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mistermikev

variable speed router questions...

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so got a new router today.  it's a porter cable 8902 with variable speed.  Brand new condition w all the goodies for $70 couldn't pass it up.

DSCN3554.thumb.JPG.b7ac6518855a7937abb40a009974faad.JPG

subsequently did this:DSCN3555.thumb.JPG.b2e437c0ce40d6326d7bb4b0aaea8fe6.JPG

and have some theories as to why but wanted to post and get some feedback. 

1) could just be this is hard wood - it's granadillo and is very dense/heavy. 

2) could be the bit I'm using (brand new) which has a very small cutting edge... it worked fine on the other side but could have been enough up/down drift that I was off the cutting edge on the top.   

3) could be the speed of this router - I'm not sure if you should run at 23k rpm in general?  I am well aware that for bigger bits you want to slow the router down as the speed at the outer edge of a large bit will be much greater than a small bit... that's the reason I got this one.  Haven't looked to see what my other pc router spins at but wondered anyway - what are your guidelines for variable speed routers for those who use a variable speed router and have used it on figured woods etc.  does more speed help?

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1 hour ago, mistermikev said:

subsequently did this:

I take it you mean the reglued pieces on the top left  and top right corners?

I assume the router was above the workpiece and you were moving the bit in an anticlockwise direction around the perimeter:

image.png

If that were the case, I'm kinda not surprised you lost the top right corner. There's not an awful lot of timber there to keep it all together, and the bit would want to shear the endgrain away as you got closer to the edge quite easily, particularly if the depth of cut was a bit too ambitious and/or you were moving quickly.

The second section I've marked with the '?', could be similar, but again depends on my assumption of the arrow indicating which way you were moving the router at the time; a small section of unsupported timber and the router bit wanting to shear the piece away from the larger mass of timber - poof! 

The fact that both pieces you're regluing are in a near straight line could indicate that there was some kind of pre-exisitng weakness along that section of grain. Maybe you just got unlucky?

Were you routing with a template? How thick is the piece you were cutting?

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1 hour ago, curtisa said:

I take it you mean the reglued pieces on the top left  and top right corners?

I assume the router was above the workpiece and you were moving the bit in an anticlockwise direction around the perimeter:

image.png

If that were the case, I'm kinda not surprised you lost the top right corner. There's not an awful lot of timber there to keep it all together, and the bit would want to shear the endgrain away as you got closer to the edge quite easily, particularly if the depth of cut was a bit too ambitious and/or you were moving quickly.

The second section I've marked with the '?', could be similar, but again depends on my assumption of the arrow indicating which way you were moving the router at the time; a small section of unsupported timber and the router bit wanting to shear the piece away from the larger mass of timber - poof! 

The fact that both pieces you're regluing are in a near straight line could indicate that there was some kind of pre-exisitng weakness along that section of grain. Maybe you just got unlucky?

Were you routing with a template? How thick is the piece you were cutting?

thank you for the response curtisa.  yes, blew out both those pieces.  I had it upside down from this pic and was taking the full 1/8" off and it is held to the mdf template below via two pieces of tape so... yes... a bit unsupported in that area.  Also was using a 1/4" bit.  Thing is I just cut a well figured piece for my other headstock with sm bit and paying no attention to grain w/o issue... but not so lucky this time.

I think I blew out the leftmost piece by routing the opposite direction on the opposite side.  Not confident I didn't do the same thing on the top piece.  I'm thinking had I been using a bigger bit I would have been able to do it without issue. 

so... appreciate the input.  what are your thoughts on router speed?  do you use a variable speed router at all?

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I generally wouldn't bother with adjusting the speed of the router, but that's just me. I have three routers in the workshop, and the only one that is variable speed is the little Makita trimmer. I've left it set at '5' since I got it and have never adjusted it. According to the manual that equates to about 27K RPM. The other two routers I have just run flat out at 22K RPM.

The smaller router gets used on smaller jobs. That also equates to using smaller bits and taking smaller bites, so I guess the higher RPM makes more sense to keep the chip load up on the smaller diameter bits, where the surface speed will be much lower than on a larger bit. But I've also never got too hung up on fiddling with variable speed, primarily because until I got the trimmer I never had the option, and secondly because when I did try playing with it it didn't make such a ground breaking difference to my work that I felt I should be adjusting it all the time.

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Routing a thin headstock cap like that is a dangerous game whatever the species and router/bit you are using. If you must use a router to shape the headstock, it's safer to glue an oversized cap on to an oversized headstock and route the lot in one go. This sort of thing has happened to me once before so I prefer to shape on the spindle sander now. It's more time consuming to get the exact shape, but there is no risk of tearout. 

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11 hours ago, curtisa said:

I generally wouldn't bother with adjusting the speed of the router, but that's just me. I have three routers in the workshop, and the only one that is variable speed is the little Makita trimmer. I've left it set at '5' since I got it and have never adjusted it. According to the manual that equates to about 27K RPM. The other two routers I have just run flat out at 22K RPM.

The smaller router gets used on smaller jobs. That also equates to using smaller bits and taking smaller bites, so I guess the higher RPM makes more sense to keep the chip load up on the smaller diameter bits, where the surface speed will be much lower than on a larger bit. But I've also never got too hung up on fiddling with variable speed, primarily because until I got the trimmer I never had the option, and secondly because when I did try playing with it it didn't make such a ground breaking difference to my work that I felt I should be adjusting it all the time.

I appreciate that.  I guess I won't worry about it for the most part... but I do have a 1.5" bowl bit that is either unbalanced or just too big to run at full speed because it vibrates more than I am comfortable using it at.  This will be nice for that and perhaps my chamfer bit and 1/2" radius.  Guess we'll see.  thanks for the response.

4 hours ago, ADFinlayson said:

Routing a thin headstock cap like that is a dangerous game whatever the species and router/bit you are using. If you must use a router to shape the headstock, it's safer to glue an oversized cap on to an oversized headstock and route the lot in one go. This sort of thing has happened to me once before so I prefer to shape on the spindle sander now. It's more time consuming to get the exact shape, but there is no risk of tearout. 

thank you AD.  for a symmetrical design like this I don't think I could get uniformity on a sander.  also, unfortunately for this headstock - if you look at the shape and consider it's being bound.  Have to bind it off the neck because of the tight curves - can't get in there to cut binding channel and not willing to do them with a chisel.  I think I can make this work tho... going to probably take it and sand it such that there is almost nothing to remove with the router... then try again removing the majority with a bigger bit... and paying a bit closer attention to direction.  wish me luck!  Might have been a better idea to make a sister template to sandwich it between.  Next time!

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These would be ideal for headstock shaping if they came a bit smaller, like 1/2" radius. Makes me think it's got to be possible to make something like that with the smallest bobbin/attachement for spindle sander. 

https://www.stewmac.com/Luthier_Tools/Tools_by_Job/Tools_for_Sanding/Robo-Sander_Flush_Trim_Sander.html?utm_source=google&utm_medium=shopping&utm_campaign=2020-01-gp&pref_currency=P&shipcalc=UK&gclid=CjwKCAiAx_DwBRAfEiwA3vwZYkSFsUtU9kMWIbR5Eng0AJ057c5WHc-Ds_y5lZUdDm2VO9N--Lr6BBoCP54QAvD_BwE

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1 hour ago, ADFinlayson said:

These would be ideal for headstock shaping if they came a bit smaller, like 1/2" radius. Makes me think it's got to be possible to make something like that with the smallest bobbin/attachement for spindle sander. 

https://www.stewmac.com/Luthier_Tools/Tools_by_Job/Tools_for_Sanding/Robo-Sander_Flush_Trim_Sander.html?utm_source=google&utm_medium=shopping&utm_campaign=2020-01-gp&pref_currency=P&shipcalc=UK&gclid=CjwKCAiAx_DwBRAfEiwA3vwZYkSFsUtU9kMWIbR5Eng0AJ057c5WHc-Ds_y5lZUdDm2VO9N--Lr6BBoCP54QAvD_BwE

have often thought about snagging those for other jobs... but for this one... a 1/4" bit won't even fit between the horn... so it'd have to be 3/16... then again if I had a 3/36" dremel stone bit and put a stack of 1/4" washers on top of it... might be able to cut a binding channel.  Probably wouldn't have the greatest edge on the bottom tho. 

but then what motivation would I ever have for sweeping the garage floor? (finding chunks of wood that went flying across the room... looking like a crack addict all on my knees searching the floor - wouldn't want to miss out on that now would we!)

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I'd personally reverse your order of assembly - shape headstock, attach cap, trim edges.

You could have the headstock shaped, glue the cap to it cut a mm or two oversize, and then use the headstock itself as the template. The cap timber would then be largely reinforced by the substrate it was permanently attached to, and the tiny amount of overhang left to remove would further minimise the risk of a piece disappearing into thin air. 

The most fragile component undergoing the most destructive operation needs the most support. Shaping the cap first is pretty risky, as you've discovered. Doing it last, however, once it's got something to 'hang on to' will give you a better chance at success.

Looking at it another way from your cabinet workshop experience, you wouldn't pre-trim a Laminex/Formica sheet before you glued it down to a bench top. You'd glue it first then run the laminate flush trimmer around all the edges to get rid of the overhang.

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13 hours ago, curtisa said:

I'd personally reverse your order of assembly - shape headstock, attach cap, trim edges.

You could have the headstock shaped, glue the cap to it cut a mm or two oversize, and then use the headstock itself as the template. The cap timber would then be largely reinforced by the substrate it was permanently attached to, and the tiny amount of overhang left to remove would further minimise the risk of a piece disappearing into thin air. 

The most fragile component undergoing the most destructive operation needs the most support. Shaping the cap first is pretty risky, as you've discovered. Doing it last, however, once it's got something to 'hang on to' will give you a better chance at success.

Looking at it another way from your cabinet workshop experience, you wouldn't pre-trim a Laminex/Formica sheet before you glued it down to a bench top. You'd glue it first then run the laminate flush trimmer around all the edges to get rid of the overhang.

thanks curtisa... that is all good advice and def accurate but the issue here is getting a binding channel in there.  the faceplate needs to be 1.5mm smaller and there was no good way i could figure to get a bit into the little 'hooks' that would have a bearing on it.   in retrospect I 'spose I could have glued it up and used my 1.5mm smaller template to cut the rebate.

I ended up cutting the rest last night, taking off only a light 1/16 each pass and it went pretty well except one of the horns had a tiny little piece fly off.  fortunately I found the piece and am getting really good at gluing on the smallest of pieces!  I probably should have used tape to reinforce those horns a bit.  will finish that little horn with a diamond needle file when it drys and I should be ok.  Really would be made a trivial task by a small cnc setup and that is more and more on my list.

thanks again for the reply!

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Make a router table. it is easier to control the part than the router. Also watch the grain in relation to feed direction, sometimes a climb cut is called for others it is a conventional cut. The amount of side depth so to speak should only be about 1/3rd of the diameter or less  of the bit for something like this. Also RPM to diameter and # flutes will affect this. Even though you are not using a CNC, researching some basic info that gives you Speed/Feed/ IPM will get you close.

MK

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3 hours ago, MiKro said:

Make a router table. it is easier to control the part than the router. Also watch the grain in relation to feed direction, sometimes a climb cut is called for others it is a conventional cut. The amount of side depth so to speak should only be about 1/3rd of the diameter or less  of the bit for something like this. Also RPM to diameter and # flutes will affect this. Even though you are not using a CNC, researching some basic info that gives you Speed/Feed/ IPM will get you close.

MK

right on, thank you for the advice.  def the grain/feed direction, climb/convention cut, and most importantly RPM/Diameter relationship is something I could stand to keep in mind more.  I write my cut direction on my body tempates to help... probably should get in the habit of writing it on every template I make.

according to some charts I've seen anything under 1" is OK up to 24k rpm.  seems like after that it drops 2k for every 1/2" diameter increase.  Don't have too many bits bigger than 1" but will keep that in mind for a few. 

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