Cutting A 6MM Wide 60 Degree Dovetail - Any Suggestions

[Anorak Bob]

My most used magnetic indicator stand does not have its original dovetailed clamp. None of the clamps I have, Mitutoyos and the Interapid ( thank you Michael G ) photographed below, will fit. I looked for a tiny dovetail milling cutter but so far I've been unsuccessful in finding such a thing.

I'm thinking of maybe two real options. Grind a single point cutter from a bit of round HSS or grind a skinny cutter for the Douglas. If I chose the latter I could mount a rotary table on the shaper to "ensure" concentricity.:rolleyes: A possibly less successful option would be to have a go with some needle files ?

Included amongst the photos are a German eBay seller's photo of a similar base with the original clamp and a couple of photos of the Interapid dismantled and displaying a bit of Swiss complexity.

Any other recommendations will be appreciated.

Bob.

[PDW]

Brownells gunsmithing supplies in the USA.

PDW

[RayG]

Any other recommendations will be appreciated.
Bob.

What about an upgrade... :) The Noga FA1500 http://www.noga.com/nogaProducts.php?prdID=FA1500

http://www.ebay.com/itm/Noga-Fine-Adjustment-Swivel-Clamp-FA1500-/201187773559?pt=LH_DefaultDomain_0&hash=item2ed7b9cc77

Ray

[Stustoys]

BT,
How could you mention using a file in the same sentence as as a shaper. As a mates father said "a shaper is just a lazy mans file":p
I use any excuse I can so the shaper can "pay" for its space. lol
How many are you going to make?
I'd be thinking about machining the dovetail first in the a piece of stock say 100mm long. I assume you'll want to cut the slot last so I'd make the blank twice as long and "double ended" so you've got something to hold onto. Though 16ish sound like a lot.

Stuart

[simonl]

Hi Bob. What Stuart said. That job sounds like its sceaming out for a shaper!

Cheers.

Simon

[Pete F]

Bob what size is the dovetail you need to make? I'll scratch around here to see what I have. Also what material are you intending to make the holder out of?

Other possible solutions would be making a single point fly cutter, or even a conventional cutter if you're keen enough! The latter not as crazy as it may sound, especially if you were to choose aluminium. I'm about to make a miniature threading bar and a similar process could be used to make a dovetail cutter. I'll put up the process here if you're interested? I'll grind mine from HSS but a similar process could be used by turning some silver steel and hardening it after turning.

The final solution would be to suggest that instead of making a one off tool just to do this one job, triangular inserts are 60 degrees :wink:

[neksmerj]

I'd make the clamp in two halves, this would make cutting the vee very simple.

Ken

[Anorak Bob]

Thank you all for the replies.

Peter, I checked out the Bownell's site, the cutters are either the correct 60 degree angle but too wide or the correct width and the wrong angle. That led me to a gunsmithing site where there was a discussion about a DIY option - http://www.homegunsmith.com/archive/T550.htm

Ray, I "upgraded" to a Noga a few years back but the adjuster struggles with the weight of a Compac 58mm DI. http://www.woodworkforums.com/showthread.php?t=134096&p=1305203#post1305203

Stu and Simon, if my Douglas doesn't start paying for its keep it might well be out the door. It is probably two years since it's been used. And I would only be making one of these clamps.
I take your point Stu about oversizing the piece to have something to hold on to.

Pete, the clamp's dovetail is only 6mm wide at its widest point. I'd probably use 1045 or 4140 because I have both and neither rust as suddenly as that gumby 1214.

And Ken, while a two piece clamp would be the easiest solution, dovetail cutting wise, the other end of the one piece clamp on the original incorporates an 8mm diameter hole for attachment of lugless back dial indicators of which I have a few. A clamp that pinches the stem is a bit simpler than a two piece affair that has to both clamp via the dovetail or by the hole.

BT

[kwijibo99]

G'day Bob,
As the dovetail is only to hold an indicator is there any reason the bottom angle really needs to be 60⁰?

Given this, you could cut your dovetail in a couple of passes with just a normal end-mill similar to the following:
Cut 1: Tilt head to cut first 60⁰ slot.
Cut 2: Tilt head to cut opposite 60⁰ slot.
Cut 2.5 (Not drawn) Drill relief hole for the spring slot
Cut 3: Use slitting saw to cut spring slot.

A bit fiddly but job done.
Cheers,
Greg.

[Anorak Bob]

Neat Greg. :2tsup:

Thinking the bottom needed to be flat steered me away from using a slitting saw or bitty endmill to cut the dovetail. Makes sense that only the sides and back corners could do the clamping.
Some of the Mitutoyo DTIs I have have integral cast dovetails. It will be interesting to see through a scope how much actual engagement there is.

Bob.

[Neil317]

Bob, I buy dovetails from AB tools in the US but I think they only go down to 1/4"

Harvey have smaller:

http://www.harveytool.com/prod/Dovetail-Cutters/Specialty-Profiles/Browse-Our-Products_202/Dovetail-Cutters_84.aspx

Costly for a 1 off at US$60 or so.

Neil

[Anorak Bob]

Bob, I buy dovetails from AB tools in the US but I think they only go down to 1/4"

Harvey have smaller:

http://www.harveytool.com/prod/Dovetail-Cutters/Specialty-Profiles/Browse-Our-Products_202/Dovetail-Cutters_84.aspx

Costly for a 1 off at US$60 or so.

Neil

Certainly not stuff for the heavy handed! A 1/16" dovetail cutter!

Thank you Neil.

[Michael G]

I like Greg's method but while not a 100% sure, suspect that the dovetail may be one of the type that requires a flat back (is there a clean metal surface for the points of the clamp to sit or are the surfaces the back and sides of the dovetail).
I needed to do a similar thing for the indicator holder I made and ended up milling a straight section for depth (around 2 or 3mm) and then using a needle file to make the undercuts. Did not take long at all.

Michael

[cba_melbourne]

Hi Bob,

Are you handy with files? I honestly believe one can file this small dovetail in less time than it takes to do it in a mill. A trinagular file just happens to have 60 degrees angles. Instead of spending money for a rarely used, tiny, fragile and expensive dovetail cutter, you could buy yourself a set of fine and coarse swiss needle files. You do not even have to do a precision job - its only to clamp a very lightweight measuring instrument, and if you end up with either a 58 or 62 degree dovetail will not matter one iota.

[KBs PensNmore]

Bob, I buy dovetails from AB tools in the US but I think they only go down to 1/4"

Harvey have smaller:

http://www.harveytool.com/prod/Dovetail-Cutters/Specialty-Profiles/Browse-Our-Products_202/Dovetail-Cutters_84.aspx

Costly for a 1 off at US$60 or so.

Neil

Not necessarily for a one of job, other people may wish for one also!!!:D
Kryn

[steamingbill]

Bob,

I dont know enough to be able to say whether or not the attached is a good idea or not.

I thought it was clever, but I don't yet have the skill to do it.

http://www.opensourcemachinetools.org/archive-manuals/Dovetail_Cutter_explanation.pdf


Bill

[KBs PensNmore]

Bob, everyone has the skill, it's up to them to realise it, in other words you can do it.:2tsup:
Kryn

[Ueee]

You could always drill your 8mm hole, slot it, then heat and bend one of the sides off at 90 deg. Then use a normal cutter, heat again and bend back. It will probably never go back 100% but it should be close.

Seeing the noga one i think it could be made from a length with half the dovetail on each end and a thin part in the middle and then bent around an 8mm rod.

Ew

[Ropetangler]

You could always drill your 8mm hole, slot it, then heat and bend one of the sides off at 90 deg. Then use a normal cutter, heat again and bend back. It will probably never go back 100% but it should be close.

Seeing the noga one i think it could be made from a length with half the dovetail on each end and a thin part in the middle and then bent around an 8mm rod.

Ew

Instead of an 8mm hole, you could drill it at 6mm say, then as Ewan has said, heat and bend one side off at 90 degrees, machine the dovetail with a normal cutter, heat again, bend back and clamp up on an appropriately sized male dovetail before redrilling to 6.5 to 6.8mm and finish by reaming to size. Finally polish and black to the usual BT standard.:D
Rob.

[Anorak Bob]

I slipped up to the shed and had a look at the fit of the Interapid clamp on both the Interapid DTI and the cast dovetailed Mitutoyo. In both cases the 60 degree sides of the clamp make continuous contact with the indicator's dovetail. There is clearance between the rear face of the clamp and the corresponding face on the DTI. Same with the Mitutoyo clamp.

For such a piddly thing you blokes have come up with interesting suggestions. With the rear of the dovetail doing little, I'm leaning heavily towards the slitting saw. That way there's only one thing to make, the clamp.

Bill, the DIY cutter recipe is of interest. I need to make a cutter or two for a tiny boring head. Michael G generously procured some 4mm hardened and unhardened rod for me a while back. The recipe would help me to get to it.

Chris and Michael, I have needle files aplenty but the saw sounds easier.http://d1r5wj36adg1sk.cloudfront.net/images/smilies/standard/rolleyes.gif
Ew and Rob, the heat and wrap sounds like fun but I bet I'd end up with a bin full of rejects because the dovetails didn't line up! http://d1r5wj36adg1sk.cloudfront.net/images/smilies/actions/doh.gif

And Kryn, thanks for the encouragement.http://d1r5wj36adg1sk.cloudfront.net/images/smilies/smile.gif

BT

[easymike29]

Do you have a surface grinder?

Gene

[eskimo]

http://www.maritool.com/Cutting-Tools-Keyseat-/-Milling-Cutters-Dovetail-Cutters-Cobalt/c78_231_235_316/p2387/Dovetail-Cutter-1/4-dia-X-60-degree-M42-Cobalt/product_info.html

or Brownells for a .245 x 60

http://www.brownells.com/gunsmith-tools-supplies/power-tools-accessories/milling-cutters/cryo-treated-dovetail-cutter-prod20728.aspx

[Anorak Bob]

No surface grinder Gene. A nice T and C though.

Don't know how I missed the Brownell's cutter Richard. It or the Mari are a temptation if I change my mind about using a saw. :)

BT

[RayG]

Do you have a surface grinder?

Gene

I'm betting you are thinking the same as me... grind down a larger size.. should be just a straight cut? Provided the skinny bit of the shank is small enough.

Ray

[desbromilow]

Don't quote me on this, but I recall there was one of the Dremel cutters which was close to 60 degrees (maybe 70 degrees), and fairly small (around 5mm at the widest) - obviously it's only HSS and takes shallow cuts, but it might be of use.

what I don't know is how well it would last on your material

Des

[easymike29]

No surface grinder Gene. A nice T and C though.BT

Try this

Gene

[Pete F]

Try this

Gene

Good suggestion, but what size wheel would you be using for that? How would you accurately dress the wheel to the appropriate angle without a sine dresser or radius and taper dresser (note: points lost for losing hand and/or having a wheel explode in your face when trying to bodge something up).

The thinnest surface grinder wheels I've seen are 1/4", and accurately dressing a wheel to specific angles isn't something to be taken lightly. Sine dressers can be picked up quite cheaply, but it's still a hundred bucks or so, and of course requires one to be purchased.

I like Ray's idea of shortening a larger cutter. They can be picked up reasonably cheaply used off ebay, and the chances are the top part of it you'll grind to will be perfectly sharp and unused.

A couple of other suggestions, for what they're worth. If you have a small t-slot cutter, step across in a series of descending steps, and then just file off the steps. I think Dremel make small cutters like this and they're likely to be cheap.

I'm a big fan of D-bit cutters, so for this one-off you could look at making up an equivalent cutter as a dovetail cutter in silver steel. Take some 6 mm silver steel, turn down a shank and leave an unturned section at the end. Turn a taper on that end so you now have a dovetail blank, section it to create a D-bit, then if it's to be used in steel harden and temper it, in aluminium I'd just leave it soft for a one-off. Note I've never made one of these, but I'm currently making a threading tool somewhat similar in HSS, so grinding instead of turning, I've just got side-tracked on something else.

[PDW]

I'm a big fan of D-bit cutters, so for this one-off you could look at making up an equivalent cutter as a dovetail cutter in silver steel. Take some 6 mm silver steel, turn down a shank and leave an unturned section at the end. Turn a taper on that end so you now have a dovetail blank, section it to create a D-bit, then if it's to be used in steel harden and temper it, in aluminium I'd just leave it soft for a one-off. Note I've never made one of these, but I'm currently making a threading tool somewhat similar in HSS, so grinding instead of turning, I've just got side-tracked on something else.

That'd work, but if I was only doing 1 or 2 I'd mill out the clearance slot then file to fit using a safe edge file. Easy to make one, buy a new triangular file & kiss 2 surfaces on a linisher.

I used to do dovetails all the time like this, for gun sights, back when I did a lot of hunting & gunsmithing. Then I bought a lathe, then a mill and it's all been downhill ever since.....

PDW

[steamingbill]

Try this

Gene

Hey - Could "this" be done with one of those really skinny wheels off a chain saw sharpener or alternatively 100 years ago would somebody simply knuckle down and do it with a hacksaw and a file ?

Bill

[Michael G]

There are lots of good suggestions for making the dove tail which if it were larger would be great. This thing is small though. Draw it out on a piece of paper - 6mm across the widest part and between 1 to 2mm deep. As far as grinding goes this is really Dremel territory. Toothed cutters whether D, fly or dovetail similarly are going to have to be really small. To make up a cutter for a one off job like this will take more time than can probably be justified. Even grinding the tool and setting up a shaper will take some time.

Based on all that I still think the only way to do it is to straight mill out most of the material (say around 1.2 DOC with a 4 to 4.5mm cutter) and then take out the corners with a needle file.

Michael

[easymike29]

Good suggestion, but what size wheel would you be using for that? How would you accurately dress the wheel to the appropriate angle without a sine dresser or radius and taper dresser (note: points lost for losing hand and/or having a wheel explode in your face when trying to bodge something up).

It's not necessary to use a thin wheel. A fat wheel can be dressed by hand to the required shape. Remember that the angle need not be accurate. It can be any angle greater than than that of the bottom of the dovetail. You're only cleaning out the corner. The flat portion is already machined or ground.

Gene

[Pete F]

Yes and how do you propose dressing it? Please don't suggest holding a single point diamond to the wheel by hand and dressing in the angle!

[cba_melbourne]

There are lots of good suggestions for making the dove tail which if it were larger would be great. This thing is small though. Draw it out on a piece of paper - 6mm across the widest part and between 1 to 2mm deep. As far as grinding goes this is really Dremel territory. Toothed cutters whether D, fly or dovetail similarly are going to have to be really small. To make up a cutter for a one off job like this will take more time than can probably be justified. Even grinding the tool and setting up a shaper will take some time.

Based on all that I still think the only way to do it is to straight mill out most of the material (say around 1.2 DOC with a 4 to 4.5mm cutter) and then take out the corners with a needle file.

Michael

It looks like the good old art of filing has been lost. At least the many answers seem to indicate that nobody feels to have the skill set to accurately file such a dovetail. Or the skills have been lost long ago by lack of practice.

The most difficult part is probably to file the dovetail straight and parallel. This can be simplified as above by first straight milling out as much as possible. Another trick would be to initially make the part 2 or 3 times as thick, file it, then mill off at both sides where the filed portions are most likely to be rounded. Or use both tricks combined.

[Anorak Bob]

It looks like the good old art of filing has been lost. At least the many answers seem to indicate that nobody feels to have the skill set to accurately file such a dovetail. Or the skills have been lost long ago by lack of practice.

The most difficult part is probably to file the dovetail straight and parallel. This can be simplified as above by first straight milling out as much as possible. Another trick would be to initially make the part 2 or 3 times as thick, file it, then mill off at both sides where the filed portions are most likely to be rounded. Or use both tricks combined.

Hey Chris,

As hard to believe as it may be, there was a time when I wielded a file or two. Don't ask what this is but the thing below was hand filed back when I was a student at WAIT. I still use my needle files. The orange boxed set of Favorites was purchased new in 1982 but my new favourite is the little No.6 cut barrette, still sporting its plastic overcoat. The die sinkers rifflers have also proven very handy over the years.

Bob

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[Anorak Bob]

I took the easiest option. Ground the teeth off a small file. I will spend a few minutes tomorrow in the corners of the dovetail with a needle file before it bathes in Blackfast.

BT


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[easymike29]

Yes and how do you propose dressing it? Please don't suggest holding a single point diamond to the wheel by hand and dressing in the angle!

The bulk of the dressing would be done by using a round Crystolon dressing stick and the finishing would be accomplished with a Norbide stick.

Gene

[simonl]

Nice work Bob, as usual!

Simon

[Pete F]

The bulk of the dressing would be done by using a round Crystolon dressing stick and the finishing would be accomplished with a Norbide stick.

Gene

Gene with due respect, everything you've said makes perfect theoretical sense. In practice however I have serious doubt that it will work as you suggest for all manner of reasons there's no point in enumerating here. I have just spent a very unpleasant hour or so going through various grinding wheels trying to find one that will hold a crisp edge, and even my hardest broke down rapidly. If you've successfully ground accurate dovetails in solid steel using the method you propose I'd say good luck to you.

[Anorak Bob]

Sometimes having too much stuff leads to forgetting about some of the stuff you might have. Advanced years probably contribute. :rolleyes:

About ten years ago I bought a Baty DTI on eBay UK and it came with the attachments pictured below. I did not know what they were intended to fit or their country of origin. I presumed they were Baty accessories but strangely the main column clamp didn't fit any of my stands and the dovetail clamp didn't really fit on any arms. It was too big to fit on the little magnetic base featured in this thread. I had the dovetail clamp poorly mounted ( too sloppy a fit ) on an Eclipse base. I had long forgotten that these components were originally together.

This morning I looked at an image in an online Tesa catalogue and it sunk in. It doesn't feature the fine adjustment but it allows the mounting of the Interapid and Mitutoyos by their 4mm shanks. The Mitutoyo DTIs are usually supplied with both 3/8" and 4mm shanks so by interchanging the arms on the little stand, I have even more flexibility.

BT

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