Through Drilling on PTP or CNC Equipment

Advice on clean hole-drilling for panels that will be exposed on both faces. June 29, 2009

I am starting to look at new machines for my closet business. We make only flat panels drilled and notched for rail or base molding. The big difference between closets and kitchens is we drill through our panels and use them as common center panels. I'm being told by salesmen that both a PTP and CNC will both drill through without blowout. I can see a CNC drilling clean since it has a spoil board but I'm skeptical about a PTP since it's up in the air. Does anyone have experience with through drilling on PTP or CNC?

Forum Responses
(CNC Forum)
From contributor K:
I do know for through drilling you need a special bit.

From contributor R:
My PTP will through-bore but the bits have to be very sharp all the time. For closets in a production environment I would not do it. For me the quality just is not there but I'm also new to the CNC scene.

From contributor S:
I have a PTP and do through drilling, you should use a v-point bit and the machine typically will have a setting to slow the bit down before exiting the panel. Both types of machine can do through drilling, the advantage of a PTP is that you can also machine on the edges of the panel. My Busellato has settings in the software that calculate the amount of through stroke needed for the v-point bits. I also did through drilling on a Gannomat line bore with v-point bits - I did not need a backer sheet.

From contributor M:
I use a Weeke BHC 250 PTP and through-bore thousands of verticals a year, with no blowout. I go through 50 bits a year and get them sharpened at least twice before I have to toss them.

From contributor I:
We drill thousands of panels through-bored on a Weeke also. We have been using solid carbid V bits and they outlast carbide tipped 10 to 1. With the solid carbide we can drill all day long for several months before they get dull and start to blow out or chip the melamine.

From contributor A:
I suggest you buy a Weeke BHX500 or Biesse Skipper100. These machines have drill banks on the top and bottom so through holes are drilled half way on each end making the holes very clean. Zero setup time is needed as these machines move the panel around instead of the panel being fixed to vacuum pods. These machines are ideal for your type of work. You can even drill two boards such as gables or symmetrical shelves in the same time as a conventional ptp would drill one board. Another thing is to use high end drills made in Japan that have a special geometry that makes a perfectly clean hole for through the board or in blind holes drilling. These high end drills cost more but are in my experience worth the money.

From contributor T:
Regardless of which machine you use the key to drilling clean through-holes is the bit. Contributor I is correct in that the solid carbide V-point bits cut cleaner and last longer than any tipped bit. I believe these are the bits that contributor A is talking about as well. The only problem people encounter with the solid carbide bits is breakage. If the bit is run too far past dull or feed too fast these bits will break easily. The best thing to avoid this is to have an amp meter on your spindle. If the amps start to climb on the amp meter during drilling the bit is dull or being overfed. Any good electrician can install an amp meter on a motor. This meter can help determine proper feed rates and watch for dulling tools on router bits as well. The FS Tool bits you are looking for would be the D45N and D45Y series depending on the overall length. Do note that they are only available in sizes from 3mm to 8mm in the through hole style bits.

From contributor A:
Machine accuracy depends on the skill and accuracy of the person programming and setting it up. Yes there is the odd machine problem but in my 14 years experience with routers of many brands, majority of the time it's a setup issue. This may include tool setup as well as proper fixturing of the part. I suggest you look at buying a used machine, there are many out there these days and go from there. SCM, Biesse, Homag are all good machines and the service is the same in terms of price for all.

From contributor M:
I agree with most of the above posts. There is one more variable to all of this yet. That is your actual material. Different melamine brands (assuming you are doing melamine panels) will give you different results no matter what machine or tooling you use. The same is true for HPL laminates too.

Overall I think you will find a pod and rail PTP to be the better choice for the type of work you are doing. With the PTP you will typically get larger drill heads (more spindles) which will allow you to drill more holes per stroke thus reducing cycle time for you. A Busellato or Weeke would be a good choice as they also allow pendulum processing. They both also do mirrored parts with one program.

From contributor M:
I have set up and programmed both types of machines. If it were me, I would go with the nested based router. You will get good clean through-holes and you won't have to worry about cutting sheets on some sort of saw prior to machining. The time you save with a larger drill head on a PTP will be erased by additional machines/labor. The routed edges will be ready for banding without the need for pre-milling. Unless you need to do a lot of edgeboring on the CNC due to lack of dedicated horizontal equipment, I'd buy the flat table CNC. The other thing to consider is that careful setup is required for both through -routing and drilling on a pod/rail machine. Pods can add up to a lot of money if your personnel doesn't have their head in the game all the time.

From contributor S:
I have also had very good experience boring through-holes on a CNC pod and rail machining center (not PTP) using solid carbide through-hole bits. However, I occasionally had problems with hardboard through-holes.

From contributor R:
My closet/cabinet shop has a Morbidelli p2p from SCM and it been a very versatile/ workhorse in the six years I have been there - minimal problems and very consistent. Id give them a call to see what they would suggest. Anytime I have a problem they always have a solution.