I’m sure you’ve all done this. Seems to me I read about a inexpensive source for spiral cut end mill bits in a recent FWW issue, I can’t find where I read it though. Also, in searching Knots for “spiral upcut”, there seems to be quite a difference of opinion about whether or not to use them.
Thanks for your input,
Eric
Replies
I use spiral endmills extensively in my pattern work. They are designed for metal cutting and may not have as much clearence as you would like,therefore they are not quite as free cutting on wood. I use the tapered cutters to machine the draft on pattern edges. Most any metal working shop will have the sharpening facilities .Since the cost,compared with router bits,is so reasonable,I usually discard the cutter when the edge is worn. On the down side,they are not readily available in carbide.
Work safely ¬¬¬¬¬¬¬¬¬¬PAT¬¬¬¬¬¬¬¬¬
I get mine from Wholesale tool.
Who ever invented work didn't know how to fish....
I buy from MSC. Their web site is http://www.mscdirect.com
One issue with spiral bits is that the helical cutting edges create an endwise force that tends to pull the bit out of the collet. This would be annoying if you were depending on a fixed depth of cut, and could be a disaster if the thing came out at top speed. On any given router, you may or may not be able to tighten the collet enough to keep the bit in place.
Uncle Dunc,
I have never used end mills although I'd like to. I never realized that they could pull out of the collet. Maybe you or others could answer some general questions. I have little experience with tools intended for metal working.
1. If the mill is a "downcutting" spiral, would that tend to keep the bit in the collet? 2. Would that give a cleaner edge to the cut? 3. Would there be problems with chip clearance.
It seems that the shaft of an end mill is always the same size as the cutting end. Many different sizes of shafts. 4. Does that mean that routers can only use 1/4" or 1/2 "end mills? I'm not aware of an adapter that lets routers accept other size shafts.
5. Since metal cutting machines run a lower speeds than routers, should the router be run at a lower speed with these bits than with wood cutting bits?
VL
I've done more machining that routing. I have a router, but I'm no router guru. The gurus my have different answers. YMMV :)
>> 1. If the mill is a "downcutting" spiral, would that tend to keep the bit in the collet?
There would certainly be a force pushing in that direction, but I think it would be more likely to lift the whole router than push the bit deeper. Unless you lean on your router a lot harder than I do. :)
>> 2. Would that give a cleaner edge to the cut?
I haven't used a downcutting bit myself, but yes, cleaner edges is the advertised advantage. There's at least one vendor that even offers a bit with a down cutting section on top and an up cutting section on the bottom so you can do edge routing or through routing and get a clean cut on both edges.
>> 3. Would there be problems with chip clearance.
That's the advertised disadvantage, you _may_ have problems with chip clearance. Going slower, or rigging a blower or a shop vac are some coping techniques.
>> It seems that the shaft of an end mill is always the same size as the cutting end. Many
>> different sizes of shafts.
Because of the pullout problem, metalheads don't like to use end mills in 3 jaw chucks. Instead they use fixed size end mill holders or collets. So, to reduce the number or holders or collets required, the shaft size is _not_ always the same as the cutting size. A quick tour through my MSC catalog showed shaft sizes of 3/16" and 1/4" to 1" by 1/8ths. Typically the cutting size is less than or equal to the shaft sizes, although when you get up to the 1" shafts, the cutting size can be quite a bit larger than the shaft size.
>> 4. Does that mean that routers can only use 1/4" or 1/2" end mills? I'm not aware of an
>> adapter that lets routers accept other size shafts.
Some manufacturers offer a 3/8" collet. I'm pretty sure Porter Cable is one of them.
>> 5. Since metal cutting machines run a lower speeds than routers, should the router be run
>> at a lower speed with these bits than with wood cutting bits?
Maybe. The limiting factors in metalworking are the machine torque required to drive the cutting edge through the material and the accelerated wear caused by operating at high temperatures. I would say as long as the router motor isn't bogging down and the chips don't come out smoking, you're good to go as fast as you like.
As someone doing routing on a more industrial scale (we use both a Wadkin pin router and a CNC router in my shop, as well as a number of hand routers) I'll add my 2 cents worth:
Down spirals tend to keep the workpiece held down to the bed a lot better. My understanding is that they were introduced (in woodworking) to overcome the problems of workpieces being pulled up off the bed on CNC routers by upcuts - a hair raising occurrence when it happens. They do give a better top edge to the work, but they really need to be used with good chip extraction if you don't want workpieces to burn when routing grooves. I'd really avoid blowing rather than sucking - unless you like a shop full of dust.
Upcut spirals do have a tendency to pull out, especially in CNC and pin routing work and more especially with plastics. The cure is to ensure that you use a decent collet - not an old tatty one - and tighten the collet up well. If a tool then does pull out you need to feed slower or take a shallower pass. Some routers simply have very poor collet designs and far too short a collet. The best hand held collet I know of is the DeWalt DW625 type (which is also found in the Casals/Freud FT2000, the Maffel/Festool 2000 watt router, etc) with the current Bosch 1/2in router being pretty much in the same league. Sorry, but I don't rate most Japanese collets in this respect - too short and/or too few contact points.
Metal cutting end mills have far shallower gullets and so must be used at lower feed and speed rates unless you want the gullets to pack with swarf and a fire to start (really!). They generally have a much faster spiral than woodworking cutters because they are designed to be used at rotational speeds measured in 100s rather than 1000s of revs/min - I reckon it's worth bearing that in mind when selecting feeds and speeds. BTW, I have tried them (and I still use them for some plastics), but, my feeling is that because they are not designed for wood the downside of slow feed rates, potential for scorching, etc. far outweighs the upside of low initial cost (remember carbide spirals are resharpenable) - but then my perspective is from the point of view of time = money.
Porter Cable also offer an 8mm collet/nut combination. DeWalt have 6mm, 8mm, 10mm and 12mm available in Europe, what about in the USA? I believe that Bosch offer a similar range on their 1/2in routers.
Good Luck
Scrit
Scrit and Uncle Dunc, thanks.
I have a Bosch 1/2 in Router with 1/2" and 1/4" collets and an external router speed control (triac?). I don't know if a 3/8 collet is available.
I'm going to get some end mills and see for myself how these things work.
VL
Carbide endmills are, in my experience, cheaper than the ones designed for wood. I have not noticed anything that would make them inferior, and you can get endmills in better grades of carbide, so some of them are actually better. you can find them at any metalworking supplier.
Andrew
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