Redrilling Plasma Cut holes.

[TJS]

I know this topic has been visited before. However, here is the way I do it. I do not like the way the peck pierce method works as sometimes it is off a few thous when going to pick up on it in my milling machine. I also cannot lesson the amps so the pierce goes all the way thru(yes I have played with pierce delay).
This is an issue when trying to get exact hole spacing. So what I do is plasma cut a smaller hole then re-drill it out. I use a carbide Mill/drill shaped end mill. This method also works to remove the bevel.

[TJS]

Here is how I locate the holes. I use a transfer punch or precision ground round stick depending on the size of the hole and what I have on hand. Also when I put the carbide cutter in the mill, I also just kiss the surface and you can see if the chamfer it makes is not centered then I adjust accordingly.
In this scenario I used my digital readout as well. So once I got it "centered" in the hole I then moved to the other hole and I was maybe 5tenths of a thou off. Good in my book for the bolt thru hole.

20240128_113241.jpg

[adbuch]

TJ - using your method how do you know that you have the "mill/drill" centered exactly on the plasma cut holes? I would think it could easily be off be at least several thousandths just the same as you mention with the "peck/pierce" method.

I just posted this and as I was posting your second post appeared. Still the same question. I follow what you are doing, and I often do the same thing for locating non-precision holes on my mill using a gauge pin, transfer punch, etc. I suppose it all depends on exactly what tolerance with the hole spacing is acceptable for the particular job.


David

[TJS]

TJ - using your method how do you know that you have the "mill/drill" centered exactly on the plasma cut holes? I would think it could easily be off be at least several thousandths just the same as you mention with the "peck/pierce" method.

I just posted this and as I was posting your second post appeared. Still the same question. I follow what you are doing, and I often do the same thing for locating non-precision holes on my mill using a gauge pin, transfer punch, etc. I suppose it all depends on exactly what tolerance with the hole spacing is acceptable for the particular job.

David

In this scenario I used my digital readout as well. So once I got it "centered" in the hole I then moved to the other hole and I was maybe 5tenths of a thou off. Good in my book for the bolt thru hole. David, I can say this is more accurate than using the HF step drill by hand to finish off the hole. I have used that method too and it works but again like you are saying it depends on the tolerance. For me the peck pierce method is very innacurate.

[adbuch]

What is the part number, manufacturer, and source for the "mill/drill" you are showing. I can see where this would be much better than using a regular drill bit for this task.

[adbuch]

I have digital readout on my Bridgeport as well, so I hear where you are coming from.

[adbuch]

For parts like the one you show, I quite often use annular cutters on the mill for creating precise holes. I've got some nice annular cutters that came with my Hougen mag drill, and purchased an R-8 adapter so that I can use the annular cutters in the Bridgeport. I run them in back gear at low speeds with lubricant and they work great.

[TJS]

For parts like the one you show, I quite often use annular cutters on the mill for creating precise holes. I've got some nice annular cutters that came with my Hougen mag drill, and purchased an R-8 adapter so that I can use the annular cutters in the Bridgeport. I run them in back gear at low speeds with lubricant and they work great.

I have many annular cutters. I made my own adapter for them on my Bpt. They are the best. Yes back gear as well.

[adbuch]

For parts like the one you show, I quite often use annular cutters on the mill for creating precise holes. I've got some nice annular cutters that came with my Hougen mag drill, and purchased an R-8 adapter so that I can use the annular cutters in the Bridgeport. I run them in back gear at low speeds with lubricant and they work great.

I have many annular cutters. I made my own adapter for them on my Bpt. They are the best. Yes back gear as well.

What is the part number, manufacturer, and source for the "mill/drill" you are showing?
Thanks,
David

[adbuch]

It says MIcro 100 Super Carbide, but what is the actual part number? And perhaps you could show some close-up pictures of the business end of the cutter.

[TJS]

I am not in my shop right now. I put the number in the comments section in my vid on YT, as someone asked the same question. The part number on the package is worn off. I was barely able to read the faint etching on the tool itself.

[TJS]

David,
I got this a long long time ago. Not sure where. The part number for what I can see etched into the tool. DM-437-490X 250m.
Package says : Micro 100 Super Carbide. This is 7/16"

Edit. THere is one on ebay. Search Micro 100 super carbide Drill Mill.
DM-437-290X

I cannot get to ebay with what I am on right now.

[adbuch]

David,
I got this a long long time ago. Not sure where. The part number for what I can see etched into the tool. DM-437-490X 250m.
Package says : Micro 100 Super Carbide. This is 7/16"

Edit. THere is one on ebay. Search Micro 100 super carbide Drill Mill.
DM-437-290X

I cannot get to ebay with what I am on right now.

Thanks TJ! I ordered several different sizes to check them out. As an alternative to plasma cutting the holes and then drilling to size, have you though about using an EasyScriber in your torch to scribe the locations, perhaps by scribing crosshairs to mark the hole centers - and then using an annular cutter to locate and drill the holes on your Bridgeport? My annular cutters have a nice pointed center piece that would be pretty easy to center on a scribed crosshair.

[TJS]

David,
I got this a long long time ago. Not sure where. The part number for what I can see etched into the tool. DM-437-490X 250m.
Package says : Micro 100 Super Carbide. This is 7/16"

Edit. THere is one on ebay. Search Micro 100 super carbide Drill Mill.
DM-437-290X

I cannot get to ebay with what I am on right now.

Thanks TJ! I ordered several different sizes to check them out. As an alternative to plasma cutting the holes and then drilling to size, have you though about using an EasyScriber in your torch to scribe the locations, perhaps by scribing crosshairs to mark the hole centers - and then using an annular cutter to locate and drill the holes on your Bridgeport? My annular cutters have a nice pointed center piece that would be pretty easy to center on a scribed crosshair.

Yes I have thought about doing cross hairs. Is it just a plus sign (+). I have not come to the point yet where I will need that accuracy and spend more time on a part. But I know someday that will come and will keep the easyscriber in mind. Thanks.
T.J.

[acourtjester]

As a DIY guy without a well equipped shop I have a different method. When creating a cut G-code my drawings have the hole positions on the DXF file. I use a dimpling procedure to mark the centers of the holes I want to drill that plasma marks them in the G-code. attached is a video of this procedure. Here is a DXF file showing the center dimple marks and the cut paths. I then use a carbide center drill using the dimples as a center punch location to make a better start for the finish drilling to size for the holes. I have used this method on many different projects.

center drill.JPG

nested DXF parts.JPG

[TJS]

Yes Tom I use the dimpling method or peck pierce however, I cannot lower the amperage to just put a divot in the material (i tried it does not take it). Command CNC does not allow it without some RS232 hookup (not sure the nomenclature). So what happens is that it makes a hole and sometimes it is not exactly in the center.

[acourtjester]

I wonder if you could use a Linuxcnc software package since Cammand CNC is Linuxcnc based. QTPlasmaC is very flexible but may not work with their THC section.

[SRdesign]

There was someone that replied to one of my questions and said that they plasma cut their holes to the size that they want them, then flip the metal over and drill on the back side…. So they are drilling out a hole that has a reverse taper. So the reverse taper guides the bit but also it doesn’t bind up in the plasma cut hole. I hope that makes sense.

[acourtjester]

the thing I had heard was Plasma cutting steel makes the edges harden and that is why it is tough to drill out under size holes.

[adbuch]

the thing I had heard was Plasma cutting steel makes the edges harden and that is why it is tough to drill out under size holes.

Tom & Steve - I agree that the plasma cut edges will be hardened and as a result tear up regular high speed steel drill bits in short order. TJ is using carbide cutters which should last much, much longer. I just ordered some to try out and I will let you know how I like them. As far as drilling, reaming, etc. from the backside - I'm really not sure how much difference that might make - if any. But it does sound like it may be worth trying, particularly if you are using drill bits to enlarge the plasma cut holes.

David

"Edge hardness This is a consequence of nitrogen, either as an 80% component of air or as pure nitrogen, being used as the plasma gas. Nitrides are formed in the cut surface to a depth of approx. 0.15mm and are very hard (upto 540 VHN)." This would equate to around 51 RC.

[TJS]

Just yesterday I had to remove the little dimple or whatever you call it to get a bolt thru in a few plates I cut. It was just a tiny one. I was in my garage shop. I had a HF step drill and chucked it up in a cordless hand drill. It worked great. I will do another vid when I have this situation again.
T.J.

[TJS]

Hey David,
Bringing this back up to the top. Have you tried any of the carbide bits you ordered. Let's see them in action.

[adbuch]

Hey David,
Bringing this back up to the top. Have you tried any of the carbide bits you ordered. Let's see them in action.

Hi TJ - I did order a 5 piece set of the drill/mills - 1/4", 5/16", 3/8", 7/16", and 1/2". I ordered them individually from several Ebay sellers. They look great, but have not had a chance to use any of them yet. I'll keep you posted.

David

[acourtjester]

not to beat a dead horse but I still use the plasma dimpling to mark hole to be drilled after. Here are images of 3/16" steel with dimple made with 25 amps with a 45 amp nozzle. With this small dimple I can use a normal drill bit to drill out the holes without a problem. Steel shown after acid bath to clean off mill scale.
TJ this method happens before the THC comes into play so I don't think you controller would have a problem with it. It is a very short burst and time off before any X or Y moving of the torch, IMHO

DSCN0630.JPG

DSCN0628.JPG

[TJS]

Tom,
I have played with this method. I played with pierce delay. The problem I have with this is it makes the hole all the way thru the material. I cannot turn the amperage down.

I also had a part the other day in where I used a step bit on the backside of the hole as stated above. Works great too. I failed to take a pic.