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I've never worked with HDF before and need to do some panel cutting work, corner radiusing and edge profiling, will ordinary woodworking rotary saw teeth & router blades cut HDF leaving fluffy edges and if so how can I avoid this, e.g. different HDF specialist blades/some other finishing method perhaps?

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    Welcome to WW.SE. I'm not sure what your question is, actually. I mean, use an appropriate saw blade to cut composites and good quality router cutter to shape it. You don't say what tools you have. When I use a new material I often sacrifice a piece so I can get a feel for how it works.
    – jdv
    Sep 14 at 11:55
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
    – Community Bot
    Sep 14 at 12:18
  • Apologies for my first and unclear post, now edited.
    – jbk
    Sep 14 at 15:20
  • I didn't want to come right out and say it in my Answer but there's some shenanigans when it comes to HDF! Based on what I've seen occasionally firsthand and read accounts about some HDF is in effect mislabelled MDF.
    – Graphus
    Sep 14 at 20:54
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Sheet goods without veneers like HDF and MDF contain a lot of glue. This means you will want to invest in higher quality carbide-tipped tooling. (I'm not even sure I've seen a pure high-speed-steel tool for sale in the usual places, but it is worthwhile stressing that this is a material that will dull HSS tools fast.)

As for straight cuts, any ATB (alternating top bevel) toothed blades will cut cleaner, but will wear out quicker than TCG (triple-chip grind) toothed blades. But we definitely want a tooth that scores and cuts because these materials tend to want to chip. 40-80 tooth blades will be sufficient, with more teeth perhaps giving you a better edge with diminishing results as you get closer to 80.

Any good quality router bit with carbide cutting edges will work fine. A case could be made for triple-flute being better than double-flute, but I've never noticed a difference in most materials (plastics being the exception). Speed-and-feed for router work is the single most important factor for best finish. This is why I'd recommend some practice runs with any new-to-you material.

(This is also a place where you can experiment with climb-cutting, which can sometimes get you a better finish, though at the expense of a tool that tends to feed itself into the work, which ruins that finish by introducing uneven, wavy cuts. Climb cutting should only be attempted on a CNC machine as it can be very dangerous otherwise - the cutter wants to "grab" the timber and throw it out, or you can even break cutters etc.).

This tooling will make a lot of dust, and so care should be taken to not clog up your equipment or your lungs.

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First be mindful that HDF, like MDF, is a class of material and not a specification, so the product can and does vary. MDF spans a range of densities and HDF does too, with the top of the first category smoothly seguing into the bottom of the second. In short, some HDF is more like MDF than other examples.

That said, if you adopt any of the numerous standard practice to help achieve clean router results with MDF you'll assuredly get as good or better results in HDF. Of course start with sharp, clean, carbide-tipped or solid-carbide bits, then select an appropriate router speed for the bit type (style and esp. diameter) and and keep careful control over your feed rate.

In addition, when routing conventionally use a second "dust pass" and use climb cutting where applicable and where you're comfortable doing so.

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    Could you define (or link to a definition of) "dust pass" for those who aren't familiar with the term?
    – FreeMan
    Sep 15 at 15:38
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    @FreeMan, I'm hoping the OP will ask a follow-on Q if he needs to.
    – Graphus
    Sep 15 at 22:26
  • This sounds like what machinists refer to as a "spring pass".
    – jdv
    Sep 16 at 19:57
  • @jdv, yes.
    – Graphus
    Sep 16 at 22:31
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    Oh, I just visited all those links and the dust pass Q&A, and with the tape trick, or the 1/64 adjustment this is more like what they call a finish pass. A spring pass is when they literally don't move the tool and get the material that was missed when the material sprung away from the tool pressure. Nice trick I knew nothing about in woodworking, though I am a n00b when it comes to router work.
    – jdv
    Sep 17 at 14:12
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Carbide or diamond cutters are best, but carbide (and probably even diamond cutters) will still generally leave a "fluffy" edge which requires sanding and sealing.

Be aware that even with carbide cutters (I do not have experience of diamond cutters so can't comment on those), your blades will dull very quickly. Where I used to work, we would run 45° chamfers along edges of MDF boards using carbide cutters in a spindle moulder (shaper) and it would only take about 20 boards (so about 50 linear meters) until the blades were noticeably dulled, misshapen and close to needing replacement or re-sharpening.

You may improve the quality of cut by doing a "roughing" pass and a "finishing" pass, if this is possible with the kind of machining you'll be doing. That is, cut/rout/chamfer it slightly oversize in your first pass, and then do a second "finishing" cut where you come in and remove the remaining milimeter or so. This will likely cause more wear on your tools though, since you're effectively running each cut twice.

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    What kind of ****ty carbide were they buying that a mere 50 linear meters was enough to noticeably miss-shape the edges? LOL Seriously though, I'm not sure how applicable spindle-moulder wear rates are to common routers and their bits. I do wonder about the quality of the carbide (like HSS not all made equally by any means!) but I suppose the main factor is the smaller diameter equates with a lower edge speed for the same RPM as you know.
    – Graphus
    Sep 15 at 7:26
  • Trend ones. They're actually quite good I think? MDF just causes tons and tons of wear, even to carbide, really. Much more wear than the dense hardwoods we were using. Also this is talking about machining out a 15x15mm chamfer at 6000RPM on a 150mm diameter spindle block, with quite high feed rates. It was an industrial level shop and the operators would push the machines hard to maximise throughput.
    – WhatEvil
    Sep 23 at 3:33
  • Sorry that was meant as a joke, it's well known that spindle moulders are very hard on their tooling (along with being extremely dangerous). From what I've read in the forums Trend used to be good but quality has slipped in recent years, and FWIW Wealdon being the usual recommendation to get instead.
    – Graphus
    Sep 23 at 6:37
  • Fair enough. I think spindle moulders' reputation for danger is outdated. There was a time (50 years ago??) when the blades on the blocks were held in place simply by clamping friction between smooth surfaces, and now and then they would throw a blade. All modern spindle tooling has extra means of securing the blades (usually a pin or a serrated grip) so this is almost unheard of. I worked with spindle moulders and in the industry for 15 years and never met or even heard of anybody injured by one. It was always one of the safer machines in my view. I knew some people hurt by saws, though.
    – WhatEvil
    Sep 24 at 20:49
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    I think they've greatly improved the quality of the guarding in the last 30 years. I have worked on what I believe to be a 1950s or '60s spindle moulder and also one produced in ~2010 and there's a pretty big difference. Also having a power feed on them makes them loads safer both because you don't have to put your hands near the tooling and because there's an extra (sturdy) object between you and the blades.
    – WhatEvil
    Sep 27 at 4:54

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