Need to get drill bits for tapping

[YotaBota]

A while ago I ordered a set of stubby bits 1/4 to 1/2 for coarse and fine thread thru KBC. Just ordered their black coated bits and they have worked out well, attached is the list and pn's. I ordered 3 sets, two sets for other members and we split the shipping. And as I don't 3D print this is my version of bit storage, simple and cheap, kinda like me. lol

 

[Dan Dubeau]

Many of the old timers I worked with over the years had their versions of that always out and on their bench. Only it contained a tap, tap drill, clearance drill, and counterbore for every screw size from 4-40 up to 3/8"-16. I always meant to make one for myself, just never got around to it. I kept my frequently used stuff in a couple small utensil dividers sitting on top of my toolbox. One for reamers, one for taps, and one for counterbores. Drills in the index, although more frequently used tap drills just ended up being tossed into the tap bin usually. I had bags of spares.

A good rule of thumb to remember for sizing tap drills is simply nominal thread size minus the pitch. For metric this is easy as both #s are contained in the thread info M8x1.25 for example would simply be 8-1.25=6.75mm, who's closest inch (letter actually) equivalent is an "H", but 17/64's will work fine too. For inch threads, it's the same deal, except we need to find the actual pitch instead of the threads per inch (TPI). Take a 1/4"-20 for example. To find the pitch it's simply 1" divided by the tpi, which is 20. So 1/20=0.05" is the pitch, or distance between crests. To find the tap drill size it's just 0.25"-0.05"=0.2". Now it's like the price is right rules except reverse. Just find the closest drill size to that without going UNDER, which is a #7 @0.201". You can't go undersized on your tap hole, but you CAN go over a bit which will just lead to smaller thread engagement like Susquatch mentions. Sometimes helpfull in harder materials, where concern over breaking a tap might be an issue, and ultimate strength from the threaded connection isn't a high priority. Well, technically you CAN go under too, but typically only once, and you'll typically end up having a bad day......

Typically the only time I ever went oversize on hole diameter was in prehardened or tough toolsteels with smaller <1/4"-20 taps. Almost all other times was just to normal recommended predrill sizes. I only did that because I didn't need high strength from the thread, but most blocks I did that on have many thousands of dollars in labour and work done to them at that point, and snapping a 6-32 tap off in a hole because I used a #36 drill would have been a bonehead move....A #35, or 34 give a LOT more cushion for breakage without giving up a detrimental amount of thread engagement I'm not doing the math on how much.....I'll leave that to the engineers that love math.... I'm pretty sure theres a simple formula/way to calculate it, but I've never needed to go that far into the weeds for my needs......

 

[StevSmar]

If you’re looking for a nice workshop book that has lots of information, including what size drills to use for what size taps, I’d recommend:
https://www.engineersblackbook.com/

Spiral Bound, the pages are dirt and grime resistant.

If you get the imperial version, then it also includes most of the metric information also.

They have an equivalent fastener book too which is good.

They’re not the be all and end all. Think of them as the book you’ll reach for 95% of the time and then needs something more in depth for the remaining 5% of the time.

 

[Tecnico]

Following on @Susquatch ’s discussion, there are recommended thread development tables for various materials, THIS ONE is at Little Machine Shop’s site. They also have a metric version.

If I’m not mistaken I think it’s covered in Machineries Handbook.

D

 

[Warlock]

The idea being that very few people enjoy tapping manually.

How true.

You are using nuts and welding both sides of the connection. In this case, you probably don't even need a threaded hole at all!

I find it is a lot easier to tap the hole, spin a nut down tight and then weld. The nut gives better support as it widens the base of the stud, removes any slight titling of the stud and makes welding easier. In my present project using 3/16" steel plate and 1/4" studs the thickness of metal from the top of the nut to the bottom of 3/16" steel plate is 0.42" (~27/64.

You have managed to peak my curiosity! What in the world are you making anyhow?

The answer is going to be a bit long.

Keep in mind I'm old school and cheap old geezer to boot. My primary hobbies are industrial sewing machines and 3D design / printing. When I need or want a particular piece of equipment to do a particular task I look at the price of a new machine and then determine is it worth my time to build or buy. Most times what I want is not commercially available or only partially covers what I want it to do or is just so expensive or requires the sewing machine to be drilled, tapped or otherwise permanently modified. All my designs do not require permanent mods to the sewing machine as it would devalue the sewing machine when I sell it. Industrial sewing machines new range from $3000 to $1000 depending on if it is a brand name or a counterfeit (clone).

Over the last year or so I needed a leather clicker press for cutting leather patterns. According to my calculations for the die size I could possibly use I would need at least a 5 ton press. A manual clicker press with a too small plate size ( https://tandyleather.ca/products/ta...-Xc-G9l7RiS0k4iRp3cXW-X5bMyBkJlpiJk4ijm0gfLV2 ) was going to be about $2800, not happening. So I bought a inexpensive Princes Auto hydraulic press similar to this one ( https://www.princessauto.com/en/20-ton-hydraulic-bottle-jack-shop-press/product/PA0009193798 ) on sale for about $200. Then I did about 20 mods and I got what I needed and this year I will do a DIY electric over hydraulic mod. With all the mods so far I will be into it for about $300 a far cry from $2800.

The present project once again is leather related. I need / want a leather embosser similar to ( https://bunkhousetools.com/home/tutorials/original-hand-crank-embossing-machine/ ) for imprinting patterns in leather belts. The cheapest one I could find with taxes is about $1200 plus the cost of the embossing wheels which in brass range from $100 - $300 each. So me being me, I spent a little time designing my version, 3D designing / printing a prototype and now I'm turning it into functional metal version. When I'm finished it will have more functions and have cost me about $150. The patterns I can 3D print embossing wheels for less then $1 each.

Thread 'Organized my drill bits'
https://canadianhobbymetalworkers.com/threads/organized-my-drill-bits.14370/

Nicely done.

 

[Susquatch]

The answer is going to be a bit long.

Nice read. Thank you!

 

[Warlock]

there are recommended thread development tables for various materials, THIS ONE

Thank you got it bookmarked.

A good rule of thumb to remember for sizing tap drills is simply nominal thread size minus the pitch. For metric this is easy as both #s are contained in the thread info M8x1.25 for example would simply be 8-1.25=6.75mm, who's closest inch (letter actually) equivalent is an "H", but 17/64's will work fine too. For inch threads, it's the same deal, except we need to find the actual pitch instead of the threads per inch (TPI). Take a 1/4"-20 for example. To find the pitch it's simply 1" divided by the tpi, which is 20. So 1/20=0.05" is the pitch, or distance between crests. To find the tap drill size it's just 0.25"-0.05"=0.2". Now it's like the price is right rules except reverse. Just find the closest drill size to that without going UNDER, which is a #7 @0.201". You can't go undersized on your tap hole, but you CAN go over a bit which will just lead to smaller thread engagement like Susquatch mentions. Sometimes helpfull in harder materials, where concern over breaking a tap might be an issue, and ultimate strength from the threaded connection isn't a high priority. Well, technically you CAN go under too, but typically only once, and you'll typically end up having a bad day.....

Good info.

If you’re looking for a nice workshop book that has lots of information, including what size drills to use for what size taps, I’d recommend:

I'll keep this one in mind.

Nice read. Thank you!

Thank. Is anyone doing 5th axis milling???

 

[PeterT]

A manual clicker press

why do they call them 'clicker' press?

 

[johnnielsen]

why do they call them 'clicker' press?

The clicker press I am familiar with have 2 buttons on the ram, 1 for each hand to press to get a stroke cycle. This ensures the operator's hands are out of harms way.

 

[Warlock]

why do they call them 'clicker' press?

When you pull the lever with the leather and die installed as the die cuts through the leather it makes a "click" sound when it cuts through the leather and hits the HDPE baseplate.

The clicker press I am familiar with have 2 buttons on the ram, 1 for each hand to press to get a stroke cycle. This ensures the operator's hands are out of harms way.

Yes the electric over hydraulic ones need build in safety features as they are powerful and fast enough to chop off your digits in a blink. You see them mostly in commercial environments where speed means dollars. A small 10 ton will cost about $12,000 and weight in around the 1200 lb mark. Sometimes a hobbyist will have an older well abused one that they picked up for cheap at auction.