Need some suggestions. I need to bore 5mm holes for line boring operation and I am wondering what the best way to do it is. I would like to use a 5mm brad point bit specifically for the job but I am ready conflicting info regarding rpm. Also if I go that route I think I will need a metric collet and I’m not sure what to get or where. Maybe a 5mm down cut and do peck drilling would be a better option? Any suggestions would be helpful.
I just need to mention that I am aware of the potential fire hazard of a down cut but please correct me if I’m wrong. If I use the peck drilling and have no dwell time and come all the way out after each cut,( I’m only going in 10mm) will I be ok?
Using a downcut bit when drilling holes is a great way to start a fire, even with peck drilling. The chips have nowhere to go.
I use an amana 46211-k downcut for my 5mm boring. I definitely almost started a fire figuring out my settings. Made some nice embers in no time at all. Don’t have your dust collection on until you are sure you aren’t creating heat. Keep your rpms low. Take small pecks. There is probably a smarter way to go about it but I do this quite often.
I’ve had good luck drilling with endmills. For 5mm I’d probably start at 16k rpm and see how it goes. You definitely want an upcut, but many of those have some pretty sharp tips and will score the hole nicely and leave you with clean cuts.
Thanks for the responses. I’ve used a 1/4" downcut making 1/4" holes about 3/8 deep peck drilling in 3 passes with very good results. About 14 in a row two rows each time and using a digital thermometer I only saw 78 degrees at the bit during cutting. I still would like to try a line boring bit though. Does anyone have any experience with them on a cnc or do you think rpm would be a concern? I’m using a Hiteco 4hp.
I drill at 12,000 rpm and 20mm/sec plunge rate 5mm brad point works grate. I’ve been doing this for years. Hope this helps
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5mm is pretty close to 3/16; you could try a 5mm drill bit in a 3/16 collet and see if it fits (try at your own risk) – I have done this with some bits that were pretty close.
I purchased this bit for evaluation. I intend to often create 5mm holes for shelf pins in cabinets in either plywood or hardwood.
It has a 1/4" shank with a 5mm brad point upcut cutter. To be upcut, the spindle must run counter clockwise. Honestly I don’t know if my AV70S/Centroid controller is capable of this, as I have never had a CCW bit.
I hope to test this out soon and find a good 5 mm solution. I have generated heat while using suboptimal bits in the past.
I don’t know specifically about your controller. The motor is not going to care as long as the direction doesn’t mess up cooling (but drilling doesn’t present much of a load, so it should run cool anyway). The Acorn supports fwd and rev. Most VFDs support both directions.
You will likely need to hook up another relay and wire into the controller though because most CNC suppliers (for sure AVID) only hook up the FWD direction since as you say, there aren’t many bits that have the other twist to them. I went through this when testing the Rapid Change ATC since that needed to also spin backwards to unscrew the collet nut.
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Where does it talk about it having to be run counter clockwise? That seems really strange.
I had the same question, but the photo of the bit shows it… it’s backwards from what you expect. Assuming the photo is correct, of course.
Yep, the bit matches the photo. Maybe these were intended for some CCW/left hand boring machine.
At least I’m not out too much money on them.
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The bit you are showing is what would go in a 32mm line boring machine in a cabinet shop. Typically they have either 13 or 23 bits and drill shelf pin/hardware mounting holes, one cycle drills either 13 or 23 holea at a time. There are also larger dual head versions with 152 spindles available. I have a 23 spindle I used before I got my cnc, it has 11 of those shown and 12 of the right hand version in it. Typically they come in 2 colors as a set either orange and black or red and black to show right or left hand drilling. I use a single right hand bit in a 10mm collect in my cnc for 5mm drilling.
Here is the bit I use.
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Thanks for the tips and industry knowledge! I love how much there is to learn in this area.
I’m also very familiar with these bits, and this is exactly what I was hoping to hear, that someone has used them in a cnc with success. Line boring machines like a Gannomat or SCMI will typically spin around 3000 to 3800 rpm which was my concern. The alternating rotation of every other bit helps to keep everything stationary, even with the incredible clamping force of the hold downs a panel would move with that many bits all spinning the same way and ramming into the edge of a panel.
Are you running these with an atc spindle? If not I would suggest a 1/4" compression and buying 1/4" shelf pins. It will save on the tool changes.
I need to do it manually. I agree about the time savings, but I think .25 holes look too big and I also use euro screws to mount my hinges and drawer slides.
Or get a 1/8" end mill and mill-drill whatever sized hole you need 
Here is another option as well. Not as fast on the feedrates for cutting, but no changes either.