drill presses, the pulley pair that gives you the lowest speed will make nicer hole in steel.

A slight chamfer at the entrance of the hole will make starting the tap easier, especially for a plug taper or bottom taper tap. And it will make the bolt head or mating part fit better against it, too. Chamfer can be done with purpose made bits or tools, but you can also use v shaped countersink bits or even HSS or carbide vee groove router bits, or center drill bits. It doesn't take much, but you do want an easy entry and also to get rid of any burr, especially on the breakthrough side of a through hole. A benefit of secure clamping is you can simply remove the drill bit and put a chamfering bit in the chuck, and it is going right where the drilling bit went, exactly, assuming your chuck is not a POS. I have even used very large twist drills to deburr a small hole prior to threading. It's not elegant but it works, especially if you have a fine feed control.

Sometimes you have to drill a hole where the entry is NOT at right angles to the surface of the part being drilled. This probably won't come up often on reel modifications, except maybe drilling a hole in a domed sideplate for a knob adjusted mag brake. As appropriate, you can use an angled block clamped to the part, so that the entry is perpendicular to the block, and then you drill through the block and into the part. For thin parts you might also want a block on the back side, so the breakthrough doesn't make a big mess of things. Another way to make an angled hole is to start the hole with an end mill. Now, an end mill is hardened, and so is your jacobs chuck, the usual type chuck for hand drills and drill presses. Hardened tool in hardened chuck is considered not so good. The chuck won't have a good grip on the end mill. You can get around this by making a bushing out of copper pipe, slit up the side and wrapped around but not overlapped, around the shank. Then the chuck will grip it tightly, if not absolutely precisely. An end mill can do a much better job of starting an angled hole than a twist drill, the common sort of drill bit. Once the hole is started, switch to the twist drill to make hole. You can use an oversize mill if you don't have exactly the same size as your drill bit. When cross-drilling through a round part such as a rod or shaft, file or mill a small flat, before centerpunching and drilling.

There are comprehensive tables and online calculators for tap drill sizes. Often there are tables for 75% engagement and 50% engagement, and as the OP says, you don't want too much engagement in steel if you don't want to break off taps in the hole. In steel you only want to go 75% when the hole is so shallow that there are only a few threads holding the screw in the part. The rest of the time, in steel, especially SS, I only shoot for 50% threads. This means a slightly bigger drill size than for the 75% threads. I think the tables for only 75% threads are so common because so many home hobbyists work with softer metals like aluminum and brass, which can be cut and machined manually and without precision equipment. You can even mill brass and aluminum on a table router. So, soft metals are more popular with the general hobby community and don't reallly mess with steel all that much. But a lot of reel upgrades involve steel because of its increased rigidity and hardness compared to brass or aluminum or copper or bronze. So be sure, when drilling a hole to be tapped in steel, that you are using the correct size bit and not the one that some guy making an aluminum fidget spinner on youtube says use. I won't bore you with the formulas because I never remember them and I would have to look them up in "Machinery's Handbook", a reference that you really should get if you do much metal work. Yes that is the actual name of the book. It was first published by a magazine called, "Machinery" and it was their handbook.It is not called as some newbies call it, "Machinist's Handbook". Most of the stuff in there, as a casual not quite a real machinist, you will never use, but ANYTHING you ever need to know about metalworking apart from maybe heat treatment of modern "super-steel" alloys, is in there. All the standards and specs for everything. Want to make a gear by hand? You need that book. Want to re-sharpen your expensive drill bits yourself without a "Drill Doctor"? You need that book. Want to make a special jigsaw blade to go into a very tight spot? You need this book. Need to make a keyway in a shaft for preventing a gear or bearing or cam from spinning? You need that book. Make your own lathe? Mini-mill? Ditto. Want to operate a pop rivet gun? Just wing it and it will come to you. But anything remotely technical, a good reference book like this will put you solidly on the right track. As a bonus, if you read it for 20 minutes you will fall into a dead sleep, so good insomnia cure.

Very well done Growley.  Adam isn't around any more, but he taught all of us hobby/neophytes important stuff.  You have just done the same. 

Has anyone put a list together of the most common taps to have on hand?