working with small diamter tools

I have a dial test indicator and whilst rotating the dial the dovetail holder snapped off. More a case of cheap junk than heavy handedness. The threads on the holders shaft had a very loose fit and it would tighten up and you turned the outer rim. Cheap metal and a tiny contact area left from where the dovetail cuts into it, sure fire fail point.

I thought i would make another holder, a larger aluminium bar would be better to start with, leaving some material left so it doesnt break again.

That got me thinking how do you cut a <5mm dovetail slot in steel? High spindle speed and slow travel? Would you slot it then cut one dovetail at a time? Or would cutting both offer better stability?

How would it differ between say a small sub 15mm piece of steel and then the same dovetail in a 100mm long piece?

Thanks.

Hi Dave,

I understand I am not the only one that has experienced destruction of the dial dovetail. I made a new one in steel, used a small slot drill to mill a slot to the correct width and then used a small triangular file to file the dovetail part into each slot wall. Not perfect by any means but it worked for me, I have been using it for over a year without problems.

Thor

I recently cut dovetails in cast iron when making my ball turning attachment. My HSS dovetail cutters are 30 degrees which was to much for the job so I used one from my woodwork router (brazed carbide) 14 degrees from memory.

Run at around 1000 RPM it cut well with no visible cutter damage.

This video might be of interest...

**LINK**

Jon

Personally, I would likely be looking to replace the quick change dovetail fixings for a more conventional hinged alternative. Some of the more expensive cheap DTI's come with replaceable backs. Although I have a couple with dovetail fittings, I still prefer the normal eye and screw type as there are very few times I need to change heads on my mag bases.

Thanks, I have seen some of his video's but not that one. Thats ideal for a small holder, what would you do with a larger piece though say 60mm or 100mm long? Filing that maybe an issue?

Didn't we have an edit post button somewhere? Typo in my title and a few elsewhere i wanted to change but its appears to be MIA.

I too had one of these small holders break ,this is one of these
jobs where a Quorn grinder is very useful.
Seen here in the album Workshop and machines a small
dovetail cutter ground up from the shank of an old 1/4 inch
end mill ,diameter across the points .210 inch.

John

I 3D printed a small block to test the size and after a bit of filing it fitted but an odd problem popped up.

Moving the lever towards me moves the needle to the right, move the lever away and sometimes it moves to the left and sometimes to the right?

Move the lever very slightly to the rear and the needle moves left for 0.2mm or 0.3mm (it varies) then the needle jumps and starts moving to the right?

Broken spring or something overshooting? Its not that old but a cheapy one. Contacted the seller and hoping they will exchange it.

Probably need to look for a better one. Proper brand

I still need a better holder though, if they do replace it the holder is likely to be just as rubbish.

X$M brand.

Metal shaper and some quality grinding time would make a small dovetail.

Only seen the shapers on youtube, I think Tubalcain did one on the fast return stroke?

How would you shape a tool for this?