To avoid these ads, REGISTER NOW!

IS there a chart for SAE tap to approximate Metric tap sizes?

L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
I have a project (brass harmonica reed plate to aluminum comb) saying to use a 4mm and a 6mm tap. I got to thinking it would be handy to have a chart showing "best" SAE equivalent sized taps to substitute for the project. I cannot find one online. Am I missing something simple here?

Yes, I know from the math that 4mm = 0.16" (4/25) and 6mm is .24 (6/25) inches. So I could look those numbers up on an SAE tap chart, But has all this been simplified into a conversion chart already?

Yes...pretty much a newb as you can tell.
 
To avoid these ads, REGISTER NOW!
W

whateg01

Well-known member
Joined
Mar 13, 2006
Messages
12,387
Location
doo dah, kansas, usa
I made a chart showing all the common sizes in SAE and metric, kinda like the drill charts that list all the common fractional, letter, number, and metric drills. I don't think I ever found one ready to use. I don't look at it often though. I know the common screw sizes. Ballpark is 0.040" per mm, so #6 (0.136") is about 3.5mm, #8 (0.164") is about 4mm, etc.
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
whateg01 said:
I made a chart showing all the common sizes in SAE and metric, kinda like the drill charts that list all the common fractional, letter, number, and metric drills. I don't think I ever found one ready to use. I don't look at it often though. I know the common screw sizes. Ballpark is 0.040" per mm, so #6 (0.136") is about 3.5mm, #8 (0.164") is about 4mm, etc.
Click to expand...
Thanks for this info. I do not understand why something like this is not easy to find online. Any chance of a scan and upload here if you have the time?
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
Rusted Nut said:
You might find a close equivalent, but I doubt the screw would hold well, and probably would not have the correct thread pitch.
Click to expand...
Thanks for the advice, but I plan on ordering the screws to fit the SAE tap. I should have been more clear in my initial post.
 
A

AJHD

Well-known member
Joined
Jan 4, 2020
Messages
3,146
Location
AZ
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
The second link/chart is the one I have. When I look up the decimal equivalents (2nd page) .24 and .16, the tap size column in that area is blank. It may be I am not understanding what seems to be a simple chart? I am suspecting this is going to be one of those "kick myself" moments!
 
B

BTL-A4

Well-known member
Joined
Feb 28, 2018
Messages
1,271
Location
Santa Clarita
AJHD said:
These charts from Starrett won't work?

Click to expand...
You can call Starrett and they might send you these for free. I got a poster and some small, card-sized versions of these. I use them all the time.
Lbrewer42 said:
I have a project (brass harmonica reed plate to aluminum comb) saying to use a 4mm and a 6mm tap. I got to thinking it would be handy to have a chart showing "best" SAE equivalent sized taps to substitute for the project. I cannot find one online. Am I missing something simple here?

Yes, I know from the math that 4mm = 0.16" (4/25) and 6mm is .24 (6/25) inches. So I could look those numbers up on an SAE tap chart, But has all this been simplified into a conversion chart already?

Yes...pretty much a newb as you can tell.
Click to expand...
There are letter and number drill sizes that might suit your needs. 6mm is 0.236", which is rally close to a B drill (0.238") and 4mm is 0.157" which is a #22 drill (0.1570"). McMaster-Carr sells singles. The shipping will not be free, but you will get them right away.

Keep in mind that a given diameter screw is tapped with a smaller bit. So, a 6mm will use a smaller drill for the hole. I think you need about 75% of the threads to engage. You should be able to get close enough with a letter/number/inch drill.
 
B

BTL-A4

Well-known member
Joined
Feb 28, 2018
Messages
1,271
Location
Santa Clarita
Lbrewer42 said:
The second link/chart is the one I have. When I look up the decimal equivalents (2nd page) .24 and .16, the tap size column in that area is blank. It may be I am not understanding what seems to be a simple chart? I am suspecting this is going to be one of those "kick myself" moments!
Click to expand...
Maybe this will help:

A M6 x 1 thread uses a 5mm tap drill. The inch equivalent is 0.1968". That would be a #8 or #9 drill.
 
A

AJHD

Well-known member
Joined
Jan 4, 2020
Messages
3,146
Location
AZ
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
I appreciate this info. I had, at one time, downloaded and printed the Starret charts.

I really need to be more specific and am sorry I have caused confusion.

The brass plates and the aluminum comb already have the holes drilled in them. The installation video for the harmonica reeds is a person in Europe saying to use a 4mm tap and a 6mm tap (he gives pitch, but I don't remember it). He mentions going online to buy the small bolts.

In the video specifically mentions an American could use the equivalent SAE tap and buy appropriate bolts to go with it. I am just looking to find the closest equivalent tap to thread the 4 mm and 6mm holes.

My uneducated guess is I will not have to use a drill on the pre-drilled holes if I use the right SAE tap?
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
Yes, I could do this. But I thought it would be good to be able to have a chart to use as well. I have a bunch of tooling left to me by my grandfathers (both were machinists) and may even have the appropriate sized tap already. I was doing homework ahead of time trying to figure all of this out. I know I have no metric taps. And for me it is not as easy as just taking a second to go physically figure it all out b/c of being disabled. I need to get as much done ahead of time as I can before trying to go find out.

I thought it would b as easy as looking up the SAE size on a chart and then digging through the drawers of tools to see if I already had the tap I needed. I don't want to spend the money if I don't have to for a job I likely only will do once.
 
D

Dave455

Well-known member
Joined
Mar 19, 2013
Messages
5,878
Location
Sussex, England
O.K.

If you are just seeking an approximate equivalent (which I suspect is what is intended) you don’t generally need a chart showing taps, just a regular metric to Imperial conversion chart.

6mm is .236 and 4mm .158 so an easy equivalent of 6mm is 1/4” (.250), which is just .014 bigger. Much below 1/4” we need to use “numbered” sizes, and the nearest to .158 is a No.8 at .164.

A 1/4” UNF and a No. 8 UNF would be similar thread pitches to metric coarse.

Both of these sizes are bigger than their metric equivalents, so you will need to open out the holes to the appropriate tapping sizes before you start.

Alternatively, I’d just obtain the taps suggested. If you’re tapping through holes in sheet material you don’t need sets, just one tap of each. 4mm and 6mm taps are something I need so often I wouldn’t want to be without them anyway.
 
M

MovingAlong

Well-known member
Joined
Aug 17, 2013
Messages
1,355
R

RoninB4

Well-known member
Joined
Jul 22, 2020
Messages
3,796
Location
Under My House
Use the chart as your final guide but you will probably find that an 8-32 (4mm) and 1/4-28 (6mm) will be your best replacements. Now a lot has to do with how sharp your taps are, brass can be easy or difficult to tap depending upon the type of brass it is. An inherited tap may be so dull that it will "squeak" as it makes threads. If it does this even with cutting oil it's because the material is squeezing the tap and it may be close to snapping off. It also depends upon how thick the brass is, thicker is more difficult. Aluminum should NEVER be tapped dry as it micro-welds material onto the tap and creates problems so always use something (even WD-40) when tapping aluminum. I suggest the 1/4-28 thread because it's not too difficult to find and the finer thread (over the more common 1/4-20) will put more thread into material if it's thin.

As a final thought for those that attempt to mix inch and metric thread/fasteners....not a good idea. The thread form itself is different, so is the root & crest for both inch and metric threads. It may seem to fit but it really doesn't and this will either damage the threads on one or give a false sense of security that the fastener works. Ignore this advice at your own risk
 
To avoid these ads, REGISTER NOW!
J

jdl25

Well-known member
Joined
Jun 12, 2010
Messages
356
I'm glad your thinking, but these things just don't translate.
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
manwithtools said:
Why would one waist this many brain cells on a question like this? Just use the right hardware...
Click to expand...
Different personality types enjoy different things. Deep research, discovery, and detangling/explaining the complex is what I thrive on.

I see this type of math as simplistic. I am old enough to remember when any 5th graded could do fractions, percents, and decimals as second nature in their head, whereas most modern "publically educated" people ( I was too) cannot do simple addition/subtraction to make change without the cash register telling them what to do.

I used to be a math teacher but am disabled and now simple things like this math do trip me up more than they used to. To tell you how weird I am, with my free time, and for FUN, I have been going back through my college calculus book and rewriting it to simplify the concepts b/c the author, IMO, is terrible at explaining things to others and should not have authored a math textbook.

So I understand why your brain cell question is valid for some people, but my personality type has a problem understanding why in the world someone would pay good money on merchandise and tickets, and spend time rooting for the same sports team year after year. In reality they know the outcome is their team is NOT every going to be THE #1 team, like they consistently scream, consistently. I see the whole professional sports system as chasing a useless dream (that is not an insult!).

But IMO neither mindset is right or wrong! It takes all kinds to make up a working society and each personality type has worthy contributions. To each his own.

BTW my periodic, but legit, brain fog from my disability was in action which is why I stated I thought I would end up kicking myself.

I know now I was looking at .016 on the chart rather than .16 (doh!) Again...simple so it got me. But I can laugh at myself while I am kicking myself!

Besides...

A wall chart is a good tool to have.

Thanks everyone...this was a learning experience, a humbling one, and I am thankful there is so much help here. You guys are great! :D
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
bob15 said:
I am sorry, this sounds like: super-hack. Why would a company make a chart that shows mismatched fastener to hole data?
Click to expand...
What I was after was that when I already have a certain sized hole, and the best metric fit is, say 6mm, then what SAE tap would likely be the best to use if I don't have access to a 6mm?

The intricate way of finding this is to convert the metric to inches (decimal). Look up the decimal number on the Starret charts above, and then find what taps are listed for that diameter.

A shortcut would be to just have a list of MM taps and beside them a list of the taps found by using that method. It just saves time.
 
P

PCustoms

Well-known member
Joined
Jul 23, 2011
Messages
23,684
Location
VT
Lbrewer42 said:
What I was after was that when I already have a certain sized hole, and the best metric fit is, say 6mm, then what SAE tap would likely be the best to use if I don't have access to a 6mm?

The intricate way of finding this is to convert the metric to inches (decimal). Look up the decimal number on the Starret charts above, and then find what taps are listed for that diameter.

A shortcut would be to just have a list of MM taps and beside them a list of the taps found by using that method. It just saves time.
Click to expand...
So make the chart?

The reason this doesn't exist is because it's hack work, of little to no interest to a machinist.

There also isn't a direct correlation. For example 6mm/1/4" threads may roughly equate, but I'm not sure the corresponding tap drills overlap.

Sorry

If I'm working on something inherently metric and I don't have the to, guess what I have to order...
 
W

whateg01

Well-known member
Joined
Mar 13, 2006
Messages
12,387
Location
doo dah, kansas, usa
Ffs! Yeah, I'm going to do the math in my head to calculate the thread pitch on sae fasteners. You are correct that metric makes that easy. But off hand, I don't just know what the thread spacing is for a 13 tpi thread. Yeah I can get the phone out and use the calculator. Or, I could look at the chart on my wall.
 
M

mikey03

Well-known member
Joined
May 17, 2024
Messages
2,231
I’m a bit of a hack sometimes tbh I’m not a machinist I don’t got a drill press and I do all of my drilling by hand so honestly a bit of the wrong size won’t make that much difference. I haven’t tapped anything yet but I picked up some used starrett tap holders I got at a good deal. And I’m going to pick up some taps soon to have on hand in case I make something.

I can use whatever I want, so will be metric because that makes sense to me. And I will prob use the standard course sizes like M6x1 and M8x1.25

So funny enough last weekend I started a spreadsheet of this stuff because all of my drill bits are SAE in 1/64 increments. I’m not done yet but I’ll give some info I figured out.

I made a column for metric size, one for SAE in fractions, and one for SAE in decimals. And I mixed them all together in order of small to big. And I made another column for which taps use that size as a drill bit. I highlighted rows probably close enough.

I used another color to highlight rows I need to buy a metric drill because I think it’s too far off. Here’s some for you:

m5x0.8 is a 4.2mm drill. It’s sandwiched between 5/32 at 3.97mm and 11/64 at 4.37mm
I think 0.2mm might be too much difference so I will get a 4.2mm drill bit. Trying to keep to around 0.1mm

But I’m planning to do some science and take some scrap metal and use a cordless drill to drill like 10 holes by hand into metal. And then measure the holes and see how much range is there. because if I have a 0.2mm range between smallest and biggest hole using the same drill bit then i guess 0.2mm is close enough.

m6x1 uses a 5mm which is prob too far between 3/16 (4.76mm) and 13/64 ( 5.16mm) so I’ll get a 5mm bit

m8x1.25 uses a 6.7mm bit according to McMaster even though the rule of thumb says 6.75 but either way, 17/64” is exactly 6.75mm and will be close enough for me

m10x1.25 uses an 8.7mm and 11/32 is 8.73mm so close enough

That’s some examples to get you started in your own spreadsheet. Like people said this is for garage hacks which I don’t mind being labeled, so that’s why I didn’t expect to find a chart online. You should find what size taps you plan to use, see if you have an SAE close enough, and if not then buy the metric bit. Or just buy a tap and drill set and be done with it.
 
M

mikey03

Well-known member
Joined
May 17, 2024
Messages
2,231
whateg01 said:
Ffs! Yeah, I'm going to do the math in my head to calculate the thread pitch on sae fasteners. You are correct that metric makes that easy. But off hand, I don't just know what the thread spacing is for a 13 tpi thread. Yeah I can get the phone out and use the calculator. Or, I could look at the chart on my wall.
Click to expand...
Yeah bro but you need to learn to do it in your head, are you going to have that chart on your wall in real life? 🤭😆😛
 
D

Doozer75

Well-known member
Joined
Oct 24, 2009
Messages
260
Location
Buffalo NY
whateg01 said:
Ffs! Yeah, I'm going to do the math in my head to calculate the thread pitch on sae fasteners. You are correct that metric makes that easy. But off hand, I don't just know what the thread spacing is for a 13 tpi thread. Yeah I can get the phone out and use the calculator. Or, I could look at the chart on my wall.
Click to expand...
To the moderator who keeps erasing my posts...
When I look up Ffs! the search returns...
Face feminization surgery and later down the search results, For Fuks Sake.
Ambiguous initialisms serve only to confuse people.
Given the fact that reigning member whategO is likely held with prominent
esteem as evidenced by his tenure here, and therefor he would be out of character
to issue such profanity as For Fuks Sake on any aspiring member here such as myself,
I can only conclude his exclamatory initialism means Face Feminization Surgery!
I am not using offensive derogatory language, like your tenured member whategO.
Why have you repeatedly censored me and deleted my posts? The name whategO
is surely satirical, as his derogatory exclamation seems to originate from an inflated
presentation of ego, and not a lack of said self. Is your censorship typical of what
can be expected here on this forum? Please explain why my retorts were deemed
inappropriate enough to censor and yet tenured member whateg0 is allowed to
post to me with his sharp tongue. Thank you.

-Doozer
 
D

Doozer75

Well-known member
Joined
Oct 24, 2009
Messages
260
Location
Buffalo NY
PS-
I have deleted my above post on the topic of the formulae for
calculating tap drill diameters. I have a rule not to talk to people
who are not listening, as it is a waste of my time an intellect.
This seems to be the case here, so I have deleted my post
of knowledge that I had previously deemed generous to share.

-Doozer
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
PCustoms said:
So make the chart?

The reason this doesn't exist is because it's hack work, of little to no interest to a machinist.

There also isn't a direct correlation. For example 6mm/1/4" threads may roughly equate, but I'm not sure the corresponding tap drills overlap.

Sorry

If I'm working on something inherently metric and I don't have the to, guess what I have to order...
Click to expand...
I was just checking to see if it had already been done before I made one. Was just wanting to avoid tedium if the info was readily available. Hence I started this thread. I am a hobbyist and had no idea a conversion chart was not something useful to an actual machinist. I see with online instructional videos people are saying they use one or the other system. I assumed when a machinist comes up against plans laid out in metric that there would be an easy tool/chart for conversion to SAE without just using a calculator.
 
R

Ryan

Administrator
Staff member
Joined
Jan 26, 2006
Messages
5,823
Location
Boulder/Koloa
Doozer75 said:
To the moderator who keeps erasing my posts...
When I look up Ffs! the search returns...
Face feminization surgery and later down the search results, For Fuks Sake.
Ambiguous initialisms serve only to confuse people.
Given the fact that reigning member whategO is likely held with prominent
esteem as evidenced by his tenure here, and therefor he would be out of character
to issue such profanity as For Fuks Sake on any aspiring member here such as myself,
I can only conclude his exclamatory initialism means Face Feminization Surgery!
I am not using offensive derogatory language, like your tenured member whategO.
Why have you repeatedly censored me and deleted my posts? The name whategO
is surely satirical, as his derogatory exclamation seems to originate from an inflated
presentation of ego, and not a lack of said self. Is your censorship typical of what
can be expected here on this forum? Please explain why my retorts were deemed
inappropriate enough to censor and yet tenured member whateg0 is allowed to
post to me with his sharp tongue. Thank you.

-Doozer
Click to expand...

Doozer75 said:
PS-
I have deleted my above post on the topic of the formulae for
calculating tap drill diameters. I have a rule not to talk to people
who are not listening, as it is a waste of my time an intellect.
This seems to be the case here, so I have deleted my post
of knowledge that I had previously deemed generous to share.

-Doozer
Click to expand...

I’m not super interested in hosting people like this… So, we are moving on.
 
W

whateg01

Well-known member
Joined
Mar 13, 2006
Messages
12,387
Location
doo dah, kansas, usa
Lbrewer42 said:
Thanks - this is has it!

Not sure how I missed seeing your post before. Much appreciated.
Click to expand...
Glad that one has what you need. I can't seem to find the original from when I made all of my charts. I know it was at least 10 years ago, and thus at least 1, maybe 2, computers ago.
 
OP
L

Lbrewer42

Member
Joined
Oct 19, 2018
Messages
22
Location
Home
Being a total newb I realize some of my ideas are not going to be what an actual machinist knows to be fact. I admit in this case it seemed logical there should be such a chart since, since, as a newb and a person who uses technical references frequently for other areas of research, I found myself facing a simple project where it would have been helpful to have such a reference.
 
W

whateg01

Well-known member
Joined
Mar 13, 2006
Messages
12,387
Location
doo dah, kansas, usa
Nothing wrong with wanting to make your life easier. I fully support the notion of knowing how to do things the hard way, but at the end of the day, the goal is to get the job done. If I can get the job done easier by making a chart that lays out a bunch of data, I'm all for that.
 
M

mikey03

Well-known member
Joined
May 17, 2024
Messages
2,231
Lbrewer42 said:
Being a total newb I realize some of my ideas are not going to be what an actual machinist knows to be fact. I admit in this case it seemed logical there should be such a chart since, since, as a newb and a person who uses technical references frequently for other areas of research, I found myself facing a simple project where it would have been helpful to have such a reference.
Click to expand...
Yeah I had the same thought and googled it and realized machinists won’t want this and couldn’t find one so I started making my own. McMaster has a table that shows tap sizes and the drill bits used so I started there and converted to 1/64” to see what was close to what I got already in drill bits
 
You must log in or register to reply here.
To avoid these ads, REGISTER NOW!
Top Bottom