Just want to check before I buy:
A #40 drill (2.489 mm) will form holes that can be used for a M3 tap (2.5 mm)?
Similarly, is a #30 drill (3.264 mm) good for a M4 tap (3.3 mm)?
I am lost with all the metric, Imperial, and American measurement units 😱.
Thank you very much in advance for any comments or advices.
Regards,
A #40 drill (2.489 mm) will form holes that can be used for a M3 tap (2.5 mm)?
Similarly, is a #30 drill (3.264 mm) good for a M4 tap (3.3 mm)?
I am lost with all the metric, Imperial, and American measurement units 😱.
Thank you very much in advance for any comments or advices.
Regards,
check here: Tap Drill Chart
Don't worry too much about the 50% and the 75% thread. This is used in the most critical applications. Use the 75% thread chart for your purpose and you will be fine.
About tapping, NEVER, EVER tap 'dry' (no lubricant), especially when you are new to this.
I found that in many metals, dipping the tap in 'Crisco' (animal fat used in pastry) will work very well. In a pinch, use any grease or motor oil you can find but if you plan on doing this often, get a proper cutting and tapping fluid such as target, rocoll etc...
Kerosene works quite well in aluminium.
Now to drill and tap a hole...
Use the best quality drill bit and tap you can afford. Go with American, European or Japanese tool brands. Yes they are more expensive, yes they work better and last forever in a hobbyist shop!
Make sure the part you want to drill and tap is well supported so that it can not move. You will need both of your hands later. You can not hold the workpiece and the drill at the same time and hope to make a good job.
Use a center punch to mark where you want the hole, I use a spring loaded punch, but in soft metal a steel punch and a small hammer is perfect. Make a 'spot' with a center drill from the punch mark, these are short and stubby drill and will not wander about when you try to start the hole.
Then drill the hole with the proper size drill. Make sure you drill true and straight, hold the drill with both hand and hold your breath when starting.
Once you are through with the drill, pull it back while keeping the drill turning. This will insure a clean hole. Do not wander the drill from left to right or front to rear as I see many people do. This may brake the bit and will make the hole larger!
In soft metal, it is always a good idea to make a shallow countersink using a larger drill bit by hand. This step is not crucial but it makes for a neater hole and also help the tap engage more easily. It will remove the burr from the edges, I don't always do it, depending how I feel on the moment! 🙂
I found over the years that the best way to tap is using a cordless drill. Remove the handle on the tap chuck and install the chuck in the drill. Set the torque clutch to a somewhat low value for small taps, and higher for larger tap. 2,5mm is about the size of a 4-40 so use a low value of clutch setting. After a couple of holes you will get the feel for it.
In many machining manual the ritual is to turn the tap one turn, then back off 1/3 turn, then turn one more turn, back off etc..
With a drill, dunk the tap in the cutting fluid, set the drill at low speed and go!
The tapping will start easy, then become a bit stiffer, this is when the clutch will go rat-tat-tat-tat.... Flip the direction button and get the tap back off a few turn, then flip the switch direction again and start.... the tap will go a bit further before the clutch engages again... do this a couple of time and you will end up with a very neatly tapped hole 🙂 and its very fast! 😎
I do a lot of tapping with #2 and #4 screws and I practically never break a tap with this method! 😎
The minimum thickness for tapping metal sheets is to have at least 2 full threads. But I found that in soft metal such as aluminium, this will not hold very well after you screw and unscrew a few times. In this case it is better to use sheet metal screws.
To recapitulate:
- Mark the center
- spot with a spot drill
- drill the hole the proper size (see chart)
- deburr the hole by hand with a larger drill if you feel so inclined
- never use a tap without lubricant
- use a cordless drill at the lower speed to tap and select a clutch value in proportion to the tap size
- have fun! 😛
Luc
PS: i
Don't worry too much about the 50% and the 75% thread. This is used in the most critical applications. Use the 75% thread chart for your purpose and you will be fine.
About tapping, NEVER, EVER tap 'dry' (no lubricant), especially when you are new to this.
I found that in many metals, dipping the tap in 'Crisco' (animal fat used in pastry) will work very well. In a pinch, use any grease or motor oil you can find but if you plan on doing this often, get a proper cutting and tapping fluid such as target, rocoll etc...
Kerosene works quite well in aluminium.
Now to drill and tap a hole...
Use the best quality drill bit and tap you can afford. Go with American, European or Japanese tool brands. Yes they are more expensive, yes they work better and last forever in a hobbyist shop!
Make sure the part you want to drill and tap is well supported so that it can not move. You will need both of your hands later. You can not hold the workpiece and the drill at the same time and hope to make a good job.
Use a center punch to mark where you want the hole, I use a spring loaded punch, but in soft metal a steel punch and a small hammer is perfect. Make a 'spot' with a center drill from the punch mark, these are short and stubby drill and will not wander about when you try to start the hole.
Then drill the hole with the proper size drill. Make sure you drill true and straight, hold the drill with both hand and hold your breath when starting.
Once you are through with the drill, pull it back while keeping the drill turning. This will insure a clean hole. Do not wander the drill from left to right or front to rear as I see many people do. This may brake the bit and will make the hole larger!
In soft metal, it is always a good idea to make a shallow countersink using a larger drill bit by hand. This step is not crucial but it makes for a neater hole and also help the tap engage more easily. It will remove the burr from the edges, I don't always do it, depending how I feel on the moment! 🙂
I found over the years that the best way to tap is using a cordless drill. Remove the handle on the tap chuck and install the chuck in the drill. Set the torque clutch to a somewhat low value for small taps, and higher for larger tap. 2,5mm is about the size of a 4-40 so use a low value of clutch setting. After a couple of holes you will get the feel for it.
In many machining manual the ritual is to turn the tap one turn, then back off 1/3 turn, then turn one more turn, back off etc..
With a drill, dunk the tap in the cutting fluid, set the drill at low speed and go!
The tapping will start easy, then become a bit stiffer, this is when the clutch will go rat-tat-tat-tat.... Flip the direction button and get the tap back off a few turn, then flip the switch direction again and start.... the tap will go a bit further before the clutch engages again... do this a couple of time and you will end up with a very neatly tapped hole 🙂 and its very fast! 😎
I do a lot of tapping with #2 and #4 screws and I practically never break a tap with this method! 😎
The minimum thickness for tapping metal sheets is to have at least 2 full threads. But I found that in soft metal such as aluminium, this will not hold very well after you screw and unscrew a few times. In this case it is better to use sheet metal screws.
To recapitulate:
- Mark the center
- spot with a spot drill
- drill the hole the proper size (see chart)
- deburr the hole by hand with a larger drill if you feel so inclined
- never use a tap without lubricant
- use a cordless drill at the lower speed to tap and select a clutch value in proportion to the tap size
- have fun! 😛
Luc
PS: i
oops! 😱 I started a PS and got diverted....
I buy many of my tools here: ACCUSIZE INDUSTRIAL
I suggest you download their catalog here: ACCUSIZE INDUSTRIAL
Most of it is irrelevant and not needed but it will give you a good Idea of what is there.
Page30 gives the details on how to order...
Taps and taps set on page 20
They are Chinese and I don't think much of them. Get the best stuff, it will last you years!
I can not find the spot drill (center drill) I am talking about but get in touch with them thy have it. Get a #3 HSS (High Speed Steel) do not buy solid carbide cutting tools at this stage. They brake like glass if mishandled, and you will mishandle them using hand tools! 😛
I buy many of my tools here: ACCUSIZE INDUSTRIAL
I suggest you download their catalog here: ACCUSIZE INDUSTRIAL
Most of it is irrelevant and not needed but it will give you a good Idea of what is there.
Page30 gives the details on how to order...
Taps and taps set on page 20
They are Chinese and I don't think much of them. Get the best stuff, it will last you years!
I can not find the spot drill (center drill) I am talking about but get in touch with them thy have it. Get a #3 HSS (High Speed Steel) do not buy solid carbide cutting tools at this stage. They brake like glass if mishandled, and you will mishandle them using hand tools! 😛
There must be a web page someplace with a consolidated listing of English and Metric threads and appropriate tap drill sizes in both measurement systems.
I have two charts printed on card stock taped to my drill press - one for English and the other for metric. I think I got them many years ago at an industrial tool show. When I tap a metric hole I find the correct metric hole size, then get the nearest English drill by referring to the decimal equivalent size. A little cumbersome, but I've seldom had need for tapping metric holes.
The idea of using a cordless drill with a slip-clutch chuck sounds reasonable but I don't have a tool like that. I bet it takes some practice to develop the right "feel" to make it work without breaking taps.
There is another discussion about tapping in a home shop in the thread "Hand Tapping Tool?" at http://www.diyaudio.com/forums/construction-tips/220877-hand-tapping-tool-2.html#post3189390
Dale
Tapping drill sizes.
Maybe this chart will be useful.
I have a laminated copy in my workshop at the side of the bench drill so it is always handy.
Maybe this chart will be useful.
I have a laminated copy in my workshop at the side of the bench drill so it is always handy.
Yeah, that's a good reference! I had to look at it for a few seconds to realize you read it right-to-left: the thread sizes are listed in the right-hand column, and you read to the left to find the proper tap drill in industry "letter" sizes, decimal inches or millimeters.
Dale
- Status
- Not open for further replies.