HSS Up cut Spiral Router Bits (from ebay!)

[Stevekane]

Good morning, Im trying my hand at some loose tennon mortices in solid pine and Ive got a brand new 12mm dia made in china High speed steel up cut spiral bit. Its a great looking bit but being hss Im wary of using it in my router, but thats what I need to do,,,so am I better on low speeds aggressive plungeing or higher speed light passes,,or any other combination,, any thoughts anyone?
Steve.

 

[Rorschach]

What are you wary about?

 

[smackie]

If it’s a bit you’ve never used before, light passes would seem to be a sensible step but that’s true for every router bit you’re not familiar with.

Practice on some pine scrap?

 

[J-G]

I suspect that the OP is concerned about the HSS Cutter getting too hot and therefore loosing its edge.

As @smackie has just said, light cuts and slow(ish) speeds during tests working both up with experience.

 

[Rorschach]

I suspect that the OP is concerned about the HSS Cutter getting too hot and therefore loosing its edge.

As @smackie has just said, light cuts and slow(ish) speeds during tests working both up with experience.

HSS is unaffected by heat unlike carbon tool steel.

 

[Stevekane]

Many thanks everyone, much appriciated, as you guessed my concern is burning out the bit, looking on the net about suggesed speeds etc for hss bits I can really only find CNC applications, but they do say that chip size and speed are the key to keeping the bit cool, but I know nothing about cnc machines but I wonder if the also run at the very fast speeds routers do? One quote was that after the task the bit should only be warm to the touch,,I dont think my router bits ever run that cool,,,or do they?
The bit looks perfect for plunging and my thoughts are to plunge to the full depth (35mm) checking the temp as I go then to sweep in small steps to tidy up, how does that sound?
Steve.

 

[smackie]

Depends on how good your chip collection is, to be honest. I’ve got a few larger shank upcutters and they throw out a lot of chips in a short period of time. Thankfully, I’ve got decent chip collection on the router but a 35mm plunge is pulling a lot of material out. If the bit is wide, you’re relying on the cutting surface underneath to clear efficiently too and a straight plunge in to full depth doesn’t give a lot of wiggle room to start with.

If it was me, I’d do it in 10mm deep passes and then do a final smoothing pass. I’m cautious tho and not in a hurry.

Router bits don’t run cool as anyone who’s tried to change a bit too quickly will testify.

 

[Stevekane]

Exactly my impression, my router bits get quite hot, I'm not in a rush so I can afford to take my time and perhaps thats the way forward in both feed rate and speed, but its no good hanging around and letting things heat up either,,,a bit of a balancing act I think, the trouble is that thinking back to hss bits they could burn in the blink of an eye.
Chip collection will be the domestic Dyson,,and the shockingly cold wind we seem to have in the garden at the moment!
Steve.

 

[J-G]

HSS is unaffected by heat unlike carbon tool steel

Simply not true - HSS is affected LESS than Carbon Steel cutters but it certainly is affected. More important though is the fact that even at the relatively low speed of a hand held Router (3-6k ish) the cutter could get hot enough to burn the wood if the depth of cut were excessive.

In my CNC Router - running between 12k and 23k I would limit the cut depth of a 12mmØ cutter to about 3mm in hardwoods, maybe 5mm in MDF (not that I use much MDF) and this would be using TCT or solid carbide tools. I do occasionally run HSS end mills but never larger than 6mmØ.

 

[Rorschach]

Simply not true - HSS is affected LESS than Carbon Steel cutters but it certainly is affected. More important though is the fact that even at the relatively low speed of a hand held Router (3-6k ish) the cutter could get hot enough to burn the wood if the depth of cut were excessive.

In my CNC Router - running between 12k and 23k I would limit the cut depth of a 12mmØ cutter to about 3mm in hardwoods, maybe 5mm in MDF (not that I use much MDF) and this would be using TCT or solid carbide tools. I do occasionally run HSS end mils but never larger than 6mmØ.

Nope, you are wrong. Altering the hardness of HSS takes a very careful tempering cycle, the sort of situations that occur in woodworking won't do it. You can get run HSS on a grinder until it is red hot and it will still be pretty much as hard as it was before.

 

[J-G]

We'll have to agree to differ @Rorschach

Though I wasn't suggesting that the HARDNESS would be altered, just that the edge (sharpness) would 'go off' sooner if the tool were subjected to heavy cuts at high speed causing high temperature.

 

[Rorschach]

Sure you can wear away the edge, you can do that with any tool, but the heat you see on the tool isn't the cause, it's a symptom. The point I was making is that heat in and of itself is not detrimental to HSS, HSS is literally designed to be hard and heat resistant. If however you are putting it in a situation where it is rubbing rather than cutting, it will heat up and it will be worn away, but this isn't because it is getting hot.

A simple way to show this is try and bend a bit of HSS, you can get it red hot with a torch but it won't bend, and if you hit it with a hammer it will snap. Let it cool and it will still be hard. Do the same test with a bit of O1 high carbon tool steel, get it red hot it will bend, let it cool it will be soft (unless you cool it really fast of course).

 

[smackie]

If however you are putting it in a situation where it is rubbing rather than cutting, it will heat up and it will be worn away

Yup. This was kind of my point mentioning the chip extraction. There’s zero point getting aggressive with a router bit if the waste isn’t cleared out efficiently, even with an upcutter. Given that @Stevekane is using a domestic Dyson, I‘m just going to note that initially plunging to 35mm and aggressively cutting out the waste is probably not a good idea, even in something soft like pine…

Of course, if you’re a door fitter ripping out deep lock mounts on a daily basis on site then you’re less worried about this stuff. But you’re also buying router bits in bulk and not worried if the bottom of the cut looks like a wood ember…

 

[Stevekane]

This is all very intresting stuff, much more informative than anything I could find on the internet in a couple of hours last night, even if there are degrees of opinion they are all valid and very informative. The bit Ive got is clearly designed to plunge so my plan was to plunge in steps along the mortice to the full depth with final sweeps to clean up, but now I think I will initially try just running from side to side in steps and seeing how it all feels, at least I now have some ideas and a bit of knowledge to fall back on.
The weather has put paid to working outside so it may be a couple of days before I report back,,,

 

[Inspector]

I find myself stunned that I agree and support Rorschach on what he has said about HHS tooling. It was designed to cut metal while near red hot until it finally gets dull, many times longer than carbon tooling at the time could. Not from the heat though. After that for a brief while special alloys were used, Stelite, Tantung, Croballoy and a couple others until Carbide came along. My spelling may be off on those examples. The thing you should be more concerned about is the bit pulling itself out of the collet. The spiral of the bit acts to pull the bit out. Clean collets in good condition and properly tightened is important.

Pete

 

[Rorschach]

I find myself stunned that I agree and support Rorschach on what he has said about HHS tooling. It was designed to cut metal while near red hot until it finally gets dull, many times longer than carbon tooling at the time could. Not from the heat though. After that for a brief while special alloys were used, Stelite, Tantung, Croballoy and a couple others until Carbide came along. My spelling may be off on those examples. The thing you should be more concerned about is the bit pulling itself out of the collet. The spiral of the bit acts to pull the bit out. Clean collets in good condition and properly tightened is important.

Pete

No matter how many times you shower the dirty feeling of agreeing with me will never wash off.

 

[johnnyb]

I've used spiral bits in the leigh fmt and they are really good. mine were from wealden. plunging a 1/2 inch hole is effortless. a mortice is made by plunging several times then going front to back. tenons are made by climb routing around first then then normal routing to the template. they remain sharp for hundreds of m and ts

 

[Bristol_Rob]

I'm sure I read that you can safely pluge 1/2 the diameter of any bit.

Take your time, don't be greedy or in a hurry and enjoy

 

[Stevekane]

An

I've used spiral bits in the leigh fmt and they are really good. mine were from wealden. plunging a 1/2 inch hole is effortless. a mortice is made by plunging several times then going front to back. tenons are made by climb routing around first then then normal routing to the template. they remain sharp for hundreds of m and ts

Many thanks Johnny, thats very intresting, I had a look at the Leigh Jig, super looking bit if kit, Ive knocked up a simple ply one to go with a 30mm guide bush, clamps to the side in a similar way but without any adjustments short of packing it out with cardboard! Your comments on the Spiral bits, are your ones Carbide I wonder? but your method of a series of plunges with final clean up sweeps were my original thought, so I might now give it a try first. I did see somthing on a very technical sight about being carefull if morticeing in ever deeper sweeps because of the stresses being exerted on the bit in a hole that is most likely narrowing ever so slightly, so plunging the sides if nothing else is probably a good plan anyway and will allow a bit of space for the cutter too.
Inspector, good point about the bit wanting to pull itself out, I dont like to murder up anything and collets get the same consideration, but I will give this spiral job an extra nip!
A better day today, so domestic duties permitting I might be giving it a go,,,
Steve.

 

[ivan]

The books generally say that you can plunge and then traverse full width up to the shank dia. For morticing, in a jig* you can drill out the waste with several plunges to full depth, and then traverse to clear the edges, better to go insteps if routing freehand.
* Woodrat or home made Bob Wearing style