Backface milling cutter

Has anyone made a backface milling cutter for spotfacing the opposit surface of a hole ?

There are back facing cutters that the cutter is attached after the mounting spindle is put through the hole, I have seen pictures of them but never seen one physically.

I think in some situations it may well be impossible to do a back face task and it may only be possible in a lathe set up with some back clearance. But I can always be surprised!

Clive

Were used all the time in the old days by the radial arm drillers ,the the bar which had a blind slot in it was put through the hole then the spotface cutter was inserted in the slot.

Hi Paul, ~Yep ! used and made lots of them in the past on both radial drils and bench / pillar drills, you must of course clamp your work to the table.

Might even have one somewhere ??? but most stayed in the stores if made for a dedicated job, but we made them mostly for convenience from silver steel, you can use BMS just as well.

As Clive says the mandrel must fit the hole and be passed through then the cutter inserted , we used round HSS and often used old damaged centre drills ground to an appropriate form and locked in with a grub screw in the bottom of the mandrel. Always a fiddley job !!

John

Hi Paul

Or silver solder and grind a tip on a mild steel shank to do the undercut and using an adjustable boring bar holder wind it out while it is starionary to the correct diameter then feed it back against the rear of the work while moving, I would back it up very slowly. (Some quite expensive boring bar holders will wind out automatically) but the manual version will work fine. Handy for a lot of boring jobs

Like the photo below

**LINK**

Cheers

John

Edited By John McNamara on 10/03/2013 11:22:48

This is what I was thinking of.

Shaft is passed thru hole and cutter attached to the underside. Should be able to use it on a mill which has chuck or collet secured with a drawbar to prevent it being pulled out.

Hi John, I already have an an adjustable boring bar holder but to try and mchine the spotface on the opposite side of an 8mm hole would be a bit too squeezy.

How much access do you have from the far side? Enough to insert a 1-piece cutter shank first?

Neil

I have one, the cutting head is loose and held on with a pin, it can be used normally, or the head turned over, and the shaft passed through the hole. Ian S C

Neil, No room to insert cutter from behind.

Ian, Do you have a suppliers name or a photo ? Is it too difficult to make ?

Paul,
If you make one don't forget that if you are driving the shank clockwise the cutter facing the work is rotating anticlockwise.

Les.

Thanks Les, I can also run my mill in reverse.

The cutter was picked up at an auction at the railways workshop back in the mid 1980s when the government sold off the lot, I think it was made at the workshops, it appears to be HSS, 5/8" diax 1/2" thick, there are 8 teeth(I think, not going out to look at this time of night), and going by Arnold Thorp in his book "Vertical Milling in the Home Workshop" (Workshop practice series no., 2), I would suggest that you do not be too accurate indexing the tooth spacing, irregular spacing reduces the effect of chatter, you want the spot face chatter free. Ian S C

There are rear face "beburring" tools used in this way feed through in forward - rerverse spindle--cutter rotates out ( like a pawl)--- retract to depth----feed off face --- forward spindle--(pawl reteacts) -- retact tool...

great for finishing thousands of holes blind....

As to where to buy one from ,,,HORN springs to mind...( "other tool supply companies are available" )

Thanks for the feed back. I have seen some on the internet but they appear to be a bit expensive to buy. Will try a couple of home grown ideas and post my results if successful.

Regards, Paul.