[keen]

I think you guys are talking about 'lead angle'.

When threadmilling on a lathe with a thread milling attachment. The attachment is tipped up or down slightly to concur with the pitch angle. (yes right angles to the thread at the centre line) My machines cutter unit is mounted in a way to allow this also. Because even at full depth the work and the cutter describe 'two arcs in contact' like this )( - on the centreline, and because the thread is usually 'V' in form, from a 3 dimensional perspective the cutter quickly clears the finished thread form. In practise tipping the cutter head (and axis) is hardly needed - this is why thread milling on a CNC is posssible - as this adjustment is not normally possible on a 3 axis CNC.

So in practice on my machine or when thread milling on a lathe the cutter head is set over a few degrees to give optimum clearance - this does not usually need to be changed.

NB some unusual thread forms require more care/consideration in this area.

[mactec54]

[/QUOTE]TomB
That is not exactly true. If you cut the thread with a single point cutting bit then the mill would be cutting just like a lathe and obviousily there would be no thread distortions. But in the Keen machine it is not a single point cutter.

I think you are not seeing something correct, the Keen machine is using a single point cutter, just as you could/would use on a mill or a lathe, it is just like any threads you cut or grind, you make ajustments to the machine or cutter to get the thread geometry correct.

Have a look at a injection molded threads, it was most likly was cut this way we have used this method for cutting mold cores threads & grinding for many years & get perfect thread generation, a lot now are done on CNC lathes/Mills, But is still is not as good as this method for cutting a mold core thread, as with a lathe it can not give you the lead out at the end of the thread that is needed for a molded thread, & for on a mill which can do this thread form the same, but you can not always fit the mold cores in a Mill to get them done, the next place it is done is on a lathe with live tooling as you can see to do this kind of threading can cost a lot of money just for the machine to do it

So you use a rotory cutter mounted on a manual lathe to cut your mold core threads because it can do a better job of cutting the thread than a normal lathe can & does not have the cost of a cnc lathe with live tooling

[agapios]

[INDENT]

I think Apapois may have been asking about a different consideration and had just compared it to big pipe threading for illustration. Since I also wondered about this effect but had not taken the time to calculate its size, I'll try to rephrase the question that I think was in Agapios' mind. A thread is a helix so at the point where the cutter contacts the stock the 'thread to be' will be advancing into the cutter along the cutter's rotation axis, while the cut thread leaves on the same axis. Unless cutter is angled to match the thread pitch angle or the cutter has concave, i.e. involuted sides , the cutter part that got into and exits the stock will undercut the sides of the thread. The cross section of the resulting thread will not be triangular. The undercut amount may be unnoticable or it may be significant, that is what I did not calculate. I think Apapois might be referring to large single cutter pipe threading, feet of diameter not small size plumbing threading, where he knows the amount of undercut is geometrically significant but functionally insignificant.

Just thinking casually it seems that it may be possible to eliminate or nearly eliminate the cutting error if the axis of the cutter is aligned at a right angle to the thread pitch instead of the stock axis, but that means the adjustment for different pitch threads is more complex than just matching the cutter lead per stock revolution to the pitch. Adding that correction could add quite a bit of cost to the machine design. Trying to make the same correction by making the cutter sides concave leads theoretically to a different cutter for every thread pitch. However, maybe a few styles would suffice as one cutter could handle a range of pitches. (This is the case with gear hobs that have similar cutting effects.)

Tom

hi

TomB you are in my mind!!

is one more i wand to say. the thread genereitor can also replace the traditional gear box on a lath...

[slatsmith]

Hi,
I've been a machinist for 25+ years and have cut & milled a thread or two ...You have come up with a neat idea ... A couple of thoughts for you ...
Going with inserts will make up for any helix angle change for different lead threads ...running an encoder on the spindle would give you the abillity to do multi-start threads ...

[RomanLini]

Keen, how does the infinitely adjustable gearing work? Do you have any diagrams or images (not video)?

[mactec54]

Hi RomanLini

This is what is in Keens Patent you will have to wait for that type of information

[keen]

Keen, how does the infinitely adjustable gearing work? Do you have any diagrams or images (not video)?

Hi Romanlini. Mactec54 has replied just as I did - Thanks mactec54 you saved me the trouble

[keen]

Hi,
I've been a machinist for 25+ years and have cut & milled a thread or two ...You have come up with a neat idea ... A couple of thoughts for you ...
Going with inserts will make up for any helix angle change for different lead threads ...running an encoder on the spindle would give you the abillity to do multi-start threads ...

Thanks slatsmith - That is now 'onboard'

[RotarySMP]

Hi Keen Kiwi,

Most innovation is a novel combination of concepts which are known, common, and available to all.

It is easy to look at your Threadexpress and say, this is just an angle grinder, a cross slide, TurboCNC on a dos box, and spindle with encoder.

Good on you for putting the bits together. The hard part is finding and satisfying a market.

It is quite possible that their is no market, which is why no one bothered putting these things together before. On the other hand it may be that the enabling technologies have only recently become available at appropriate cost, and you have something that there is a strong latent demand for.

Given that about half the people here could whip up one of these using an angle grinder, a cross slide, a mini mill head from LMS, turbocnc/Mach3 or EMC, and your video as a plan, if there is a market, you won't have it alone for very long.

[RotarySMP]

Since "correct" threads require a define root radius, you would still need a different cutting bit for nearly every thread.

[mcarvey]

Have you tried it with a different cutter in the angle grinder? You may be able to use something like a woodruff cutter to use the machine as a pseudo-lathe. Could potentially be quite useful depending on where the machine is used. Also there are obviously a number of potential attachments that you could put on it (hack saw blade guide, some sort of alignment block that allows you to spotdrill in the center radially, etc) Find the market, think of what their needs are, and determine what attachments, if any, make sense.

[slatsmith]

"RotarySMP "Since "correct" threads require a define root radius, you would still need a different cutting bit for nearly every thread. "

6 insert sizes will cover any extrenal V-thread 128 to 7 TPI ...
Checked the price of dies for a portable threading machine lately or the price of a machine ? This is one sweet idea .Can't get cheaper on tooling than single point ....

A multi point thread milling cutter would need more ponies to keep it spinning and tooling would get pricey ....

[keen]

It is easy to look at your Threadexpress and say, this is just an angle grinder, a cross slide, TurboCNC on a dos box, and spindle with encoder.

Hi Rotarysmp. I mentioned in the video that the machine could be produced for about the cost of a drill press. I dont want to give clues about the design, but I do want it understood that it is very simple, unique, and low cost to manufacture.

[keen]

Since "correct" threads require a define root radius, you would still need a different cutting bit for nearly every thread.

Hi RotarySMP. Yes in theory you are right, but for years precision threads have been screw cut in Lathes with hand ground HSS bits and only approx root rads. As long as the root rad is not too large the exact rad is not critical in most practical applications.

However I agree there will be some specific applications where your point is valid.

[keen]

"RotarySMP "Since "correct" threads require a define root radius, you would still need a different cutting bit for nearly every thread. "

6 insert sizes will cover any extrenal V-thread 128 to 7 TPI ...
Checked the price of dies for a portable threading machine lately or the price of a machine ? This is one sweet idea .Can't get cheaper on tooling than single point ....

A multi point thread milling cutter would need more ponies to keep it spinning and tooling would get pricey ....

Hi slatsmith. Yes insert tooling would allow more accurate threads. Perhaps this could be used for precision end users - and about 3 sizes of fly cutter type tooling for budget/general purpose users.

[keen]

Have you tried it with a different cutter in the angle grinder? You may be able to use something like a woodruff cutter to use the machine as a pseudo-lathe. Could potentially be quite useful depending on where the machine is used. Also there are obviously a number of potential attachments that you could put on it (hack saw blade guide, some sort of alignment block that allows you to spotdrill in the center radially, etc) Find the market, think of what their needs are, and determine what attachments, if any, make sense.

Hi mcarvey. Yes I was thinking of those options. It could be quite a versatile, portable little machine.

You are right - first find the market!

[keen]

It is quite possible that their is no market, which is why no one bothered putting these things together before. On the other hand it may be that the enabling technologies have only recently become available at appropriate cost, and you have something that there is a strong latent demand for.

Hi rotarySMP. You make some good logical points.

Re no market. The machine is incredibly useful - even in an average machine shop with lathes etc - a thread can be very quickly set and cut - much quicker and a much cleaner thread/thread run out than doing it on a lathe.

But just having a good product is not the whole story I agree!

[307startup]

I would buy one, or the plans if you decide that going into production isn't worth the volumes you would want to see...

It is quite possible that their is no market, which is why no one bothered putting these things together before. On the other hand it may be that the enabling technologies have only recently become available at appropriate cost, and you have something that there is a strong latent demand for.

Hi rotarySMP. You make some good logical points.

Re no market. The machine is incredibly useful - even in an average machine shop with lathes etc - a thread can be very quickly set and cut - much quicker and a much cleaner thread/thread run out than doing it on a lathe.

But just having a good product is not the whole story I agree!

[keen]

I would buy one, or the plans if you decide that going into production isn't worth the volumes you would want to see...

Cheers 307startup - keep the feedback coming!

[dang]

Nice machine. As regarding the machine's market, I'd think that the sale of plans and components would be the best bet. Again, it's an inspired bit of engineering. Good luck.