Turning down the shank of dovetail cutter

[wongster]

Hello folks,

I've still not able to work on the QCTP holder as I'm not able to locate a suitable dovetail cutter for my sherline mill.  The only piece I can find of smallest size in the hardware shop is a 12mm shank, 25mm wide cutter.  The shank has some threads on its end.

I'm have this MT #1 ER16 collet holder with 10 pieces of collets from 1mm to 10mm.  Nothing in my boxes can hold the dovetail cutter with its 12mm shank.  The shop owner told me to turn down the shank to 10mm but I cracked my head on how to hold it in my sherline lathe to do that.

Anyone has some suggestions for me to work on?  I don't mind experimenting a bit as I move along as that will help in my learning.  Or should I just ship in a right size cutter from US/UK?

Appeciate any help.

Regards,
Wong

[Dean W]

Hi Wong;
You can get cutters with the proper shank size from the US, if you can afford the shipping.  It could be a little
expensive.  My dovetail cutters are 3/8" shank, which is a standard size for one of the Sherline arbors. 
Since you already have the ER16 collet setup, I think I would search locally for a 10mm shank cutter. 

Another way would be to get a Sherline arbor and bore it to 12mm to take the cutter you already have.
They make arbors that mount directly to the spindle, and you can drill and bore them to the size you want.

Yet another way;  The dovetail cutters I have here have a small center spot in each end.  Providing the shank
isn't just as hard as the cutting end, mount it between centers, drive the cutting end with a plastic or wooden
driver, and turn down the shank to 10mm.  Be careful not to put pressure on the cutting flutes if you try this.
They will break if you much pressure against them while driving them.  If you can get a face plate dog fastened
around the shank directly behind the cutting flutes, that would be better.

One other thing, not directly related to fitting your tool to your machine, but should probably be mentioned;
A 25mm cutter is BIG for a Sherline machine.  You will need to run it slow, and take light cuts. 

Dean 

[wongster]

Thanks Dean. Wish I could find a smaller cutter locally. Ordered from the sherline distributor here. Will take 2 to 3 weeks to reach me. Besides, the slot I'm cutting from is only 0.8"+. The final width of the dovetail should be 1.049". A bit of a challenge to use this cutter for my 1st dovetail cutting exercise.

I was thinking about holding between centre but am scratching my head on driving it. You mentioned about a wood or plastic driver, do you have a pic of how it looks like? Is it a diy item or off the shelf?

As for sherline arbor, are you referring to the endmill holder? The largest is 3/8" and I do not know if I have enough "meat" on it to bore out the 12mm hole. I'll check it out when I get home. It it can be done, it would be the simplest solution.

Regards,
Wong

[Dean W]

Hi Wong;
The Sherline arbor I was talking about is like the endmill holder, but has no hole in it.  I looked on the Sherline site, and
see they want $30 for one (!), and they no longer show blank ones. 
A2Z makes them for a reasonable $5.  They screw onto the spindle nose and you can cut it for whatever size you need.
Made of free machining steel, and is about 1" in diameter.  Plenty large enough for 12mm.
http://www.a2zcorp.us/store/Category.asp?Cguid={8B982514-64DD-4D5B-9BA6-020F24000020}&Category=BlankArbor%3ASherline

If that link breaks, try this:  http://tinyurl.com/37czrjc

For a dog to drive it between centers, something very simple like this will do.  You would need one slightly larger
since your cutter is larger.  The dovetail cutter shown is 3/4" (19mm) diameter.








For a piece of wood or plastic, I meant that in case you can't rig up some kind of dog driver like the pics above.
You would need a thin piece of wood with a hole in the center, and about twice the size of the end of the dovetail
cutter.  Plastic would do, too.  It would need to be soft plastic, or rubber.  Something the cutting edges of the cutter
could bite into when you pressed it against the face plate.  The dead center has to go through the hole to meet the
center hole in the cutter.    I think you would do better to make up a small dog out of aluminum.  It could just be made
from scrap.

Considering how narrow the dovetail is that you're cutting, you would do better with a smaller cutter, if you can find one.
It's going to barely fit your work piece on the size you got, and that means cutting both sides of the dovetail at once.

Dean

[andyf]

Hi Wong,

Trevor Rymell, one of my co-moderators on a Yahoo machining group, lives in Singapore, so I asked him where he buys small tools. You have already ordered your dovetail cutter, but for future reference he says:

"I've bought most of my mill tooling from Chan Man Lee Trading Co. Pte Ltd 75 Rowell Road
Tel: 62946338 who are one of the big Dormer agents here. They also sell a number of other European and Asian brands (they constantly tell me how expensive it's getting to import brands like Dormer).  You could mention this company to him and suggest he asks for Kelly and mentions my name."

(Dormer is a reputable UK brand)

Andy

[wongster]

Andy,

Thanks!!! You have uncovered a gem for me! I just shifted to my new office which is about 15 mins to 20 mins walk from Rowell Road. Hope they entertain small purchases. I'll give them a call tomorrow. Mist of the shops there closed around 5 to 6pm.

Not many folks here have machining as a hobby. Steve Wan of another forum, a fellow Singaporean, has been searching for hobbyists in this. Hope to have our own support group.

Really appreciate your help. Appreciate if you could thank Mr Rymell on my behalf.

Regards,
Wong

[wongster]

For a piece of wood or plastic, I meant that in case you can't rig up some kind of dog driver like the pics above.
You would need a thin piece of wood with a hole in the center, and about twice the size of the end of the dovetail
cutter.  Plastic would do, too.  It would need to be soft plastic, or rubber.  Something the cutting edges of the cutter
could bite into when you pressed it against the face plate.  The dead center has to go through the hole to meet the
center hole in the cutter.    I think you would do better to make up a small dog out of aluminum.  It could just be made
from scrap.

Considering how narrow the dovetail is that you're cutting, you would do better with a smaller cutter, if you can find one.
It's going to barely fit your work piece on the size you got, and that means cutting both sides of the dovetail at once.

Dean

Hi Dean,

Thanks for the pics.  The aluminum dog looks like a possibility for my current skill (or lack of it).  Even if I finally end up buying a smaller cutter, it solves the question I always have in my mind about turning something down with odd looking ends.  I may still try to turn it down to get a feel of how it works.

I aim to clear all my work and meetings as early as I can tomorrow so that I can run down to the shop mentioned by Trevor Rymell in Andy's post.  Hope they have it in store.

Regards,
Wong

[wongster]

Just called the shop. All their dovetails have 12mm shank. Looks like I either wait for my shipment or to try turning down using the alu dog suggested by Dean. Ordering the arbor from A2Z will also take some time... Anyone has a private jet to lend me free of charge. Best with pilot and serving crew. I can be like the Macau's Stanley Ho, who get his staff to fly in here to get some special durians. Durians are not allowed on commercial flight.

But the shop is still a good future source for tooling.

Regards,
Wong

[wongster]

I couldn't stop myself. Couldn't wait for the shipment of the dovetail cutter which is of the right size.  I went over to the shop 2 days ago and purchase the Dormer dovetail cutter.  Expensive stuff but I just have to get something.  While I was there, I also bought a countersink cutter.

The dovetail cutter has shank of 12mm.  There are 2 small holes at each end that I can mount between centers.  I waited patiently till tonight (Friday night) for turn down the shank but I was disappointed.  I'm able to use the dog and surface plate that came with my sherline lathe but I'm not able to move my right hand tool to the end of the shank at tailstock end.  The tailstock spindle was turned to the max.  Some pics attached to show what I mean.

Appreciate any advice.

Thanks.
Wong

[andyf]

Well, one of the advantages of turning between centres is that you can turn one end of he work, then reverse it and turn the other, and things will stay concentric.

Sometimes it works, even for me 
Andy

[AdeV]

Can you not rotate the QCTP so the cutter will reach the end? OK, the cutting angle won't be ideal, but it should still cut.

OR... it's hard to tell from the photo, but is the QCTP mounted in the left-most T-slot of the cross-slide? Could it be mounted in the right-hand T-slot?

[wongster]

Well, one of the advantages of turning between centres is that you can turn one end of he work, then reverse it and turn the other, and things will stay concentric.

Hi Andy,
I was thinking of only turning down enough at the end of the shank to fit the ER16 collet.  Maybe I'll swap out the QCTP to the sherline rocker toolpost which is smaller.  Will give it a shot and report back.

Thank you.

Regards,
Wong

[wongster]

Can you not rotate the QCTP so the cutter will reach the end? OK, the cutting angle won't be ideal, but it should still cut.

OR... it's hard to tell from the photo, but is the QCTP mounted in the left-most T-slot of the cross-slide? Could it be mounted in the right-hand T-slot?

Hi Ade,

The QCTP is mounted to the left most slot.  I've tried the right slot.  The body of the QCTP hit the body of the tailstock.  Maybe I'll try extending the tool bit out a little.  Hope it wouldn't flex too much.

Thanks for your input.

Regards,
Wong

[Bernd]

I'd take the quick change holder off and just use the tool strapped to the table with a couple of straps at the proper hight.

If you need a picture of what I mean let me now and I'll set up my Sherline up lathe to show what I mean.

Bernd

[wongster]

Thanks Bernd.  Would strapping down the tool hold it firm enough for cutting?  A pic or 2 will be very much appreciated.

Regards,
Wong

[Dean W]

Just put the normal tool post for that lathe on the slide and go at it, Wong.  That QC setup is kind of enormous.

Dean

[wongster]

Thanks Dean. I have decided to dig out the normal rocker tool post to do it when I get home from work.

Regards,
Wong

[wongster]

Finally managed to turn the shank down to slightly below 10mm (not due to my intent but a miscalculation).  The dovetail cutter now fit nicely on my ER16 10mm collet.

I started with the 1/4" HSS tool but after the 2nd pass, it wouldn't cut anymore.  Saw that the cutting edge was gone....  Changed to my carbide tool.  A little difficult to set a good cutting angle (too upright for my comfort) but the result turned out to my satisfaction.

Thank you folks for guiding me on this.  I'll start working on my tool holder for the QCTP so that I can use my little boring tool of 4mm shank.

Regards,
Wong

[Bernd]

Thanks Bernd.  Would strapping down the tool hold it firm enough for cutting?  A pic or 2 will be very much appreciated.

Regards,
Wong

I'm sure it would. Pics will be coming in a day or two.

If you don't see any soon give me a  .

Bernd

[Dean W]

Glad you got it done, Wong.  Show us what you make!

Dean

[wongster]

Bernd, thank you.

Dean, nothing much to take pic for the reduced shank. I'll take my process of making the holder. Haven't started but thinking about the brass nut to hold the holder in position on the QCTP. Maybe I should start work and worry about that later.

Regards,
Wong

[Dean W]

I meant, show us what you make with the dovetail cutter. 

[Bernd]

Hey Wongster, here's the pics. This how I would do it. The pics will give you a general idea of what I was talking about.







Hope this gives you some ideas.

Bernd

[wongster]

I meant, show us what you make with the dovetail cutter. 

Hi Dean,

I know what you meant  

I'm presented with a dilemma yesterday due largely to my laziness. I've 3 pieces of aluminum block of 3/4" thick. The height of the tool holder is given in the drawing as 1" x 2" x 3/4". I can use the 3/4" thickness of the stock for the height of the holder to save on extra work of having to mill it down if I lay it out on the stock the other way round. Some skim cut is needed to clean up the rough surface. But I would only be able to work on one piece at a time this way.

How would you approach this from a big piece of raw stock?

Regards,
Wong

[wongster]

Bernd,
Thanks! One question though; how do you ensure that the tool doesn't move side way while cutting?

Regards,
Wong

[AdeV]

Thanks! One question though; how do you ensure that the tool doesn't move side way while cutting?

The idea, I think, is that you screw that bolt down sufficiently hard that the cutter simply cannot move, except under exceptional forces - which you shouldn't encounter as you'll stall the lathe first.

The one issue I have with Bernd's setup as pictured (although I appreciate it's only an example), is that the bulk of the hold-down force will be over the bar to the left of the strap piece, and not over the cutter... Ideally, you want the bolt as close to the cutter as possible. If you're worried about movement, add a second clamp on the other side for extra stabilty, a bit like the attached C-o-C drawing.

[Bernd]

AdeV got it right. The bad part about locating the the hold down bolt will be the point at which the slots in the table will line up with the setup you will need.

It can be moved around untill the ideal condtion is found as Ade V's drawing shows and should be done like that if it is possible. Sometimes it's not. Which could be the case of the Sherline table and were the t-slots are located.

Bernd

[wongster]

Thanks AdeV and Bernd.  I was looking at the Sherline cross slide to see if I have sufficient space between the 2 slots for this setup.  The rocker toolpost solved the problem for me but adjusting tool height was rather a pain.

One more item to my knowledge bank.

Regards,
Wong