• April 2025 Turning Challenge: Turn an Egg! (click here for details)
  • Congratulations to Kelly Shaw winner of the March 2025 Turning Challenge (click here for details)
  • Congratulations to Guillaume Fontaine for "Nebules" being selected as Turning of the Week for April 6, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

RPM for single point cutter?

Bill Alston

Bill Alston

Joined
Jan 10, 2024
Messages
751
Likes
400
Location
Bournemouth, UK
I don’t have an ornamental lathe but would like to try something like the image below. It was done with a single point cutter mounted in the head stock but I’m wondering if I could use one of my routers mounted on a compound table instead. I’m thinking though that a router, even on its lowest speed is too fast for a single point cutter. Thoughts?

IMG_9274.jpeg
 
I think I’ve found an answer to my own question, together with an alternative solution. The minimum speed on my router is 11,500 RPM. This type of cutter has a maximum recommended RPM of 12,000 so should be suitable for making the small shallow cuts I intend to take. I’m pretty sure these kinds of speeds are too high for a single point cutter.

IMG_9275.jpeg
 
If I read your advertisement correctly, the cutter is ~2” in diameter.

Comparing this to the use of a dado blade on a table saw, the dado blade would spin around 3,400 rpm. Maybe you can compare an 8” blade run at 3,400 rpm has the same surface feet/minute at the cutter as a 2” blade running around 13,600 rpm. But that is scary to me.
——————————————
Keyway cutters on milling machines are also similar. The recommended surface feet/minute for these on plastic is 200 (https://internaltool.com/docs/reference/saf-keyway-cutters.pdf). That equates to a 2” cutter spinning at

200 ft/min * 12 in/ft / (2 * pi in/rev) = 389 rpm

Note: I welcome any input a machinist may have for this.
——————————————
The drilling charts say that a 2” Forstner bit should be revolved at 500 rpm. Other large cutters have similar speed recommendations when drilling.
——————————————
It seems to be well balanced, but it will still be cutting only a small part of the rotational circle; Maybe only 10° of the circle, leaving 350° spinning in the air.
——————————————
Regardless, I believe that running this cutter at 12,000 rpm will be too fast and probably unsafe.

If I were to use such a cutter in a drilling spindle on my rose engine, I’d run the bit at a speed around 200-500 rpm.
 
Thanks for your input Rich. I don’t disagree with you but the linked cutter is designed to be used in a router and as far as I can tell none of them I’ve seen run any lower than 10,000 RPM. The description does also state a maximum of 12,000 RPM. I think I may beg the question on a wood working forum to see what the general consensus is. Failing that I’ll contact one of the router manufacturers to see what they say. I do agree though, that cutter does seem pretty large for those kind of speeds. I have seen even larger ones though! :confused:
 
Last edited:
Darryl Fective said:
But will a router bit like that give you enough depth? At some point, wou;dn't the base of the router interfere?
Click to expand...
That did occur to me. The router I’m using is quite slim but I need to take some measurements to see how far down a box I can cut.

This is the type I have. I’m having trouble finding a 43mm mount in the UK at a reasonable price, I may have to make my own.

IMG_9314.jpeg
 
I think people have answered your question. The problem is the router bits that might do this won't extend down far enough to more than Maybe 2 rows. You can but metal working fly cutters but they typically come in 3/8" or 1/2" shanks that won't fit the smaller trim routers.
 
john lucas said:
I think people have answered your question. The problem is the router bits that might do this won't extend down far enough to more than Maybe 2 rows. You can but metal working fly cutters but they typically come in 3/8" or 1/2" shanks that won't fit the smaller trim routers.
Click to expand...
Much depends on the size of cutter. I’ve just measured the nose of my router and using a 6mm wide cutter I can get at least 8 rows.
With a 5mm cutter maybe 10. For something like Box, or another fine grain timber that can take fine detail, I’d like to use these sort of size cutters.
It will be a while before I can try it as I still need to get a compound table which will likely need some modifications. And of course it looks like I’ll need to make a motor mount. I already have some material for that, just a matter of finding some time.
 
With a 3mm cutter I have done 11 rows and could have done more but I was using a CNC motor with an ER11 collet chuck. If making a box you can always do the carving on the lid separately from the base of a box. This is a Boxwood box made with the 3mm cutter. The other photo shows the cutter and motor on my Rose Engine.

IMG_2672.JPG
IMG_3470 copy.jpg
 
Last edited:
colinsp said:
With a 3mm cutter I have done 11 rows and could have done more but I was using a CNC motor with an ER11 collet chuck. If making a box you can always do the carving on the lid separately from the base of a box. This is a Boxwood box made with the 3mm cutter. The other photo shows the cutter and motor on my Rose Engine.

View attachment 60963
View attachment 60962
Click to expand...
That looks nice Colin, and the 3mm looks really good. I might have to revise my cutter sizing. I did think about a spindle motor but they seem quite expensive and run at a high speed.
I’ve been looking at a long nose electric die grinder but can’t seem to find a low speed version. Most of the are 25,000 to 33,000 rpm.

Edit: Colin, how many steps did you make on that box, 24?
 
Bill Alston said:
That looks nice Colin, and the 3mm looks really good. I might have to revise my cutter sizing. I did think about a spindle motor but they seem quite expensive and run at a high speed.
I’ve been looking at a long nose electric die grinder but can’t seem to find a low speed version. Most of the are 25,000 to 33,000 rpm.

Edit: Colin, how many steps did you make on that box, 24?
Click to expand...
Bill

I have 2 3 and 4 mm cutters that I got from Wealden. Excellent quality and not too expensive. The motor I got from Aliexpress https://www.aliexpress.com/item/1005004522599165.html and it wasn't too expensive. It is variable speed so you can slow it down to a very low rpm. Yes it was a 24 peak rosette.
 
Thank very much for all that Colin, much appreciated. ;)

Edit: have you seen these Colin, I spotted it when I first started looking at this type of cutter a few days ago.

IMG_9320.jpeg
 
Last edited:
colinsp said:
With a 3mm cutter I have done 11 rows and could have done more but I was using a CNC motor with an ER11 collet chuck. If making a box you can always do the carving on the lid separately from the base of a box. This is a Boxwood box made with the 3mm cutter. The other photo shows the cutter and motor on my Rose Engine.

View attachment 60963
View attachment 60962
Click to expand...
It seems to be working at the minimal cut depth shown but I would be cautious running a 2" diameter bit on a 1/4" shank with that much extension from the collet. Many bits, such as the one shown in post #2 above, have a maximum extension marked on the shaft for a reason.
 
Kevin Jenness said:
It seems to be working at the minimal cut depth shown but I would be cautious running a 2" diameter bit on a 1/4" shank with that much extension from the collet. Many bits, such as the one shown in post #2 above, have a maximum extension marked on the shaft for a reason.
Click to expand...
I don't use the one in post#2 I use an alternative which is smaller in diameter and it is inserted the correct length for an ER11 collet.
 
Kevin Jenness said:
Not inexpensive, but this is a good quality long nose variable speed die grinder with a 1/4" collet. Makita 7-28k rpm grinder
Click to expand...
That looks good. Not cheap at £240 though, and as it’s 110 volt I’d need to buy a site transformer, another £110.
Thanks for the heads up though, I’ll have another look again. ;)

Edit: I’ve found a 240V at £260. I don’t have that kind of money for something that won’t be used very often. :(
 
Last edited:
Bill, put 'CNC spindle motor' into Amazon. There are various at lots of different prices. Most use an ER11 collet chuck so you can use Dremel cutters and 1/4" router cutters and the reach is sufficient for most boxes without danger.
 
colinsp said:
Bill, put 'CNC spindle motor' into Amazon. There are various at lots of different prices. Most use an ER11 collet chuck so you can use Dremel cutters and 1/4" router cutters and the reach is sufficient for most boxes without danger.
Click to expand...
I did look at those but most of them seem to spin too fast. I’ve also seen some 8mm shank cutters I’d like to use.
The variable speed Makita die grinder with 8mm collet is the best bet - just too expensive. I’ll try my router once I get all the other bits.
 
Bill Alston said:
I did look at those but most of them seem to spin too fast. I’ve also seen some 8mm shank cutters I’d like to use.
The variable speed Makita die grinder with 8mm collet is the best bet - just too expensive. I’ll try my router once I get all the other bits.
Click to expand...
Don't forget that all of those come with a variable speed so you can reduce from the maximum. I use one with no issues.
 
Thanks again Colin. I’ve noticed that I could get a larger collet Chuck to fit the spindle on that motor.
I’m having a problem sourcing a suitable table at the moment. I’ve seen a 300 x 140 that would do the job nicely but the delivery cost is over twice that of the table!
 
I’ve ordered a small compound table. I’m hoping I can make a larger table for it if it’s worth the effort. I won’t know until it arrives but I have the tools if it is.

 
Last edited:
Colin, I’m not sure if this is of any interest but I’m part way through my router jig and remembered I bought a small collet Chuck with an 8mm shaft to use as a short extension in my router. I gave it a quick spin today to see what it was like and it seems ok. I just grabbed the nearest lump of wood, donned a face shield and spun it up. Only made a few cuts but It seems to work ok. The cutter is as far into the chuck as it goes if anyone is wondering. I don’t think I’ll need the extension very often but it’s there if I do.
More work to do on the jig, including a clear plastic (PETG) cover to shield the cutter.

IMG_9540.jpeg
 
Bill, That looks good to me, you may want to seat the cutter a little deeper into the ER11 collet unless it has a particularly long shaft. With the ER11 collet you can get smaller ones and the use Dremel carbide cutters and also small CNC machine cutters usually 1/8" or metric equivalent. I take shallow cuts and increase the depth as I go rather than taking a big bite for additional safety. I also stand out of the line of fire at all time just in case.
 
colinsp said:
Bill, That looks good to me, you may want to seat the cutter a little deeper into the ER11 collet unless it has a particularly long shaft. With the ER11 collet you can get smaller ones and the use Dremel carbide cutters and also small CNC machine cutters usually 1/8" or metric equivalent. I take shallow cuts and increase the depth as I go rather than taking a big bite for additional safety. I also stand out of the line of fire at all time just in case.
Click to expand...
Thanks for the additional info Colin. The cutter is as far into the collet as it will go.
 
I finished the jig the other day so I thought I’d make a holder for a single point cutter. I really didn’t think this would work but I spun it up on the lowest speed on my router and it seems fine. I was expecting there to be a bad vibration. Test 2 will be trying it on some timber. It will be handy if this works as I’ll be able to grind my own profiles in HSS blanks. The one in the picture is 4mm diameter.
I also made a jig block for holding the cutters for shaping/sharpening on my belt grinder.

IMG_9593.jpeg
 
You must log in or register to reply here.
Back
Top