Graver slips underneath steel

[mmatisoff]

I'm new to the world of mini lathes (or any lathe). Last evening (and the evening before that) I sat down to practice cutting steel and brass. Everything went well so long as I didn't put too much pressure on the graver. The slightest pressure on the metal being cut by moving the graver and cross-slide forward made the graver slip under the metal that I'm trying to cut. I tried raising the graver a little to see if that would help, but it didn't cut any better.

I want to pare down a steel nail to form an arbor and pivot. I've seen it done a couple of times using a watchmaker's lathe; but, I want to do the same thing with my Taig mini lathe. Any advice is much appreciated.

 

[jasonh]

Graver?..... This forum mostly talks about tool bits- typically square hss stock ground to a tool profile. The cutting edge/point of the tool is typically on centre. It sounds like your graver is flexing and getting dragged under the work. Get some 1/4" tool stock and try that. That should be stiff enough.

E.g.

http://www.grizzly.com/products/HSS-Square-Tool-Bits-1-4-x-2-1-2-L/G1507

 

[enfieldbullet]

sharpen your graver.(you'll get tired of hearing this one)

turn speed down.

your 'footing' might also be off, you have to present the graver with the correct form.

look for a mr. Pahlow in youtube (user spahlow) , he has several videos which show the correct cutting action.

 

[chipenter]

A Graver is a hand tool and the side not the point is not used for cutting , the graver point goes past the tangent of the work and the wrist turned so that the cutting edge is resting on the work , for cutting left to right turn the wrist to the right and vice versa .

 

[MCRIPPPer]

are you sure you arent using a wood lathe to try and cut metal?

 

[Tin Falcon]

In days of yore when this hobby was young gravers were used to cut metal. If you go to archive.org or google books there are many circa 1900 books on model engineering that explain this process.
In present times we use tool bit clamped to t a tool holder and the tool is moved by turning cranks or cnc program moves the tool with motors.

The old method will work but use caution as some old methods are dangerous by modern standards.

With any tool proper spindle speed and tool position is important.
Tin

 

[GWRdriver]

With any tool proper spindle speed and tool position is important. -
Tin

Tin is absolutely right - of great importance, especially if you are using something akin to a clockmaker's graver, like this one I made from 1/8" round HSS. The tool rest needs to be set as close to the point of contact as possible and the spindle speed needs to be very high, from 4k to 10k rpm, or the tendency will be for the tool to dig in and be pulled or flipped, and my guess is the Taig isn't capable of speeds high enough to have this work out well for you. Also a graver needs to be razor sharp or it will simply skip over the work.

 

[GWRdriver]

With any tool proper spindle speed and tool position is important. -
Tin

Tin is absolutely right - of great importance, especially if you are using something akin to a clockmaker's graver, like this one which I made from 1/8" round HSS. The tool rest needs to be set as close to the point of contact as possible and the spindle speed needs to be very high, from 4k to10k rpm, and my guess is the Taig isn't capable of speeds high enough to have this work out well for you. Also the graver needs to be razor sharp or at speed it will just skip off the surface of the work.

 

[Tin Falcon]

Look for books by Paul Nooncree Hasluck like the metal turners handy book and Lathe work.
http://archive.org/details/metalturnershan00haslgoog

http://archive.org/details/lathework00haslgoog

http://archive.org/details/modelengineersh00haslgoog

so if you really want to use gravers on the lathe research the old books and use extreme caution .

IMHO some of the old ways are useful and some are antiquated. reading the old books shows use how easy we have it in the modern home workshop. but this is a hobby lean the old ways as you like but be safe.

GW in the days of Mr Hasluck the foot pedal driven lathe was the norm. I can not imagine a foot petal lathe producing the speed you mention and I expect the bearings of the time to be Babbitt bearings. Hmm

Tin

 

[enfieldbullet]

GW in the days of Mr Hasluck the foot pedal driven lathe was the norm. I can not imagine a foot petal lathe producing the speed you mention and I expect the bearings of the time to be Babbitt bearings. Hmm

Tin

watchmaker's lathes most had plain bronze bearings or no bearings at all as is the case with the 'turns'. they would have two dead centers and a carrier with a pulley.

you can use the graver slower, just takes practice.

it is a hard little tool to master though. in turning and engraving as well.

 

[mmatisoff]

Thanks everyone. The error is mine. I used the wrong terminology. My mentor was showing me how to reduce a steel nail to 0.16" diameter using a watchmaker's lathe and gravers. I'm using a Tail lathe and meant to say tool bit. I've sharpened the tool bits three times. Once they are sharp, the brass peels away in long curly strands; however, every so often, the tool bit slips under the workpiece bending the brass and damaging the tool bit. I'm cutting brass at 3340 rpm and steel at the 500 rpm. I believe I know what the problem: I'm trying to remove too much metal at one pass. I'm still in the process of learning how much metal to remove on each pass. The other problem is cutting steel. Almost without exception, when I attempt to cut HSS steel, the tool slips under the workpiece. In this case, the metal doesn't bend; however, the tool bit does get damaged. Furthermore, in those rare cases when the steel does cut, the metal crumbles apart instead of peels away as it does with brass. Any suggestions would be most helpful. Marty

 

[Tin Falcon]

first of all how are you grinding your tool bits. I mean rake angles. Brass is fine with zero back rake steel you need about 15 degree back rake.
second of all sounds like you need a steady rest. ir you have more than 3-4 times the diameter sticking out it needs to be supported. Also make sure the tool is on center. if it above center and it flexes it will dig in and cause problems.
I am still concerned about spindle rpm . get a speed and feed chart or calculator or use and on line one. And some steel just does not cut well . get a piece of 12L14 cut it and you will be spoiled it is the standard for machinabilty in steel.


Download and read Army TC 9-524 it will give a lot of basic information.
hope this helps.

If you can photograph your set up. this will help us help you .
Tin