Make a 5/8"tap

[morrisman]

hi

I am thinking of making a LH 5/8-8 ACME tap in order to make some bronze nuts .

Would silver steel be OK as a base metal ? ( chronos sells it in 12"lengths ) And, would it also tap into cast iron OK as I have some cast iron round stock as an alternative to the bronze ?

Thanks Mike

[Abratool]

Mike
The Silver Steel would be my first choice.
It would need to be hardened & then tempered to a dark straw or light brown after your machining work.
I will be away for a while so will be out of contact for a short time.
Hope all goes well for you.
regards
Bruce

[BobL]

I'd be interested to know what they charge for shipping on an item like that.
Thanks

[morrisman]

here we have a lesson :2tsup:

http://rick.sparber.org/gt.pdf

[morrisman]

I'd be interested to know what they charge for shipping on an item like that.
Thanks

Around ten bucks

[Clubman7]

You can buy one cheap enough.

Rdgtools HSS Acme Tap 5 8" x 8 TPI LH High Speed New | eBay (http://www.ebay.com/itm/RDGTOOLS-HSS-ACME-TAP-5-8-x-8-TPI-LH-HIGH-SPEED-NEW-/370793707039?pt=UK_Home_Garden_PowerTools_SM&hash=item565506f61f)


Don't know of the quality though.

[morrisman]

You can buy one cheap enough.

Rdgtools HSS Acme Tap 5 8" x 8 TPI LH High Speed New | eBay (http://www.ebay.com/itm/RDGTOOLS-HSS-ACME-TAP-5-8-x-8-TPI-LH-HIGH-SPEED-NEW-/370793707039?pt=UK_Home_Garden_PowerTools_SM&hash=item565506f61f)


Don't know of the quality though.

Yes I spotted that . I would rather make one and in the process learn how to do it ... that way I can make more taps later on when I need a odd size tap for a special job :2tsup:.

Mike

[Grahame Collins]

Hi,

Mintech in Brisbane has 5/8 ' silver steel for $26 for 300mm.Postage is likely to be a bit cheaper than from Chronos.

If it helps
Grahame

[Ueee]

Hi Mike,
Something Phil suggested to me when i was musing about the Rivetts screws. Turn the new screw a few inches linger than required and also leave an inch or so of plain shaft. You can then cut the extra off and make it into the tap. The tap should then make a nut that matches the screw exactly.....if you turn the screw form dead on symmetrical. I have a pic somewhere of measuring with one wire for ACME threads...i'll try and find it.

Cheers,
Ew

Found it.....

[morrisman]

Hi Mike,
Something Phil suggested to me when i was musing about the Rivetts screws. Turn the new screw a few inches linger than required and also leave an inch or so of plain shaft. You can then cut the extra off and make it into the tap. The tap should then make a nut that matches the screw exactly.....if you turn the screw form dead on symmetrical. I have a pic somewhere of measuring with one wire for ACME threads...i'll try and find it.

Cheers,
Ew

Found it.....

OK Ewan.. I understand . Thanks for the wire measuring info drawing . I plan on using silver steel for the tap . I will make the tap using the same tool and setup I will use for making the acme leadscrew itself , so in theory they should be a match .

The only thing I am unclear on, is what size minor diameter hole do I need to bore in the blank piece of bronze for the 5/8 ACME tap ? Do I need 2-3 thou of clearance for the minor diameter of the leadscrew ? Mike

[scottyd]

More than that. The black book suggests 10 thou top and bottom. That is, the valley is 10 thou deeper like you said, but the tap should be made 10 thou bigger than the major diameter to give relief on the top of the threads too. The only contact should be the walls of the thread.

-From memory-

[Ueee]

I was going to make the rivetts screws from silver steel, they are o:Unly 7/16. One is LH and one is RH. You may also want to wrap the tap in stainless foil so there is no oxidizing when hardening.

Ew

[morrisman]

Hi

Been grinding the #8 ACME threading tool... it is going OK, but I need to measure the tip width . The book says it should be .041" wide .

I don't have one of those ACME thread gauges and I don't want to pay a exhorbitant price and wait 10 days for one from O/S .

Is there an easy way to measure the tip width ?

Mike

[Michael G]

Have a look here -

http://www.woodworkforums.com/f65/your-latest-project-121056/index33.html#post1488715

Phil solved that issue

Michael

[morrisman]

Have a look here -

http://www.woodworkforums.com/f65/your-latest-project-121056/index33.html#post1488715

Phil solved that issue

Michael

I forgot about Phils fancy gizmo..........:2tsup: neat idea . Problem is it will take me a week to make one :( Mike

[Stustoys]

I'd think if you have some longish dowel pins or some ground rod you could make something in the spirit of Phils in less than a week. Turn the "spaces" to suit your dowel/rod. Mount the dowel/rod in the lathe chuck and the tool on the tool post(just like you were cutting the thread).
Am I missing something?

Stuart

[.RC.]

I am also at the point I have to make an ACME tap... I was going to use 4140 to make it, it will harden to 50HRC...

Mine has to be similar to Mike's but instead of 5/8 has to be 0.6"...

Maybe he could make one for me when he is in the tap making mood... :D

[morrisman]

I'd think if you have some longish dowel pins or some ground rod you could make something in the spirit of Phils in less than a week. Turn the "spaces" to suit your dowel/rod. Mount the dowel/rod in the lathe chuck and the tool on the tool post(just like you were cutting the thread).
Am I missing something?

Stuart


Yes , that is a way to go . A bit of lateral thinking :2tsup: Thanks .. Mike

[morrisman]

I am also at the point I have to make an ACME tap... I was going to use 4140 to make it, it will harden to 50HRC...

Mine has to be similar to Mike's but instead of 5/8 has to be 0.6"...

Maybe he could make one for me when he is in the tap making mood... :D

.6" is a rather odd diameter for a ACME thread ? What is it for RC

Make another :no:

[Ueee]

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

[morrisman]

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

Ewan ,

That sounds a little esoteric BUT

That is what I did the first time I did a 8 TPI ACME thread on the lathe , making a leadscrew. After cutting the initial groove with a thin thread form to remove the bulk of the metal in the groove , I finished off with a ACME shape tool - I thought that ACME tool was the correct size, in that case a commercial insert . Turns out it was the wrong size insert :? - it was supposed to be a 8 tpi thread form insert , as sold on fleabay , but what it was, was actually a 6 tpi insert :no:

So I now have a 8TPI ACME leadscrew with a 6 TPI threadform ... for the junk bin .

[.RC.]

.6" is a rather odd diameter for a ACME thread ? What is it for RC



The 10EE...

I could buy an aftermarket cross slide screw and nut for it but they are over US$300...

If you are planning to use a DRO, it does not really matter how the thread turns out so long as it is good and backlash is not a lot...

[scottyd]

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

Ive done a few now, 10tpi in 4140 and a 5tpi in some mysterium, both multiple times done on fairly tired hercus 9in lathes. I never ran into a need to use two different profile tools. However, I did deliberately grind the tool to be narrower than spec. Id cut the thread to full depth, then realign the tool (using the cross and compound slide against each other) in the opposite direction of the thread movement, and line it up for another series of passes. Using trig you can calculate how far across youre moving and some wire gauging and maths can yeild how much wider you have to go.

This made grinding the tool a lot easier too, all I needed to get right was the angles and take some of the point off. Worked a treat in the end.

[Michael G]

I did something similar to Scotty, but used a pin gauge to check the width of land at the bottom of the thread. Seemed to work.

Michael

[PDW]

I thought it was better to rough the thread out first with a square tool, then cut the acme form? That way you can make the cutter undersize and leave the compound at 90deg and use it to bring the cut to the right width. Keep in mind i have never cut an acme thread......

Ew

That's how I do mine, and I've done quite a few. Square threads are dead easy to cut and you then only need to clean up the flanks to get an acme thread form, rather than cutting on all 3 faces (or at minimum, 2 and skimming the third) going at it with an acme tool form.

I *think* that the huge collection of Valenite TC tips I inherited has some acme form tools there but I'm not about to look ATM. There are literally hundreds of boxes of inserts and I don't have a list of what the magic numbers mean, so I have to open every box and use the Mk 1 eyeball.

PDW

[Steamwhisperer]

Oops wrong thread.

Phil

[morrisman]

I managed to make the measuring device OK

I mounted the shaft in the lathe as Stuart suggested , works well :2tsup:

My tip is .008" too wide, so a little more careful grinding is needed .. Mike

[Steamwhisperer]

Damn after all that hard work.
Ah well, back to the KISS principle.
Well done Mike

Phil

[morrisman]

I am still playing around with taps , practice makes perfect :?

The silver steel I got from Chronos or RDG is horrible stuff - It is very difficult to get a good finish on it .

The flanks of the threads have scouring on them , even though the tool is sharp .

I am yet to buy a ball end mill for the fluting ........... Mike

[Ueee]

Looks good Mike.

Is there enough straight section of the tap to get the nut fully threaded?

As far as i am aware, you don't really need a ball end cutter for the flutes, you can use a straight cutter (with radius corners perhaps) and just mill out the flutes. If you take the cut over the center line you will get a slightly positive cutting angle. Not the best pic but this shows it Leadscrew nuts (http://bbs.homeshopmachinist.net/threads/19707-Leadscrew-nuts?highlight=rolled%20acme)

Cheers,
Ew

[morrisman]

Looks good Mike.

Is there enough straight section of the tap to get the nut fully threaded?

As far as i am aware, you don't really need a ball end cutter for the flutes, you can use a straight cutter (with radius corners perhaps) and just mill out the flutes. If you take the cut over the center line you will get a slightly positive cutting angle. Not the best pic but this shows it Leadscrew nuts (http://bbs.homeshopmachinist.net/threads/19707-Leadscrew-nuts?highlight=rolled%20acme)

Cheers,
Ew
Hi Ewan

Yes the taper on that first tap pictured has a long taper, I plan on making a second tap with a short taper , this will be for the 2nd finishing cut into the nut .

I ground the end square on the T&C grinder .

I was wondering about the cutter for the flutes, a straight cutter or a ballend ?

Yes a positive cutting angle on the edges would be good , I will set it up and see how it works out .

When cutting the tap threads on the lathe , I will speed up the rpm to maybe100 , this may help with a better finish . I have been using 50 rpm .

Mike

[morrisman]

this looks interesting
Acme Screws & Thread Rods | Dependable Acme Threaded Products (http://www.dependableacme.com/)

[morrisman]

This is the second tap in 5/8 - 8 LH

I could only take .003" cuts when thread cutting as the material tends to tear and leave scour marks on the thread flanks if deeper cuts are taken .

The neighbour has a oxy set for the hardening and tempering .

Mike

[Ueee]

Hi Mike,
I have started making a 7/16" 10 tpi RH tap for the Rivett. I have had the same problems with the O-1, had to take small cuts. I roughed mine out first with a .030" wide tool, the surface on the bottom of the cut was appalling. With a tool ground to a a nose width of a bit less than .030" (the root width needed to be .03707") i cut the LH flank first, then went to size on the RH flank. I was only taking .01mm cuts at a time. The steel was cutting beautifully with these tiny cuts. I used flood coolant for the roughing and some tap magic for the final cuts.

Measuring to size was a pain though, the formula i attached earlier is all good and well, but with 10tpi i would have needed a .04872" dia wire.....not some thing i have! I calculated the measurement required over a .055" thread wire, it seems to have worked just fine. A pic of my workings is attached, i'll put the pics of the tap in the Rivett thread where they belong.

Cheers,
Ew

[Michael G]

I calculated the measurement required over a .055" thread wire, it seems to have worked just fine. A pic of my workings is attached, i'll put the pics of the tap in the Rivett thread where they belong.


I confess to bypassing the calculations - I draw up what it should be in AutoCAD, including the wire sizes I have and then measure from the drawing the target dimension.

Michael

[morrisman]

Hi Mike,
I have started making a 7/16" 10 tpi RH tap for the Rivett. I have had the same problems with the O-1, had to take small cuts. I roughed mine out first with a .030" wide tool, the surface on the bottom of the cut was appalling. With a tool ground to a a nose width of a bit less than .030" (the root width needed to be .03707") i cut the LH flank first, then went to size on the RH flank. I was only taking .01mm cuts at a time. The steel was cutting beautifully with these tiny cuts. I used flood coolant for the roughing and some tap magic for the final cuts.

Measuring to size was a pain though, the formula i attached earlier is all good and well, but with 10tpi i would have needed a .04872" dia wire.....not some thing i have! I calculated the measurement required over a .055" thread wire, it seems to have worked just fine. A pic of my workings is attached, i'll put the pics of the tap in the Rivett thread where they belong.

Cheers,
Ew

Ewan

That is good info from you

I used the 1942 Advanced Machine work book to work out the depth of thread etc .

BTW I was using neatsfoot oil but it didnt seem to be very effective.. I need some of that tap magic stuff !

[morrisman]

Info I copied from a forum :2tsup:


With a tap, you want the cutting edges hard and sharp. You want the shank softer and tough.

You want it hard, but you don't want to burn the steel.

Take some iron wire, like the auto repair people use, and wrap the tap up in wire. NOT the zinc plated stuff! Now dip the tap in liquid hand soap. Neatness does not count, just cover it with plenty of wire and dip in soap.

The wire and soap will help exclude air from the tap and help keep it from oxidation during heating.

The other thing the wire does is give you something to hang onto while you do it! http://cdn.homemodelenginemachinist.com/images/smilies/grin.gif

Silver solder flux works here too, I am told, though I have'nt tried that.

Heat it up to "Cherry Red" and keep it there for a couple of minutes.

Quech in your "appropriate liquid" vertical while moving it around.

Remove the wire, and clean the tap.

Once you harden the tap, check it with a file. Should be harder than woodpecker lips! http://cdn.homemodelenginemachinist.com/images/smilies/grin.gif

Now clean and polish the cutting edges really well. MIRROR SMOOTH take your time, this part is important!

With the tap pointing up, and looking at the CUTTING EDGES with a magnifying glass, heat the SHANK at the bottom with the torch with a gentle flame....JUST THE VERY BOTTOM WHERE YOU TURN THE TAP WITH A WRENCH!

As the tap gets hotter, you will watch the color move up the tap toward the cutting edges.

When the CUTTING EDGES turn a pale straw yellow, quench immediately in you "appropriate liquid". This will stop the tempering process, leave the shank softer and tougher, and just temper the cutting edges.

The cutting edges at the front of the tap doe most of the work, and need to be hard, so don't over do it.

This is how the clockmakers make they're tools, and it works well for me....just go easy with the torch, it won't take much to do this

If you go too far, you have to go back to the beginnig and harden it again....and most steels don't like doing this too many times. practice on a piece of steel first, just to get the feel for it.

Practice,practice, practice.... The best way to learn is to do, get a piece of tool steel and harden it, you'll find out. THEN make your tap...

[Abratool]

Info I copied from a forum :2tsup:


With a tap, you want the cutting edges hard and sharp. You want the shank softer and tough.

You want it hard, but you don't want to burn the steel.

Take some iron wire, like the auto repair people use, and wrap the tap up in wire. NOT the zinc plated stuff! Now dip the tap in liquid hand soap. Neatness does not count, just cover it with plenty of wire and dip in soap.

The wire and soap will help exclude air from the tap and help keep it from oxidation during heating.

The other thing the wire does is give you something to hang onto while you do it! http://cdn.homemodelenginemachinist.com/images/smilies/grin.gif

Silver solder flux works here too, I am told, though I have'nt tried that.

Heat it up to "Cherry Red" and keep it there for a couple of minutes.

Quech in your "appropriate liquid" vertical while moving it around.

Remove the wire, and clean the tap.

Once you harden the tap, check it with a file. Should be harder than woodpecker lips! http://cdn.homemodelenginemachinist.com/images/smilies/grin.gif

Now clean and polish the cutting edges really well. MIRROR SMOOTH take your time, this part is important!

With the tap pointing up, and looking at the CUTTING EDGES with a magnifying glass, heat the SHANK at the bottom with the torch with a gentle flame....JUST THE VERY BOTTOM WHERE YOU TURN THE TAP WITH A WRENCH!

As the tap gets hotter, you will watch the color move up the tap toward the cutting edges.

When the CUTTING EDGES turn a pale straw yellow, quench immediately in you "appropriate liquid". This will stop the tempering process, leave the shank softer and tougher, and just temper the cutting edges.

The cutting edges at the front of the tap doe most of the work, and need to be hard, so don't over do it.

This is how the clockmakers make they're tools, and it works well for me....just go easy with the torch, it won't take much to do this

If you go too far, you have to go back to the beginnig and harden it again....and most steels don't like doing this too many times. practice on a piece of steel first, just to get the feel for it.

Practice,practice, practice.... The best way to learn is to do, get a piece of tool steel and harden it, you'll find out. THEN make your tap...
Mike
Yep, have done this plenty of times & it works.
The tempering can be a bit tricky as its easy to overheat, I have found it best if you just take it slowly on the heating, of the shank, as you outlined, so that a straw to light brown is reached.up around the cutting edges. Sometimes it can be rushed & the tempering operation is ruined.
regards
Bruce
ps
I just did a test on the lathe parting off Silver Steel with varying lubricants
Tried Neatsfoot Oil, Tap Magic, Straight undiluted soluble Oil, & Soluble Oil.
The winner seemed to be the Soluble oil, in a flood.

[morrisman]

Mike
Yep, have done this plenty of times & it works.
The tempering can be a bit tricky as its easy to overheat, I have found it best if you just take it slowly on the heating, of the shank, as you outlined, so that a straw to light brown is reached.up around the cutting edges. Sometimes it can be rushed & the tempering operation is ruined.
regards
Bruce
ps
I just did a test on the lathe parting off Silver Steel with varying lubricants
Tried Neatsfoot Oil, Tap Magic, Straight undiluted soluble Oil, & Soluble Oil.
The winner seemed to be the Soluble oil, in a flood.


Thanks Bruce

Have you ever made a morse taper tap ? I guess it is a similar thing to makinga threading tap , but without the thread.. mike

[Abratool]

Mike
I think you may be referring to a roughing style, Morse Taper Reamer. Have not made one of these, although it would not be too difficult.
They are available at reasonably low prices, but I have not had the use for one.
regards
Bruce

[morrisman]

Mike
I think you may be referring to a roughing style, Morse Taper Reamer. Have not made one of these, although it would not be too difficult.
They are available at reasonably low prices, but I have not had the use for one.
regards
Bruce

yes Bruce

I meant to write morse taper reamer , but I have taps on the brain right now :rolleyes:

[morrisman]

The taps are finished but it remains to be seen if they actually work :o

[matthew_g]

The taps are finished but it remains to be seen if they actually work :o
I had a visit with Mike (morrisman) today as I was in his neck of the woods, and witnessed these taps in the flesh.
I have no doubt that they will work, Mike has done exceptionally well and should be extremely proud of himself.
Now that I have said that, I will accept that Colchester as payment Mike..:lolol:

[.RC.]

Last week I got my 0.6X8tpi ACME tap made and tapped the nut... As explained earlier mine is made out of 4140 steel but left the steel as supplied, so it's hardness is only 30 or so on the Rockwell C scale..

3 flutes, and the cutting and back edge was ground on the TC grinder as the flute cutting left a very very jagged edge...

Cutting the thread int he nut was not easy, but it got done.... taper angle is 3 degrees included angle...